Scientists have noticed the largest glare ever recorded by the nearest solar neighbor, the star Proxime Centauri.
The research that appears today in The Astrophysical Journal Letters, was run by the University of Colorado Boulder and could help shape the hunt for life outside the Earth’s solar system.
CU Boulder astrophysicist Meredith MacGregor explained that Proxima Centauri is a small but powerful star. It is located just four light-years or more than 20 trillion miles from our own sun and houses at least two planets, one of which may look something like Earth. It is also “red dwarf”, a name for a class of stars that are unusually tiny and cloudy.
Proxima Centauri has about one-eighth the mass of our own sun. But don’t let that fool you.
In their new study, MacGregor and her colleagues observed Proxima Centauri for 40 hours using nine telescopes on earth and in space. In the process, they got a surprise: Proxima Centauri ejected a torch or burst of radiation that begins near the surface of the star, which ranks among the most violent seen anywhere in the galaxy.
“The star has become normal up to 14,000 times brighter when viewed in ultraviolet wavelengths ranging from a few seconds,” said MacGregor, an assistant professor at the Center for Astrophysics and Space Astronomy (CASA) and the Department of Astrophysics and Planetary Sciences (APS) at CU Boulder.
The team’s findings suggest new physics that could change the way scientists think about stellar flashes. They also do not bode well for any squishy organism brave enough to live near a volatile star.
“If there was life on the planet closest to Proxima Centauri, it would have to look completely different from anything on Earth,” MacGregor said. “A man on this planet would have a bad time.”
The star has long been the target of scientists hoping to find life outside the Earth’s solar system. Proxima Centauri is nearby, for starters. It also hosts one planet, called Proxima Centauri b, which is located in what researchers call the “habitable zone” – the region around the star that has the appropriate temperature range to retain liquid water on the planet’s surface.
But there is a reversal, MacGregor said: Red dwarfs, which rank among the most common stars in the galaxy, are also unusually vibrant.
“A lot of the exoplanets we’ve found so far are around these types of stars,” she said. “But the catch is that they’re much more active than our sun. They flash much more often and more intensely.”
To see how much Proxima Centauri blazed, she and her colleagues performed what was approaching a coup in the field of astrophysics: They aimed nine different instruments at a star for 40 hours over several months in 2019. Those eyes included the Hubble Space Telescope, a large millimeter array Atacama (ALMA) and NASA’s exoplanet transit satellite (TESS). The five of them recorded a massive torch from Proxime Centauri, recording the event because it produced a wide range of radiation.
“It’s the first time we’ve had this kind of multi-wavelength coverage of a stellar torch,” MacGregor said. “You’re usually lucky if you can get two instruments.”
The technique provided one of the deepest flash anatomies of any star in the galaxy.
The event in question was recorded on May 1, 2019 and lasted only 7 seconds. Although it did not produce much visible light, it generated a huge wave of both ultraviolet and radio, or “millimeter” radiation, respectively.
“In the past, we didn’t know that stars could flash in the millimeter range, so this is the first time we’ve looked for millimeter flashes,” MacGregor said.
These millimeter signals, MacGregor added, could help researchers gather more information about how stars generate flashes. Currently, scientists suspect that these bursts of energy occur when magnetic fields near the star’s surface twist and burst with explosive consequences.
All in all, the observed reflection was approximately 100 times stronger than any similar chimney seen from the Earth’s sun. Over time, such energy can take away the planet’s atmosphere and even expose life forms to deadly radiation.
This type of torch may not be a rare occurrence on Proxima Centauri. In addition to the big boom in May 2019, researchers recorded many other torches during the 40 hours spent watching the star.
“The planets of Proxime Centauri hit something like this not once a century, but at least once a day, if not several times a day,” MacGregor said.
The findings suggest that more surprises may be being prepared from the nearest solar companion.
“There will probably be even stranger types of torches that show different types of physics that we haven’t thought about before,” MacGregor said.