Depiction of Galileo demonstrating his astronomical telescope.2009 has been designated the International Year of Astronomy (IYA), in celebration of the 400th anniversary of Galileo first pointing the new invention of the telescope at the sky.

(Almost as famous as this act of opening our eyes to wonders we'd never witnessed, Galileo was tried by the Inquisition for pointing out that there were more things in heaven than were imagined by Church doctrine–but that's another story altogether…)

It's an intriguing fact that, beyond the Sun merely being a bright disk, the Moon a not-so-bright and slightly mottled disk, the stars pinpoints of light and the planets pinpoints of light that move, everything we have learned about the universe and the objects in it we have learned in the last four centuries, since the invention of the telescope and Galileo's putting it to it's most famous use: astronomy.

Galileo saw on the Moon craters, mountains, and valleys, and likened the "uneven, rough… depressions and bulges" to Earth's geographical features. Venus was revealed to undergo lunar-like phases, which provided controversial insight into the layout of the Solar System. Jupiter had four small "star-like" moons that moved around it–which defied Church doctrine holding that everything in the universe goes around the Earth. And Saturn possessed jug-handle-like protrusions, whatever those were!

It may be difficult to imagine what Galileo was feeling when he made these discoveries of things we take for granted. How exciting to peer through that celestial peephole and discover that the Moon is another world, and that there are worlds out there that had never been seen or imagined before. Sure, new discoveries about Mars keep rolling in, and we're finding a new extrasolar planet about every month–but the excitement about these discoveries is tempered by the fact that we already suspected things like these as possibilities. For Galileo, the magnified astronomical sky was practically a blank canvass.

Back to IYA 2009–what's going on? Who's promoting this, and what is being done to celebrate?

NASA is promoting it, and many different organizations (including Chabot and the Eastbay Astronomical Society) are participating in a number of ways: star parties, special programs, special events, and good old fashioned put-your-eye-to-this-telescope-and-gawk public observing activities.
Honestly, there's nothing like looking through a telescope–and it doesn't have to be a large one. I don't doubt that I first became inspired into astronomy when, as a child, my family would take me to Chabot Observatory to look through the telescopes.

When the new Chabot Space & Science Center reopened the telescopes after the move to our present site, I found all of the childhood wonder flooded back when I put my eye to the eyepiece to regard Saturn. There's an excitement that simply can't be achieved by looking at photographs. You just have to experience it for yourself, as Galileo did four centuries ago…

MESSENGER's color filter imaging capability reveals variations
in color on Mercury too subtle for the human eye.
Photo credit: NASA/MESSENGERLike a snow-bird relative vacationing in warmer climate localities and sending back picture postcards of their trip, NASA's MESSENGER spacecraft has made yet another swing past our Solar System's innermost planet, Mercury. But, like the traveler who just can't seem to get enough sightseeing in, this was another whirlwind flyby set to the furious tempo of a camera snapping pics–about 1200 in all…

Did MESSENGER find anything new, since its first flyby back in January? Here are a few highlights:

• Prominent "ejecta" rays streaking out from several large craters–previously revealed only by radar imaging from Earth, now photographed for the first time.

• 30% more of Mercury's largely unexplored surface than had been revealed by the Mariner 10 flybys in the 70's and MESSEGNER's own first flyby last January (spacecraft–namely Mariner 10 and MESSENGER–have now imaged 95% of Mercury's surface).

• "Hyper-color" (my own word) imaging of surface features that reveal variations in color too subtle for the human eye to notice, providing information on soil and rock composition.

I'm a planet junkie–and Mercury has always had a special place in my imagination. One might think of Mercury as the least interesting planet, in our Solar System as well as among dozens of "exoplanet" systems yet discovered. After all, it's a small, dry, cratered, and airless lump of rock and dust, resembling for the most part Earth's Moon. Consider, however, the point of view of someone who's favorite place on Earth is dry, dusty Death Valley, and my enamorment might not come as such a surprise.

In my imagination I see towering cliffs, enormous, deep crevasses, wide, flat dusty plains, bright brights in sunlit patches and dark darks in shadow….

But it's really its differences from Earth that make Mercury such an appealing exotic vision. Being where it is, 36 million miles from the Sun (about a third the Earth-Sun distance), the sunlight striking the Mercurian landscape is six times brighter–imagine that! And not just the visible light spectrum, but all the wavelengths of light the Sun puts out are free to impact Mercury's surface, unimpeded by an atmosphere: infrared, ultraviolet, X-rays, and potent burst of gamma rays rain down intensely on the planet's plains, mountains, and craters.

Speaking of the Sun, its behavior in Mercury's skies is, to say the least, zany. Mercury orbits the Sun in about 88 days (Earth days), but rotates so slowly that a single Mercurian day (the time from one high noon to the next) is about 115 Earth days. Not only does that mean sun-up to sun-down lasts roughly a couple of months, but that Mercury's orbital motion has a greater effect than its rotation on the Sun's apparent motion through its sky. The complicated relationship between Mercury's year and its day also causes the Sun to go "retrograde" at times–that is, periodically halt its progress from one horizon to the other and temporarily go in the opposite direction.

So, our prodigal vacationer MESSENGER has its itinerary straight: a climate with the brightest, warmest sunlight, pristine landscapes, long sunny days, and big skies that perform tricks for its amusement. Now, if only there was a beach…

Artistic rendition of exoplanet Gilese 436 b, created in Celestia
In the past fifteen years, the search for other Earths– and possibly life– outside our own solar system has taken off. As of May 2008, 293 extrasolar planets have been confirmed. Most of these planets are big, gas giants like our own Jupiter but new technology is helping astronomers get closer to finding earth sized planets. To find an extrasolar planet scientists first identify a star and then, using different methods, look to see if there is a planet, or planets, orbiting the star. It’s estimated that at least 10% of sun-like stars have planets.

