Proxima Centauri amazes us again: a possible second low-mass planet is found orbiting the nearest star to the Sun
The candidate planet is orbiting the star at a distance 1.5 times greater than that separating the Earth from the Sun
The study, with the participation of an IEEC researcher at ICE-CSIC, is published in the journal Science Advances.

New observations of Proxima Centauri, the nearest star to the Solar System at a distance of 4.2 light-years, have made it possible to reveal the presence of a candidate low-mass planet orbiting the star at a distance 1.5 times greater than that separating the Earth from the Sun.

The discovery, published today in the journal Science Advances, was made by an international team including Guillem Anglada-Escudé, a researcher from the Institute of Space Studies of Catalonia (IEEC  — Institut d’Estudis Espacials de Catalunya) at the Institute of Space Sciences (ICE - CSIC) and was led by Mario Damasso (National Institute for Astrophysics-Astrophysical Observatory of Turin), and Fabio Del Sordo (University of Crete and the Institute of Astrophysics at FORTH), thanks to the data collected with spectrographs installed in Chile. Compared to other candidates discovered around more distant stars, Proxima c - as it has been named - is an ideal planet in that complementary techniques can be used to confirm its existence and better characterize it in the near future.

Proxima Centauri is a red dwarf star about 8 times less massive than the Sun; Proxima b, a (most likely) rocky planet, was discovered orbiting the star within its habitable zone in 2016. Proxima b was found by analyzing the star’s radial velocities from spectra collected with the UVES and HARPS spectrographs that are installed, respectively, on the Very Large Telescope array in Cerro Paranal and on the 3.6-m La Silla telescope, both belonging to the European Southern Observatory in Chile. Following this discovery, further Proxima observations were made in 2017 with HARPS as part of the Red Dots project, with the aim of studying this planetary system in greater detail.

The team coordinated by Damasso and Del Sordo have analyzed these new measurements, for a total of about 17 years of observations. In doing so, they revealed the presence of a signal with a period of 5.2 years that is compatible with the existence of a second planet with a minimum mass of about 6 times the mass of the Earth, and with an orbital radius of 1.5 astronomical units (i.e., similar to the average distance between Mars and the Sun).

"According to our analysis, the presence of this periodic signal seems very convincing, and the available data do not seem to indicate a clear physical cause other than the presence of a planet, although we still cannot completely rule out other explanations," Damasso says. "In fact, it is very difficult to find a planet with a relatively low minimum mass and such a long orbital period by only using the radial velocity technique" underlines Damasso. “A signal like the one we found could be due to a cycle of magnetic activity of Proxima, which can mimic the presence of a planet. Further observations are therefore needed to confirm our discovery over the next few years.”

"It is a fascinating result," says Del Sordo, "we are adding a new piece to the knowledge of our closest planetary system." He then adds: “The signal we have found is at the limit of instrumental capabilities. In our study, we show that astrometric data taken with the Gaia satellite is expected to play a decisive role in confirming the existence of this planet. The position of Proxima c's orbit is not easily explained by current models of planetary formation and evolution, and many questions are thus being raised on how it could have formed just over 5 billion years ago."

"Apart from the exciting science in the paper, we are very happy about this because it is the result of early releasing data and the resulting spontaneous collaboration with the lead authors of the paper. For example, several of the Red Dots team members further contributed to the paper and are co-authors, and it also includes contributions from pro-Am astronomers from the American Association of Variable Stars Observers that also participated in the public campaign”, says Guillem Anglada-Escudé, who led the Red Dots observations and corresponding public campaign. 


- Red Dots project

More information

This research is presented in the article "A low-mass planet candidate orbiting Proxima Centauri at a distance of 1.5 AU" by M. Damasso et al., published in Science Advances on 15 January 2020.

The Institute of Space Studies of Catalonia (IEEC  — Institut d’Estudis Espacials de Catalunya) promotes and coordinates space research and technology development in Catalonia for the benefit of society. IEEC fosters collaborations both locally and worldwide and is an efficient agent of knowledge, innovation and technology transfer. As a result of over 20 years of high-quality research, done in collaboration with major international organisations, IEEC ranks among the best international research centers, focusing on areas such as: astrophysics, cosmology, planetary science, and Earth Observation. IEEC’s engineering division develops instrumentation for ground- and space-based projects, and has extensive experience in working with private or public organisations from the aerospace and other innovation sectors.  

IEEC is a private non-profit foundation, governed by a Board of Trustees composed of Generalitat de Catalunya and four other institutions that each have a research unit, which together constitute the core of IEEC R&D activity: the University of Barcelona (UB) with the research unit ICCUB — Institute of Cosmos Sciences; the Autonomous University of Barcelona (UAB) with the research unit CERES — Center of Space Studies and Research; the Polytechnic University of Catalonia (UPC) with the research unit CTE — Research Group in Space Sciences and Technologies; the Spanish Research Council (CSIC) with the research unit ICE — Institute of Space Sciences. IEEC is integrated in the CERCA network (Centres de Recerca de Catalunya).


PR_Image1 Proxima Centauri
Caption: Artistic representation of the planetary system around Proxima Centauri.
Credit: Lorenzo Santinelli


IEEC Communication Office
Barcelona, Spain

Rosa Rodríguez Gasén

Lead Scientist at IEEC
Institute of Space Science (ICE-CSIC)
Barcelona, Spain

Guillem Anglada-Escudé
Attached Documents
Generalitat de CatalunyaUniversitat de BarcelonaUniversitat Autònoma de BarcelonaUniversitat Politècnica de CatalunyaConsejo Superior de Investigaciones CientíficasCentres de Recerca de Catalunya