The Huygens probe scheduled to land on Saturn's giant moon Titan, Jan. 14th, "is another advanced spacecraft system that is a crucial part of the overall Cassini mission," according to the official NASA Cassini-Huygens website.

Whew! There's one bland, matter-of-fact description of a scientific and astronomical marvel. It is the kind of statement government agencies seem genetically predisposed to put out.

But, hey, this is an astronomy blog, not a government press release. Huygens is one amazing probe functioning on so many levels that its difficult to know where to begin to describe what it has already accomplished, and what it yet hopes to accomplish.

What I'll try to do here, in a decidedly non-technical way, is consider what the instrumentation engineers and scientists placed on the probe can do and just what the mission's astronomers hope Huygens will discover about Titan as it plunges into the unknown (but certainly hostile) environment on the perennially shrouded moon.

Here's a brief description of the six instruments and what each is designed to do.

1. The Huygens Atmospheric Structure Instrument (HASI). This is "a suite of sensors that will measure the physical and electrical properties of Titan's atmosphere," says NASA.

Scientists are interested in determining the density of Titan's atmosphere, the thermal properties of the atmosphere, and if the probe is able to land on Titan's surface and transmit back information, whether its surface is liquid and, if so, whether there is wave movement.

2. Doppler Wind Experiment (DWE). This is a pretty technical function. The DWE, by using an oscillator, will detect the Doppler shift as the probe parachutes down. The shift might possibly affect communications from the probe back up to the mother ship.

DWE will allow the communications suite to make adjustments and thereby provide a very stable communication frequency. In lay terms, the DWE will let the probe send the data it records to Cassini.

3. Descent Imager/Spectral Radiometer (DISR). This instrument will detect radiation in the atmosphere as well as determine light properties from the Sun as these properties are diffused by Titan's cloudy atmosphere.

Scientists can calculate mass from such data.

4. Gas Chromatograph Mass Spectrometer (GCMS). This is a gas chemical analyzer designed to identify and measure chemicals in Titan's atmosphere.

One of the critical measurements it can perform is the composition (solid or liquid) of Titan's surface in the event of a safe landing.

5. Aerosol Collector and Pyrolyser (ACP). If you think Earth has a challenge with its ozone layer, imagine what Titan faces. ACP will be able to chemically analyze the aerosols in Titan's atmosphere. It will sample the aerosols during descent and "prepare the collected matter (by evaporation, pyrolysis and gas products transfer) for analysis" by the Huygens Gas Chromatograph Mass Spectrometer (GCMS), which it conveniently has transported for more than a billion miles.

6. Surface-Science Package (SSP). The SSP contains a number of sensors designed to determine the physical properties of Titan's surface at the point of impact, especially and most importanly whether the surface is solid or liquid. This is no small feat and needs to be done immediately should the environment the probe finds itself in upon landing be so corrosive as to degrade Huygens ability to continue conducting experiments and/or transmit data up to Cassini.

SSP employs an acoustic sounder, which as the probe descends will be "listening" for solid or liquid surfaces. If the surface is liquid, then other sensors mentioned above will kick in and measure Titan's density, temperature and light-reflecting properties, thermal conductivity, heat capacity, and electrical permittivity.

After 17 years, a few critical hours...

Some scientists and engineers from the European Space Agency have been working on the Huygens probe for 17 years, from mission statement to design construction, testing, launch (seven years ago), and now data harvest.

Jan. 14 isn't just circled on their calendar. They have only one day on their calendar. That date is part of their DNA, and nightmares.

The entire "drop" through Titan's atmosphere to its surface will take about two-and-a-half hours. If the probe is able to function after landing it will have approximately 30 minutes of battery life left to continue sending data to Cassini.

Retransmission from Cassini to Earth will take from 68 to 84 minutes between the spacecraft and the ground station. Cassini's orbit around Saturn must be such that it has a clear path to beam data to Earth.

The distance of this transmission you ask? It will vary from 8.6 to 10.6 Astronomical Units (An AU is the distance of the Earth to the Sun).

The power source Cassini will use to do this: Oh, a solar-powered battery with a charge about as powerful as that in your electronic wristwatch.

It's the end of the year and what better way for stargazers to close it out than by viewing the best meteor shower of 2004?

The Geminid meteor shower occurs mid-December every year. Usually it comes in second to the mid-August Perseid meteor shower for eliciting "oohs" and "ahs." (There's the warm-nights bias factor, plus more observers on vacation in the summer).

Not this year. The Perseids eat Geminids cosmic dust. Peaking on Dec. 13 after 10 p.m. ET - with no moon - the Geminids pull into first-place for viewing.

The moon will be at new phase Dec. 11. On the peak night, the moon will be a skinny crescent, low in the west-southwest at dusk and setting before 6 p.m. That means the sky will be dark and moonless for the balance of the night, making for perfect viewing conditions. [According to British meteor astronomer Alastair McBeath.]

The best time to look is tonight. If you stay outside for a few hours around midnight expect to see dozens-to-hundreds of "shooting stars," (with the usual caveat -- provided there are no clouds).

Where should you look? Anywhere, says NASA.

Geminids streak all over the sky. Trace some backwards: they all lead to a radiant point in the constellation Gemini. This year the radiant lies next to Saturn - a beautiful coincidence. Gemini and Saturn are high overhead at midnight, easy to find.

Now, about earthgrazers. The first dark hours after sunset are when Earthgrazers appear, says Joe Rai, writing for Space.com

Earthgrazers are long, bright shooting stars that streak overhead from a point near to even just below the horizon. Such meteors are so distinctive because they follow long paths nearly parallel to our atmosphere

The constellation Gemini is the area of the sky at which Earth's atmosphere bumps into the stream of debris coming off the comet (or asteroid - see below) and hence the name Geminids for the "shooting stars." Gemini begins to come up above the east-northeast horizon just after twilight. So that's when you might see the first  Geminids. It's this time that offers the best chance of catching an earthgrazer - a streaking meteor running horizontally to your field of view.

It's also the best time to bring young children outside who have school the next day.

Now, for some history of the Geminids.

Astronomers know that the source of the shower is asteroid 3200 Phaethon. It has a cloud of dust trailing it and that's what the Earth bumps into, like a bug on the windshield of a fast-moving car. When tiny bits of dust traveling at 80,000 mph hit our atmosphere they flame out in glowing meteors (visible under cloudless, moonless skies).

NASA thinks that:

Asteroid 3200 Phaethon might have gotten a tail, of sorts, by bumping into another asteroid. 3200 Phaethon spends much of its time in the asteroid belt. Hitting a neighbor could have created a cloud of debris that follows 3200 Phaethon around the solar system.

That's one idea. Another is that 3200 Phaethon is a comet - a dead one. It died from too much sun. Every year and a half, 3200 Phaethon dives inward from the asteroid belt. Passing only 2 million miles from Earth's orbit, it approaches the sun closer than Mercury does. Repeated sunbaking could have vaporized all of 3200 Phaethon's ice long ago, leaving behind a rocky skeleton with a dribble of comet dust in its wake.

Space. com says that "locations from Europe and North Africa east to central Russian and Chinese longitudes are in the best position to catch the very crest of the shower, when the rates conceivably could exceed 120 per hour, or two every minute.

Predictions for select cities from Space.com -

When sinker ball pitcher Derrick Lowe takes the mound for the Boston Red Sox Wed. evening Oct, 27, look for the mother of all sinker balls to be served up at 8:14 p.m. CST. Weather permitting, a total lunar eclipse will be visible to fans at Busch Memorial Stadium

Should Fox Sports not point its camera up in the sky, look outside your front door to the east and you'll see the beginning of a total lunar eclipse, the first ever to happen during a World Series game.

Wednesday's eclipse favors the Western Hemisphere with most Americans getting a ringside seat.

Baseball is a game driven by statistics so, thanks to space. com, here are a few stats as to why there hasn't been an eclipse during a World Series game:

This notable Fall Classic owes partly to the fact that from 1903 through 1970, the World Series was only played during the daytime (The World Series was not played in 1904.)

In 1971, night Series games were introduced. But no total lunar eclipse since that time has occurred at just the right time.

There were two close calls during the 1980s.

In 1985, a total lunar eclipse on Oct. 28 came the day after the final game of the World Series between the St. Louis Cardinals and Kansas City Royals. The following year, another total eclipse occurred on Oct. 17. But that was the day before the start of the Series between the New York Mets and the Boston Red Sox.

The Sox missed the eclipse and the win in 1986. Not so in 2004. Lowe's sinker will repeatedly disappear from the field of vision of Cardinal batters as readily as its heavenly counterpart will disappear in the starry night. That big black empty space up there will be the number of runs the Cardinals score.

