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

By Georgina Torbet Published September 11, 2022

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.

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.

“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.

Topics

Tech News

Georgina Torbet

Space Writer

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

Space

James Webb captures image of the most distant star ever discovered

A massive galaxy cluster called WHL0137-08 contains the most strongly magnified galaxy known in the universe’s first billion years: the Sunrise Arc, and within that galaxy, the most distant star ever detected, nicknamed Earendel.

The James Webb Space Telescope has captured a stunning image of the most distant star ever discovered. Discovered by Hubble in 2020, the star named Earendel is located an astonishing 28 billion light-years away. While in the previous Hubble image, the star was only visible as a small blob, these new observations from Webb are detailed enough to reveal information about the star like its type and information about the galaxy in which it resides.

The Webb image shows a galaxy cluster called WHL0137-08, which is so massive that it bends spacetime and acts like a magnifying glass for the more distant galaxies behind it. Some of these distant galaxies being magnified include one called the Sunrise Arc, which hosts Earendel. The Sunrise Arc is located near the end of one of the spikes from the bright central star, at around the five o'clock position. A zoomed-in version of the image shows the Arc and Earendel within t.

Space

Hubble watches an extreme exoplanet being stripped by its star

This artist's illustration shows a planet (dark silhouette) passing in front of the red dwarf star AU Microscopii.

Of the many strange exoplanets discovered to date, one of the most extreme has to be a world called AU Mic b. This Neptune-sized planet orbits close enough to its star that a year there lasts just over a week, and it is bombarded by dramatic flares from its host star which cook the planet with radiation.

Recently, Hubble observed this system to learn more about the relationship between the exoplanet and its star, technically called AU Microscopii. The planet's hydrogen atmosphere is blown away by radiation from the star, but there were confusing findings that seemed to show that no atmosphere was being lost at some times, but significant amounts of atmosphere were lost at other times.

Space

Webb spots water vapor in a planet-forming disk

An artist's concept portraying the star PDS 70 and its inner protoplanetary disk.

One of the big open questions about Earth and how life formed here is where the planet's water came from. Water is essential to life as we know it, but many scientists think that water did not originally form on Earth -- rather, it may have been carried here by asteroids. Recently, though, astronomers have discovered water vapor in the planet-forming region of a star, suggesting that future planets which form here might have access to water right from the start.

The study used the James Webb Space Telescope to look at star PDS 70, which is cooler and much younger than our sun. The star has two gas giant planets orbiting it, but it is also still forming planets and has two protoplanetary disks of dust and gas swirling around it. The inner disk, which is in a region comparable to the distance of the Earth from the sun, is where the water vapor was detected.