Skip to comments.First Solid Evidence for a Rocky Exoplanet
Posted on 09/20/2009 2:53:01 PM PDT by Dallas59
The longest set of HARPS measurements ever made has firmly established the nature of the smallest and fastest-orbiting exoplanet known, CoRoT-7b, revealing its mass as five times that of Earth's. Combined with CoRoT-7b's known radius, which is less than twice that of our terrestrial home, this tells us that the exoplanet's density is quite similar to the Earth's, suggesting a solid, rocky world. The extensive dataset also reveals the presence of another so-called super-Earth in this alien solar system.
"This is science at its thrilling and amazing best," says Didier Queloz, leader of the team that made the observations. "We did everything we could to learn what the object discovered by the CoRoT satellite looks like and we found a unique system."
In February 2009, the discovery by the CoRoT satellite  of a small exoplanet around a rather unremarkable star named TYC 4799-1733-1 was announced one year after its detection and after several months of painstaking measurements with many telescopes on the ground, including several from ESO. The star, now known as CoRoT-7, is located towards the constellation of Monoceros (the Unicorn) at a distance of about 500 light-years. Slightly smaller and cooler than our Sun, CoRoT-7 is also thought to be younger, with an age of about 1.5 billion years.
Every 20.4 hours, the planet eclipses a small fraction of the light of the star for a little over one hour by one part in 3000 . This planet, designated CoRoT-7b, is only 2.5 million kilometres away from its host star, or 23 times closer than Mercury is to the Sun. It has a radius that is about 80% greater than the Earth's.
The initial set of measurements, however, could not provide the mass of the exoplanet. Such a result requires extremely precise measurements of the velocity of the star, which is pulled a tiny amount by the gravitational tug of the orbiting exoplanet. The problem with CoRoT-7b is that these tiny signals are blurred by stellar activity in the form of "starspots" (just like sunspots on our Sun), which are cooler regions on the surface of the star. Therefore, the main signal is linked to the rotation of the star, with makes one complete revolution in about 23 days.
The place to go if you want a long lasting tan.
Paging Sylvester Stallone...
Just noticed something...Sylvester Stallone and George W. Bush were born on the same day (July 6, 1946).
The problem I have with these inferred ‘planets’ is that they all (even the putative gas giants) seem to be in ultra-tight orbits around their primaries. Is that really a stable situation? And if it isn’t - if it’s one that only lasts for a while - how come we’re seeing it so often?
I dunno, but I suspect we’re drawing conclusions from a faulty model.
Clicking through the list on Planet Quest I see most of the planets have tight or very oval orbits. Of course it may be that the big ones or the ones close in are all we can detect right now.
Smallest exoplanet is shown to be a solid, rocky world
ESA | 09/16/09
Posted on 09/16/2009 6:28:15 PM PDT by KevinDavis
also of interest?
Noisy star masks planet’s true size [ Corot-2b ]
Australian BC | Thursday, 9 July 2009 | Heather Catchpole
Posted on 07/15/2009 9:21:26 AM PDT by SunkenCiv
|· join · view topics · view or post blog · bookmark · post new topic · subscribe ·|
|Google news searches: exoplanet · exosolar · extrasolar ·|
When can we start shipping off the NeoComs?
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.