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Researchers discover planet in the habitable zone of an ultra-cool star

Georgina Torbet
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Even though we’ve discovered over 5,000 exoplanets, or planets outside of our solar system, most of these aren’t very Earth-like. They’re often much bigger than Earth, being more like gas giants Saturn and Jupiter than small and rocky, and relatively few are located in the habitable zone where liquid water could exist on their surface. That’s why it’s exciting when a planet comparable to Earth is discovered in its habitable zone — as one such recently discovered planet is.

Researchers looked at a planet called LP 890-9b or TOI-4306b, previously discovered by NASA’s Transiting Exoplanet Survey Satellite. Using a ground-based telescope called SPECULOOS (Search for habitable Planets EClipsing ULtra-cOOl Stars), they studied the planet which is around 30% larger than Earth and orbits extremely close to its star, with a year lasting just 2.7 days.

The telescopes of the SPECULOOS Southern Observatory gaze out into the stunning night sky over the Atacama Desert, Chile.
The telescopes of the SPECULOOS Southern Observatory gaze out into the stunning night sky over the Atacama Desert, Chile. ESO/ P. Horálek

While the researchers were looking at this planet, they also discovered another planet in the same system. This second planet, named LP 890-9c or SPECULOOS-2c, is around 40% larger than Earth and orbits further out from the star with an orbital period of 8.5 days. Because the star is much smaller and cooler than our sun, that places this second planet within the habitable zone.

Artist’s view showing the red star and its two planets, together with some of the telescopes used for the discovery.
Artist’s view showing the red star and its two planets, together with some of the telescopes used for the discovery. University of Birmingham / Amanda J. Smith

“This second planet receives about the same amount of stellar radiation as our Earth receives from the Sun and could therefore potentially have liquid water on its surface,” one of the researchers, Robert Wells of the University of Bern, said in a statement. However, Wells warns that we shouldn’t assume that the planet would be comfortable for life based purely on its position. For example, in our solar system, Venus is close to being in the habitable zone but it has extremely high temperatures and pressure on its surface which makes it inhospitable for life.

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To learn more about the recently discovered planet, the researchers want to study it using the James Webb Space Telescope to look at its atmosphere and see if it is really potentially habitable.

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“To be able to answer whether this planet can indeed hold liquid surface water or not, we need to learn more about it,” Wells said. “This requires detailed observations – for example with the James Webb Space Telescope.”

The research will be published in the journal Astronomy & Astrophysics.

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Georgina Torbet
Georgina Torbet
Space Writer
Georgina is the Digital Trends space writer, covering human space exploration, planetary science, and cosmology. She…
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