Go Sox. Even the stars are aligned for a championship!

The most memorable line from the 1950’s comedy series “The Honeymooners” starring Jackie Gleason is unquestionably: “One of these days Alice! Pow-zoom, up to the moon!”

But this month, for backyard astronomers at least, we'll be echoing Ralph Cramden's jubilant phrase: “How sweet it is.”

There will be a total lunar eclipse - at a civilized hour, at a time of year (in the US) when the night air is crisp but not cold, and when humidity is low to boot. And there is no need for eye protection. “How sweet it is.”

The eclipse will be high but not too high (30-35 degrees) in the eastern sky. Taking the kids out to see it won’t cause them to sleep through classes the next day. The only wrinkle, a small one, is on the west coast since the eclipse starts a tad before sunset. But by 6:45 p.m., PDT, the moon will look as good (or rather, not look at all) in Hollywood, Calif. as in Hollywood, Florida.
On Oct. 27 (please, no clouds), anyone in North and South America will be able to look up at the night sky and say: “How sweet it is.”

Stages of an eclipse

There are stages to an eclipse. As it commences, it will start looking redder and dimmer around 8:00 p.m. (EDT). Look north-northeast above the horizon and by 8:06 p.m. (EDT) the moon will have moved into the northern half of Earth's outer shadow - what astronomers call the penumbra. During this time the moon begins to dim and turn a copper-red because the only sunlight reaching it is sunlight passing through Earth's atmosphere.

At exactly 9:14 p.m. (EDT) the moon will start to disappear from sight (entering the umbra). It takes the moon several hours to pass completely through the umbra. Totality - when the moon is completely dark - begins at 10:23 p.m. It will last an unhurried 1 hour and 22 minutes. (Totality varies depending on the position of the observer, the Earth, and the planet's shadow. My figures are for a latitude of 40 degrees.)

The most exciting minutes will be those just before totality at 10:23 p.m. By 10:15 p.m. (EDT) a fingernail slice of white moon will be visible at lunar northeast, soon to go dark, a black sphere with an eery presence floating amidst the twinkle of stars.

The total eclipse will end at 11:45 p.m. (EDT) The moon re-emerges and is completely visible at 12:45 a.m. (EDT). At this point the moon will again seem reddish, but not quite as deep a hue as earlier in the evening. (See 'Shine on harvest moon' for an explanation.)

Shadow lessons

Bear in mind (and this is a good geometry lesson for the mathematically inclined), Earth's shadow has two parts, the umbra and penumbra. "The umbra is the region of total shadow - if we were within this portion of the Earth's shadow, we could not see the Sun at all. The penumbra is the region of partial shadow - if we were in the penumbra, we would see part of the Sun peeking around the edge of the Earth."

Just remember the lesson from earth science class: stand outside (on a sunny day of course) and extend your hand at eye level over smooth ground. The shadow cast by your hand has both an umbra and penumbra. The higher you hold your hand, the more obvious the penumbra will become.

The word "eclipse" comes from the Greek word ekleipsis, which means abandonment. It was not a happy word, per se. It aroused deep, primitive fear, and uncertainty.

Not so today. Our star, our planet, and our satellite engage in a perpetual orbital dance. We three are closest of gravitational partners.

Ok, so the harvest moon coming to the northern latitudes at the end of the month just doesn't mean what it did to past generations. Today, in the US, Canada, and most of Northern Europe, maybe three-to-five percent of the population are farmers. No one needs the extra light for overtime in the fields.

But that doesn't change the fact that the time between sunset and moonrise on successive nights in late September is shorter than at any other time of the year.

Even if we live in the most urban setting, we can check out the eastern horizon after sunset from Sept. 27-30 and revel in the moonlight.

The view is one of the most compelling in nature. The amplitude of the orange-tinged orb seems animate, as if freezing earthlings in their tracks. Some advice: find a high point over a flat horizon – the ocean, a knoll on the Great Plains, a mountain top, even the top floor of a skyscraper. (And hang in there Aussies! A similar phenomenon to the harvest moon is observed in southern latitudes at the spring equinox on about March 21.)

The harvest moon is always the full moon closest to the autumnal equinox. On the 27th, the full moon rises at sunset per the norm, but then, for several nights after that, it will appear just 25 minutes or so later each night at 40 degrees latitude (and can even rise earlier than the previous night above 60 degrees). This stems from the tilt of Earth at this time of year. There are key variations in our satellites’ travels across the sky and around our planet. In the northern latitudes, September is when these variations are most visible. (The full moon following the harvest moon, which exhibits the same phenomena in a lesser degree, is called the hunter's moon. But more on that, and a total lunar eclipse next month in a future blog.)

Why does the moon look bigger on first appearance over the horizon?

It is an old lunar mystery known as the "moon illusion." As the moon “peeks” over the rim of the earth, we see it swell to enormous size and then, in just a few hours climb “up” and (as the Earth rotates on its axis) appear to melt like a giant snowball.

Timothy Ferris offers an explanation in his book, "Seeing in the Dark." When confronted with a phenomenon beyond its sensory experience, the human mind creates its own impression and an object near the horizon is perceived as larger than something high in the sky. Psychologists also say that the moon looks bigger on first rising because primitive centers in the brain react to it as a threat due to it’s being on a horizontal plane, “eye-to-eye.” The threat diminishes as the plane moves from horizontal to vertical.

More empirically, the distorting influence of atmosphere is the main factor. We look through much more air – and pollution - when the moon is on the horizon, than when it is high overhead.

One final note for the romanticists. Bring an auditory dimension to your moonlight stroll, be it in city, suburb, or country. Hum the chorus from the classic show tune “Harvest Moon.”

Shine on, shine on harvest moon up in the sky. I ain't had no lovin' since April, January, June, or July. Snowtime ain't no time to stay outdoors and spoon. So shine on, shine on harvest moon, for me and my gal.

As day follows dawn, space flight follows the telescope.

James Oberg points this out in his article in the September issue of Astronomy magazine. He takes it as a simple rule of our human thought-adventure with space.

Galileo looked up and saw craters on the moon. Eventually, we would want to travel where we could see, and, albeit centuries later, we walked on the moon.

Mr. Oberg cites a set of complex mathematical computations made in the 17th century by Joseph Louis Lagrange (1736-1813), an Italian-French mathematician as indicative of how astronomy can give a boost to space flight.

Lagrange’s calculations resulted in what are called the Lagrange Points. These points measure where a spinning object, in gravitational relation to two other larger spinning objects, would stop spinning and remain stable.

Such a point, when out in space, would be one sweet spot to park a telescope.

NASA is using Lagrange’s calculations to locate where it will orbit the James Webb Space Telescope (JWST), the successor to the Hubble Space Telescope (HST), reports Astronomy. Plans are for the new light bucket, which NASA will launch in 2011, to “hang out” in 2011 four times farther away from Earth than the moon, where the gravity of the Sun and Earth merge to "produce a relatively stable gravity field." NASA calls this the SEL.2 spot.

Now, I don’t understand the math NASA is using (it really is rocket science). But I do understand the pull of Lagrange's logic as it relates to the further exploration of space.

The mathematician "discovered five special points in the vicinity of two orbiting masses where a third, smaller mass can orbit at a fixed distance from the larger masses. More precisely, the Lagrange Points mark positions where the gravitational pull of the two large masses precisely cancels the centripetal acceleration required to rotate with them."

Once the JWST is up and orbiting at SEL.2 "reusable space tugs" and "the energy to get to that point in space" could be tapped. Astronomical instruments could then give way to explorer craft, launched towards asteroids or flybys of Mars, suggests Oberg.

Oberg concludes his article: "It's curious, but just as it has in centuries past, the new astronomy of tomorrow will point the way for exploring space."

Lagrange, space tugs, orbiting space telescopes – just do the math.

August’s "night of the shooting stars” approaches.

The annual Perseid meteor shower begins this weekend. And though it takes a few days to really get going. why not get started Saturday evening for a few hours.

The first meteors will provide a smattering of light streaking across the night sky, building up to their peak on the night of Aug. 11, after 10 p.m. and continuing through dawn on Aug. 12, after which the Perseids dribble off, a few per hour over the next few nights.

There's good news on the always critical moon front – our sometimes luminous satellite is fully cooperating by not being in the night sky during the peak shower. Dark moonless skies provide a great backdrop to the Perseids.

I’ve written about the Perseids before so I don’t have too much to say about them other than that they are a focal point in my astronomical year. I’ve put in for vacation time and plan to take the 12th off so I can stay up all night on the 11th. (August is warm, even in New England.) This will let me drive well away from metropolitan Boston’s light pollution, find a dark field, and lie on the top of my Subaru Outback, toes pointed northeast, to watch the speeding travelers in our neck of the universe.

