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Space NASA

James Webb Space Telescope Detects Water Vapor Around Alien Planet (space.com) 25

The James Webb Space Telescope (JWST) has detected water vapor around a distant rocky planet located 26 light-years away. "The water vapor could indicate the presence of an atmosphere around the extrasolar planet, or exoplanet, a discovery that could be important for our search for habitable worlds outside the solar system," reports Space.com. "However, the scientists behind the discovery caution that this water vapor could be coming from the world's host star rather than the planet itself." From the report: The exoplanet, designated GJ 486 b, orbits a red dwarf star located 26 light-years away in the Virgo constellation. Although it has three times the mass of Earth, it is less than a third the size of our planet. GJ 486 b takes less than 1.5 Earth days to orbit its star and is probably tidally locked to the red dwarf, meaning it perpetually shows the same face to its star.

Red dwarfs like the parent star of GJ 486 b are the most common form of stars in the cosmos, meaning that statistically speaking, rocky exoplanets are most likely to be found orbiting such a stellar object. Red dwarf stars are also cooler than other types of stars, meaning that a planet must orbit them tightly to remain warm enough to host liquid water, a vital element needed for life. But, red dwarfs also emit violent and powerful ultraviolet and X-ray radiation when they are young that would blast away the atmospheres of planets that are too close, potentially making those exoplanets very inhospitable to life.

That means astronomers are currently keen to discover if a rocky planet in such a harsh environment could manage to both form an atmosphere and then hang on to it long enough for life to take hold, a process that took around a billion years on Earth. [...] Even though GJ 486 b's host star is cooler than the sun, water vapor could still concentrate in starspots. If that is the case, this could create a signal that mimics a planetary atmosphere. If there is an atmosphere around GJ 486 b, then radiation from its red dwarf parent star will constantly erode it, meaning it has to be replenished by steam from the exoplanet's interior ejected by volcanic activity.
The research appears in a paper on arXiv while it awaits publication in the journal Astrophysical Journal Letters. You can read more about it via NASA.
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James Webb Space Telescope Detects Water Vapor Around Alien Planet

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  • by Viol8 ( 599362 ) on Wednesday May 03, 2023 @07:17AM (#63493656) Homepage

    "Although it has three times the mass of Earth, it is less than a third the size of our planet."

    Wtf?? Assuming a third the size means a 3rd the radius then it has 3 times the mass in 1/28th the volume which means its 84 times denser! There is no known substance of that density that can exist other than the cores of stars or white dwarf material so WTF is it? It certainly isn't a "rocky" planet!

    • by Ormy ( 1430821 )
      A third of the size could mean a third of earth's volume, so the mean density would only need to be 9x that of earth. However that figure is still roughly double the density of the most dense elements such as platinum/iridium/osmium. So still WTF?
    • Re:Density!! (Score:4, Informative)

      by mistergrumpy ( 7379416 ) on Wednesday May 03, 2023 @07:32AM (#63493680)
      Lousy journalism - 2.8 earh masses, 1.3 earth radii according to this [nasa.gov]. So "less than a third bigger than our planet"

      Unless it was written by a hallucinating AI.
    • It's probably an inaccurate figure, but theoretically you can have really dense small planets if gas giants are stripped to their cores. Not that dense though. It would be rebound without the pressure.
    • by minkwe ( 222331 )

      A planet 1.3 x The earth's radius would have a mass of 2.2 x Earth's mass. At 2.8, the density is only 1.2x that of the earth. Given the low precision of all the numbers, I won't be surprised if it was actually just the same density as Earth.

  • With an optical angular resolution of about a tenth of an arc-second (i.e., about one thirteen millionth of tau), looking at an object 26 light years away, back-of-the-envelope trigonometry says each individual pixel in the image is going to represent an area 148 million miles across. In other words, if the planet is far enough away from the star to be in a distinct pixel, and the star in question is similar to the sun, it's definitely too cold out there for water vapor to exist, even in a vacuum. It woul
    • each individual pixel in the image is going to represent an area 148 million miles across.

      By coincidence, that's pretty close to 1.0 AU (the average distance from Sun to Earth). Probably just coincidence though.

      However, the given (TFS) orbital period of the planet of 1.5 days would require a "star" mass of (mental calculation from Kepler's laws) about 200 solar masses. Which would be a bright star. Certainly a candidate for the largest star in the Milky Way (caveats : known to this date ; not enveloped in

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