Artist’s impression of the surface of a super-Earth orbiting Barnard’s Star
Artist’s impression of super-Earth orbiting Barnard’s Star
Barnard’s Star in the constellation Ophiuchus
Widefield image of the sky around Barnard’s Star showing its motion
Videos
ESOcast 184 Light: Super-Earth Orbiting Barnard’s Star (4K UHD)
Artist’s impression of Barnard’s Star and its super-Earth
Exploring the surface of a super-Earth orbiting Barnard’s Star (Artist’s impression)
Red Dots campaign uncovers compelling evidence of exoplanet around closest single star to Sun
The nearest single star to the Sun hosts
an exoplanet at least 3.2 times as massive as Earth — a so-called
super-Earth. One of the largest observing campaigns to date using data
from a world-wide array of telescopes, including ESO’s planet-hunting
HARPS instrument, have revealed this frozen, dimly lit world. The newly
discovered planet is the second-closest known exoplanet to the Earth.
Barnard’s star is the fastest moving star in the night sky.
A planet has been detected orbiting Barnard’s Star, a mere 6 light-years away. This breakthrough — announced in a paper published today in the journal Nature — is a result of the Red Dots and CARMENES projects, whose search for local rocky planets has already uncovered a new world orbiting our nearest neighbour, Proxima Centauri.
The planet, designated Barnard's Star b, now steps in as the second-closest known exoplanet to Earth [1]. The gathered data indicate that the planet could be a super-Earth,
having a mass at least 3.2 times that of the Earth, which orbits its
host star in roughly 233 days. Barnard’s Star, the planet’s host star,
is a red dwarf, a
cool, low-mass star, which only dimly illuminates this newly-discovered
world. Light from Barnard’s Star provides its planet with only 2% of the
energy the Earth receives from the Sun.
Despite being relatively close to its parent star — at a
distance only 0.4 times that between Earth and the Sun — the exoplanet
lies close to the snow line, the region where volatile compounds such as water can condense into solid ice. This freezing, shadowy world could have a temperature of –170 ℃, making it inhospitable for life as we know it.
Named for astronomer E. E. Barnard,
Barnard’s Star is the closest single star to the Sun. While the star
itself is ancient — probably twice the age of our Sun — and relatively
inactive, it also has the fastest apparent motion of any star in the
night sky [2].
Super-Earths are the most common type of planet to form around low-mass
stars such as Barnard’s Star, lending credibility to this newly
discovered planetary candidate. Furthermore, current theories of
planetary formation predict that the snow line is the ideal location for
such planets to form.
Previous searches for a planet around Barnard’s Star have
had disappointing results — this recent breakthrough was possible only
by combining measurements from several high-precision instruments
mounted on telescopes all over the world [3].
“After a very careful analysis, we are 99% confident that the planet is there,”
stated the team’s lead scientist, Ignasi Ribas (Institute of Space
Studies of Catalonia and the Institute of Space Sciences, CSIC in
Spain). “However, we’ll continue to observe this fast-moving star to
exclude possible, but improbable, natural variations of the stellar
brightness which could masquerade as a planet.”
Among the instruments used were ESO’s famous planet-hunting HARPS and UVES spectrographs. “HARPS
played a vital part in this project. We combined archival data from
other teams with new, overlapping, measurements of Barnard’s star from
different facilities,” commented Guillem Anglada Escudé (Queen Mary University of London), co-lead scientist of the team behind this result [4]. “The combination of instruments was key to allowing us to cross-check our result.”
The astronomers used the Doppler effect
to find the exoplanet candidate. While the planet orbits the star, its
gravitational pull causes the star to wobble. When the star moves away
from the Earth, its spectrum redshifts;
that is, it moves towards longer wavelengths. Similarly, starlight is
shifted towards shorter, bluer, wavelengths when the star moves towards
Earth.
Astronomers take advantage of this effect to measure the
changes in a star’s velocity due to an orbiting exoplanet — with
astounding accuracy. HARPS can detect changes in the star’s velocity as
small as 3.5 km/h — about walking pace. This approach to exoplanet
hunting is known as the radial velocity method, and has never before been used to detect a similar super-Earth type exoplanet in such a large orbit around its star.
“We used observations from seven different instruments,
spanning 20 years of measurements, making this one of the largest and
most extensive datasets ever used for precise radial velocity studies.” explained Ribas. ”The combination of all data led to a total of 771 measurements — a huge amount of information!”
“We have all worked very hard on this breakthrough,” concluded Anglada-Escudé. “This
discovery is the result of a large collaboration organised in the
context of the Red Dots project, that included contributions from teams
all over the world.
