Researchers Detect Largest, Violent Flare from the Sun’s Nearest Neighbor

Researchers have discovered that the star Proxima Centauri, the closest neighbor of the Sun, emitted the largest flare to be ever recorded.

Headed by the University of Colorado Boulder (CU Boulder), the study could allow scientists to shape the quest for life beyond the solar system of Earth. The findings were recently published in The Astrophysical Journal Letters.

Meredith MacGregor, an astrophysicist from CU Boulder, explained that Proxima Centauri is a tiny but powerful star. It hosts at least two planets and is located only four light-years or over 20 trillion miles from the Sun. One of these planets may resemble something like Earth.

Proxima Centauri is also a “red dwarf” and this term is given to a group of stars that are unusually dim and small. This star has around one-eighth the mass of the Sun. But this can be misleading.

In the latest analysis, MacGregor and her collaborators watched the Proxima Centauri star for a duration of 40 hours with the help of nine telescopes in space and on the ground. During the process, the team got a surprise: Proxima Centauri produced a violent flare or a burst of radiation that starts close to the star surface. This flare is ranked as one of the most powerful to be ever observed in the galaxy.

The star went from normal to 14,000 times brighter when seen in ultraviolet wavelengths over the span of a few seconds.

Meredith MacGregor, Astrophysicist, Department of Astrophysical and Planetary Sciences, University of Colorado Boulder

MacGregor is also an assistant professor at the Center for Astrophysics and Space Astronomy (CASA).

This latest discovery hints at novel physics that could transform the way investigators think about stellar flares and does not bode well for squishy organisms that are sufficiently brave to live close to the volatile star.

“If there was life on the planet nearest to Proxima Centauri, it would have to look very different than anything on Earth. A human being on this planet would have a bad time,” added MacGregor.

Active Stars

For a long time, the star has been a target for investigators who are hoping to detect life beyond the solar system of Earth. For a start, the Proxima Centauri star is very close and it also hosts a solitary planet, called Proxima Centauri b. This planet resides in the so-called “habitable zone”—an area around a star that has the precise temperature range for harboring liquid water on a planet’s surface.

However, there is a twist in the story. Red dwarves, which are ranked as the most common stars in the galaxy, are also unusually lively, added MacGregor.

A lot of the exoplanets that we’ve found so far are around these types of stars. But the catch is that they’re way more active than our sun. They flare much more frequently and intensely.

Meredith MacGregor, Astrophysicist, Department of Astrophysical and Planetary Sciences, University of Colorado Boulder

To observe the number of flares produced by Proxima Centauri, MacGregor and her collaborators pulled off similar to a coup in the domain of astrophysics: they focused nine different instruments at the star for a duration of 40 hours over the course of many months in 2019.

These eyes comprised NASA’s Transiting Exoplanet Survey Satellite (TESS), the Atacama Large Millimeter Array (ALMA), and the Hubble Space Telescope. Five of them captured the giant flare from Proxima Centauri, recording the phenomenon as it created a broad radiation spectrum.

“It’s the first time we’ve ever had this kind of multi-wavelength coverage of a stellar flare. Usually, you’re lucky if you can get two instruments,” added MacGregor.

Crispy Planet

This method provided one of the most comprehensive anatomies of a flare from any star found in the galaxy. On May 1^st, 2019, the team observed the event in question that lasted only 7 seconds. Although it did not create plenty of visible light, it did produce a massive surge in both radio, or “millimeter,” and ultraviolet radiation.

“In the past, we didn’t know that stars could flare in the millimeter range, so this is the first time we have gone looking for millimeter flares,” added MacGregor.

According to her, these millimeter signals could allow scientists to collect more data about how flares are generated by stars. At present, investigators believe that such bursts of energy take place when magnetic fields close to the surface of a star twist and snap with violent consequences.

On the whole, the observed flare was around 100 times stronger than any analogous flare observed from the Sun. In due time, this energy can remove the atmosphere of a planet and may even expose life forms to harmful radiations.

This kind of flare may not be a rare event on the Proxima Centauri star. Apart from the big boom that occurred in May 2019, the team captured several other flares during the 40-hour period they spent observing the star.

Proxima Centauri’s planets are getting hit by something like this not once in a century, but at least once a day if not several times a day.

Meredith MacGregor, Astrophysicist, Department of Astrophysical and Planetary Sciences, University of Colorado Boulder

The results indicate that there might be more surprises in store from the nearest companion of the Sun.

“There will probably be even more weird types of flares that demonstrate different types of physics that we haven’t thought about before,” concluded MacGregor.

Other co-authors of the new study include Steven Cranmer, associate professor in APS and the Laboratory for Atmospheric and Space Physics (LASP) at CU Boulder; Adam Kowalski, assistant professor in APS and LASP at CU Boulder and also from the National Solar Observatory; Allison Youngblood, a research scientist from LASP; and Anna Estes, undergraduate research assistant in APS.

The study was funded by the Carnegie Institution for Science, Arizona State University, NASA Goddard Spaceflight Center, the University of Maryland, the University of North Carolina at Chapel Hill, the University of Sydney, CSIRO Astronomy and Space Science, Space Telescope Science Institute, Johns Hopkins University, the Center for Astrophysics | Harvard & Smithsonian, and the University of British Columbia.

Journal Reference:

MacGregor, M. A., et al. (2021) Discovery of an Extremely Short Duration Flare from Proxima Centauri Using Millimeter through Far-ultraviolet Observations. The Astrophysical Journal Letters. doi.org/10.3847/2041-8213/abf14c.