Once astronomers have found an extrasolar planet, also called an exoplanet, they look to see if it is in the Goldilocks zone. This is an area of space in which a planet is just the right distance from its' parent star so that the surface is neither too hot nor too cold. A habitable temperature means that the planet could possibly host liquid water, an ingredient for life.

A number of exoplanet findings have come from astronomy teams in Switzerland and near San Jose at Lick Observatory. Astronomers at Lick made news in the fall of 2007 when they discovered 55 Cancri. The discovery of the five-planet system came after nearly 20 years of observations. Also in 2007, astronomers with the Geneva Extrasolar Planet Search Program discovered the most earth-like planet ever found. Gilese 581 c lies in the Goldilocks Zone, it's surface temperature ranges from an estimated 32 degrees Fahrenheit to 102 degrees Fahrenheit. The research team that discovered the new planet believes it may have a developed atmosphere and be covered with oceans.

Curious to see how astronomers hunt for extrasolar planets, I took the trip up the long, windy road to the top of Mt. Hamilton. It is a beautiful drive up to the observatory and it's wise to take your time so that you can enjoy the ideal California landscape of rolling hills dotted with oak trees and wildflowers. The 365 sharp curves along the 19 mile road will also slow you down.

At the top of Mt. Hamilton are several white domes dotting the 4,200-foot crestline. From Lick Observatory you can see forever– not just across the vast northern California landscape but out into our own galaxy and beyond. By coincidence, the night I was there astronomer Debra Fischer confirmed five new planets outside our solar system. The discovery was the culmination of five years of watching these specific planets from Lick's 3-meter Shane Telescope. Fischer and her colleague Geoff Marcy will publish their findings soon. These two astronomers are obsessed with looking for exoplanets, they just returned from the Andes mountains in Chile, where they spent day and night for several weeks hunting for planets. But Fischer and Marcy are not the only ones who have caught the exoplanet bug.

Scientists at NASA are nearly ready to launch a bus-sized telescope into space. NASA's Kepler Telescope which will orbit our sun, will be trained on a hundred thousand stars at a time. It may be our best chance yet for finding new life in outer space. The telescope is scheduled to launch in February. Kepler will find planets by looking for tiny dips in the brightness of a star caused by planetary transits.

Make sure to check out our photo set on Flickr which includes: photos of Lick Observatory; the Kepler testbed at NASA Ames in Mountain View; the Kepler spacecraft assembly in Boulder, Colorado; and artists' renditions of exoplanets discussed in this report.You can also hear our radio story on the search for exoplanets, watch the Planet Hunters TV story online and find additional links and resources.

Artist concept of a Neptune-sized planet
orbiting the star 55 Cancri. Credit: NASAAnother milestone has been reached in the two-decade old search for "extrasolar planets," a.k.a exoplanets– planets that orbit stars other than our Sun. In November it was announced that the leading exoplanet research team– the California and Carnegie Planet Search Team, led on the California side by U. C. Berkeley’s Dr. Geoff Marcy– has succeeded in detecting five, count 'em, five planets orbiting the same parent star.

The star, 55 Cancri, a Sun-like star in the constellation Cancer, has been under exoplanet surveillance for 20 years, and yielded the secret of its first planet in 1996. Over the years of continued observations, one by one more planets in its retinue have been coaxed out of the data.

Personally, moments like this are an impetus to step back and reflect on the state of our understanding of the universe. How much more we know now than we did when I was a starry-eyed child back in the 1960s! We knew of no planets beyond our Solar System when I was a kid. In fact, further observation of our own Solar System has, ironically, reduced the number of planets at home from nine to eight! Even pictures of places like Mars, and certainly the moons of outer solar system planets like Jupiter and Saturn, were blurry, grainy images lacking much detail.

Now, more than 260 planets orbiting other stars have been found (although we don't have actual pictures of them at this point). Still, going from my childhood, when exoplanets were theoretical and the question was still asked whether our Solar System is somehow special, even unique, to have planets at all, to today's solid body count of "worlds out there"…is simply breathtaking.

Most exoplanet detections are made by the measurement of the slight wobbling motion a star makes due to the gravitational pull of any planets it might possess. You might be imagining astronomers taking video of a star and playing it back at high speed to see it slither like a snake– but that isn't how it's done. Instead, the measurement is made using the Doppler Shift– observing changes in the star's speed by measuring the corresponding change in the wavelength of its light. (This is the same way that the Highway Patrol nabs speeders on the freeway, using radio-frequency waves.)

So what’s the 55 Cancri system like? Well, by virtue of the fact that current exoplanet detection techniques can only reveal large planets–gas giants like Jupiter, Saturn, Uranus, and Neptune– all five of the 55 Cancri planets are such. One of them, in fact, is four times the size of Jupiter–and another, Neptune-sized world orbits so close that it only takes only 2.8 days to make one circuit around its star. Not much like the Solar System we know and love–but there's plenty of room for variety in the universe, after all.

The next big move in the exoplanet hunt will be for Earth-sized planets orbiting their stars at Earth-like distances– a feat to be attempted by NASA's Kepler mission coming up in 2008. As always, stay tuned…

Benjamin Burress is a staff astronomer at The Chabot Space & Science Center in Oakland, CA.

latitude: 37.8148, longitude: -122.178