Notes
[1] The only stars closer to the Sun make up the triple star system Alpha Centauri. In 2016, astronomers using ESO telescopes and other facilities found clear evidence of a planet orbiting the closest star to Earth in this system, Proxima Centauri. That planet lies just over 4 light-years from Earth, and was discovered by a team led by Guillem Anglada Escudé.
[2] The total velocity of
Barnard’s Star with respect to the Sun is about 500 000 km/h. Despite
this blistering pace, it is not the fastest known star. What makes the
star’s motion noteworthy is how fast it appears to move across the night
sky as seen from the Earth, known as its apparent motion. Barnard’s
Star travels a distance equivalent to the Moon's diameter across the sky
every 180 years — while this may not seem like much, it is by far the
fastest apparent motion of any star.
[3] The facilities used in this research were: HARPS at the ESO 3.6-metre telescope; UVES at the ESO VLT; HARPS-N at the Telescopio Nazionale Galileo; HIRES at the Keck 10-metre telescope; PFS at the Carnegie’s Magellan 6.5-m telescope; APF at the 2.4-m telescope at Lick Observatory; and CARMENES at the Calar Alto Observatory. Additionally, observations were made with the 90-cm telescope at the Sierra Nevada Observatory, the 40-cm robotic telescope at the SPACEOBS observatory, and the 80-cm Joan Oró Telescope of the Montsec Astronomical Observatory (OAdM).
More Information
This research was presented in the paper A super-Earth planet candidate orbiting at the snow-line of Barnard’s star published in the journal Nature on 15 November.
The team was composed of I. Ribas (Institut de Ciències de
l’Espai, Spain & Institut d’Estudis Espacials de Catalunya, Spain),
M. Tuomi (Centre for Astrophysics Research, University of Hertfordshire,
United Kingdom), A. Reiners (Institut für Astrophysik Göttingen,
Germany), R. P. Butler (Department of Terrestrial Magnetism, Carnegie
Institution for Science, USA), J. C. Morales (Institut de Ciències de
l’Espai, Spain & Institut d’Estudis Espacials de Catalunya, Spain),
M. Perger (Institut de Ciències de l’Espai, Spain & Institut
d’Estudis Espacials de Catalunya, Spain), S. Dreizler (Institut für
Astrophysik Göttingen, Germany), C. Rodríguez-López (Instituto de
Astrofísica de Andalucía, Spain), J. I. González Hernández (Instituto de
Astrofísica de Canarias Spain & Universidad de La Laguna, Spain),
A. Rosich (Institut de Ciències de l’Espai, Spain & Institut
d’Estudis Espacials de Catalunya, Spain), F. Feng (Centre for
Astrophysics Research, University of Hertfordshire, United Kingdom), T.
Trifonov (Max-Planck-Institut für Astronomie, Germany), S. S. Vogt (Lick
Observatory, University of California, USA), J. A. Caballero (Centro de
Astrobiología, CSIC-INTA, Spain), A. Hatzes (Thüringer
Landessternwarte, Germany), E. Herrero (Institut de Ciències de l’Espai,
Spain & Institut d’Estudis Espacials de Catalunya, Spain), S. V.
Jeffers (Institut für Astrophysik Göttingen, Germany), M. Lafarga
(Institut de Ciències de l’Espai, Spain & Institut d’Estudis
Espacials de Catalunya, Spain), F. Murgas (Instituto de Astrofísica de
Canarias, Spain & Universidad de La Laguna, Spain), R. P. Nelson
(School of Physics and Astronomy, Queen Mary University of London,
United Kingdom), E. Rodríguez (Instituto de Astrofísica de Andalucía,
Spain), J. B. P. Strachan (School of Physics and Astronomy, Queen Mary
University of London, United Kingdom), L. Tal-Or (Institut für
Astrophysik Göttingen, Germany & School of Geosciences, Tel-Aviv
University, Israel), J. Teske (Department of Terrestrial Magnetism,
Carnegie Institution for Science, USA & Hubble Fellow), B.
Toledo-Padrón (Instituto de Astrofísica de Canarias, Spain &
Universidad de La Laguna, Spain), M. Zechmeister (Institut für
Astrophysik Göttingen, Germany), A. Quirrenbach (Landessternwarte,
Universität Heidelberg, Germany), P. J. Amado (Instituto de Astrofísica
de Andalucía, Spain), M. Azzaro (Centro Astronómico Hispano-Alemán,
Spain), V. J. S. Béjar (Instituto de Astrofísica de Canarias, Spain
& Universidad de La Laguna, Spain), J. R. Barnes (School of Physical
Sciences, The Open University, United Kingdom), Z. M. Berdiñas
(Departamento de Astronomía, Universidad de Chile), J. Burt (Kavli
Institute, Massachusetts Institute of Technology, USA), G. Coleman
(Physikalisches Institut, Universität Bern, Switzerland), M.
