Kepler mission astronomers, including co-investigator Bill Cochran of The University of Texas at Austin, announced today the spaceborne telescope has found five new gas giant planets orbiting close to Sun-like stars.
"The discovery of these planets demonstrates that Kepler is performing extremely well," Cochran said. "We fully expect to achieve the primary mission goal of discovering potentially habitable Earth-size planets."
Cochran and Texas colleagues Michael Endl and Phillip MacQueen used two telescopes at the university's McDonald Observatory in West Texas to help confirm these planet discoveries, which were announced at the 215th meeting of the American Astronomical Society in Washington, D.C.
"I'm glad to be part of the Kepler mission from the beginning, and I'm excited about where we go from here," Cochran said, noting he's been working on Kepler and progenitor spacecraft ideas for a decade.
NASA launched Kepler March 6, 2009 on a mission to find Earth-size planets using the "transit method"--watching for dips in a star's brightness that could indicate a planet is passing in front of the star. In its first 44 days of science operations, Kepler has monitored about 150,000 stars and confirmed five new planets. These discoveries confirm Kepler is on track to find more planets.
The five new planets are gas giants, ranging in size from about 40 percent to about 1.7 times the size of Jupiter. One planet, Kepler 4-b, is about the same size as Neptune. Several of the new planets have unexpectedly low densities. The new planet Kepler 7-b is one of the lowest density planets yet discovered.
Ground-based follow up is essential to Kepler's planet-discovery process. The spacecraft identifies stars that may harbor planets, but it's up to astronomers using telescopes at a number of observatories on the ground to confirm or disprove they exist.
Cochran's team uses two telescopes at McDonald Observatory for this: the 9.2 meter Hobby-Eberly Telescope (one of the world's largest) and the 2.7 meter Harlan J. Smith Telescope.
"There are two types of follow up," Cochran explained. Once a candidate star is identified, he said, "it's first observed by either the 2.7-meter Harlan J. Smith Telescope at McDonald Observatory or similar-size telescopes at other observatories. This step is done to determine what type of star it is--to eliminate any stars whose light simply mimics the signature of a transiting planet (such as an eclipsing binary star)."
According to Cochran, the Harlan J. Smith Telescope has been used to vet 60 to 70 planet possibilities from Kepler.
This crucial step also will tell astronomers if the star is a good candidate for more intense follow-up using larger ground-based telescopes. "Not all of them are," he said. "A candidate can be disqualified if the star is too active or rotates too fast, processes which make a star's light difficult for astronomers to decode. Those stars may indeed host planets, but astronomers will have to wait for future technology to confirm them," Cochran said.
"We look at the ones that survive the recon work, and prioritize them. If a star is a good candidate for further study, it is passed on to a large telescope like the Hobby-Eberly Telescope (HET) at McDonald Observatory or the Keck 1 Telescope in Hawaii."
Besides its large size, "the strength of HET is its queue-scheduling system," Cochran said. That means astronomers can look at these stars at the exact star-planet orbital configuration they desire, to get data most likely to reveal the planet's presence and characteristics. So far, Cochran said, his team has used HET to follow up about five to 10 strong planet candidates. In the future, he elaborated, this feature of the giant telescope will be especially useful in studying any candidate stars Kepler finds that might host multiple small planets.
Kepler is a NASA Discovery mission funded by NASA's Science Mission Directorate at NASA Headquarters in Washington, D.C. NASA's Ames Research Center in Moffett Field, Calif. is responsible for the ground system development, mission operations and science data analysis. NASA's Jet Propulsion Laboratory in Pasadena, Calif. managed Kepler's mission development. Ball Aerospace and Technologies Corp. of Boulder, Colo., was responsible for developing the Kepler flight system and supports mission operations.
Established in 1932, The University of Texas at Austin McDonald Observatory near Fort Davis, Texas, hosts multiple telescopes undertaking a wide range of astronomical research under the darkest night skies of any professional observatory in the continental United States. McDonald is home to the consortium-run Hobby-Eberly Telescope, one of the world's largest, which will soon be upgraded to begin the HET Dark Energy Experiment. An internationally known leader in astronomy education and outreach, McDonald Observatory is also pioneering the next generation of astronomical research as a founding partner of the Giant Magellan Telescope.