Kepler’s second light: K2 mission discovers its first exoplanet
Artist rendition of the Kepler Space Telescope operating in a new mission profile called K2.. Credit: NASA/JPL-Caltech
After some creative engineering and a collaboration between astronomers and engineers, NASA’s Kepler telescope was able to make a comeback after being crippled by a reaction wheel failure. The new technique takes advantage of solar winds and revived the planet-hunting telescope, enabling it to take on a new mission, dubbed K2. On Dec. 18, 2014, NASA announced that the telescope discovered its first exoplanet of the new mission.
“Like a phoenix rising from the ashes, Kepler has been reborn and is continuing to make discoveries. Even better, the planet it found is ripe for follow-up studies,” stated lead author Andrew Vanderburg of the Harvard-Smithsonian Center for Astrophysics.
Kepler is designed to search the cosmos in hopes of locating planets outside of the Solar System, referred to as extra-solar planets (exoplanets). The telescope was named after the famed astronomer, Johannes Kepler, who is considered to be the founder of celestial mechanics and planetary motion. Currently, the Kepler telescope has confirmed 996 exoplanets, with over 4,000 potential exoplanet candidates to explore.
Infographic showing how the Kepler space telescope continued searching for planets despite two busted reaction wheels. (Click to enlarge) Credit: NASA Ames / W Stenzel
Kepler relies on four pointing devices in order to stabilize itself to focus properly. In order to function properly, the telescope needs at least three of the four wheels to function consistently. After two of its four reaction wheels (pointing devices) failed, NASA had to discontinue using Kepler during the summer of 2013.
“Last summer, the possibility of a scientifically productive mission for Kepler after its reaction wheel failure in its extended mission was not part of the conversation,” said Paul Hertz, NASA’s astrophysics division director at the agency’s headquarters in Washington. “Today, thanks to an innovative idea and lots of hard work by the NASA and Ball Aerospace team, Kepler may well deliver the first candidates for follow-up study by the James Webb Space Telescope to characterize the atmospheres of distant worlds and search for signatures of life.”
Unfortunately, Kepler is unable to be repaired, so some creative engineering was required to revive the telescope. Scientists determined they could use pressure from the sunlight to act as a “virtual reaction wheel”. As a result, the K2 mission commenced and was approved budgetarily to operate through 2016. The only downside to the new technique is that Kepler will need to reposition itself every 83 days, in order to keep sunlight out of its viewfinder. On the other hand, the technique allows for the observation of supernovae and star clusters.
Kepler-62f, an exoplanet that is about 40 percent larger than Earth. Discovered by Kepler, it’s located about 1,200 light-years from the Solar System in the constellation Lyra. Credit: NASA/Ames/JPL-Caltech
“Due to Kepler’s reduced pointing capabilities, extracting useful data requires sophisticated computer analysis,” CFA added in a statement. “Vanderburg and his colleagues developed specialized software to correct for spacecraft movements, achieving about half the photometric precision of the original Kepler mission.”
The new mission aims to continue the search for new exoplanets, but to widen the search to close, bright stars that harbor planets, and study those planets in greater detail to better understand their composition.
In order to detect exoplanets, Kepler employs the transiting technique, meaning it observes a star and waits for a planet to cross in front or “transit” the planet. By detecting dips in the starlight, Kepler can detect a planet. The smaller the planet, the smaller the dip in starlight will be. Thus, the easiest planets to find are larger planets orbiting dim stars.
After employing the use of the “virtual reaction wheel”, the telescope was tested to ensure this technique would be able to give Kepler the stability it needed to focus precisely. Andrew Vanderburg, a graduate student at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, is the lead researcher on the mission and after studying data collected by the spacecraft during a February test discovered that Kepler had detected a new exoplanet.
Relative sizes of habitable zone planets Kepler-69c, Kepler-62e, Kepler-62f, compared with Earth, as discovered by the Kepler telescope. Credit: NASA/Ames/JPL-Caltech.
The discovery was then confirmed by the HARPS-North spectrograph of the Telescopio Nazionale Galileo in the Canary Islands after HARPS spotted the wobble of the star caused by the planet’s gravitational tug as it orbits.
The new exoplanet, named HIP 116454b, is classified as a super-Earth, measuring 2.5 times the size of Earth, but with a mass 12 times that of Earth. HIP 116454b is located approximately 180 light-years from Earth and rotates its star very quickly – once every 9.1 days.
Planets like HIP 116454b – smaller than Neptune, but larger than Earth – are scientific treasure troves of data and ideal candidates for follow-up observations. By using Kepler data in combination with data collected from ground-based instruments, astronomers are able to learn a great deal about exoplanets, including their mass and even if they are rocky or gaseous worlds. Based on these measurements, astronomers determined that this planet is most likely a water world or a planet with a Neptune-like atmosphere surrounding a rocky core.
NASA’s Kepler Space Telescope prior to launch. Photo Credit NASA
“The Kepler mission showed us that planets larger in size than Earth and smaller than Neptune are common in the galaxy, yet they are absent in our Solar System,” said Steve Howell, Kepler/K2 project scientist at NASA’s Ames Research Center in Moffett Field, California. “K2 is uniquely positioned to dramatically refine our understanding of these alien worlds and further define the boundary between rocky worlds like Earth and ice giants like Neptune.”
Manufactured by Ball Aerospace & Technologies Corp., Kepler was launched in 2009 atop a United Launch Alliance Delta II rocket from Cape Canaveral Air Force Station Space Launch Complex 17B located in Florida.
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