Cortés-Contreras (Centro de Astrobiología, CSIC-INTA, Spain), J. Crane
(The Observatories, Carnegie Institution for Science, USA), S. G. Engle
(Department of Astrophysics & Planetary Science, Villanova
University, USA), E. F. Guinan (Department of Astrophysics &
Planetary Science, Villanova University, USA), C. A. Haswell (School of
Physical Sciences, The Open University, United Kingdom), Th. Henning
(Max-Planck-Institut für Astronomie, Germany), B. Holden (Lick
Observatory, University of California, USA), J. Jenkins (Departamento de
Astronomía, Universidad de Chile), H. R. A. Jones (Centre for
Astrophysics Research, University of Hertfordshire, United Kingdom), A.
Kaminski (Landessternwarte, Universität Heidelberg, Germany), M. Kiraga
(Warsaw University Observatory, Poland), M. Kürster (Max-Planck-Institut
für Astronomie, Germany), M. H. Lee (Department of Earth Sciences and
Department of Physics, The University of Hong Kong), M. J.
López-González (Instituto de Astrofísica de Andalucía, Spain), D. Montes
(Dep. de Física de la Tierra Astronomía y Astrofísica & Unidad de
Física de Partículas y del Cosmos de la Universidad Complutense de
Madrid, Spain), J. Morin (Laboratoire Univers et Particules de
Montpellier, Université de Montpellier, France), A. Ofir (Department of
Earth and Planetary Sciences, Weizmann Institute of Science. Israel), E.
Pallé (Instituto de Astrofísica de Canarias, Spain & Universidad de
La Laguna, Spain), R. Rebolo (Instituto de Astrofísica de Canarias,
Spain, & Consejo Superior de Investigaciones Científicas &
Universidad de La Laguna, Spain), S. Reffert (Landessternwarte,
Universität Heidelberg, Germany), A. Schweitzer (Hamburger Sternwarte,
Universität Hamburg, Germany), W. Seifert (Landessternwarte, Universität
Heidelberg, Germany), S. A. Shectman (The Observatories, Carnegie
Institution for Science, USA), D. Staab (School of Physical Sciences,
The Open University, United Kingdom), R. A. Street (Las Cumbres
Observatory Global Telescope Network, USA), A. Suárez Mascareño
(Observatoire Astronomique de l'Université de Genève, Switzerland &
Instituto de Astrofísica de Canarias Spain), Y. Tsapras (Zentrum für
Astronomie der Universität Heidelberg, Germany), S. X. Wang (Department
of Terrestrial Magnetism, Carnegie Institution for Science, USA), and G.
Anglada-Escudé (School of Physics and Astronomy, Queen Mary University
of London, United Kingdom & Instituto de Astrofísica de Andalucía,
Spain).
ESO is the foremost intergovernmental astronomy
organisation in Europe and the world’s most productive ground-based
astronomical observatory by far. It has 16 Member States: Austria,
Belgium, the Czech Republic, Denmark, France, Finland, Germany, Ireland,
Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland
and the United Kingdom, along with the host state of Chile and with
Australia as a Strategic Partner. ESO carries out an ambitious programme
focused on the design, construction and operation of powerful
ground-based observing facilities enabling astronomers to make important
scientific discoveries. ESO also plays a leading role in promoting and
organising cooperation in astronomical research. ESO operates three
unique world-class observing sites in Chile: La Silla, Paranal and
Chajnantor. At Paranal, ESO operates the Very Large Telescope and its
world-leading Very Large Telescope Interferometer as well as two survey
telescopes, VISTA working in the infrared and the visible-light VLT
Survey Telescope. ESO is also a major partner in two facilities on
Chajnantor, APEX and ALMA, the largest astronomical project in
existence. And on Cerro Armazones, close to Paranal, ESO is building the
39-metre Extremely Large Telescope, the ELT, which will become “the
world’s biggest eye on the sky”.
Links
Contact
Ignasi Ribas (Lead Scientist)
Institut d’Estudis Espacials de Catalunya and the Institute of Space Sciences, CSIC
Barcelona, Spain
Tel: +34 93 737 97 88 (ext 933027)
Email: iribas@ice.cat
Guillem Anglada-Escudé
Queen Mary University of London
London, United Kingdom
Tel: +44 (0)20 7882 3002
Email: g.anglada@qmul.ac.uk
Calum Turner
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6670
Cell: +49 151 1537 3591
Email: pio@eso.org
Source: ESO/News
