The newly discovered planet Corot-Exo-7b transiting in front of its star (left, illustration by Klaudia Einhorn), and Venus in front of the disk of the Sun on June 8, 2004 (right, photo by Martin Sloboda). As the sizes of both the stars and the planets are similar, a transit of Corot-Exo-7b would look very similar to the Venus transit.
The planet has a radius which is 1.75 times larger than that of the Earth, and has six to thirteen times the mass of Earth. The star is a main sequence star with roughly the same composition as the Sun, with slightly less mass and a slightly lower temperature. However, distance of the planet to the star is only 1.7 percent of the distance of the Earth from the Sun - hence the revolution period, or "year", of the planet is only 20 hours, and its surface temperature is estimated to be between 1,000 and 1,500 degrees Celsius.
The planet was discovered by the European satellite mission Corot - hence its name, Corot-Exo-7b, meaning the first planet in the 7th planetary system discovered by Corot. Corot uses the transit method to search for new planets: When a planet passes in front of the disk of a star, the light of the star is slightly dimmed.
Here is the light curve of Corot-Exo-7, the star around which the planet is in orbit, showing a drop in brightness of the order of 10-4:
Mass, radius, and orbital parameters of the planet could be extracted from this measurement, and further observations and data analysis using the radial velocity method, the method which had led to the first detection of an exoplanet back in 1995.
So, it's indeed the first Earth-like planet at a Sun-like star - unfortunately, at a temperature close to the melting point of iron.
- Press release by the Observatoire de Paris: "Super-Earth found! The smallest transiting extrasolar planet ever discovered".
- Corot-Exo-7b fact sheet of the Extrasolar Planets Encyclopaedia
Tags: Astronomy, Exoplanet, Corot