Ultra-Hot ‘Super-Earth’ Exoplanet 65 Light-Years Away May Have No Atmosphere

Illustration of the terrestrial super-Earth GJ 1252 b, located about 65 light years from Earth. Credit: NASA/JPL-Caltech

GJ 1252 b is a rocky, terrestrial “super-Earth” that was discovered in 2020. Astronomers gave the exoplanet further examination and found that it might have very minimal atmosphere or maybe no atmosphere at all.

The planet, which orbits an M-type star, is “the smallest exoplanet for which we have such tight constraints on its atmosphere”, said lead author Ian Crossfield. He is an astronomer and assistant professor at the University of Kansas.

Super-Earths are a class of planets unlike any other in our solar system. They have a mass greater than that of the Earth but do not exceed 10 times its mass. This means they are more massive than Earth but lighter than ice giants like Neptune and " data-gt-translate-attributes="[{" attribute="">Uranus. They can be made of gas, rock or a combination of both.


Astronomers often discover and study exoplanets by observing how much light the planets block as they pass in front of their host stars, a technique known as the “transit method.” GJ 1252 b, an exoplanet about 65 light-years away with a radius 1.18 times larger than Earth, was discovered in 2020 by NASA’s Transiting Exoplanet Survey satellite (TESS) with this method. Astronomers in this new study observed the exoplanet with the Spitzer Space Telescope before it retreated and were able to get a closer look at the planet and its atmosphere.

Using Spitzer, the team detected a secondary eclipse. This happens when a planet passes behind a star and the light from the planet is blocked. The planet’s light comes from its own infrared radiation (or heat), as well as light reflected from the star.


Astronomers looking for signs of life in the cosmos are focusing on a number of different details in exoplanets. Many of these details serve as a comparison between the exoplanet and Earth, as Earth remains the only planet where we have confirmed the presence of life.

GJ 1252 b is not much larger than Earth. However, it is much hotter because it is closer to its star. Plus, as astronomers discovered in this study, it’s missing a lot of atmosphere.

“We are only just beginning to know how often and under what circumstances rocky planets can retain their atmosphere,” said astronomer and study co-author Laura Kreidberg, director of atmospheric physics of exoplanets (APEx department of the Max Planck Institute). for astronomy. “This measurement is an indication that for the hottest planets, thick atmospheres are unlikely to generally survive.”

To determine what the exoplanet’s atmosphere might look like (if there is one), astronomers measured infrared radiation from GJ 1252 b as its light was obscured during a secondary eclipse. These observations revealed the planet’s scorching daytime temperature, which is estimated at 2,242 degrees. Fahrenheit (1228 degrees Celsius). In fact, GJ 1252 b is so hot that gold, silver, and copper would all melt on the planet.

The exoplanet’s expected temperatures, relative to atmospheric models, suggest it likely has a surface pressure of less than 10 bar (for reference, Earth’s surface pressure is around 1 bar). To be stable for a long time, it is possible that this exoplanet has an atmosphere with a density like that of Earth, an atmosphere up to 10 times denser than that of Earth, or even no atmosphere.

Given its extreme temperatures and low surface pressure, astronomers on this team predicted that GJ 1252 b likely has no atmosphere at all. It is currently the smallest exoplanet for which scientists have such a precise idea of ​​its atmosphere.

Fun facts

GJ 1252b is an exoplanet that was first detected with TESS and then studied further with Spitzer before the telescope’s mission ended in 2020. With further exploration using the James Webb Space Telescope (JWST) , researchers could impose even stricter constraints on the atmosphere of this planet. , an exciting possibility.

“At the time, Spitzer was the only facility in the known universe that could do these kinds of measurements. Now Spitzer has been turned off, but JWST is there and at these wavelengths it is much more sensitive than Spitzer was. So what we did with difficulty with Spitzer, we can now start doing easily and for more rocky planets with JWST,” Crossfield said.

“JWST observations in the infrared have the potential to reveal the surface properties of hot, rocky planets like this. Different rock types have different spectral signatures, so we could potentially tell what rock type GJ 1252b is. done,” Kreidberg added.

Investigating GJ 1252 b further with JWST represents an exciting possibility for scientists, as it would be interesting to confirm an atmosphere on such a small and hot exoplanet as it would also be fascinating to explore the composition of a planet like this without atmosphere at all. .

A team from the University of Kansas, led by Crossfield, conducted this study which uncovered strange new details about the atmosphere of GJ 1252b. The study, published in the Astrophysical Journal Letters.

Reference: “GJ 1252b: A Hot Terrestrial Super-Earth Without Atmosphere” by Ian JM Crossfield, Matej Malik, Michelle L. Hill, Stephen R. Kane, Bradford Foley, Alex S. Polanski, David Coria, Jonathan Brande, Yanzhe Zhang, Katherine Wienke, Laura Kreidberg, Nicolas B. Cowan, Diana Dragomir, Varoujan Gorjian, Thomas Mikal-Evans, Björn Benneke, Jessie L. Christiansen, Drake Deming and Farisa Y. Morales, September 23, 2022, Astrophysical Journal Letters.
DOI: 10.3847/2041-8213/ac886b

Researchers from the University of California, Riverside, " data-gt-translate-attributes="[{" attribute="">Nasa‘s Jet Propulsion Laboratory (JPL), Caltech/IPAC-NASA Exoplanet Science Institute, University of Maryland, Carnegie Institution for Science Earth and Planets Laboratory, Max Planck Institute for Astronomy, McGill University, University of New Mexico, Albuquerque, NM, and the Institute for Research on Exoplanets at the University of Montreal.

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