A decidedly unromantic take on the Perseids is to think of them as bugs bouncing off our planet’s windshield (atmosphere). Tiny grains of sand collide with our atmosphere at 132,000 m.p.h. as our planet crosses orbits with them from a northeasterly direction.

Once heated in the atmosphere, they are visible for only a second or two but their incandescent images linger in memory much longer.

Maybe it is the warm, summer nights coupled with for many, the fact that when a child, a parent took you out to see them. Perhaps for the first time, you had a glimpse of mom or dad behaving like a child too - "oohing" and "aahingd" at the meteors whizzing in the starry night.

More meteor facts.

It’s been almost two weeks since the Cassini probe pulled off its orbital two-step through the rings of Saturn.

The astronomy community exuberantly viewed initial photos beamed to mother ship Earth across more than two billion miles of our solar system. Cries of “compelling,” “unexpected,” “outstanding” greeted each download. Then, sotto voce, the already familiar refrain: “They raise more questions than answers,” about Saturn, its rings, and the tantalizingly mysterious moon Titan.

Scientists never expected signs of life. They do hope to find organic chemicals that might serve as the building blocks of life.

My first reactions to the pictures, on the other hand, were not the ones I had expected, not even close. I guess my frame of reference was tied to the first photos from the Hubble Telescope that amazed both me and the world. These are not Hubble photos, yet, anyway.

The “Hubble effect” had me looking long and hard off into a galactic wonderland, glimpses of miracles in starlight.

The Cassini “effect” has me thumbing through my trusty astrophysic’s text, bonding with the electromagnetic spectrum, as I force myself to think in long and short-wavelengths, high and low-frequencies so that I get a better sense of how, and therefore what, Cassini has begun to tell us.

Besides the visible spectrum, Cassini “sees” in ultraviolet and infrared. Its images reflect and interpret Saturn in ways our senses could only imagine. (Trust me, it will be primarily interpretations, not facts, that result from the Cassini. Already, what’s been recorded is too novel for previous predictions and hypothoses to stand up.)

Specifically, pictures coming back from Cassini in the infrared (which allows for “looking through dense cloud cover”) and ultraviolet, (which allows for seeing minute, “invisible” properties of an object) spectrum forced me into considering the role radiation plays in communicating information.

Cassini’s pictures, taken with the most elaborate and sophisticated instrumentation ever sent aloft, humbled me when I thought how little the information that streams along the visible spectrum actually is when compared to the full electromagentic spectrum, and how much more there is to learn outside what I can see with my own eyes. (The infrared and ultraviolet bracket the narrow visible spectrum with which we actually see. There are also xrays, gamma rays, and radio waves.)

Cassini can "see" in wavelengths of light and energy that the human eye cannot. The instruments on the spacecraft can "feel" things about “magnetic fields and tiny dust particles that no human hand could detect.”

The remote sensing instruments can calculate measurements from a great distance. This set includes both optical and microwave sensing instruments including cameras, spectrometers, radar and radio.

The Nasa/JPL site offers the following description of Cassini’s sensors:

In many ways, the spacecraft's instruments can be classified to the way human senses operate. Your eyes and ears are "remote sensing" devices because you can receive information from remote objects without being in direct contact with them. Your senses of touch and taste are "direct sensing" devices. Your nose can be construed as either a remote or direct sensing device. You can certainly smell the apple pie across the room without having your nose in direct contact with it, but the molecules carrying the scent do have to make direct contact with your sinuses. Cassini's instruments can be classified as remote and microwave remote sensing instruments, and fields and particles instruments. These are all designed to record significant data and take a variety of close-up measurements.

Yes, I know there is much to learn about Saturn, and the almost daily surprises confronting NASA and JPL astronomers, especially from its moon Titan, that bigger than Mercury object whirling about Saturn in our solar system.

But first and foremost, thanks to pictures taken at wavelengths that only a bat or insect could see, there is a much richer way of perceiving the world around us. We can delight in the expectation that distant planetary mysteries, and proximate phenomena here on earth, will open up before our very “eyes.”

Ever since the astronomy bug bit me I’ve been hooked on Saturn. It is by far my favorite backyard telescope target, even more than the four moons of Jupiter or the stars of Trapezium (four of them) inside the heart of the Orion Nebula.

It takes Saturn 29 years to orbit the sun. Twice in that cycle it comes closest to earth for the best viewing (last summer was one of those times). Now, with the Cassini probe soon to be literally orbiting Saturn, the pictures should be awesome! (See Cassini orbit insertion.)

Be still my beating heart as we consider what Cassini is going to show us starting with the first pictures to be sent back late Wednesday and early Thursday morning. It takes 1 hour and 23 minutes for a message from Cassini to reach Earth. At precisely 10:56 p.m. (EDT) the orbiter will fire its rockets and begin to brake in preparation for entering orbit around Saturn.

I’ve written on Saturn before, specifically how it's the "lord of the rings." I’ve characterized Saturn's gossamer bands as the best looking dirt and ice in the universe, a mere 30-50 feet thick in some places, with a width of around 300,000 miles.

One of the questions the astronomy community hopes the Cassini project will more fully answer is how these rings appear so bright from such a great distance (Jupiter has rings and so does Neptune and Uranus, but try to see them with an amateur telescope – you can't.)

As we begin our coverage of Cassini's exploration of Saturn, let’s make a comparison. Below is one of the "best" pictures to date of the rings. It is a "detail" of the rings and was taken just last May by NASA's Hubble telescope. Let’s see what images the orbiting satellite Cassini sends us on Thursday morning and compare them to the Hubble picture.

One final point. See the large gap, or break in the rings? This gap is called the Cassini division and is named after the Italian astronomer Giovanni Cassini who discovered it in 1676 and in whose honor the satellite and current mission was named.

Be sure to read other Monitor coverage of Cassini: A slingshot ride through Saturn's marvel of ice, dust; Rings, as you've never seen 'em

Remember as a child walking by some big old mansion just around the block from where you lived. You’d never been inside. It loomed large in your young imagination, beckoning.

Did anyone live there? If the door suddenly swung open, what would it look like inside? Should you go up and ring the doorbell and ask if you could come in?

And then one day, actually one night, Halloween, and a chance to go inside fell in your lap. You were brave enough to go up, ring the doorbell, stammer out “trick or treat,” and hopefully sneak a peek inside. You were asked to come inside.

Well, the galactic equivalent of that childhood experience happens next week. After a seven-year space flight covering more than 2.2 billion miles, the Cassini space probe approaches Saturn, our solar system’s second largest planet.

The small craft begins a four-year tour of duty circling Saturn. It will orbit the ringed planet 76 times, studying 7 of the 31 known moons circling the lord of the rings. Cassini will make 45 flybys of Titan, the Saturn moon of most interest to astronomers. Liquids have been detected on the giant moon’s surface (it’s bigger than the planet Mercury) which might sustain “life." Cassini has 12 different sets of scientific instruments crammed on board. Telescopes and cameras can read nearly every wavelength from radio to ultraviolet.

And just like it took courage to go up and ring the doorbell of that neighborhood mansion on Halloween night, NASA scientists and program coordinators have to summon up courage as they send the probe on a close encounter with Saturn’s rings. Cassini will literally pass through gaps in the rings twice in a 96-minute engine burn before it settles into orbit around Saturn. Bear in mind the rings are made up of dust and ice (some chunks as big as a house) kept in rotation by gravity and the odd small meteor or orbiting “shepherd moon” sweeping out debris between the rings.

Questions abound!

• Just what makes up the interior of the planet?
• Does it have a rocky core? Is it metallic?
• How powerful is its magnetosphere (a magnetic shield that affects, some would say protects, a planets atmosphere from harmful solar radiation)?
• What is the gravitational interplay between Saturn’s many moons and its prominent ring system? By studying the rings close up and how they formed will we unlock further clues in planet formation throughout our galaxy and in galaxies beyond our own? Cassini will let us do this at different wavelengths.
• What about the odd auroras observed on Saturn, what kind of magnetic force causes them?

And then there’s all that dust and ice circling the planet, making those beautiful, sunlight reflecting rings. What are they made of? Does the material come from our galaxy or, perhaps a supernova exploding millions, maybe billions of years ago, before being sucked up in the gravitational interplay between Saturn, it’s moons, our solar system's biggest planet Jupiter, and the sun?

For the next month this blog will “grab the rings,” reporting and reflecting on what we discover about this gas-giant in our corner of the cosmos.

