The CoRoT satellite, operated by the French space agency CNES, has discovered a Jupiter- sized planet orbiting a star similar to the Sun in the constellation Serpens Cauda at a distance of 1500 light-years from the Earth. The parameters of this gas giant, which has features in common with the majority of exoplanets discovered so far, represents a valuable standard model when it comes to identifying new Jovian-type bodies with moderate temperatures.
This European-led discovery has involved 60 astronomers worldwide, including LCOGT and UCSB scientists Drs. Tim Lister, Rachel Street, Marton Hidas, and Avi Shporer.
“CoRoT-9b is the first transiting exoplanet that is definitely similar to a planet in our Solar System.” says Dr. Marton Hidas. “What’s special about this planet is that compared to other transiting planets it is a temperate planet,” explains Dr. Rachel Street, “with great potential for future studies concerning its physical characteristics and atmosphere.”
Analysis of the planet’s transits has provided more information on CoRoT-9b than for other exoplanets of the same type. More than 400 exoplanets have been discovered so far, 70 of them through the transit method. A transit occurs when a celestial body passes in front of its host star and blocks some of the star’s light. This type of eclipse causes a small drop in the apparent brightness of the star and enables the planet’s mass, diameter, density and temperature to be deduced. The fact that CoRoT-9b takes 95 Earth days to orbit its star demonstrates the usefulness of Space observations in finding planets with long orbital periods, a very difficult task when observing from the ground. Indeed, its period is about 10 times longer than that of any planet previously discovered by the transit method.
The CoRoT satellite identified the planet after 150 days of continuous observations during the Summer of 2008. Due to the nature of CoRoT measurements, any detection requires verification using ground-based telescopes. This was done by the Faulkes Telescope North (FTN), located on Mt. Haleakala on the Hawaiian island of Maui. FTN is a 2 meter telescope, part of the LCOGT network. “Since a transit occurs only once every 95 days, FTN was at the right place at the right time to observe the transit on September 2009, thereby confirming the CoRoT detection”, says Dr. Tim Lister, who carried out the FTN observations, in collaboration with other telescopes across the globe.
The astronomical community has been looking during the last decade for a transiting extra-solar planet with a "pure, isolated" history of evolution, without the contamination and interference of its parent star.
“The new planet keeps a relatively large distance from its central star, similar to
the orbit of Mercury around the Sun.” says Dr. Avi Shporer, “permitting the application of
planetary evolution models without corrections, as have been needed with other transiting
planets, orbiting their parent stars in close-in orbits, with a typical orbital period of under a
week.” The planet is mostly made of hydrogen and helium, but it may contain up to 20 Earth
masses of heavier elements including rock and water under high pressure. It is thus very similar
to the Solar System’s giant planets, Jupiter and Saturn.
The international team of astronomers participating in the discovery notes that while temperate
gas giants are so far the largest known group of planets, CoRoT-9b is the first transiting planet
of this kind. The discovery will lead to a better understanding of such commonly occurring
planets and open up a new field of research to understand the atmospheres of moderate- and
low-temperature planets.
For more information please see the official ESO press release.
