It’s an artist’s impression of Earth – sized, rocky exoplanet GJ 1132 b, located 41 light – years away around a red dwarf star. Scientists using NASA’s Hubble Space Telescope have found evidence that this planet lost its original atmosphere but found a second one containing a toxic mixture of hydrogen, methane and hydrogen cyanide. Hubble detected the “fingerprints” of these gases while the mother star’s light filtered through the atmosphere of the exoplanet. The planet is too far away and too dull to be photographed by Hubble. It illustrates what astronomers believe is going on in this remote world. Under the smoky, hazy atmosphere of the planet, there may be a thin crust that is only a few hundred feet thick. Melted lava beneath the surface continues through volcanic fissures. Gases seeping through these cracks appear to be constantly replenishing the atmosphere, which would otherwise be removed by syrupy radiation from the planet’s nearby star. The gravity of another planet in the system is likely to break the surface of GJ 1132 b and look like a cracked eggshell. This is the first time that a so-called ‘secondary atmosphere’ has been detected on a planet outside our solar system. Credit: NASA, ESA and R. Hurt (IPAC / Caltech)
To orbit a red dwarf star around 41 light-years is an terrestrial, rocky exoplanet named GJ 1132 b. In some ways GJ 1132 b has intrigue parallels with the earth, but in other ways it is very different. One of the differences is that the smoky, hazy atmosphere contains a toxic mixture of hydrogen, methane and hydrogen cyanide. Scientists using NASA’s Hubble Space Telescope have found evidence that this is not the original atmosphere of the planet, and that the first one was blown away by radiant radiation from the nearby parent star of GJ 1132 b. It is believed that the so-called ‘secondary atmosphere’ is formed as molten lava beneath the planet’s surface constantly flows up through volcanic fissures. Gases seeping through these cracks seem to be constantly replenishing the atmosphere, which would otherwise also be stripped by the star. This is the first time that a secondary atmosphere has been detected in a world outside our solar system.
Scientists using NASA’s Hubble Space Telescope have found evidence that a planet orbiting a distant star may have lost its atmosphere but gained a second one through volcanic activity.
It is believed that the planet, GJ 1132 b, started as a gaseous world with a thick hydrogen blanket of atmosphere. This so-called “sub-Neptune”, which begins several times the diameter of the earth, presumably lost its original hydrogen and helium atmosphere due to the intense radiation of the hot, young star orbiting it. Within a short period of time, such a planet would be stripped to a bare core about the size of Earth. That’s when things got interesting.
To the surprise of astronomers, Hubble observed an atmosphere that, in their theory, is a “secondary atmosphere” that is currently present. Based on a combination of direct observational evidence and inference through computer modeling, the team reports that the atmosphere consists of molecular hydrogen, hydrogen cyanide, methane and also contains an aerosol haze. According to the modeling, the aerosol haze is based on photochemically produced hydrocarbons, similar to smog on Earth.
Scientists interpret the current atmospheric hydrogen in GJ 1132 b as hydrogen from the original atmosphere that was absorbed into the molten magma mantle of the planet and is now slowly being released by volcanic processes to form a new atmosphere. It is believed that the atmosphere we see today is constantly replenished to balance the hydrogen escaping into space.
“This is very exciting because we believe the atmosphere we are seeing now has regenerated, so it could be a secondary atmosphere,” said study co-author Raissa Estrela of NASA’s Jet Propulsion Laboratory (JPL). said in Southern California. “At first we thought these highly irradiated planets might be pretty boring because we believed they had lost their atmosphere. But we, along with Hubble, looked at the existing observations of this planet and said, ‘Oh no, there’s a atmosphere.’
The findings could have implications for other exoplanets, planets outside our solar system.
“How many terrestrial planets do not start as terrestrial regions? Some can start as sub-Neptunes, and they become terrestrial animals through a mechanism that vaporizes the primordial atmosphere with photo. This process works early in a planet’s life, when the star is warmer, “said lead author Mark Swain of JPL. “Then the star cools down and the planet just sits there. So you have this mechanism where you can boil the atmosphere down in the first 100 million years, and then things go down. And if you can restore the atmosphere, maybe you can do it. hou. ‘
This plot shows the spectrum of the atmosphere of an terrestrial, rocky exoplanet, GJ 1132 b. The orange line represents the model spectrum. For comparison, the observed spectrum is shown as blue dots representing the mean data points, along with their error bars. This analysis is consistent with GJ 1132 b which is primarily a hydrogen atmosphere with a mixture of methane and hydrogen cyanide. The planet also has aerosols that cause light scattering. This is the first time that a so-called ‘secondary atmosphere’, which was replenished after the planet lost its primordial atmosphere, is detected in a world outside our solar system. Credit: NASA, ESA and P. Jeffries (STScI)
In some ways GJ 1132 b, about 41 light-years from Earth, has seductive parallels with the Earth, but in some respects it is very different. Both have similar densities, similar sizes and similar ages and are about 4.5 billion years old. Both started with a hydrogen-dominated atmosphere, and both were hot before cooling. The team’s work even suggests that GJ 1132 b and Earth have similar atmospheric pressures on the surface.
But the planets have different formation histories. It is not believed that the earth is the surviving nucleus of a sub-Neptune. And the earth orbits at a comfortable distance from our sun. GJ 1132 b is so close to his red dwarf star that he completes a orbit around his host every day and a half. This extreme proximity keeps GJ 1132 b temporarily closed and shows the same face to its star at all times – just as our moon keeps one hemisphere permanently towards the earth.
“The question is, what keeps the mantle warm enough to stay liquid and propel volcanism?” asked Swain. “This system is special because it offers the opportunity for a lot of tidal warming.”
Tidal heating is a phenomenon that occurs through friction when energy from a planet’s orbit and rotation is distributed as heat within the planet. GJ 1132 b is in an elliptical orbit, and the tidal forces acting on it are strongest when it is closest to or far from its host. At least one other planet in the host’s system also draws gravity to the planet.
The result is that the planet is “pumped” or stretched by this gravity. That tidal heat keeps the mantle liquid long. A nearby example in our own solar system is Jupiter’s Moon Io, which has continuous volcanic activity due to a tug of war from Jupiter and the neighboring Jovian moons.
Given the warm interior of GJ 1132 b, the team believes that the cooler, overarching crust of the planet is extremely thin, perhaps only hundreds of feet thick. It’s too weak to support anything like volcanic mountains. The flat terrain can also crack like an eggshell due to the bending of the tide. Hydrogen and other gases can be released through such cracks.
NASA’s emerging James Webb Space Telescope has the ability to observe this exoplanet. Webb’s infrared vision could allow scientists to see up to the planet’s surface. “If there are magma pools or volcanism going on, the areas will be warmer,” Swain explained. “It will generate more emissions, and so they will likely be watching the actual geological activity – which is exciting!”
The team’s findings will be published in an upcoming issue of The Astronomical Journal.
Study illuminates the fates of the planetary atmosphere in the distance
Detection of an atmosphere on a rocky exoplanet. arXiv: 2103.05657 [astro-ph.EP] arxiv.org/abs/2103.05657
Provided by ESA / Hubble Information Center
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