by Using the Hubble Space Telescope, astronomers have discovered that the atmosphere of a relatively small planet outside the solar system is rich in water vapor. Don’t plan a vacation to this destination just yet, though. The planet’s surface is hot enough to melt lead, making it a steamy world inhospitable to life as we know it.
Specifically, the team behind this finding says that the extrasolar planet, or exoplanet, named GJ 9872d exhibits Venus-like temperatures of 752 degrees Fahrenheit (400 degrees Celsius). But that doesn’t mean this discovery isn’t exciting.
While scientists have previously detected water vapor in the atmospheres of many extrasolar planets, the Hubble Telescope’s observations of this hot and steamy world, named GJ 9827d, is the smallest exoplanet to have this vital feature discovered. around him so far.
“The discovery of water on GJ 9827d is exciting because it is the smallest planet yet where we have detected an atmosphere,” Laura Kreidberg, team member and director of the Max Planck Institute for Atmospheric Physics of Exoplanets, told Space .com. “It brings us closer than ever to characterizing Earth-like worlds.”
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GJ 9827d is about twice as wide as Earth and orbits a star called GJ 987, located about 97 light-years away in the constellation Pisces. The planet is just one of three Earth-like worlds orbiting this star, which appears to be around 6 billion years old.
“This was the first time we can show directly by detecting the atmosphere, that these planets with a water-rich atmosphere can really exist around other stars,” Björn Benneke, team member and scientist at the Trottier Institute for Exoplanet Research at the Université de Montréal, said in a statement. “This is an important step towards determining the prevalence and diversity of atmospheres on the rocky planets.”
However, a big question remains: What kind of planet is GJ 9872d?
“The nature of these small planets, two to three times the size of Earth, is really uncertain,” Kreidberg said. “They could be true Super-Earths, with a big rocky core and a light atmosphere on top, or they could be something completely different, like a water world made mostly of water ice with no output in our own solar system.”
A water world or a hydrogen-rich mini-Neptune?
Hubble observed GJ 9827d for three years and watched as the world crossed the face of its star, or “transited” it, 11 times. Because elements and chemical compounds absorb light at specific wavelengths, as light from a parent star passes through the planet’s atmosphere, it carries the fingerprint of the elements that comprise the planet itself.
Currently, the astronomers behind this discovery are not sure whether Hubble detected a small amount of water in a puffy, hydrogen-rich atmosphere when it examined GJ 9872d — or, if the planet’s atmosphere is mostly water.
“ should either be an exciting result, whether there is a dominant water vapor or just a tiny species in a hydrogen-dominant atmosphere, said Pierre-Alexis Roy, lead author of the research and a scientist at the Trottier Institute for Research on Exoplanets at Université de Montreal, in the statement.
If GJ 9872d has spent its 6 billion year life close to its parent star, the intense radiation should have boiled off any primordial hydrogen present, leaving the tiny planet in an atmosphere of water vapor dominated by him. This seems to be supported by the fact that attempts to detect hydrogen around GJ 9872d have so far failed.
Alternatively, if GJ 9872d still clings to a hydrogen-rich envelope and is bound to water, it would be classified as a mini-Neptune, a type of planet that is less massive than Neptune but still resembles the system’s ice giant of the sun while possessing a thick atmosphere. hydrogen and helium.
On the other hand, the exoplanet could be like a larger and hotter version of Jupiter’s moon Europa, which is believed to harbor twice as much water as Earth sealed under a thick icy crust. “The planet GJ 9827d could be half water, half rock. And there would be a lot of water vapor on top of some smaller rocky bodies,” said Benneke.
If GJ 9827d still had a thick atmosphere of water vapour, this would suggest that it was born further away from its star – where the temperature would be lower – before moving to the position we see today.
As a result of this migration, the exoplanet would be blasted with more radiation from its host star, which would turn possible ice on GJ 9827d into liquid water and water vapor. Any hydrogen present would have been heated, and eventually began to leak from the planet’s atmosphere due to the earth’s relatively low gravity; this leakage may still be occurring as astronomers observe the exoplanet today.
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“Until now, we have not been able to directly detect the atmosphere of such a small planet. And we are now slowly getting into this regime,” said Benneke. “At some point, as we study the smaller planets, there must be a transition where these small worlds no longer have hydrogen, and they have atmospheres more like Venus, which has dioxide carbon over.”
GJ 9827d has been studied with Hubble after marking the planet as a prime target for a follow-up investigation with the James Webb Space Telescope (JWST). This work is already underway, and the $10 billion telescope is able to provide more data about this possible water life.
“GJ 9827d is being observed by JWST to learn more about its atmospheric composition and search for additional molecules such as carbon dioxide,” Kreidberg said. “The observations are ongoing, and we will have more answers soon!
“I hope we can solve the issue of water worlds once and for all.”
The team’s research was published last year in The Astrophysical Journal Letters.
