Astronomers have a new way of studying stars: to take advantage of meteorological satellites orbiting the Earth.
This is the conclusion of a new article that presents new data from a Japanese meteorological satellite that happened to observe the red supergiant star. Betelgeuse during a period of unexplained darkening. Random observations could be a new tool for astronomers trying to understand how a red supergiant star loses too much and eventually explodes as supernova.
The second brightest star in the world constellation of Orion, Betelgeuse (pronounced “bet-orl-gerz” or “beetlejuice”) is the 10th brightest star in the night sky. But from October 2019 to February 2020, it was drastically reduced to about two-thirds of its normal brightness. This so-called “great attenuation” event led to speculation that it was about to explode like what scientists call an IIP-type supernova, which it will certainly do in the next 100,000 years.
Related: Orion and his dark star Betelgeuse shine on a star observer in this sentimental photo of the night sky
The scientists who analyzed the event mainly used data from terrestrial optical telescopes. Astronomers mainly concluded that Betelgeuse’s darkening was the result of its surface cooling, a new band of dust forming around it, or both.
Terrestrial telescopes cannot see through the dust and gas of the cosmos, which requires infrared vision. This is because Earth’s atmosphere it blocks infrared radiation as well as X-rays, gamma rays and most ultraviolet rays. Therefore, only space observatories can see infrared light, and this includes weather satellites such as Himawari-8 (opens in a new tab), one of the geostationary meteorological satellites of the Japan Meteorological Agency.
And Himawari-8’s astrophysics debut began in an unlikely place: Twitter.
“We saw a tweet saying the moon was in his pictures,” Daisuke Taniguchi, Ph.D. astronomy student at the University of Tokyo and first author of the paper, he told Space.com. “I chatted with [third author] Shinsuke One on the use of meteorological satellites for astronomy, found that Betelgeuse was in the field of view of Himawari-8 and realized that perhaps the Great Darkening of Betelgeuse could be investigated. “
Himawari-8 has been located at 22,236 miles (35,786 kilometers) above the Earth’s equator since 2015 to study weather and natural disasters (including the eruption of the Hunga Tonga-Hunga Haʻapai volcano on January 15). Although the satellite is up there to photograph the Earth every 10 minutes, the edges of its images include stars.
Taniguchi and his colleagues were able to see Betelgeuse in images taken throughout the life of Himawari-8 and measured its brightness approximately every 1.7 days between January 2017 and June 2021. And the Advanced Himawari The satellite imager (AHI) studied Betelgeuse in two ways.
“In the near optical and infrared wavelength ranges, the circumstellar dust obscures the light from the stellar surface,” Taniguchi said, explaining that researchers, such as astronomers limited to using terrestrial telescopes, were able to estimate the amount of circumstellar. dust around Betelgeuse.
However, the circumstellar dust only emits light from infrared media. “By observing this medium infrared light we can see the dust itself and we can directly measure the time series of the amount of dust around Betelgeuse,” Taniguchi said. The team concluded that the “big blackout” of 2019 and 2020 was caused by two factors in almost equal proportion: the star’s temperature dropped by about 250 degrees Fahrenheit (140 degrees Celsius) and the dust went condensate of hot gas around the star.
Crucially, this theory agrees with the findings of astronomers using terrestrial telescopes. For example, a study conducted by the Chinese Academy of Sciences cites a giant sunspots and temperature fluctuations while results the Very Large Telescope of the Southern European Observatory in Chile and the Hubble Space Telescope suggested Betelgeuse expelled a huge cloud of gas that cooled and condensed into dust.
Scientists’ new findings suggest that meteorological satellites could be used as space telescopes for astronomy. “It allows us to obtain high-frequency time series of medium-infrared images, which are difficult to acquire with the usual astronomical instruments,” the document says. In addition to not being able to record near-infrared data, terrestrial telescopes lose sight of some stars for a few months as the sun drifts in front of them.
“This is a possibility I haven’t seen much explored before,” Emily Levesque, author of The Last Stargazers and an astronomer focused on red supergiant stars at the University of Washington who did not participate in the new research, told the space. . how.
“It certainly depends in part on serendipity, but observations like these could turn out to be a fabulous resource for bright, close red supergiants,” he said. “Especially because they could complement the upcoming capabilities of the James Webb Space Telescopewhich is very suitable for observations of more faint objectives. ”
Observing stars in the middle infrared is the best way to directly observe the emission of dust around them, Levesque said, because it can help create a multi-wavelength image of massive stars. its evolution. After all, mass loss and dust production play a key role in the red supergiant stage of a star.
“The average infrared has also been historically difficult to observe,” he said, adding that NASA will soon be shut down. SOFIA The airborne observatory has filled a void, while JWST will soon become an invaluable medium-sized infrared resource. “Combined with creative solutions like the ones presented in this paper, we look forward to continuing to build a much clearer view of red supergiants in this wavelength range in the coming years.”
The authors have already started using Himawari-8 data for other stellar projects. “I think our concept of using a weather satellite as a space telescope is useful for a variety of topics in astronomy, especially in stellar astrophysics of the time domain,” Taniguchi said. in the emerging area focused on how astronomical objects change over time. . His group is using Himawari-8 data to make a catalog of how older stars vary in infrared brightness over time and also to look for fleeting infrared signals.
Around 548 light-years away (opens in new tab), Betelgeuse is the closest red supergiant star to the solar system. It is 15 to 20 times the mass of the sun and about 900 times larger. If the giant were at the center of our solar system, then Mercury, Venus, Earth, Mars, and the asteroid belt would be inside Betelgeuse.
And whenever Betelgeuse becomes a supernova, it could glow as bright as a full moon for a few months. The end result will be a neutron star in the center of a beautiful bubble of bright material created by the explosion. However, scientists still don’t know exactly how a red supergiant star behaves in the weeks before it explodes.
The search is described in aa paper (opens new tab) published Monday (May 30) in the journal Nature Astronomy.
Jamie Carter is the author of “A star-watching program for beginners (opens in a new tab) “(Springer, 2015) and edit WhenIsTheNextEclipse.com. Follow him on Twitter @jamieacarter. follow us on Twitter @Spacedotcom or on Facebook.