Now that Venus’s moment in the sun ... well, it’s 6.4 hours of transit ... is over, don’t let this much awaited event slip out of your mental orbit.

Truth be told, the black punch-out in the smiley face of our solar system’s heat source that millions witnessed on Tuesday is such a simple yet profound image, that I hope it ripens into a much more lasting consideration of humanity’s place in the cosmos.

“Visually, Venus resembled a large, perfectly round sunspot,” writes Astronomy Magazine. And my response to that accurate, if understated description is: "Oh, yeah, it was that simple - just an image. And E=MC2 is only an equation.'

Since Einstein's famous equation, physics has become cosmology and cosmology has become physics.
By the simple act of watching the image of Venus replicate a moving eye-patch across a giant fireball I trust that cosmologists sprang up all over the world as well.

The rise of relativity theory and quantum mechanics, accompanied by a technological revolution in instrumentation, created information out of not only visible light, (which is the light by which we watched the transit of Venus) but also radio waves and microwaves, infrared and ultraviolet light, and X-ray and gamma rays. Einstein's equations opened humanity's eyes to a whole new universe. But the sheer mathematics of it risked turning the starry night into a nexus, not of infinite wonder (or terror), but cold, unrelenting calculations.

And then along comes a unique event like the transit of Venus. The experience triggered in me memories of the Perseid meteor shower in summer. At first, the meteors are quite visible and just seeing them is enough. But then the imagination asks: Where did they come from? What are they made of? How did someone know they would arrive at just this time and in just this place out of the vastness of the cosmos?

Seeing this one slice of Venus's orbit pass in front of the Sun easily suggests our own Earth's orbit around the Sun. The more one studies the orbits of planets, the gravitational pull of the Sun, the fact that our solar system acts like a planet in our Milky Way galaxy, and that our galaxy works in turn like a planet around other galaxies, and then again as a cluster of galaxies around other clusters of galaxies, our humanity impels us to stop and ponder our place in it all.

By this very act of pondering we gain some dominion over the infinite, how we can feel at home in our universe with its more than 100 billion galaxies, each with its billions of stars – one transit at a time.

Whether you were one of the millions who watched part, or even most of the transit, the Internet now lets the awe of seeing Venus move across the sun fix itself in your imagination through lasting images from around the globe. Here are some great websites for looking at photos of the transit. Use them as a vestibule to further thought adventures about time, space, and consciousness.

P.S. Venus was easy to spot with the naked eye - properly protected. It's diameter was 1/32 (about 3 percent) of the Sun's. If you had a friend with a telescope, or went to a public viewing spot, it was seen easily, at all magnifications. I had recommended for those who wanted to watch the transit online that there would be webcasts available. I listed The European Southern Observatory’s site. Many webcasts of the transit were unavailable or extremely slow due to high traffic. The ESO reports it was getting 1,500 hits per second about a half hour after the transit began. Sorry about that.

On June 8 Venus will take 6 hours, 12 minutes and 30 seconds to pass in front of the Sun. The last transit was 1882. Of course, where you stand, and how you protect your eyes from the sun's harmful radiation, are critical.

First, the obvious. You will only be able to see the transit during daylight hours. (See figure 3) If it’s nighttime in your part of the planet, you’re out of luck (sort of – see below).

Venus nudges against the east face of the sun at precisely 05:13:29 Greenwich Universal Time (that’s 5:13 a.m. in Greenwich, England). Astronomers call this first contact. In North America it means that when the sun rises Venus will already be more than half-way across our solar system's furnace, and by 7:25 a.m. EDT, will no longer be in front of the sun. If you live west of St. Louis (except Alaska, which is far enough north to catch part of the transit) you’ll have to wait until April of 2012 for your next opportunity.

Thanks to the Web, no matter where you live, you can watch the entire transit live. The European Southern Observatory based in Chile will have it live on their website. Viewing a virtual image of the transit means no concerns about solar filters to portect the eyes. Go there now and book mark the page.

I plan to be up 1:13 a.m. in Boston to log on and watch the first contact as well as what is called second contact at 1:32:55 a.m. Boston time (5:32:55 a.m. Greenich or Universal time) when the complete orb of Venus slips completely inside the Sun's circumference.

A word of caution -and I'm speculating here - but it will be interesting to see if the observatory's servers will be up to the traffic and have the bandwidth to meet the demands that I am sure will be made upon it.

Solar filters

We’ve written many times about not looking directly at the sun. Adults and most teenagers know this. The concern is with younger children who are hearing about a transit or an eclipse for the first time and don't realize the potentially harmful effects that may occur by looking directly into the sun with the naked eye.

So, to repeat: Watch young children. Be very carefull. Looking at the sun without a proper solar filter is the equivalent of putting your eyeballs in a microwave oven and turning it on high. Enough said.

Obviously, the safest way to watch the transit is to go to the website mentioned above. But the thrill of actually seeing a planet move in front of a star, not virtually but literally, warrants the effort. Many high school and university science classes will have safe viewing sites. Check them out on the web or in your local newspaper. If you have an astronomy enthusiast as a friend he or she will likely be setting up a telescope – with a certified filter. Ask to grab a peek.

One of the most widely available filters for safe solar viewing is shade number 14 welder's glass, which can be obtained from welding supply outlets. Another inexpensive alternative is aluminized mylar that is manufactured specifically for solar observation.

Unlike the welding glass, mylar can be cut to fit any viewing device. If you are thinking of buying or making a filter for observing the transit of Venus be sure to closely read the following two excellent articles from Sky & Telescope magazine: "Solar Filter Safety;" and
"Solar filter suppliers."

See related articles: Captain Cook, the transit of Venus, and a little trip to Tahiti; Here comes the Sun - and Venus; Check out Venus at its brightest

Captain James Cook, navigator, explorer, and discoverer, still but a lieutenant in the British Navy, witnessed and took measurements of the June 3, 1769 transit of Venus from the south-Pacific island of Tahiti.

Why sail half-way around the world through uncharted waters to land on an as of then unmapped island to do such a thing you ask? The reason was simple, and profound for his times – to determine how far away the Sun was from Earth. In an age of sail, such a fact would be of immense value in navigating the world’s oceans.

First, a thought experiment. Erase from memory all you know of distance. Stand on a flat plain, either day or night and look towards the heavens.

How far away is the Sun, the stars? What in your human experience would offer insight into the unimaginable distances – after all, 93,000,000 miles is the closest star to Earth – you look across. The ancient Greeks, for instance, thought the planet Jupiter (Zeus in Greek mythology) was just a little distance above Mt. Olympus.

Given the limited instrumentation of Cook's day, the exact timing of the transit of Venus was believed to be the only way to precisely fix the distance to the Sun. It offered a solution to a problem of immense consequence by using a methodology known to every schoolboy of that age – geometry.

The principle Cook was to employ dated to the ancient Greek geometers: parallax. Parallax gives a means of measuring distance.

A simple way to conduct a parallax experiment is to just fix on an object across the room from where you are standing. Cover one eye as you look at it. Then, cover that eye and open the other. A "shift" or angle occurs in perception. The two different points of view of the same object, from the same spot, create an optical triangle.

The Greeks proved that if you know the distance from one eye to the other, or the two different points from which you view the same fixed object, plus the angle created by the parallax, it should be possible to figure out the distance to the object viewed.

Of course, you would need one honking large triangle to get a fix on the Sun. The base of your triangle, and the one employed in Cook's time, was the diameter of the Earth. It was impossible to get one any longer. Take a measurement of the transit from two opposite points on the globe, compute the angle and voila! Length of the sides of the triangle would equal the distance from Earth to Sun.

A skilled mathematician and surveyor, the Yorkshire farm lad so impressed his naval superiors by the accuracy of his observations of a solar eclipse in 1766 that he was given command of the ship "Endeavor." His mission: "catch" the transit of Venus for the British Royal Society and King George III.

From his south-Pacific observatory, Cook, in collaboration with others measuring the transit of Venus from other locations on the globe, would become a point at the joining of two sides of a giant triangle. (see figure 2).

Unfortunately for Cook, and scientists of the era, Venus's cloudy cover did not let observers see, or fix, the exact time at which the planet entered and exited the Sun’s orb. Variations in timing the transit were too great to allow for precise computing of the distance to our closest star.

Cook’s expedition came up with a distance of approximately 123 million kilometers to 157 million kilometers. Not the kind of accuracy that NASA could use to send a spacecraft, say, to Mars, but nevertheless, much better than previous estimates. More precise measurements of Earth’s distance from the Sun (an Astronomical Unit or AU by astronomers) would have to wait for better instrumentation and different methodologies than available to Cook.

