The James Webb Space Telescope (JWST) from the United States has succeeded in observing water vapor around an exoplanet outside the solar system. Still, there is still work to be done to determine if the water vapor comes from the planet, or the star the planet orbits. However, researchers expect that this discovery will be a breakthrough in the search for other planets where life can live outside the solar system.
Researchers from the National Aeronautics and Space Administration (NASA), the University of Arizona, the Johns Hopkins Institute for Astrophysics, the University of Michigan, the University of Bristol in the UK, and the University of Imperial College London reported on the 1st that the James Webb Space Telescope is orbiting a dwarf red 26 light years away from Earth in the direction of Virgo. It has been reported that water vapor is trapped in the atmosphere of a hot rocky planet (GJ486b).
James Webb is the largest space telescope ever developed by the United States, Europe and Canada at a cost of 13 trillion won over 25 years. It was launched into space on Christmas Day 2021 and reached an observation point 1.5 million kilometers from Earth in January last year. The full-scale space observation began in July last year.
The planet on which water vapor was discovered is estimated to be a third the size of Earth, but three times the mass. It has so far been confirmed that it only takes 1.5 Earth days to orbit the red dwarf. Because the planet orbits very close to the star, its surface temperature reaches 430 degrees and water evaporates, making it a difficult environment to exist in. The red dwarf that this planet orbits is also statistically the most common form of a rocky planet like GJ486b orbiting a common star in the universe.
Also, because red dwarfs are cooler than other types of stars, planets orbiting them must orbit close enough to keep the temperature warm enough to hold water, which is an essential element for life . However, because red dwarfs emit powerful ultraviolet and X-rays during the early stages of their birth, they blow up the atmospheres of nearby planets, making it difficult for life to exist.
Scientists are focusing on finding out if rocky planets in these harsh environments can form atmospheres and maintain them long enough to support life on Earth for about a billion years.
The research team pointed the near-infrared spectrometer (NIRSpec), a science probe of the James Webb Space Telescope, at GJ486b and saw the planet crossing or passing through the surface of the star. The research team found traces of water vapor even in an environment where water is difficult to exist.
As the planet orbits in front of a red dwarf, the star shines through its atmosphere. Because different elements and compounds absorb and emit different wavelengths of light, the light emitted by a planet as it travels around a star can reveal the composition of its atmosphere. Finding these ‘chemical fingerprints’ in starlight filtered through a planet’s atmosphere is called transmission spectroscopy.
The research team observed GJ486b twice, and each time the planet passed they found that the star was only an hour away. The team analyzed the data collected using three far-field methods and found a spectral pattern with interesting peaks in the short-wave infrared. Scientists determined that water vapor was the likely cause of the peak.
“We’re pretty sure that the signal we found this time definitely indicates water,” said Sarah Moran, a professor at the University of Arizona.
In fact, water vapor has been found in sunspots of stars before. Also found on the Sun, these sunspots are dark, cool stellar regions that form when a dense magnetic field rises to the surface from deep within a star. These sunspots are responsible for phenomena such as solar flares and coronal mass ejections (CMEs). The research team believe that the red dwarf, the mother star of GJ486b, has a lower temperature than the sun, but it is likely that water vapor is concentrated in the sunspot region, and this may have formed water vapor around the planet.
Professor Ryan MacDonald of the University of Michigan said, “We have not seen the planet cross a sunspot while passing through a red dwarf, but it is difficult to be certain that this star does not have a sunspot.”
The research team estimates that if there is an atmosphere on this planet, it may be continuously destroyed by the radiation from the red dwarf, and the water vapor that is ejected through the volcanic activity of the inside the planet adding to it.
The scientific world believes that additional observations will be needed to determine whether the water vapor captured by the James Webb Space Telescope came from an exoplanet’s atmosphere and how much water exists. The research team decided to use the mid-infrared telescope (MIRI) on the James Webb Space Telescope to investigate the surface of the planet that faces the star permanently. In the future, the research team said they would integrate multiple instruments to determine whether the planet has an atmosphere.
This research was approved for publication in the astrophysical journal Letters and published on the archive (arXiv.org), a pre-publication site for a thesis.
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arXiv, DOI: https://doi.org/10.48550/arXiv.2305.00868
