Astronomers have zeroed in on a world they believe could have the right conditions for a thick atmosphere and an ocean half the size of the Atlantic.
exoplanet – a world revolving around a star other than the sun – is LHS 1140 b, and is about 48 light-years away from Earth, in the constellation Cetus. The planet is slightly less than twice the size of Earth.
A team of scientists noted The James Webb Space Telescope at LHS 1140 b twice in December 2023. Using a special instrument called a spectrograph on the powerful telescope, which is a collaboration between NASA and its European and Canadian ROOM counterparts, they looked for signs of an atmosphere.
“LHS 1140 b is one of the best small exoplanets in the habitable zone capable of supporting a thick atmosphere,” said University of Michigan-based exoplanet study co-author Ryan MacDonald. STATEMENT“and we just might have found evidence of air on this world.”
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The James Webb Space Telescope has observed the exoplanet LHS 1140 b, which may be an icy world similar to Jupiter’s moon Europa, left, or may have a bull’s-eye ocean in front of its star.
Credit: B. Gougeon / Université de Montréal illustration
Exoplanet hunters have invented names for different types of planets. Many of the known worlds travel in tight circles around their host stars. The smaller planets are mainly divided into two groups, known as super-Earths and mini Neptunes. Although both types are larger than Earth and smaller than Neptune, super-Earths can be up to 1.75 times the size of our planet, while mini-Neptunes are two to four times the size of Earth.
The team’s goal was to determine whether LHS 1140 b was a hydrogen-rich mini-Neptune or a scaled-down version of Earth. covered with water and ice. Their study immediately ruled out mini-Neptune because LHS 1140 bi lacked the features of a large, puffy atmosphere. This means that the exoplanet could be rocky and have other similarities to our planet.
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“But can we say anything about the atmospheric composition of this super-Earth?” MacDonald said on X, formerly Twitter. “This is where things get really exciting.”
The researchers’ analysis found possible evidence that the planet has a thick, nitrogen-rich atmosphere like Earth’s, which is 78 percent nitrogen. The result of the study, accepted for RELEASE IN The Astrophysical Journal Letterscomes from a technique called transmission spectroscopy.
This method studies starlight filtered through the planet’s atmosphere. Molecules within the atmosphere absorb certain wavelengths of light, or colors. By splitting light like a prism into its basic parts—a rainbow—astronomers can discover which segments of light are missing to understand the composition of an atmosphere.
LHS 1140 b rotates a red dwarf star – a star much smaller and cooler than the sun – at a distance that would probably cause the planet’s surface to freeze. But if LHS 1140 b had an atmosphere, the world could experience a greenhouse effect, making a liquid ocean possible. The team also found that the exoplanet is less massive than expected, possibly indicating that 10 to 20 percent of it is water by weight.
“We just might have found evidence of air on this world.”
Most astronomers agree that knowing what’s inside the atmosphere of another planet is crucial in the search for habitable worlds. NASA has jokingly called Earth’s atmosphere its “security blanket”: without it, the kind of life that thrives here wouldn’t exist. This cocoon holds oxygen in the air and filters out harmful ultraviolet radiation from the sun, keeping our world warm. Additionally, it creates pressure that allows liquid water to exist on the surface.
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Scientists have found signs of atmospheres surrounding many exoplanets over the past 20 years, but they have all been gas giant planetsHOW Jupiter, with an envelope composed mainly of hydrogen. The hunt for an Earth-like world wrapped in a protective atmosphere has so far eluded astronomers, but Webb has recently helped scientists find candidates such as 55 Cancer of OR GJ 486banother exoplanet study that MacDonald co-authored.
The team’s analysis of LHS 1140 b suggests that this exoplanet is an icy world with a bull’s-eye ocean about 2,500 miles wide on the side that always faces its star. The surface temperature in the center of the ocean can be close to a cool 68 degrees Fahrenheit.
“We will need years of additional observations to provide a concrete detection of an atmosphere in LHS 1140b,” MacDonald said at X, “but it is promising that the initial detection is paying off!”