Press Release

Scientists discover planet orbiting closest single star to our Sun

1 October 2024

The image is an artist’s impression of an exoplanet. A rusty planet looms in the forefront, half of its sphere taking up most of the frame. The top of the planet is brown and red, illuminated by a small star shining in the distance. The lower part of the sphere is shrouded in darkness. The star is aligned with the planet, in the middle of the image. Compared to the giant planet, the star looks small. In the black background are some very tiny stars.

Using the European Southern Observatory’s Very Large Telescope (ESO’s VLT), astronomers have discovered an exoplanet orbiting Barnard’s star, the closest single star to our Sun. On this newly discovered exoplanet, which has at least half the mass of Venus, a year lasts just over three Earth days. The team’s observations also hint at the existence of three more exoplanet candidates, in various orbits around the star.

Located just six light-years away, Barnard’s star is the second-closest stellar system — after Alpha Centauri’s three-star group — and the closest individual star to us. Owing to its proximity, it is a primary target in the search for Earth-like exoplanets. Despite a promising detection back in 2018, no planet orbiting Barnard's star had been confirmed until now.

The discovery of this new exoplanet — announced in a paper published today in the journal Astronomy & Astrophysics — is the result of observations made over the last five years with ESO’s VLT, located at Paranal Observatory in Chile. “Even if it took a long time, we were always confident that we could find something,” says Jonay González Hernández, a researcher at the Instituto de Astrofísica de Canarias in Spain, and lead author of the paper. The team were looking for signals from possible exoplanets within the habitable or temperate zone of Barnard’s star — the range where liquid water can exist on the planet’s surface. Red dwarfs like Barnard’s star are often targeted by astronomers since low-mass rocky planets are easier to detect there than around larger Sun-like stars. [1]

Barnard b [2], as the newly discovered exoplanet is called, is twenty times closer to Barnard’s star than Mercury is to the Sun. It orbits its star in 3.15 Earth days and has a surface temperature around 125 °C. “Barnard b is one of the lowest-mass exoplanets known and one of the few known with a mass less than that of Earth. But the planet is too close to the host star, closer than the habitable zone,” explains González Hernández. “Even if the star is about 2500 degrees cooler than our Sun, it is too hot there to maintain liquid water on the surface.”

For their observations, the team used ESPRESSO, a highly precise instrument designed to measure the wobble of a star caused by the gravitational pull of one or more orbiting planets. The results obtained from these observations were confirmed by data from other instruments also specialised in exoplanet hunting: HARPS at ESO’s La Silla Observatory, HARPS-N and CARMENES. The new data do not, however, support the existence of the exoplanet reported in 2018. 

In addition to the confirmed planet, the international team also found hints of three more exoplanet candidates orbiting the same star. These candidates, however, will require additional observations with ESPRESSO to be confirmed. “We now need to continue observing this star to confirm the other candidate signals,” says Alejandro Suárez Mascareño, a researcher also at the Instituto de Astrofísica de Canarias and co-author of the study. “But the discovery of this planet, along with other previous discoveries such as Proxima b and d, shows that our cosmic backyard is full of low-mass planets.”

ESO’s Extremely Large Telescope (ELT), currently under construction, is set to transform the field of exoplanet research. The ELT’s ANDES instrument will allow researchers to detect more of these small, rocky planets in the temperate zone around nearby stars, beyond the reach of current telescopes, and enable them to study the composition of their atmospheres.

Notes

[1] Astronomers target cool stars, like red dwarfs, because their temperate zone is much closer to the star than that of hotter stars, like the Sun. This means that the planets orbiting within their temperate zone have shorter orbital periods, allowing astronomers to monitor them over several days or weeks, rather than years. In addition, red dwarfs are much less massive than the Sun, so they are more easily disturbed by the gravitational pull of the planets around them and thus they wobble more strongly. 

[2] It’s common practice in science to name exoplanets by the name of their host star with a lowercase letter added to it, ‘b’ indicating the first known planet, ’c’ the next one, and so on. The name Barnard b was therefore also given to a previously suspected planet candidate around Barnard's star, which scientists were unable to confirm.

More information

This research was presented in the paper “A sub-Earth-mass planet orbiting Barnard’s star” to appear in Astronomy & Astrophysics. (https://www.aanda.org/10.1051/0004-6361/202451311)