For an excellent website showing the voyage of Cook to Tahiti, check out - South Seas: voyaging and cross-cultural encounters in the Pacific (1760-1800)

For an extended mathematical discussion of parallax check out: Approximated method for the calculation of the parallax.

Next: Actual times of Venus’s transit of the Sun on June 8.
Previous: Here comes the Sun - and Venus (by Jim Bencivenga)

On June 8, Venus will pass in front of the Sun's face.

Prepare for a media blitz. It will be all transit, all the time as the airwaves, newspapers, and Internet, herald this unique phenomenon of planetary alignment.

Despite saturation coverage, hunker down in the privacy (and awe) of your own imagination. Contemplate the mathematical precision in predicting the transit given the distances and magnitude of the objects involved. No hype should diminish your sense of wonder.

Given that there are more than a billion stars in our Milky Way galaxy and more than a billion billion galaxies in the known universe, just why is one tiny - about 80% the size of Earth - little planet’s passing in front of a star such a big deal? Because we are conscious of it. Venus’s passing in front of our Sun is not an unrecorded, inanimate event. (See figure 1)

In our tiny little corner of the universe we sojourn with our sister planet and we simultaneously imagine our own Earth as it orbits the Sun, sustained by the hostile fire of our star's nuclear explosions that seed life-giving photosynthesis across the frigid emptiness of space.

Only six transits of Venus have occurred since the telescope was invented in the early seventeenth century: (1631, 1639) (1761, 1769) (1874, 1882). Notice, that transits occur in pairs with eight year separations between the two transits in the pair. (So you’ve got a second chance in case you miss this one next month. More than likely you’ll want to come back and see it again.)

Intervals of about 105 or 122 years elapse before a pair of transits occurs. More than one century will elapse before they occur again. You may grow tired of hearing: "The last time Venus transited the Sun was in the year 1882; no living human has ever seen this event." Don't!

More compelling: Few humans – maybe hundreds - have ever seen Venus cross the Sun's disk (more on this in a future blog).

A few facts: the only planets that can transit the Sun are those with orbits smaller than Earth's orbit, i.e., Mercury and Venus. Mercury, being much closer to the Sun, makes 13 to 14 transits a century. We had one a year ago on May 7.

Photos of Venus taken by some of the world's great telescopes will amplify the image of this cloud-covered sojourner crossing a sea of fire. Viewing the transit of this tiny black dot will heighten awareness of the size, scale and velocity of planets. Ultimately, we will connect our own water planet in relation to the myriad of stars that fill the heavens, all of which are yoked by the same laws of motion and gravity.

There is much more to say. Rather than attempt to do so in one comprehensive article we plan to update – to blog this blog – from now until June 8th. We will offer tips on how to safely view the transit; where on the planet it will be visible, with exact times; links to websites on the subject; and a photo gallery from professional and amateur alike of some of the better pictures taken of the transit.

One final thought. Another message you will hear over and over: "Never look directly at the sun with the naked eye or unfiltered telescope." This one you can't hear enough. The temptation will be to sneak a peak. It is up to every adult to keep children from the optical equivalent of playing in traffic. (Parents and teachers should verbally beat youngsters over the head with this advice.)

Next: Captain Cook and Venus. (by Jim Bencivenga)

Sometimes the appetizer is better than the main course.

When it comes to Venus, June 8 is the main course. For the first time in 122 years (1882) it will transit (move across) the Sun. Professional and amateur astronomers alike will be out in the thousands to watch the second planet drop in front of our solar system's central star. (More on this in a future astronomy blog).

But for anyone else looking up into the starry night this coming weekend, Venus's spectacular brightness will prove to be visually more tasty than the transit on June 8. Under clear skies, it will be a sight to behold.

Check out the West-Southwest skies May 1st, 2nd or 3rd. Venus will be at its brightest (and closest to Earth Saturday evening). It will shine at a magnitude of –4.51.(Remember, for astronomers, negative numbers represent brighter objects and only the Sun and moon are brighter when Venus is this close to earth.)

In fact, it is so bright that, if it is a cloudless day with deep blue skies, keen observing will pick it out in the middle of the day. At noon on Saturday or Sunday look almost due east. Your gaze should be half-way down from the the Sun (which will be more Southeast. Make sure NOT to look directly at the sun).

There’s Venus.

Venus’s orbit about the Sun takes 225 days, with its distance from the Sun being almost three-quarters of the Earth's. Its disk will be 25 percent illuminated with sunlight reflecting off its clouds. That’s what makes it glow so brightly in the starry night. In just the past month it increased in visible size nearly 40 percent.

If you're fortunate enough to be out in the country and the night is cloudless, find a dark stand of trees. Turn your back towards Venus and look for your shadow. Silhouette cast by planet-light: Now that is an astronomical hors d'oeuvre! (by Jim Bencivenga)

Ok, trust me. You really should do this.

Tomorrow night, Wednesday, go to bed early. Set the alarm for 11:30 p.m. Plan on getting up as if you were starting the day.

Am I crazy, you ask?

No, the annual Lyrid meteor shower peaks through the night into Thurs. morning. Wouldn’t it be a shame to sleep while huge fireballs streak across the heavens, some for up to 30 seconds.

Let's hope the clouds cooperate – by being absent. The moon already has. It won’t be visible at all, making for extra dark skies, especially if you live in the country or make the effort to drive to a dark spot far from city lights.

Most years, star gazers can expect to see one or two Lyrid shooting stars every few minutes. But every decade or so there’s a burst of activity and up to 90 meteors in a single hour might flame-out in the sky. Maybe this year will be one of those nights.

But here’s another reason to look skyward. The Lyrids are the oldest recorded meteor shower. According to Chinese records, they were observed in 687 BCE as "stars that fell [like] rain." Just imagine, as you gaze at these stellar fireworks, you bond with fellow humans who have done the same for more than 2600 years.

What is that bond? To see and wonder, perhaps to fear, but always to be conscious of the wider, limitless universe we inhabit.

Nasa’s Science@Nasa website notes that

The Lyrid meteor stream is associated with the periodic comet Thatcher C/1861 G1, whose orbit is tilted nearly 80 degrees with respect to the plane of the solar system. Because the comet spends most of its time well away from the planets, it is nearly immune to significant gravitational perturbations. This is probably the reason why the debris stream has remained stable and the Lyrid shower has been observed for so many centuries.

Thatcher won’t return to our part of the solar system for another 300 years or so.

You want to find a comfortable spot. Dress warmly. Bring a thick blanket or lounge chair to lean back on. Look skyward East-Northeast. Fix on the brightest star in that direction, Vega at 0 magnitude. (If you live along the Atlantic seaboard, it’s well worth the effort to drive to a secluded beach. There won’t be any lights from London or Paris backlighting your view!)

The meteors emanate from the constellation Lyra (the Harp), hence their name – Lyrids. Lyra is the radiant, the point at which the stream of debris left by the comet Thatcher collides with Earth’s atmosphere. It is the area of the sky from which the meteors appear to radiate.

Another sky marker is Cygnus, the swan, also known as the "Northern Cross." The radiant is above and to the right of Cygnus.

Something else makes the Lyrids special, besides their predictability. They collide with Earth's atmosphere nearly head-on. This causes them to appear like a giant fireball coming at you from directly overhead. The angle of contact makes them seem as if "turbo charged," resulting at times in a spectacularly bright, glowing trail of light.

No need for a telescope or binoculars. Meteors can appear in any part of the sky. Their trails, though, tend to point back toward the radiant, or the constellation, Lyra.

Like all meteor showers, the higher the shower's radiant, the wider the field of view and the better the chance of seeing meteors.

Just one more reason why you have to get up so late. The radiant will be highest in the sky after midnight. (by Jim Bencivenga)

Last we wrote, excitement was growing at the prospect of two comets appearing in the spring sky. What was still to be determined was just how bright they would appear in the northern hemisphere.

Good news.

Latest word from the Harvard-Smithsonian Center for Astrophysics (CfA) is that they are going to be plenty bright for naked-eye observations.

Officially known as C/2001 Q4 (NEAT) and C/2002 T7 (LINEAR), the two visitors from beyond the Oort Cloud (see below) go by the popular names NEAT and LINEAR. Our blog of 3/24/ said: "Because NEAT and LINEAR are 'newcomers' transiting our solar system, it remains to be seen just how visible they will become. Their orbits are not fully known. But in a few weeks astronomers will more accurately predict their paths and their magnitude."

NEAT will be the neatest (sorry, couldn’t resist). It will be high in the western evening sky of the northern hemisphere during the latter part of May. The nights of the 18, 19, and 20th around 10 p.m. should be ideal because there will be no moon.

