A new camera called OPTIC (Orthogonal Parallel Transfer Imaging Camera), built at the University of Hawaii, has clarified our view of the distant world known as WASP-10b. Transits are helpful because they allow us to measure the size of the observed planets, and in this case, WASP-10b turns out to be not one of the most bloated exoplanets yet found, as once thought, but one of the densest. Orbiting some 300 light years from Earth, the planet’s diameter is now known to be only six percent larger than Jupiter’s, although it is three times more massive, with a corresponding density three times that of Jupiter.


OPTIC is mounted on the University of Hawaii’s 2.2-meter telescope on Mauna Kea. If you compare what it can do with its highly sensitive and stable detector to the best results from charge-coupled devices (CCDs), you find a photometric precision two to three times higher. According to this news release from the university’s Institute for Astronomy, that’s comparable to the most recent results from the Hubble Space Telescope for stars of the same brightness. Says team member Joshua Winn (MIT), “This new detector design is really going to change the way we study planets. It’s the killer app for planet transits.”

Image: When the planet WASP-10b crosses the disk of its star, WASP-10, the brightness of the star decreases, allowing scientists to measure the precise size of the planet. Credit: UH/IfA.

WASP-10 is a K-class star about 75 percent as massive as the Sun, one of only nine known low-mass planet host stars within 200 parsecs. More on the WASP-10b findings in Johnson et al., “A Smaller Radius for the Transiting Exoplanet WASP-10b,” available online.