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Scientists Discover Exoplanet Less Than Twice the Mass of Earth
Snowblindeye writes with this excerpt from the European Southern Observatory:
"Well-known exoplanet researcher Michel Mayor today announced the discovery of the lightest exoplanet found so far. The planet, 'e,' in the famous system Gliese 581, is only about twice the mass of Earth. The team also refined the orbit of the planet Gliese 581 d, first discovered in 2007, placing it well within the habitable zone, where liquid water oceans could exist. Planet Gliese 581 e orbits its host star — located only 20.5 light-years away in the constellation Libra ('the Scales') — in just 3.15 days. 'With only 1.9 Earth-masses, it is the least massive exoplanet ever detected and is, very likely, a rocky planet,' says co-author Xavier Bonfils from Grenoble Observatory. Being so close to its host star, the planet is not in the habitable zone. But another planet in this system appears to be. ... The planet furthest out, Gliese 581 d, orbits its host star in 66.8 days. 'Gliese 581 d is probably too massive to be made only of rocky material, but we can speculate that it is an icy planet that has migrated closer to the star,' says team member Stephane Udry. The new observations have revealed that this planet is in the habitable zone, where liquid water could exist. '"d" could even be covered by a large and deep ocean — it is the first serious "water world" candidate,' continued Udry."
If you would like to know more, download Celestia, an open source project to cruise around the universe in 3D.
:-)
Just select "go to object" and type in "gliese 581", you'll get the orbits of the different planets already found too.
The neat thing is, you can just "cruise" around, speed up time to see how stellar objects move, and so on... Quite cool
Any sufficiently advanced incompetence is indistinguishable from malice - Grey's Law
One interesting thing about Gliese 581 d not being made of rock is that it might have almost the same surface gravity as Earth:
Volume of a sphere=(4/3)*pi*radius^3
radius of sphere=((.75/pi)*volume)^(1/3)
volume=mass/density
radius=((.75/pi)*mass/density)^(1/3)
mass=7.5*mass of earth
density=2kg/liter (twice that of water)
acceleration due to gravity=Gravitational constant*Mass of planet/(radius)^2
thus, plug this into google=
(Gravitational constant)*(7.5*mass of the earth)/((7.5*mass of the earth)/(2kg/liter)*.75/pi)^(2/3)
google gives us: 9.7764354 m / s^2
Yay!
Now, we just need a breathable atmosphere! And light-speed spaceships (or faster)!
The significance is that our methodology is improving. Only in the past decade or so have we been able to identify stars with possible planets. Only in the past year or two have we been able to directly image a planet (or separate it's image from the parent star). What we know of the planets is based on how close it's orbit is to the star, it's estimated mass, and in a few recent cases, based on limited spectroscopic information.
Now that Kepler's working, over the next 2-3 years we should have a flood of these reports. (keep in mind Kepler's only imaging a 10 x 10 degree patch of sky) In the next decade we will develop the means to directly image a nearby terrestrial sized planet.
All of the planets imaged so far are relatively close, on a galactic scale. A few 10's of light years. There's more than enough information out there to explain how far that is from a human perspective. Let's just say, that based on current technology, none of our great-grand children will get an up close look. (although I suppose we could do a fly by of something like the Gliese 581 system, with a probe, in the next 3-4 generations, if we tried hard enough.