Astrobiology Top 10: COROT Sets its Sights on the Stars

COROT – Convection, Rotation, and planetary Transits — is a space telescope designed to search for extrasolar planets and to study stars.

This artist’s image shows a system with a star much like our Sun and a gas-giant planet similar to Jupiter. Most of the more than 260 exoplanets known today are gas giants 5 to 4,000 times larger than Earth, and are thought to be uninhabitable for life as we know it.
Credit: NASA/JPL-Caltech/T. Pyle, SSC

Launched in late December of 2006, COROT mission scientists declared they had detected their first exoplanet, COROT-Exo-1b, on May 3, 2007. The planet is 1.3 times as massive as Jupiter and is very close to its host star, orbiting it every 1.5 days.

The second planet discovered by COROT recently was confirmed by ground-based observations. COROT-exo-2b orbits a star similar to our Sun, somewhat more massive and cooler, but more active. It is located about 800 light-years from Earth in the direction of the constellation Serpens. COROT-exo-2b is a giant planet, 1.4 times larger and 3.5 times more massive than Jupiter. Its average density of 1.5 grams per cubic centimeter is also somewhat higher than Jupiter’s. This massive planet orbits its star in a little less than two days from a distance of about six times the stellar radius.

The extrasolar planets discovered by COROT reveal themselves by “transiting” their star. Transit detection looks for starlight blocked by a planet as it crosses in front of its star from Earth’s point of view. Therefore, COROT will not be able to detect planets that orbit their stars at inclination angles not observable from Earth.

So far, most of the over 260 extrasolar planets found to date are massive gas giants like Jupiter. Astronomers hope planetary transit hunts like the COROT mission will find rocky worlds about the size of Earth. COROT will be able to spot short-period transits of 50 days or less, so only planets orbiting close to their stars will be discovered by this mission.

The COROT mission is planned to last for two and a half years. During that time, COROT will observe about 120,000 stars. Astronomers expect to find between 10 to 40 rocky worlds, as well as many gas giants, in each star field that COROT will observe.

As a planet passes in front of its parent star, the brightness of the star decreases.
Credit: Hans Deeg

Every 150 days COROT will move to conduct new observations in a different star field. The telescope recently completed a 150-day observation sequence towards the region of the galactic center. On October 23, COROT began a new long observation which will last until March 2008.

COROT also will help astronomers learn more about the physics of stars by studying “starquakes” — acoustical waves generated from a star’s interior that ripple across the surface and alter the star’s brightness. The nature of the ripples will allow astronomers to calculate the star’s precise mass, age and chemical composition. 30 stars have been observed as part of the study of stellar seismology so far. The stars observed by COROT range from objects similar to our own Sun to older or more massive stars.

The mission is led by the French national space agency, CNES. The European Space Agency (ESA) provided the optics for the telescope, tested the payload, and is providing support throughout the mission.

Related Web Sites

Opening an Eye to the Stars
COROT Nets its First Planet
Finding Earth’s Twin
Rocky Worlds
Searching for Pale Blue Dots