Scientists have spotted the largest eruption on record from the sun’s closest neighbor, the star Proxima Centauri.
The research, which appears today in Letters from the astrophysical journal, was led by the University of Colorado at Boulder and could help shape the hunt for life beyond the Earth’s solar system.
UC Boulder astrophysicist Meredith MacGregor explained that Proxima Centauri is a small but powerful star. It is just four light years or more than 20 trillion kilometers from our own sun and is home to at least two planets, one of which may resemble Earth. It is also a “red dwarf,” the name of a class of stars that are unusually small and dark.
Proxima Centauri has about one eighth the mass of our own sun. But don’t be fooled.
In their new study, MacGregor and his colleagues observed Proxima Centauri for 40 hours using nine telescopes on the ground and in space. In the process, they got a surprise: Proxima Centauri ejected a flare, or burst of radiation that begins near a star’s surface, which ranks among the most violent seen in the galaxy.
“The star went from normal to 14,000 times brighter when viewed in ultraviolet wavelengths within seconds,” said MacGregor, assistant professor at the Center for Astrophysics and Space Astronomy (CASA) and the Department of Astrophysical and Planetary Sciences (APS) at CU Boulder.
The team’s findings suggest new physics that could change the way scientists think about stellar eruptions. They also don’t bode well for any spongy organism brave enough to live near the volatile star.
“If there was life on the planet closest to Proxima Centauri, it would have to be very different from anything on Earth,” MacGregor said. “A human being on this planet would have a hard time.”
The star has long been a target for scientists hoping to find life beyond Earth’s solar system. Proxima Centauri is nearby, for starters. It is also home to a planet, designated Proxima Centauri b, which resides in what researchers call the “habitable zone” – a region around a star that has the right temperature range to harbor liquid water on the surface of it. ‘a planet.
But there’s a twist, MacGregor said: Red dwarfs, which rank among the most common stars in the galaxy, are also unusually alive.
“A lot of the exoplanets we’ve found so far are around these types of stars,” she said. “But the catch is, they are much more active than our sun. They are blazing much more frequently and intensely.”
To see how much Proxima Centauri is breaking out, she and her colleagues pulled off what looks like a coup in astrophysics: They pointed nine different instruments at the star for 40 hours over the course of several months in 2019. Those eyes included NASA’s Hubble Space Telescope, Atacama Large Millimeter Array (ALMA), and Transiting Exoplanet Survey Satellite (TESS). Five of them recorded the massive Proxima Centauri rocket, capturing the event as it produced a broad spectrum of radiation.
“This is the first time we’ve had this kind of multi-wavelength coverage of a stellar rocket,” MacGregor said. “Usually you’re lucky if you can get two instruments.
The technique has delivered one of the most in-depth anatomies of a rocket lit by any star in the galaxy.
The event in question was observed on May 1, 2019 and lasted only 7 seconds. Although it didn’t produce much visible light, it did generate a huge surge of ultraviolet and radio radiation, or “millimeters.”
“In the past, we didn’t know stars could blaze by the millimeter, so this is the first time we’ve looked for millimeter flares,” MacGregor said.
These millimeter signals, MacGregor added, could help researchers gather more information about how stars generate flares. Currently, scientists suspect that these bursts of energy occur when magnetic fields near a star’s surface twist and break with explosive consequences.
In all, the observed rocket was about 100 times more powerful than any other similar eruption seen from the sun of Earth. Over time, such energy can strip a planet’s atmosphere and even expose life forms to deadly radiation.
This type of push is perhaps not uncommon on Proxima Centauri. In addition to the big boom of May 2019, researchers recorded many other flares in the 40 hours of staring at the star.
“The planets of Proxima Centauri are affected by something like this not once a century, but at least once a day, if not several times a day,” MacGregor said.
The results suggest that there may be more surprises in store from the companion closest to the sun.
“There will probably be even weirder types of flares that demonstrate different types of physics that we hadn’t thought of before,” MacGregor said.