Super-Neptune Discovered Just 12 Light-Years Away | Astronomy – Sci-News.com
Astronomers have discovered a super-Neptune exoplanet orbiting a star in the binary system Gliese 15.
An artist’s impression of two exoplanets orbiting a pair of red dwarfs. Image credit: NASA / JPL-Caltech / T. Pyle / Sci-News.com.
Gliese 15 is a system composed of two red dwarf (of M1- and M-3.5 type) stars.
Also known as GJ 15, HD 1326 and Groombridge 34, it resides 11.6 light-years from Earth and is approximately 3 billion years old.
In 2014, a research team led by University of Hawaii astronomer Andrew Howard announced the discovery of a super-Earth around Gliese 15A, a larger star in the system.
Named Gliese 15Ab, the planet has a period of just 11.44 days and a mass three times that of Earth. It’s also super-heated, with a surface temperature of 530 degrees Fahrenheit (276 degrees Celsius).
In a new study, Dr. Matteo Pinamonti from the Astrophysical Observatory of Torino and colleagues analyzed observations of the Gliese 15A star made by the HARPS-N spectrograph on the Italian Telescopio Nazionale Galileo and the High Resolution Echelle Spectrometer on the Keck Telescope.
The team relied on the ‘radial velocity’ method of planet detection, which can reveal tiny wobbles as orbiting planets pull on their parent star.
This technique enabled the scientists to spot one more exoplanet around Gliese 15A.
Dubbed Gliese 15Ac, the planet is 36 times the mass of Earth, making it a so-called super-Neptune.
“With its period of 7,600 days (20.8 years), Gliese 15Ac is the longest-period sub-Jovian planet detected up to date with the radial velocity method,” Dr. Pinamonti and co-authors said.
“With the confirmed presence of two widely spaced planetary mass companions, Gliese 15A is now the multi-planet system closest to our Sun.”
“Its orbital architecture constitutes a very important laboratory for the investigation of formation and orbital evolution scenarios for planetary systems in binary stellar systems.”
The team’s paper was published in the journal Astronomy & Astrophisics.
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M. Pinamonti et al. 2018. The HADES RV Programme with HARPS-N at TNG. VIII. GJ15A: a multiple wide planetary system sculpted by binary interaction. A&A 617, A104; doi: 10.1051/0004-6361/201732535