The team is composed of J. I. González Hernández (Instituto de Astrofísica de Canarias, Spain [IAC] and Departamento de Astrofísica, Universidad de La Laguna, Spain [IAC-ULL]), A. Suárez Mascareño (IAC and IAC-ULL), A. M. Silva (Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, Portugal [IA-CAUP] and Departamento de Física e Astronomia Faculdade de Ciências, Universidade do Porto, Portugal [FCUP]), A. K. Stefanov (IAC and IAC-ULL), J. P. Faria (Observatoire de Genève, Université de Genève, Switzerland [UNIGE]; IA-CAUP and FCUP), H. M. Tabernero (Departamento de Física de la Tierra y Astrofísica & Instituto de Física de Partículas y del Cosmos, Universidad Complutense de Madrid, Spain), A. Sozzetti (INAF - Osservatorio Astrofisico di Torino [INAF-OATo] and Istituto Nazionale di Astrofisica, Torino, Italy), R. Rebolo (IAC; IAC-ULL and Consejo Superior de Investigaciones Científicas, Spain [CSIC]), F. Pepe (UNIGE), N. C. Santos (IA-CAUP; FCUP), S. Cristiani (INAF - Osservatorio Astronomico di Trieste, Italy [INAF-OAT] and Institute for Fundamental Physics of the Universe, Trieste, Italy [IFPU]), C. Lovis (UNIGE), X. Dumusque (UNIGE), P. Figueira (UNIGE and IA-CAUP), J. Lillo-Box (Centro de Astrobiología, CSIC-INTA, Madrid, Spain [CAB]), N. Nari (IAC; Light Bridges S. L., Canarias, Spain and IAC-ULL), S. Benatti (INAF - Osservatorio Astronomico di Palermo, Italy [INAF-OAPa]), M. J. Hobson (UNIGE), A. Castro-González (CAB), R. Allart (Institut Trottier de Recherche sur les Exoplanètes, Université de Montréal, Canada and UNIGE), V. M. Passegger (National Astronomical Observatory of Japan, Hilo, USA; IAC; IAC-ULL and Hamburger Sternwarte, Hamburg, Germany), M.-R. Zapatero Osorio (CAB), V. Adibekyan (IA-CAUP and FCUP), Y. Alibert (Center for Space and Habitability, University of Bern, Switzerland and Weltraumforschung und Planetologie, Physikalisches Institut, University of Bern, Switzerland), C. Allende Prieto (IAC and IAC-ULL), F. Bouchy (UNIGE), M. Damasso (INAF-OATo), V. D’Odorico (INAF-OAT and IFPU), P. Di Marcantonio (INAF-OAT), D. Ehrenreich (UNIGE), G. Lo Curto (European Southern Observatory, Santiago, Chile [ESO Chile]), R. Génova Santos (IAC and IAC-ULL), C. J. A. P. Martins (IA-CAUP and Centro de Astrofísica da Universidade do Porto, Portugal), A. Mehner (ESO Chile), G. Micela (INAF-OAPa), P. Molaro (INAF-OAT), N. Nunes (Instituto de Astrofísica e Ciências do Espaço, Universidade de Lisboa), E. Palle (IAC and IAC-ULL), S. G. Sousa (IA-CAUP and FCUP), and S. Udry (UNIGE).

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Links

Contacts

Jonay I. González Hernández
Instituto de Astrofísica de Canarias
Tenerife, Spain
Tel: +34 922 605 751 or +34 922 605 200
Email: jonay.gonzalez@iac.es

Alejandro Suárez Mascareño
Instituto de Astrofísica de Canarias
Tenerife, Spain
Tel: +34 658 778 954
Email: alejandro.suarez.mascareno@iac.es

Serena Benatti
INAF - Osservatorio Astronomico di Palermo
Palermo, Italy
Tel: +39 091 233270
Email: serena.benatti@inaf.it

João Faria
Département d’astronomie de l’Université de Genève
Geneve, Switzerland
Tel: +41 22 379 22 76
Email: joao.faria@unige.ch

André M. Silva
Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto
Porto, Portugal
Tel: +351 226 089 830
Email: Andre.Silva@astro.up.pt

Bárbara Ferreira
ESO Media Manager
Garching bei München, Germany
Tel: +49 89 3200 6670
Cell: +49 151 241 664 00
Email: press@eso.org

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About the Release

Release No.:eso2414
Name:Barnard's Star
Type:Milky Way : Star
Facility:Very Large Telescope
Instruments:ESPRESSO
Science data:2024A&A...690A..79G

Images

The image is an artist’s impression of an exoplanet. A rusty planet looms in the forefront, half of its sphere taking up most of the frame. The top of the planet is brown and red, illuminated by a small star shining in the distance. The lower part of the sphere is shrouded in darkness. The star is aligned with the planet, in the middle of the image. Compared to the giant planet, the star looks small. In the black background are some very tiny stars.
Artist’s impression of a sub-Earth-mass planet orbiting Barnard’s star
The image is an artist’s representation of the nearest stars to the Sun. In the lower part of the image is the Sun, surrounded by four semicircles that increase in size. Each semicircle indicates a certain distance from the Sun. The closest one coincides with a series of tiny white spots that represent the objects of the Oort cloud, located one light-year away. The second semicircle indicates two light-years away. The third semicircle indicates four light years away, and coincides approximately with two adjacent large spots that represent stars. These spots are yellow and red, the former being twice the size of the red one. These are labelled Alpha Centauri A&B and Proxima Centauri, respectively. The fourth semicircle indicates six light-years away and coincides with an orange spot the size of the Sun. This represents Barnard’s star. Around the same semicircle there are two smaller red stars, unlabelled, with a third one positioned a bit further away.
The nearest stars to the Sun (infographic)
Barnard’s Star in the constellation Ophiuchus
Barnard’s Star in the constellation Ophiuchus
The image shows a photograph of the night sky, focused on a very specific area surrounding Barnard’s star. Barnard’s star is in the middle of the image and appears as a tiny red spot. Close to this spot are a yellow and a blue spot, one above each other. Each spot is also Barnard’s star, albeit photographed in a slightly different position. The picture is cluttered with countless stars that are seen in different sizes and colours, ranging from white to yellow and red. Barnard’s star appears tiny compared to the largest stars photographed here.
Widefield image of the sky around Barnard’s Star showing its motion

Videos

New planet discovered orbiting closest single star to our Sun | ESO News
New planet discovered orbiting closest single star to our Sun | ESO News
Animation of a sub-Earth-mass planet orbiting Barnard’s star
Animation of a sub-Earth-mass planet orbiting Barnard’s star
Animation of a sub-Earth-mass planet orbiting Barnard’s star
Animation of a sub-Earth-mass planet orbiting Barnard’s star
Barnard’s Star in the Solar neighborhood
Barnard’s Star in the Solar neighborhood
The radial velocity method for finding exoplanets
The radial velocity method for finding exoplanets
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