NEAT will reflect sunlight at a magnitude of 1.1, possibly lower, in the first week in May. (Reminder: Magnitude is of greatest relevance if you don't have a telescope. It is a scale of an object's brightness. The unaided human eye under very dark skies can see an object at 6.5 magnitude. The lower the magnitude, the greater the visibility.)

Because the moon will be full the first few days of May, we won't really get a good look at NEAT's tail until May 6 or later. From Atlanta-Dallas-Los Angeles looking West-Southwest around 9 p.m. it will be 15 degrees elevation. (The further north you live, the lower on the horizon it will be.) The dog star Sirius (a magnitude of –1.47 and the brightest star in the evening sky) will just be setting. It will be just beneath NEAT. Look for Sirius as a pointer to the comet.

Also note that West-Northwest of Sirius, the planets Venus, Mars and Saturn will be in a tight row with Venus the brightest object in the night sky, magnitude –4.5. By May 15 (when there will be little moonlight) NEAT will be clearly visible higher in the sky, above and directly in line with the three planets.

Imagine the omens such a phenomenon might have portended to the ancients, whose lives were ruled by the comings and goings of the night sky and these planet "gods" in a way we post-Copernicans can only imagine.

Hint to parents
If you want to instill a love of geometry in your ten to fifteen year-olds, get out each night around 9 p.m. Observe from the same dark location. Bring graph paper and chart the changing location and elevation of the comet each night relative to the three planets and other prominent stars. You will, if you haven’t already, sown the seeds for a keen interest in solid, not just plane, geometry.

Comet LINEAR will be more challenging to observe because it appears in the early morning hours later in April and early May. It will be quite low in the eastern sky. You will need a flat, open view of the dawn horizon as it barely peaks over the edge of the earth.

LINEAR will never get to a greater magnitude than 2.6 and will quickly fade to 3.7 and then fade below naked-eye visibility by the end of May. It will make a brief evening appearances in early June, but again, low on the western horizon and quite dim.

One positive aspect of LINEAR – in the pre-dawn moments the tail will be visible first. Remember, the visible white tail is on the side of the comet opposite the Sun, so the tail will precede the actual body of the comet on the horizon as the pre-dawn sun rises.

Oort Cloud*
The Oort Cloud is an immense spherical cloud surrounding our solar system. It spreads out about 3 light years, some 20 trillion miles (that's trillion) from the Sun. Its vast distance leaves it at the edge of the Sun's "orb of physical, gravitational, or dynamical influence."

The cloud is made of galactic "debris," including comets. Comets are typically tens of millions of kilometers apart. As SolarViews.com points out, "They are weakly bound to the sun, and passing stars and other forces can readily change their orbits, sending them into the inner solar system or out to interstellar space. This is especially true of comets on the outer edges of the Oort cloud."

As spring turns to summer both NEAT and LINEAR will return to the outer regions of our solar system, never to be seen again. (by Jim Bencivenga)

Good things come in pairs.

This spring two comets make their first appearance in our solar system. They will grace the starry night in late April and May.

Seeing one comet is a thrill, but two, and possibly on the same night, albeit at different times, well – be still my beating heart.

They are officially known as C/2001 Q4 (NEAT) and C/2002 T7 (LINEAR) but go by the popular names NEAT and LINEAR.

Both have been tracked by powerful telescopes reports the Harvard-Smithsonian Center for Astrophysics (CfA) which hosts the Central Bureau for Astronomical Telegrams, a comet monitoring program.

Of the two, chances are better for a spectacular view of NEAT. It will be high in the western evening sky of the northern hemisphere during the latter part of May. The nights of the 18, 19, and 20th around 10 p.m. should be ideal to observe it because there will be no moon. Just find a dark field away from city lights.

LINEAR’s trajectory stays close to the sun and will be fairly low on the eastern horizon in April and early May. It will be visible in the pre-dawn hours and will require a flat, open expanse for good viewing.

Though both will be in the night sky on the same nights, it is unlikely they will be visible simultaneously (unless you can hitch a ride on the International Space Station).

Because NEAT and LINEAR are "newcomers" transiting our solar system, it remains to be seen just how visible they become. Their orbits are not fully known. But in a few weeks astronomers will more accurately predict their paths and their magnitude.

Magnitude is of greatest relevance if you don't have a telescope. It is a scale of an object's brightness. The unaided human eye under very dark skies can see an object at 6.5 magnitude. The lower the magnitude, the greater the visibility.

When comet NEAT was first seen in August 2001 by the Near Earth Asteroid Tracking program (NEAT and hence the comet’s name), it was visible at 20th magnitude - only the most powerful telescopes could see it. NEAT is likely to shine at 1 or 2 magnitude according to the CfA. That would equal a very bright star, and of course, it will have a white tail.

Comet LINEAR was discovered by the Lincoln Laboratory Near Earth Asteroid Research program (LINEAR and hence its name) in October 2002. It is currently visible under very dark skies at about magnitude 6. Binoculars or a telescope are necessary for most city dwellers or anyone living in a large metropolitan area.

Comets are frozen balls of ice and dirt that typically originate in the far reaches of the solar system (well beyond the planet Pluto, but still under the influence of the Sun’s gravity). They are leftovers from when the planets were forming, sweeping up all matter in their orbital paths. Comets escaped the gravitational fields of the major planets, and were never incorporated into planets.

This is one of the facets that makes them of such keen interest to astronomers as they harken back to a time before the planets were formed, more than 4.5 billion years ago. Investigating comets is a way to study the origins of matter in the universe.

A single orbit for some of thse comets can take tens of thousands of years. Their appearance is totally unpredictable until they transit the inner solar system in a journey around the sun and back out beyond Pluto.

Since most of a comet's orbit is distant from the Sun, its nucleus is frozen. This is why comets are sometimes referred to as "dirty snowballs." More than half of a comet's substance is frozen liquid.

As a comet nears the Sun, solar radiation in the form of heat boils surface material, which then surrounds the comet in a coma, or head. The heads and tails of gas and dust are visible because they reflect sunlight, giving a comet its signature trait. The visible white tail is on the side of the comet opposite the Sun. The luminous material grows brighter the closer the comet comes to the Sun and extends for millions of miles.

Each time a comet orbits the Sun, it loses some of its ice or liquid material. Astronomers call the molecules that comprise these liquids, "volatiles." Eventually, after eons, the volatiles burn off, leaving the comet just another rocky mass in the solar system. For this reason, comets are said to be "short-lived, on a cosmological time scale." Many scientists believe that some asteroids are extinct comet nuclei, comets that have lost all of their volatiles.

So bear in mind that as you gaze up at a comet, it is making a sacrifice. By allowing itself to be seen, it literally burns up. You couldn't offer a better expression of thanks for this cosmic gesture than to look long and wonderingly at NEAT and LINEAR in the starry night. (by Jim Bencivenga)

By Jim Bencivenga

March weather comes in like a lion and goes out like a lamb. Ok, the cliché is pretty much true in most of North America. But let me tell you why I’m keen that the lamb part happens near Boston this time around.

I don’t want any clouds messing my view of the starry night March 25-30, especially the 29th. All five planets visible to the naked eye - Mercury, Venus, Mars, Saturn, Jupiter - will grace the evening sky right after sundown.

Find a nice open field, or unobstructed 180 degree horizon as far from city lights as you can. Look for brilliant Venus in the west and sparkling Jupiter in the east. Looking at Venus, extend your left arm all the way, then put your left fist up so as to block it from view.

Now, look to the right and below your thumb’s knuckle and you’ll see, rarely visible because always close to the Sun, Mercury. It sits closest to the horizon in the visible rung extending upwards and curving left of the five planets known to the ancient Greeks as “wanderers.” (From the 15th to the end of the month, Mercury makes its best appearances in the northern hemisphere.)

Keep covering Venus with your left fist. Mars sits above and to the left of your pinky, about a fist and-a-half in separation. Next, move your fist to cover Mars and look about another two fists to the left and you’ll see Saturn, serene as its rings (albeit invisible to the unaided eye) twirl.

You can put your arm down now. Crane well to the left (east). Gas-giant Jupiter, king of the planets, glows against the blackness of space. It is at the highest point of its orbit. And with a pair of binoculars, look for its circling four Galilean (inner) moons.

Each of the planets will appear pretty much in the same place each night. But wow, does the moon move across the sky.

And if the skies are clear, consider getting out each night to watch how the moon swings from being a sliver just right of Mars on the 25th to a half-swollen orb perched between Saturn and Jupiter on the 30th. The moon, besides going from full to invisible every month, also rises 12 degrees further east each night.

