Using data from ESO’s High Accuracy Radial Velocity Planet Searcher (HARPS) instrument, a multinational team of astronomers has uncovered evidence for a second giant exoplanet orbiting in the nearby, young star Beta Pictoris (β Pictoris).
Two giant planets, Beta Pictoris b and c, orbit the nearby, young star Beta Pictoris. Image credit: P. Rubini / A.-M. Lagrange.
Young planetary systems, aged between 5 million and 50 million years old, offer an interesting opportunity to study the early stages of planet formation and evolution.
The very young Beta Pictoris system is an emblematic example of such systems.
It lies around 63 light-years from Earth and is estimated to be only 20 million years old.
It hosts a circumstellar disk of gas and dust and a huge number of exocomets, some of which were seen falling onto the star.
It also harbors Beta Pictoris b, a gas giant approximately 9 to 13 times the mass of Jupiter.
Discovered in November 2008, the planet has a day length of 8 hours and orbits the parent star every 22 years at a distance of about 9 AU (9 times the Earth-Sun distance).
The Beta Pictoris planetary system. Image credit: P. Rubini / A.-M. Lagrange.
The newly-discovered planet, named Beta Pictoris c, has a mass of about 9 times that of Jupiter and is much closer to the star.
The planet orbits at 2.7 AU on an eccentric orbit and has an orbital period of roughly 1,200 days.
It was discovered by Dr. Anne-Marie Lagrange from the Institut de Planétologie et d’Astrophysique de Grenoble and colleagues.
“We had to analyze more than 10 years of the HARPS high-resolution spectroscopic data in order to indirectly detect the presence of Beta Pictoris c,” the astronomers said.
They hope to find out more about the planet from data from ESA’s Gaia satellite and from the future Extremely Large Telescope now under construction in Chile.
“Because its semi-major axis is substantially smaller than that of Beta Pictoris b, Beta Pictoris c may transit its star,” they explained.
“A transit of Beta Pictoris c would allow its atmosphere to be explored, while a transit of its Hill sphere — the region in which a planet dominates the attraction of satellites — would allow for the search for moons or circumplanetary rings.”
The discovery is reported in a paper in the journal Nature Astronomy.
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A.-M. Lagrange et al. Evidence for an additional planet in the β Pictoris system. Nature Astronomy, published online August 19, 2019; doi: 10.1038/s41550-019-0857-1
