* Astronomy

A new study of the planet, which orbits a star 500 light years away, has shown that its density is similar to Earth's, indicating it is a solid rocky world.
Known as COROT-7b, it was discovered in February this year by the European space telescope COROT, which had been tracking the star it circles.

Read more

Astronomers find rocky planet outside solar system
Astronomers have finally found a place outside our solar system where there's a firm place to stand - if only it weren't so broiling hot.
As scientists search the skies for life elsewhere, they have found more than 300 planets outside our solar system. But they all have been gas balls or can't be proven to be solid. Now a team of European astronomers has confirmed the first rocky extrasolar planet.

Read more

Title: Composition and fate of short-period super-Earths: The case of CoRoT-7b
Authors: Diana Valencia, Masahiro Ikoma, Tristan Guillot, Nadine Nettelmann

Context. The discovery of CoRotT-7b, a planet of radius 1.68 ±0.09 R_Earth, with an orbital period of 0.854 days demonstrates that small planets can orbit extremely close to their star.
Aims. Several questions arise concerning this planet, in particular concerning its possible composition, mass and fate. Methods. We use knowledge of hot Jupiters, mass loss estimates and models for the interior structure and evolution of planets to understand its composition, structure and evolution.
Results. Although detailed modelling should address this problem, we show that a relatively significant mass loss ~10^11 g/s is to be expected, independently of the planet's composition. Given the closeness to the star, we find that the planet size is compatible with the observations only if the planet contains less than 1% of its mass in hydrogen and helium and less than 20% in steam. Due to the significant evaporation rate, it is most likely that the planet is made only of iron and silicates, which implies that its mass should be in the range 5 to 15 M_Earth. However, the origin of CoRoT-7b is unknown: It may have always had a terrestrial composition, it may be the remnant of a Uranus-like ice giant, or a gas giant with a small core that would have been entirely stripped of its gaseous envelope.
Conclusions. Our predictions can be tested by measurements of the planet mass and possibly by the detection of evaporating silicates, with a rate that should be within an order of magnitude that measured for HD209458b.

Read more (4909kb, PDF)

COROT has found the smallest terrestrial planet ever detected outside the Solar System. The amazing planet is less than twice the size of Earth and orbits a Sun-like star. Its temperature is so high that it is possibly covered in lava or water vapour. About 330 exoplanets have been discovered so far, most of which are gas giants with characteristics similar to Jupiter and Neptune. The new find, COROT-Exo-7b, is different: its diameter is less than twice that of Earth and it orbits its star once every 20 hours. It is located very close to its parent star, and has a high temperature, between 1000 and 1500°C. Astronomers detected the new planet as it transited its parent star, dimming the light from the star as it passed in front of it.