Key Takeaways:

  • Astronomers found an Earth-sized exoplanet 40 light-years away called Gliese 12 b. It may be slightly warmer than Earth.
  • Gliese 12 b orbits its star every 12.8 days and is slightly smaller than Earth. Its surface temperature is estimated at 42°C (107°F), which is lower than most confirmed exoplanets.
  • Scientists don’t know if Gliese 12 b has an atmosphere, which is crucial for determining if it’s habitable.
  • If Gliese 12 b has an atmosphere, it could reveal why Venus and Earth are so different.
  • Gliese 12 b could be a good candidate for further study with the James Webb Space Telescope.

An unusual and intriguing finding has been made by astronomers: an exoplanet 40 light-years away that resembles Earth and may be slightly warmer than Earth. In the Monthly Notices of the Royal Astronomical Society, a new paper titled “Gliese 12 b, A Temperate Earth-sized Planet at 12 Parsecs Discovered with TESS and CHEOPS,” was released.

Gliese 12 b is a potentially habitable planet that orbits its host star every 12.8 days. It is slightly smaller than Earth and has a surface temperature estimated at 42°C (107°F), which is lower than the majority of the 5,000+ exoplanets that have been confirmed to date.

That is assuming it has no atmosphere, however, which is the crucial next step to establishing if it is habitable. It could have no atmosphere at all, an atmosphere more like that of Venus—which went through a runaway greenhouse effect that turned it into a 400°C (752°F) hellhole—or an atmosphere unlike any other in our solar system.

Finding the answer is crucial because it would indicate whether Gliese 12 b can sustain temperatures high enough for liquid water—and maybe life—to exist on its surface. It would also provide light on how and why Venus and Earth evolved in such different ways.

It is described as “the nearest, transiting, temperate, Earth-size world located to date” and may be a candidate for additional James Webb Space Telescope research.

Proxima Centauri b is the nearest Earth-like exoplanet to us, situated just four light-years away, and it’s also possibly the most well-known. We still have a lot to learn about it, though, because it is not a transiting world. Among other things, we need to find out if it has an atmosphere and whether it could support life.

The transit method, in which a planet passes in front of its star from our point of view and causes a dip in the brightness of the host star, is used to find the majority of exoplanets.

Certain wavelengths of the star’s light are absorbed by the exoplanet’s atmosphere as it travels through it during a transit. Telescopes such as the Webb can identify a set of chemical fingerprints from the transit because different gas molecules absorb different colors.

Gliese 12 b may also be important because it could shed light on whether cool stars, which make up the majority of stars in our Milky Way galaxy, can support temperate planets with atmospheres and are thus habitable.

It orbits a cool red dwarf star called Gliese 12, which is almost 40 light-years away from Earth in the constellation Pisces.

According to Shishir Dholakia, a doctoral student at the Center for Astrophysics at the University of Southern Queensland in Australia, “Gliese 12 b represents one of the best targets to study whether Earth-size planets orbiting cool stars can retain their atmospheres, a crucial step to advance our understanding of habitability on planets across our galaxy.”

Along with Larissa Palethorpe, a PhD candidate at University College London and the University of Edinburgh, he co-led a research team.

The exoplanet’s host star is about 27% of the size of our sun and has a surface temperature that is around 60% of our own star.

Nonetheless, the gap between Gliese 12 and the newly discovered planet is only 7% of the length that separates Earth and the sun. As a result, Gliese 12 b receives from its star roughly 85% of what Venus receives and 1.6 times as much energy as Earth does from the sun.

Potentially habitable 'exo-Venus' with Earth-like temperature discovered
Gliese 12 b’s estimated size may be as large as Earth or slightly smaller — comparable to Venus in our solar system. This artist’s concept compares Earth with different possible Gliese 12 b interpretations, from one with no atmosphere to one with a thick Venus-like one. Credit: NASA/JPL-Caltech/R. Hurt (Caltech-IPAC)

Because of this variation in solar radiation, the planet’s surface temperature is strongly influenced by its atmospheric conditions, which makes it significant. The average surface temperature on Earth is 15°C (59°F), in contrast to the estimated 42°C (107°F) surface temperature of Gliese 12b.

“Atmospheres trap heat and—depending on the type—can change the actual surface temperature substantially,” Dholakia said. The planet’s “equilibrium temperature,” or what it would be if it had no atmosphere, is what we are quoting.

“Much of the scientific value of this planet is to understand what kind of atmosphere it could have. Since Gliese 12 b gets in between the amount of light as Earth and Venus get from the sun, it will be valuable for bridging the gap between these two planets in our solar system.”

Palethorpe added, “It is thought that Earth’s and Venus’s first atmospheres were stripped away and then replenished by volcanic outgassing and bombardments from residual material in the solar system.

“The Earth is habitable, but Venus is not due to its complete loss of water. Due to its temperature difference between Earth and Venus, Gliese 12 b’s atmosphere may hold valuable insights into the habitability pathways that planets follow during their formation.”

The researchers’ discovery was aided by observations made by NASA’s TESS (Transiting Exoplanet Survey Satellite), which they shared with another team in Tokyo.

“We’ve found the nearest, transiting, temperate, Earth-size world located to date,” Astrobiology Center in Tokyo project assistant professor Masayuki Kuzuhara said. Kuzuhara and University of Tokyo project assistant professor Akihiko Fukui led the research team.

“We know of only a handful of Earth-like temperate planets that are both near enough to us and meet other requirements needed for this kind of study, called transmission spectroscopy, using current facilities,” stated Michael McElwain, co-author of the Kuzuhara and Fukui paper and a research astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

“To better understand the diversity of atmospheres and evolutionary outcomes for these planets, we need more examples like Gliese 12 b.”

Gliese 12 b is roughly the same distance from Earth as the TRAPPIST-1 system, at 40 light-years.

This is made up of seven planets, all roughly in Earth’s size range and likely rocky, orbiting a red dwarf star.

Three of these are in the habitable zone but at least two—and probably all of them—have no atmosphere and are likely barren, dismissing hopes when they were first discovered eight years ago that they could be water worlds hosting life.

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