As you appreciate how it changes position, you can trace the imaginary line in the sky it glides along. Astronomers call this line the ecliptic, a heavenly highway that traces the plane of the earth’s orbit, along which the Sun, moon, and the other planets, appear to move.

And if the clouds cooperate in the beginning of the month, there’s something else not to miss. Comet LINEAR C/2002 T7 will be visible in binoculars in the northern hemisphere from March 1 until about the Ides (15th), when it will be too close to the Sun to observe. It will hang low, its tail trailing in the western sky about an hour after sunset. By mid-April, having completed its orbit of the sun, it will reappear in the east and on this leg of its galactic journey, it will be visible to the naked eye just before dawn.

More on this comet, and another naked eye comet, Comet NEAT C/2001 Q4, in the next astronomy blog.

By Jim Bencivenga

She’s back.

Just look to the southwestern sky after sunset and the purest, whitest light this side of the sun dances against the black backdrop of space.

Venus.

She’ll be in our evening skies through the Spring. It will be eight years before the planet shrouded in clouds (all the better to reflect sunlight) will be this close to Earth again.

And if you’re fortunate enough to be far away from city lights, this weekend (as well as any evening between Feb. 20-24 when there is little if any moon), look for your shadow by the light of Venus. Find an open grove of trees. Stand where you have an unobstructed view of the planet and see the faint shadow you, and the surrounding trees, cast.

Awesome.

For even better viewing of Venus, get your hands on a pair of binoculars. Have them handy Jan. 24 and Feb. 23. Venus and the scantiest of crescent moons perch side by side. Venus will be sparkling to the right with a fingernail of light showing on the bottom side of the moon to the left. The contrast makes for one galactic odd couple. A Venetian, lunar rendezvous summons for me an image of the comings and goings of friendships. For the next three nights watch how the two, like friends in our busy lives, meet, pass, then distance themselves, while the memory of their encounter remains.

With or without binoculars note the darkened, faintly illuminated outline of the moon. What you are looking at since it is so close to sunset is earthshine, sunlight reflected off Earth bouncing off the moon back to Earth. Add in the sunlight bouncing off Venus casting a faint shadow back on Earth, and you’ll be bouncing with the thought that this subtle, galactic glimmer includes you, the planet you are standing on, a satellite that revolves around the planet you are standing on, a planet reflecting light all from the star that gives life to our planet and makes our solar system go - the sun.

Just standing will never be the same again!

And finally, because Venus is so bright in the night sky it is impossible to see her phases without a telescope or powerful binoculars. If you have access to a telescope, get ready for a Galilean moment. Focus on the second planet from the sun right after sunset. The first time Galileo did this he observed that Venus had phases just like the moon. Galileo had an "a ha" moment. Venus must be orbiting the Sun, like the moon orbits earth. Then, if Venus, likewise Earth must orbit the Sun. Rather than being at the center of the universe, Galileo knew he was standing on a planet that circled the true center of the universe.

by Jim Bencivenga

Want to see a "sooo way-better" show than "Lord of the Rings: The Return of the King" this holiday season?

Find a friend with a telescope, or better, check out any one of the hundreds of open-to-the public non-profit and university run telescopes and take in the real "Lord of the Rings" – Saturn. (Just google telescopes/observatory plus where you live.)

On Dec. 31 Saturn will be 748.3 million miles from our planet. Believe me, this is close. Since it takes Saturn 29.4 years to orbit the Sun - it’s closer to Earth than at any time since 1973. The next time it will be this close won’t be until January of 2034.

By New Year’s eve Saturn will be shining as bright as it can get, at a magnitude of –0.5. (see chart below)

This is because it will be opposite the Sun (astronomers call this opposition). When viewed from Earth, Saturn will rise as the Sun sets and will reach its highest point in the southern sky at midnight, setting as the Sun rises.

But it gets better.

The ringed planet’s rings are not always tilted for optimal viewing form Earth. Sometimes they are edge on, and would appear, if they did at all, as if the planet had a midriff buldge.

Right now and for the rest of the winter, the rings are breathtakingly tilted for viewing through a telescope – more than 25 degrees to our line of sight. As the rings "capture" reflect light, the planet itself looks brighter (so a bright moon will not impair seeing it, but of course, moonless nights are best viewing).

Gaze at the moon through a good telescope and you will remark on how sharp the lens is. Look at Saturn for the first time through a telescope and you will forget the telescope altogether, too in awe of the glowing halo girdling the planet. See http://www.csmonitor.com/2002/0926/p17s01-stss.html

Prior to Galileo, Saturn was the most distant planet humans could see. Neptune, Uranus, Pluto, were invisible to the unaided eye. In 1610, the Tuscan inventor recorded seeing some "bumps," a bulge around the middle of the planet. But his instrument's resolution was not powerful enough to distinguish the rings. The Dutch astronomer Christian Huygens, with a more powerful telescope than Galileo, first saw the rings in 1659. Fascination with Saturn has not ceased since.

Astronomers estimate that the total mass of the rings, if crunched into a ball, would make a satellite 180 miles in diameter. They are astonishingly thin – a mere 30 to 50 feet in some places. Their width is a little less than 300,000 miles, but highly reflective – visible to us from a distance more than six times the distance Earth is to the sun.

Eric Chaisson, who teaches astrophysics at Harvard and was a member of the design team for the Hubble telescope, says of the rings in his astronomy text "Astronomy Today": "Stars can occasionally be seen through them, like automobile headlights penetrating a snowstorm."

Remember, to the ancients the sky was a flat tapestry upon which the stars hung, and the "wanderers," the planets, moved about. Saturn, being the most distant planet visible to the naked eye, seemed to take the longest in its journey across the sky. Longest equaled slowest, equaled oldest to the ancient imagination, hence Father Time.

There’s no small irony that Saturn reaches opposition and comes so close to Earth on New Year’s Eve, when we ring out the old year with the new, and father time is supplanted by the new year’s child.

Since ancient history, time has been identified with Saturn (Roman deity of time, Cronos or Kronos to the Greeks). The mythic story is one of the oldest and still holds us in its spell. In mythology, he was the son of Uranus (heaven or sky-father) and Gaea (earth-mother) and the youngest of the twelve Titans. Mom knew that dad was never going to give up his power to her sons, so she plotted with her youngest, Saturn, to kill dad off (remember, this is Greek mythology).

Gaea took some flint, a mineral of her own being, and made a sickle and gave it to Saturn to complete the deed. It was the tool by which life was cut down at the time of harvest and was crescent-shaped like the moon, symbolic of cyclic rise and fall.

The myth goes on to teach that Saturn's emasculation of Uranus, making him king of the Titans, begins a change of the generations, the footsteps of time which no one and no generation can escape.
Hence, the sickle (and later, the scythe linked to the harvest each year) symbolized the cruel and unrelenting flow of time which, in the end, cuts down all things.

by Jim Bencivenga

If astronomers had a Top Ten hit parade, the tune at the top of the charts for November would be, "Here Comes the Sun," by the Beatles.

More than three weeks into what is being touted as the most dramatic and unpredicted chain of solar eruptions ever observed, the sun continues to hurl enormous bubbles of super-heated, charged particles, 13 times the size of Earth, into space.

What’s going on? What triggers these solar explosions? And how do they affect Earth?

Researchers still aren’t sure.

In simplest terms, the sun -- the energy dynamo of our solar system -- is suffering an intense, sustained, tangling and twisting of its magnetic field. The blast furnace where nuclear fusion throbs in our 4-plus billion year old stellar-cooker sun "overheats" and has to let off this heat in the form of energy.

Varying rotation rates of the gaseous sun at different latitudes create multiple electromagnetic fields that wrestle each other (think different layers on a cake spinning at different rates). These tangled fields obstruct the escaping energy from the hot plasma at the center of the sun from racing to the surface. The resulting distortions cause intensely fluctuating temperatures at the escape point (the photosphere or surface of the sun where electromagnetic radiation vents). Eventually, convoluted energy spikes the sun’s surface. We see these distortions as sunspots, black blotches easily as large as Jupiter, some many times so.

But please, don’t think of these black sunspots as "not hot." They are incredibly hot, just "cooler" than the escaping energy all around. Convection is what causes them to look (from Earth) black.

Periodically, the distortions that create sunspots intensify and fold back on themselves and intensify again. Then, something literally explodes. The bigger sunspots continue to reload, fire, and reload and fire again. From such intense energy distortions come the solar flares and coronal mass ejections (CME).

This is what scientists think is going on right now.

Scientists cannot predict when a flare will occur. But when it happens our third rock from the sun is bombarded by enormous and violent electromagnetic winds. It is what causes beautiful aurora borealis to appear. The bigger the flare (plus the direction it erupts relative to Earth), the more southerly the latitude in which the aurora becomes visible.

