The innovative Deep Impact spacecraft, which sent a coffee-table sized penetrator slamming into comet Tempel-1 almost three years ago, has now begun its new job as “super-Earth” planet hunter “EPOXI”.
Artist impression of the Deep Impact flyby spacecraft releasing its impactor towards comet Tempel-1 in July 2005. The flyby spacecraft has been re-christened EPOXI and will begin its new assignment to hunt for super-Earth exoplanets. Image: NASA.
EPOXI is a combination of two separate science investigations, one consisting of the Extrasolar Planet Observations and Characterisation (EPOCh) and the other of the flyby of comet Hartley-2, planned for 2010, called the Deep Impact eXtended Investigation (DIXI), which follows in the footsteps of the hugely successful Deep Impact mission in July 2005 which revealed in unprecedented detail the surface of a comet and the effects of impact into such a finely powdered surface.
For the majority of May, EPOXI was trained on the red dwarf star GJ436, 32 light years from Earth. This star has a Neptune sized planet circling it every 20 to 30 days in an unusually eccentric orbit.
“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,” says Drake Deming, EPOXI’s Deputy Principal Investigator. “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." Deming and his team are in the process of analysing the results of these data.
In addition to targeting the red dwarf star, EPOXI imaged the Earth over three 24-hour periods, measuring its rotational light curve at visible wavelengths from the ultraviolet to the near-infrared. These observations will help to calibrate future observations of Earthlike 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. Transit events such as this will help planetary scientists to deduce the nature and composition of exoplanetary systems.
Deep Impact captured this beautiful image of the impact into Comet Tempel-1 three summers ago. Dust and gas streaming from the point of impact is lit up in the impact flash. Image: NASA.