Hunt for superearth planets underway

NASA Goddard Space Flight Center scientist, Dr. Drake Deming, will present an update on the EPOXI mission on June 2, 2008 at the 212th American Astronomical Society in St. Louis, MO.

The mission which uses the Deep Impact spacecraft has begun its search for "super Earth" planets. The EPOXI team has focused its attention on the star GJ436.
This red dwarf star which is 32 light-years from Earth has a Neptune-sized planet that transits in front of the star. Spitzer observations have shown that this Neptune-sized planet has an oval shaped orbit (eccentric).

"Tidal forces from the star should have made the orbit circular, unless there is another planet whose gravitational tug pulls the orbit into an oval shape, said Drake Deming, Deputy Principal Investigator for the Deep Impact extended mission, EPOXI. "If that second planet lies in the same orbital plane as the Neptune-sized planet then we should see it transit. The transit would be too shallow to be spotted by ground-based telescopes, and EPOXI is the only space mission that can look at GJ436 nearly continuously for several weeks."

The orbital period of the "super Earth" is not precisely known, but the EPOXI team estimates it to be in the range from 20 to 30 days. EPOXI has been observing the system from May 5 - May 28. Deming and his team are in the process of analyzing the results of these data.

In addition to targeting the red dwarf star for study, EPOXI imaged the Earth over three 24-hour periods. EPOXI measured the Earth's rotational light curve at visible wavelengths from the ultraviolet to the near-infrared. These observations will help to calibrate future observations of Earth-like exoplanets. EPOXI obtained a particularly interesting view of the Earth on May 29, when the Moon passed in front of the Earth as viewed from the spacecraft. This "transit" of the Moon is an event that may also be observed to occur for Earth-like exoplanets, and it may help us to deduce the nature of their surface features.

EPOXI is a combination of two separate science investigations. The investigations consist of the Extrasolar Planet Observations and Characterization (EPOCh), and the flyby of comet Hartley 2, called the Deep Impact eXtended Investigation (DIXI) which is lead by Dr. Michael A'hearn at the University of Maryland. Deming is the Principal Investigator on the EPOCh investigations. EPOCh observations began in January 2008. Professor A'Hearn is the Principal Investigator for the combined EPOXI mission.

Credit: NASA/JPL-Caltech/UMD/GSFC.

As part of the EPOXI mission's objectives to characterize the Earth as a planet for comparison with planets around other stars, the spacecraft looked back at Earth collecting a series of images. The Earth-Moon system is seen with the Moon beginning its transit in front of Earth. It was taken on May 29, 2008 through three filters: blue, green and orange, centered at 450, 550 and 650 nm respectively, while the spacecraft was 0.33 AU (49,367,340 km and 30,675,43 miles) from Earth.