All experts agree that the current CMEs have been one of the stormiest periods of activity ever witnessed. The number of intense flares, some blasting out within a day of one another, is unprecedented. Auroras are being seen as far south as Texas and Florida.

Now, before we go into the physics of these flares (we’ll do that in a followup blog), let us give some context, some perspective, a sense of scope, awe, wonder, disbelief, wow, 'good lord!,' to the forces and fields of energy erupting from the Sun.

To begin to comprehend the powerful source of energy blasting away at the center of our solar system (don’t even try and wrap your head around the fact that there are a billion billion of these stars in the Milky Way alone, just think about the one little sun that makes for life on our water planet) one needs to shift the psyche so that it computes reality as "an order of magnitude."

Ramp up your sensibility:

"Every second, [the sun] produces an amount of energy equivalent to the detonation of about 100 billion one-megaton nuclear bombs. Six seconds worth of solar energy output, suitably focused, would evaporate all of Earth’s oceans. Three minutes would melt our planet’s crust. The scale on which the sun operates simply defies Earthly comparison ," writes Eric Chaission, astrophysicist, author, professor of physics at Tufts University and director of the Wright Center for Innovative Science Education.

The sun is more than 1.4 million kilometers (869,919 miles) wide. It contains 99.86 percent of the mass of the entire solar system (next time you stand on the shore of either the Atlantic or Pacific ocean, realize you’re not even looking at a bead of perspiration on the forehead of a gnat relative to the mass of the Sun).

More than a million Earths can fit inside that orange orb humankind has reveled at since the dawn of consciousness.

Next: The sun’s energy is so enormous that when it has a solar storm, it’s more than a dark and windy night here on Earth. What happens to communication gear and sensitive electronic equipment when coronal mass ejections occur?

For more information check out these sites:

Strongest solar flare on record:
http://www.space.com/scienceastronomy/xtreme_flare_031105.html

Great solar storm of 1859: http://www.space.com/scienceastronomy/mystery_monday_031027.html

Soho solar flare photos: http://sohowww.nascom.nasa.gov/hotshots/2003_11_04/

It’s pretty  obvious something is going on with the sun and for the most part we have don’t have a clue. It’s a fascinating subject to investigate, at the intersection of astronomy, physics, engineering, electromagnetism, chemistry, and  geology.

We have some theories, but don’t understand how two new Jupiter-sized sunspots, coincident with multiple near-record breaking electromagnetic solar flares blasting out at more than 4 million miles per hour  from the sun’s inner core, will make their presence known on planet Earth.

But first, don’t look directly at the sun, as it can cause serious harm. Second, don’t look directly at the sun. Am I clear on not looking directly at the sun? It would be the equivalent of taking a pistol, putting six bullets in the six chambers and playing Russian ruelette with your eyes.

If you really do want to get a glimpse of these sunspots, either go online www.space.com, or find a friend with a quality solar filter on her telescope. I can assure you, viewing these two, new huge sunspots is, as the expression goes, "totally awesome."

What we’re going to do here and in the next two or three Scitech blogs is offer an overview on the solar phenomenon currently taking place, the aurora borealis that is one of the historic indicators of such activity, and what it all might mean to us, from using our cellphones, flying in an airplane, to watching the NFL Sunday afternoon on Satellite TV (now that’s important).

Today’s blog offers some historic context.

Before satellites gave us the knowledge that there were electromagnetic bursts of pure energy emanating from the sun in the form of giant solar flares, or that there was a continuous solar wind washing over our planet, humankind, unwittingly, only acknowledged the influence of such solar eruptions as lights flickering in the northern night sky – the Northern Lights. We did not know what caused them, only that they were there, and they were beautiful and mysterious.

When satellites went up into space in late 1957 and took readings of the upper atmosphere and beyond we learned a lot. Instrumentation discovered the Van Allen radiation belts, and the role they played in filtering the solar wind – actually measurements correlated with solar flares. Something a  Norwegian scientist Kristian Birkeland attempted to measure, without fully understanding what it was that he was measuring. His original data gathering at research stations in frigid northern Norway at the dawn of the 20th century began the modern scientific investigations of the Northern Lights. (For obvious geographic reasons, Norwegian scientists are prominent in Aurora research).

Aurora borealis is the scientific name for the Northern Lights. The expression was first used by Galileo in 1619. He coined the term to suggest the similarity of what he viewed in the night to an early dawn emanating from the north, rather than the east. The "Lights" sometimes appear to those who live at low or intermediate latitudes in the northern hemisphere.

The term was not fully developed by the famous astronomer. The reason given for his lack of detail (an aberration from his normal approach to matters scientific) is that at the time the Roman Inquisition severely limited what Galileo could and could not say publicly. It is believed his writings on the subject were made under the name of his student Mario Guiducci.

Galileo discussed the Northern Lights in support of his idea that the earth was not the center of the established universe. Correct on this major Copernican point, he was wrong in thinking that the aurora was caused by sunlight reflecting from the high atmosphere, suggesting that the aurora was sunlight glinting off the high atmosphere, bouncing off the polar icecap, falling snow, or ice crystals.

When a great scientist makes a mistake, it can last a long time. Galileo’s mistake lasted almost four centuries. But, as imprecise as Galileo was, compare his observations to the earliest known record of the “Lights.” More than 2,000 years old, it comes to us in written form from China in 208 BCE:

"During the night luminous clouds were seen, gold and white, with long streamers, which lit up the hills. Some think it is Heaven’s Sword, but others think that it is a deep hole with a large blazing fire in the sky."

Consider further the record of myths and popular imaginings of the aurora in the northern hemisphere. There is no geographic bias here. The aurora in both the northern and southern hemispheres (aurora australis), though simultaneous, are more readily viewed in the northern latitudes. There just weren’t, and aren’t, many people living near magnetic south. (Australian aboriginal myths from the "Dreamtime" are one exception.)

For the Lapps in northern Scandinavia the luminosity pulsing across the sky was fierce and powerful. The lights could be Odin’s messengers, the Valkyries. This sisterhood linked the phenomena to omens of war and bloodshed. The belief persisted for centuries. In Norway, they became "blood lights," the souls of departed warriors newly engaged in heavenly battles.

Parents in Iceland warned children that the risk of their hair catching on fire from the Lights was great. In the presence of the Lights a person was foolish not to wear a hat.

Gradually, explanations for the ghostly shimmering took on a more naturalist hue. Myth gave way to folklore: "the Lights were reflections from the silvery shoals of herring swimming close to the water’s surface, or that they were the light bouncing off icebergs rocking in the polar sea; that they were created by sunlight reflecting off the wings of migrating geese, or off swans trapped in the polar ice flapping desperately to free themselves," writes Lucy Jago in,  The Northern Lights, (Alfred A. Knopf, 2001).

By the early 19th century, Galileo’s intuitions and observations had evolved (mutated) into the premise that the aurora were the result of sunlight reflecting from ice crystals suspended high in the atmosphere.
Concurrently, developments in electromagnetism, and the discovery and exploration of the magnetosphere began. The more robust the scientific evidence in these two fields, and the closer the linkage between them, the more scientific were the connections to the "ghostly" lights. Like the dominant star in a binary pair gravitationally absorbing its weaker companion, magnetosphere research absorbed the formerly imaginative fancies given the lights.

Next: Modern discoveries

Jim Bencivenga

Saturday night, Nov. 8, dinnertime.

Your date will be here soon. Just step outside, look east. Your tryst is getting ready, has been for the last few hours.

What’s going on? What date is this?

The moon is passing through, "encountering," the shadow cast by the southern half of the earth, as the third rock from the sun gets between the moon’s reflected light and the source of that reflection, the sun. Your date will be visible from all of North America - a lunar eclipse.

The moon will be completely blocked by the Earth’s shadow. Astronomers call this totality. It last 25 minutes, starting at 8:06 p.m. Eastern Standard Time and until 8:31 p.m.. The moon will look like a Christmas ornament gone over to the dark side.

Of course, even more fascinating than watching a totally blocked-out moon, and which only folks on the night side of the Earth see, is how the white orb gets nibbled until it is, literally, a mere shadow of itself. Europe gets to see every stage of this eclipse. Here in the US the beginnings of the eclipse start around 5 p.m. in the eastern states. The effect will be minimal but with close inspection you will note a slight “dimming” of the moon’s light. Over the course of a few hours, the Moon darkens and Earth’s umbra, (shadow) turns it a deep red color, filtered and bent by Earth’s atmosphere until the moon disappears completely.