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| Kepler-16b, seen in this artist's impression, orbits two stars and has double sunsets, just like Tatooine in Star Wars. (Image credit: Tim Pyle/NASA/JPL-Caltech) |
A rare exoplanet which orbits around two stars at once has been detected
using a ground-based telescope by a team led by the University of
Birmingham.
The planet, called Kepler-16b, has so far only been seen using the Kepler
space telescope. It orbits around two stars, with the two orbits also
orbiting one another, forming a binary star system. Kepler-16b is located
some 245 light years from Earth and, like Luke Skywalker's home planet of
Tatooine, in the Star Wars universe, it would have two sunsets if you could
stand on its surface.
The 193cm telescope used in the new observation is based at the Observatoire
de Haute-Provence, in France. The team were able to detect the planet using
the radial velocity method, in which astronomers observe a change in the
velocity of a star as a planet orbits about it.
The detection of Kepler-16b using the radial velocity method is an important
demonstration that it is possible to detect circumbinary planets using more
traditional methods, at greater efficiency and lower cost than by using
spacecrafts.
Importantly the radial velocity method is also more sensitive to additional
planets in a system, and it can also measure the mass of a planet—its most
fundamental property.
Having demonstrated the method using Kepler-16b, the team plans to continue
the search for previously unknown circumbinary planets and help answer
questions about how planets are formed. Usually, planets formation is
thought to take place within a protoplanetary disc—a mass of dust and gas
which surrounds a young star. However, this process may not be possible
within a circumbinary system.
Professor Amaury Triaud, from the University of Birmingham, who led the
team, explains: "Using this standard explanation it is difficult to
understand how circumbinary planets can exist. That's because the presence
of two stars interferes with the protoplanetary disc, and this prevents dust
from agglomerating into planets, a process called accretion.
"The planet may have formed far from the two stars, where their influence is
weaker, and then moved inwards in a process called disc-driven migration—or,
alternatively, we may find we need to revise our understanding of the
process of planetary accretion."
Dr. David Martin, from the Ohio State University (U.S.), who contributed to
the discovery, explains "Circumbinary planets provide one of the clearest
clues that disc-driven migration is a viable process, and that it happens
regularly."
Dr. Alexandre Santerne, from the University of Marseille, a collaborator on
the research explains: "Kepler-16b was first discovered 10 years ago by
NASA's Kepler satellite using the transit method. This system was the most
unexpected discovery made by Kepler. We chose to turn our telescope and
recover Kepler-16 to demonstrate the validity of our radial-velocity
methods."
Dr. Isabelle Boisse, also from the University of Marseille, is the scientist
in charge of the SOPHIE instrument that was used to collect the data. She
said: "Our discovery shows how ground-based telescopes remain entirely
relevant to modern exoplanet research and can be used for exciting new
projects. Having shown we can detect Kepler-16b, we will now analyse data
taken on many other binary star systems, and search for new circumbinary
planets."
The research is published in Monthly Notices of the Royal Astronomical
Society.
Reference:
BEBOP III. Observations and an independent mass measurement of Kepler-16
(AB) b – the first circumbinary planet detected with radial velocities,
Monthly Notices of the Royal Astronomical Society,
DOI: 10.1093/mnras/stab3712
Tags:
Space & Astrophysics