A super-Earth

A new super-Earth found by an international team of astronomers from United States, Italy, Switzerland, Great Britain, Canada and Portugal, directed by Andrew Vanderburg from Harvard-Smithsonian Center for Astrophysics and characterized thanks to HARPS-N.
A new super-Earth was found by an international team of astronomers, the United States, Italy, Switzerland, Great Britain, Canada and Portugal, directed by Andrew Vanderburg Harvard-Smithsonian Center for Astrophysics (CfA) using data collected during observations of test mission K2, which lasted nine days in February 2014.



For four years, the Kepler space telescope has observed continuously the same region of the sky, looking very small fluctuations in brightness of more than 150,000 stars, due to the transit of planets in front of them. Kepler’s observations have revolutionized the search for exoplanets, with the discovery of at least 1000 until today confirmed planets, and more than 3200 candidates.
In May 2013, while a good part of the Kepler data had yet to be analyzed, the second of the four gyroscopes was damaged. The very high accuracy in the measurement of the stellar luminosity feature of Kepler is obtained with a very precise aiming system, which requires the use of at least three gyroscopes. So when he broke the second, ending the original mission of Kepler, many thought that would be the end of the use of the satellite.
Nothing further from the truth! Researchers and engineers did not want to give up an alternative use of the space telescope. Thus they planned a mission, where the satellite would observe several regions along the ecliptic, with the help of solar radiation pressure to control the pointing together gyroscopes survivors.
The new mission was called K2, and its job was to continue the search for extrasolar planets and observe star clusters, active galaxies and supernovae.
And Kepler has kept its promises! This is confirmed by the discovery and characterization of the first planet from the “second life” of Kepler, K2. Since the capacity of pointing Kepler is reduced, to extract accurate data, a very sophisticated analysis is necessary. Vandenburg and his colleagues have developed specialized software to correct the movements of the satellite, achieving an accuracy which is about half that of the original Kepler mission. Analyzing the data they have thus realized that Kepler had observed a planetary transit. Other transits were then revealed in a less obvious with the satellite MOST.
“We needed an authoritative confirmation of this result, like the one that just HARPS-N has to offer,” says satisfied Emilio Molinari, director of the Telescopio Nazionale Galileo (TNG) in La Palma, Canary Islands, where the instrument HARPS-N is fixed.
“The extremely precise measurements of HARPS-N confirmed that it was indeed a planet and also give us valuable information about its properties such as mass and density”, adds Molinari.
The team determined the radial velocities of the planetary system HIP116454 from observations of HARPS-N obtained between July and September 2014. The new planet HIP 116454b, has a diameter of 32200 km, two and a half times the size of Earth, and HARPS-N has shown that its mass is approximately twelve times that of the Earth. This makes HIP 116454b a super-Earth, a class of planets that do not exist in our solar system. The average density suggests that the planet is a world of “ocean” (made up three-quarters of water and a quarter of rock) or a mini-Neptune with an extended gaseous atmosphere. Astronomers predict a planet’s temperature close to 400 degrees Celsius.



HIP 116454b has an orbital period of 9.1 days and then orbits at about 13.5 million km from its star, 11 times closer than the Earth-Sun distance. The central star, HIP 116454, is an orange star, a little smaller than the sun, in the constellation of Pisces to about 180 light years from us.
“HARPS-N has already discovered and characterized many extrasolar planets, but we are particularly happy to find HIP116454b because this is the first planet confirmed in the new life of Kepler”, says Giampaolo Piotto, an astronomer at the University of Padua and co-author of the work. The scientific article with the discovery has been accepted for publication in The Astrophysical Journal.

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