Exoplanets: The search for habitable planets has just narrowed


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The hunt for life-sustaining planets it may just be significantly reduced.

Scientists have long hoped and theorized that the most common type of star in our universe—called an M dwarf—could host nearby planets with atmospheres that are potentially carbon-rich and perfect for life. But in a new study of a world orbiting an M dwarf 66 light-years from Earth, researchers found no signs of such a planet supporting an atmosphere.

Without a high-carbon atmosphere, it is unlikely that a planet would be hospitable to life. Carbon molecules are ultimately considered the building blocks of life. And the findings don’t bode well for other types of planets orbiting M dwarfs, said study author Michelle Hill, a planetary scientist and doctoral student at the University of California, Riverside.

“The radiation pressure from the star is enormous, enough to explode a planet’s atmosphere,” Hill said in a post on the university’s website.

M dwarf stars are known to be volatile, emitting solar flares and throwing radiation at nearby celestial bodies.

But for years, the hope was that the relatively large planets orbiting M dwarfs might be in the Golden Kidney environment, large enough to be close enough to their tiny star to keep it warm and clinging to its atmosphere.

The nearby M dwarf, however, may be too intense to maintain an intact atmosphere, according to new research published in The Astrophysical Journal Letters.

A similar phenomenon occurs in our solar system: the Earth’s atmosphere is also damaged by the explosion of the stars around it, the sun. The difference is that the Earth has enough volcanic and other gas-emitting activity to replace the loss of the atmosphere and make it nearly undetectable, according to the study.

However, the M dwarf planet analyzed in the study, GJ 1252b, “could have 700 times more carbon than Earth, and still not have an atmosphere. It would build up at first, but then shrink and erode,” study author and UC Riverside astrophysicist Stephen Kane said in a news release.

GJ 1252b orbits less than a million kilometers from its home star, named GJ_1252. The planet reaches a sweltering daily temperature of 2,242 degrees Fahrenheit (1,228 degrees Celsius), according to the study.

The planet’s existence was first suggested by NASA’s Transiting Exoplanet Survey Satellite, or TESS, mission. Astronomers then ordered the nearly 17-year-old Spitzer Space Telescope to look around in January 2020, less than 10 days before Spitzer was to be turned off for good.

The investigation into whether GJ 1252b had an atmosphere was led by astronomer Ian Crossfield of the University of Kansas and involved a collection of researchers from UC Riverside, NASA’s Jet Propulsion Laboratory, Caltech, University of Maryland, Carnegie Institution for Science, Max Planck. Institute of Astronomy, McGill University, University of New Mexico and University of Montreal.

They analyzed the data produced by Spitzer, looking for signatures of emissions or signs that a gas bubble could have engulfed the planet. The telescope caught the planet as it passed behind its home star, allowing researchers to “look at the starlight as it passes through the planet’s atmosphere,” giving it “a spectral signature of the atmosphere,” or lack thereof, Hill said.

Hill added that he wasn’t surprised to find no sign of the atmosphere, but he was disappointed. It’s looking for moons and planets in “habitable zones,” and the results have made seeing worlds orbiting the ubiquitous M dwarf stars a little less interesting.

Researchers hope to shed even more light on these types of planets with the help of the James Webb Space Telescope, the most powerful space telescope to date.

Webb will soon set its sights on the TRAPPIST-1 system, “which is also an M dwarf star with a bunch of rocky planets around it,” Hill said.

“There is great hope that it will be able to tell us whether these planets have an atmosphere around them,” he added. “I guess M dwarf fans are probably holding their breath right now to find out if there is an atmosphere around these planets.”

However, there are still many interesting places to hunt for habitable worlds. In addition to looking at planets further away from M dwarfs that may be more likely to harbor atmospheres, there are still about 1,000 stars like the sun relatively close to Earth that orbit their planets in habitable zones, according to a UC Riverside publication about the study. .