A new Earth-sized planet has been discovered orbiting a star that will live for 100 billion years

Researchers using global robotic telescopes have discovered an Earth-sized planet, SPECULOOS-3 b, orbiting an ultracool red dwarf within Milky Way. This planet, tidally locked and likely lacking an atmosphere due to intense radiation, offers new insights into long-lived red dwarfs, which are predicted to be among the last stars to burn in the universe.

Our galaxy is a treasure trove of red stars. In fact, more than 70% of the stars in the Milky Way are M dwarfs, also known as red dwarfs. These stars are cool and dim compared to our Sun, but they often blast orbiting exoplanets with high-energy radiation, especially early in their lives. And these «lives» last a a long time time. Stars like our Sun burn out for about 10 billion years before turning into hungry red giants that devour all nearby planets. M dwarfs continue to burn for 100 billion years or more, perhaps offering a foothold for life and an even longer window for life to evolve.

An international team using robotic telescopes around the world recently spotted an Earth-sized planet orbiting an ultracool red dwarf, the darkest and longest-lived star. When the universe becomes cold and dark, these will be the last stars to burn.

Discovery

The exoplanet SPECULOOS-3 b is about 55 light years from Earth (really close when you consider the cosmic scale!) and almost the same size. For a year there, one orbit around the star lasts about 17 hours. The days and nights, however, may never end: the planet is considered tidally locked, so that the same side, known as the day side, always faces the star, like the Moon faces the Earth. The night side would be locked in endless darkness.

An artist’s concept of the exoplanet SPECULOOS-3 b orbiting its red dwarf star. The planet is about the size of Earth, while its star is slightly larger than Jupiter – but much more massive. Credit: Lionel Garcia

Research on ultra-cold dwarfs

In our corner of the galaxy, ultra-cool dwarf stars are ubiquitous. They are so faint that their planetary population is largely unexplored. The SPECULOOS (Search for Planets EClipsing ULTra-coOOl Stars) project led by Michael Gillon of the University of Liège in Belgium is designed to change that. Ultra cool dwarf stars are scattered across the sky, so you need to observe them one at a time for weeks to have a good chance of detecting transiting planets. For that you need a special network of professional telescopes. This is the concept of SPECULOOS.

«We designed SPECULOOS specifically to explore nearby ultra-cool dwarf stars in search of rocky planets,» Gillon said. «With the SPECULOOS prototype and crucial help OUR Spitzer Space Telescope, we discovered the famous TRAPPIST-1 system. It was a great start!»

Gillon is the lead author of the paper announcing the discovery of the planet, published on May 15, 2024 Astronomy of nature. The project is a real international undertaking, in partnership with the universities of Cambridge, Birmingham, Bern, Massachusetts Institute of Technology and ETH Zurich.

The star SPECULOOS-3 is thousands of degrees cooler than our Sun with an average temperature of about 4,760 F (2,627 C), but it showers its planet with radiation, meaning it probably has no atmosphere.

Seeing a star, let alone a planet, is a feat in itself. «Even though this red dwarf is more than a thousand times dimmer than the Sun, its planet orbits much, much closer to Earth, heating the planetary surface,» said co-author Catherine Clark, a postdoctoral fellow at NASA’s Jet Propulsion Laboratory in Southern California.

Fun facts

• Although the planet is around the size of Earth, its star is only slightly larger than Jupiter – but much more massive.
• The planet receives almost 16 times more energy per second than the Earth receives from the Sun.
• Did you catch the cookie link? The SPECULOOS planet finder shares its name with Spice Cookies. Both are from Belgium. sweet!

Next steps

SPECULOOS-3 b is an excellent candidate for follow-up observations by the James Webb Space Telescope. Not only could we learn about atmospheric potential and surface mineralogy, but it could also help us understand the stellar neighborhood and our place in it.

»We are making great strides in our study of planets orbiting other stars. We have now reached the stage where we can detect and study Earth-sized exoplanets in detail. The next step will be to determine whether any of them are habitable, or even habitable,» said Steve B. Howell, one of the planet discoverers at NASA’s Ames Research Center in Silicon Valley.

For more on this discovery:

Reference: “Detection of an Earth-sized exoplanet orbiting a nearby ultracool dwarf star SPECULOOS-3” Michaël Gillon, Peter P. Pedersen, Benjamin V. Rackham, Georgina Dransfield, Elsa Ducrot, Khalid Barkaoui, Artem Y. Burdanov, Urs Schroffenegger , Yilen Gómez Maqueo Chew, Susan M. Lederer, Roi Alonso, Adam J. Burgasser, Steve B. Howell, Norio Narita, Julien de Wit, Brice-Olivier Demory, Didier Queloz, Amaury HMJ Triaud, Laetitia Delrez, Emmanuël Jehin, Matthew J. Hooton , Lionel J. Garcia, Clàudia Jano Muñoz, Catriona A. Murray, Francisco J. Pozuelos, Daniel Sebastian, Mathilde Timmermans, Samantha J. Thompson, Sebastián Zúñiga-Fernández, Jesús Aceituno, Christian Aganze, Pedro J. Amado, Thomas Baycroft, Zouhair Benkhaldoun, David Berardo, Emeline Bolmont, Catherine A. Clark, Yasmin T. Davis, Fatemeh Davoudi, Zoë L. de Beurs, Jerome P. de Leon, Masahiro Ikoma, Kai Ikuta, Keisuke Isogai, Izuru Fukuda, Akihiko Fukui, Roman Gerasimov, Mourad Ghachoui, Maximilian N. Günther, Samantha Hasler, Yuya Hayashi, Kevin Heng, Renyu Hu, Taiki Kagetani, Yugo Kawai, Kiyoe Kawauchi, Daniel Kitzmann, Daniel DB Koll, Monika Lendl, John H. Livingston, Xintong Lyu, Erik A. Meier Valdés, Mayuko Mori, James J. McCormac, Felipe Murgas, Prajwal Niraula, Enric Pallé, Ilse Plauchu-Frayn, Rafael Rebolo, Laurence Sabin, Yannick Schackey, Nicole Schanche, Franck Selsis, Alfredo Sota, Manu Stalport , Matthew R .Standing, Keivan G. Stassun, Motohide Tamura, Yuka Terada, Christopher A. Theissen, Martin Turbet, Valérie Van Grootel, Roberto Varas, Noriharu Watanabe, and Francis Zong Lang, May 15, 2024. Astronomy of nature.
DOI: 10.1038/s41550-024-02271-2