A camera that could detect a moth passing in front of a lit window a thousand miles away could help a University of Hawaii astronomer and his colleagues learn what “;Super Earth”; planets are like.

About 300 planets are known to orbit other stars in our Milky Way galaxy and most have masses like Jupiter, a so-called gas giant. About 10 are called Super Earth planets, with masses about five or 10 times the mass of Earth.

“;We're finding planets between Earth and Neptune (20 Earth masses) and we don't know anything about these things,”; said John Johnson of the UH Institute for Astronomy. “;They're small enough to have solid surfaces, but do they have them? Are they covered completely in water? Do they have gaseous atmospheres that are not good for life? We are curious to know if Super Earth type planets would be habitable if found in the right condition.”;

Using a camera on the UH 2.2-meter telescope on Mauna Kea developed by astronomer John Tonry, Johnson and his team measured the precise size of a planet, WASP-10b, when it passed in front of its star, WASP-10, along the line of sight from Earth. WASP stands for the Wide-Angle Search for Planets, a program to detect exoplanets—those around other stars.

The camera enabled the researchers to measure a small drop in brightness that occurred during the “;planet transit,”; when the planet passed in front of the star.

Tonry designed the Orthogonal Parallel Transfer Imaging Camera and scaled it up for the Pan-STARRS prototype telescope on Haleakala, Maui, to hunt for potentially dangerous asteroids. It is the largest digital camera in the world.

Discussing his research in an interview, Johnson, a National Science Foundation astronomy and astrophysics postdoctoral fellow, said a camera was being used in Arizona that Tonry built as a test to show it could work.

“;I was looking for a way of measuring the radius of a planet more precisely,”; Johnson said. Astronomers had been doing it but it required five or six nights on a telescope, “;a huge investment of time,”; he said. “;I wanted to do it in higher precision in a single night.”;

He said Tonry told him he had a camera that might suit his purposes and he arranged to have it shipped here during the summer and put on the UH 2.2-meter telescope.

“;It worked the first time out,”; Johnson said.

WASP-10b, one of the densest planets known, is three times more massive than Jupiter, but its diameter is only 6 percent larger.

Calculations with that level of precision, Johnson said, are what “;you would need to transit Earth-size planets.”;

The detector has three to four times higher precision that that of typical charge-coupled devices (CCDs) used in scientific and consumer digital cameras, and it's two to three times higher than the best CCDs—comparable to recent results from the Hubble Space Telescope for stars of the same brightness, the scientists reported.

“;The new detector design is really going to change the way we study planets,”; Joshua Winn, team member from the Massachusetts Institute of Technology, said in a news release. “;It's the killer app for planet transits.”;

Astronomers have used other techniques to find Super Earth planets, Johnson said, “;but we don't know any aligned just right to transit their star. Our goal now is to look at the known Super Earths and see if any of them transit. If they do transit, we can measure their radius, and if we have their radius, we can measure their surface properties—whether they have a large, thick atmosphere, are covered completely in water or have a solid surface you can walk around.”;

Working with Johnson and Winn are MIT graduate student Joshua Carter and Nicole Cabrera, a Georgia Institute of Technology student who was in the IFA's Research Experiences for Undergraduates Program last summer.

The Astrophysical Journal Letters is publishing their findings.

Johnson said the group has a lot of time scheduled on the UH 2.2-meter telescope next semester and they will be looking for a transiting Super Earth.

“;We're really excited,”; he said. “;It's the first viable opportunity to really see a transit of one of these.”;