When Will We Know?
While it's still one of the best bets available, it is still uncertain as to whether Gliese 581c is truly "Earth like…." So when will we know? According to a Nature article published on the 3rd of May, "…if the geometry is right, [Sasselov's] team should see the star dim on 7 May as the planet passes in front of it" (Nature 447, Sanderson).
This observation is extremely important to continuing research about Gliese 581c. If the transit acrosss Gliese 581 is made, scientists will be able to determine the planet's density and maybe even it's atmospheric composition.
We'll see how this pans out in the next week or so…..
How on Earth did they Find It?
Just briefly, in a previous post, I mentioned HARPS (High Accuracy Radial velocity Planet Searcher), the instrument used to first detect the presence of Gliese 581c. Detecting the presence of a star in a distant galaxy requires enough technology as it is, but finding a planet around a star is quite a chore! Here's a excerpt from an American.com article titled "What a New, Earth-like Planet Could Mean"…
"The particular High Accuracy Radial velocity Planet Searcher (HARPS) instrument used by the La Silla team detected velocity variations corresponding to about 9 km/hr—the speed of a person walking—from 120 trillion miles away." http://www.american.com/archive/2007/april-0407/what-a-new-earth-like-planet-could-mean
Despite the sensitivty of such an instrument, the true size of the planet will remain unknown until scientists can catch a glimse of Gliese 581c as it passes in front of Gliese 581 (the red dwarf star of Gliese 581c). The size of the shadow will enable scientists to more accurately calculate the size of the planet.
Another baffling idea: Every observation of the star is of its state over 20 years ago….that's the time it takes for light to reach Earth from Gliese 581c. As the American.com article mentions, if "inhabitants" of Gliese 581c were monitoring radio wave transmissions from Earth, they would just now be watching our TV shows from the 1980s….
Viewing Gliese 581c with a Telescope
Due to Gliese's size and distance (20.40 light years away), it isn't visible with the naked eye. But for you astronomers out there with telescopes, here's some information compliments of http://www.sky-map.org.
Sky Map is a great (and free) star catalog, especially if you haven't invested in expensive astronomy software!
The Data:
Constellation: Libra
Right ascension: 15h19m27.51s
Declination: -07°43'19.4"
Apparent magnitude: 10.621
Distance: 6.269 parsecs
Proper motion RA: 0
Proper motion Dec: 0
B-T magnitude: 12.086
V-T magnitude: 10.742
Search for more at:
http://server1.sky-map.org/starview?object_type=1&object_id=1407267
If you're interested, there's also a great conversation going on over at www.sciencechatforum.com. Marshall, one of the moderators posted this about Gliese 581 c:
"AND ITS REAL EASY TO FIND IF YOU CAN SPOT SCORPIO because it is right by scorpio's head where his antennas would be pointing.
Scorpio is an easy thing to spot because it has this question mark fishhook of a tail. And the head is 4 stars with three stars kind of fanning out from the fourth. Like a 3-finger boyscout salute. This three-prong or "trident" head points directly at the Libra patch of sky.
which is where GLIESE 581 resides, with its warm wet planet. Whose year is only thirteen of our days long."
You can view the entire thread here: http://www.sciencechatforum.com/bulletin/viewtopic.php?p=44849&sid=0b020bc6850f675179e205658fc73f9d.
Good luck astronomers!! And Happy tracking! 
The Discovery of Gliese 581c
A discovery revealed to the world on the April 24th, 2007, Gliese 581c is being heralded as the most probable candidate for a "Second Earth" to date. An older planet, the possibility for life is much higher than on any previous planetary discoveries, claim scientists. The discovery was made by HARPS (High Accuracy Radial Velocity for Planetary Searcher), a very precise and accurate spectrograph.
Facts:
1.) Discovered by scietists at Grenoble University in France.
2.) Gravity — Approximately 1.6 times that of Earth.
3.) Atmosphere — it has one! It's composition is (so far) unknown.
4.) Small — only about 1.5 times the diameter of the Earth.
5.) Relatively Close — Gilese 581c is approx. 20 light years away (120.5 trillion miles!); a distance making the planet available to further observation and analysis.
6.) "Goldilocks Zone" — temperatures range from approximately 0 to 40 degrees Celsius, making liquid water on the planet's surface a possibility.
7.) Sun — Red Stars mean lower temperatures. This allows the planet's proximity to it's sun not result in higher surface temperatures.
8.) 1 Gliese 581c Year = 13 Days of Earth Time (1 rotation around its sun!)
Stay tuned for future updates about Gliese!!!