A visual comparison of the size of Earth and CoRoT-7b.  (Source:
With surface temperatures hot enough to vaporize silica, scientists probably won't find much life here.

February of last year saw a small but possibly noteworthy extra-solar planet discovered by the French CoRoT mission. The CoRoT device, launched December 27, 2006, lives a dual-purpose mission. It both searches for extra-solar planets and measures stars for active seismology. CoRoT stands for Convection Rotation and planetary Transits, and these transits are what generally give away extra-solar planets far away from home.

In October of last year, the CoRoT team confirmed that the planet discovered in February, named CoRoT-7b, was the first extra-solar planetary body that came close to being Earth-like in stature and composition. CoRoT-7b orbits its home star CoRoT-7, usually classified as a G9V yellow dwarf (our Sun is a G2V classification for comparison and slightly larger), along with relative CoRoT-7c, somewhere in the area of 490 light years from Earth. CoRoT-7 can be found in or near the constellation Monoceros.

For the astronomically interested, Monoceros is not a bright constellation; it's brightest star coming in at 3.93 magnitude with several between four to six. However, it is easily found as it resides just west and south of the easily identified Orion constellation. Drawing a line between Betelgeuse of Orion and Sirius of Canis Major will get you pretty near to Gamma Monocerotis, the second brightest star in the constellation, and one end of its line form.

Other than CoRoT-7, Monoceros’s area also contains other astronomical bodies of note, including a trinary star system, two binary star systems, one of which is the well-known Plaskett’s Star, and V838 Monocerotis, a star which flared in January of 2002 and produced stunning images via the Hubble Space Telescope.

Getting back to CoRoT-7b, researchers have inferred a great deal about the planet using various astronomical means. It is so far the closest to Earth in size found outside our solar system, coming in at just 1.7 earth radiuses. It is also similar in density to Earth, though it has a mass about five times greater. But this is about where the similarities end.

CoRoT-7b is a hot planet. Very very hot. It is so close to its star that its lit face burns at an estimated 4,000F while its dark side could drop as low as minus 350F. The planet’s orbital duration is also the shortest of any known planet, whirling around CoRoT-7 in a mere 20.5 hours. The distance between 7b and 7 is a mere 2.5 million kilometers. For comparison, Mercury is roughly one third the size of Earth, orbits the Sun at just over 46 million kilometers distance at perihelion in a period just under of 88 days and has surface temperatures of a balmy 800F to minus 300F.

CoRoT-7b is thought to be mostly composed of iron, but not as densely as Earth. Any volatile atmosphere would likely have been stripped away by the intense heat of CoRoT-7, though some scientists have proposed it may have metallic atmosphere which rains out minerals.

To make 7b even more notable as an extra-solar, Earth-like planet, scientists at the University of Washington have recently disclosed that unless the planet has a perfectly circular orbit, it is likely the most geologically active planetary body yet known. A variance between its orbital aphelion and perihelion (furthest and closest from its orbital center point) as little as 250 kilometers would cause great stress and friction to the planet's interior, driving what could be a planet-wide volcanic system. Jupiter’s moon Io, the most active body in our solar system, would look like an afternoon breeze compared to 7b’s hurricane winds.

Though the planet has much more mass than Io, and even Earth, there are almost certainly no liquid oceans to absorb tidal forces in the way Earth’s do. The gravitationally driven geological processes would closely mimic Io’s, as Jupiter and its other large moons tug on it during its orbit, but would be much more extreme due to the magnitudes greater of the forces being applied.

Though the find and subsequent analysis of CoRoT-7b has been a great achievement for astronomers, planetary scientists and planet finders, it is still not the life-harboring extra-solar planet most hope to discover. Given the number and type of extra-solar planets discovered thus far, it may require even more precise measuring systems floating above our atmosphere to catch the tiny tugs and magnitude fluctuations an Earth-sized planet would affect on a Sun-sized star.

"Because it is easier to detect planets that orbit close to their host stars, a significant fraction of the first wave of rocky planets being found outside our solar system may be more Io-like than Earth-like," explains UW postdoctoral researcher of astronomy and astrobiology Rory Barnes.

However, if the last twenty or even ten years of space programs have taught us anything, it’s that we have nowhere to go but up.

"The Space Elevator will be built about 50 years after everyone stops laughing" -- Sir Arthur C. Clarke

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