Proxima Centauri's no good, very bad day

February 26, 2018, Carnegie Institution for Science
The brightness of Proxima Centauri as observed by ALMA over the two minutes of the event on March 24, 2017. The massive stellar flare is shown in red, with the smaller earlier flare in orange, and the enhanced emission surrounding the flare that could mimic a disk in blue. At its peak, the flare increased Proxima Centauri's brightness by 1,000 times. The shaded area represents uncertainty. Credit: Meredith MacGregor

A team of astronomers led by Carnegie's Meredith MacGregor and Alycia Weinberger detected a massive stellar flare—an energetic explosion of radiation—from the closest star to our own Sun, Proxima Centauri, which occurred last March. This finding, published in Astrophysical Journal Letters, raises questions about the habitability of our Solar System's nearest exoplanetary neighbor, Proxima b, which orbits Proxima Centauri.

MacGregor, Weinberger and their colleagues—the Harvard-Smithsonian Center for Astrophysics' David Wilner and Adam Kowalski and Steven Cranmer of the University of Colorado Boulder—discovered the enormous flare when they reanalyzed observations taken last year by Atacama Large Millimeter/submillimeter Array, or ALMA, a radio telescope made up of 66 antennae.

At peak luminosity it was 10 times brighter than our Sun's largest flares when observed at similar wavelengths. Stellar flares have not been well studied at the wavelengths detected by ALMA, especially around of Proxima Centauri's type, called M dwarfs, which are the most common in our galaxy.

"March 24, 2017 was no ordinary day for Proxima Cen," said lead author MacGregor.

The flare increased Proxima Centauri's brightness by 1,000 times over 10 seconds. This was preceded by a smaller flare; taken together, the whole event lasted fewer than two minutes of the 10 hours that ALMA observed the star between January and March of last year.

Stellar flares happen when a shift in the star's magnetic field accelerates electrons to speeds approaching that of light. The accelerated electrons interact with the highly charged plasma that makes up most of the star, causing an eruption that produces emission across the entire electromagnetic spectrum.

Proxima Centauri's no good, very bad day
An artist's impression of a flare from Proxima Centauri, modeled after the loops of glowing hot gas seen in the largest solar flares. An artist's impression of the exoplanet Proxima b is shown in the foreground.Proxima b orbits its star 20 times closer than the Earth orbits the Sun. A flare 10 times larger than a major solar flare would blast Proxima b with 4,000 times more radiation than the Earth gets from our Sun's flares. Credit: Roberto Molar Candanosa / Carnegie Institution for Science, NASA/SDO, NASA/JPL

"It's likely that Proxima b was blasted by high energy radiation during this flare," MacGregor explained, adding that it was already known that Proxima Centauri experienced regular, although smaller, x-ray flares. "Over the billions of years since Proxima b formed, flares like this one could have evaporated any atmosphere or ocean and sterilized the surface, suggesting that habitability may involve more than just being the right distance from the host star to have liquid water."

A November paper that also used these ALMA data interpreted its average brightness, which included the light output of both the star and the flare together, as being caused by multiple disks of dust encircling Proxima Centauri, not unlike our own Solar System's asteroid and Kuiper belts. The authors of that study said that the presence of dust pointed to the existence of more planets or planetary bodies in the stellar system.

But when MacGregor, Weinberger, and their team looked at the ALMA data as a function of observing time, instead of averaging it all together, they were able to see the transient explosion of radiation emitted from Proxima Centauri for what it truly was.

"There is now no reason to think that there is a substantial amount of dust around Proxima Cen," Weinberger said. "Nor is there any information yet that indicates the star has a rich planetary system like ours."

Artist animation of a red dwarf star similar to Proxima Centauri, the nearest star to our sun. New analysis of ALMA observations reveal that Proxima Centauri emitted a powerful flare that would have created inhospitable conditions for planets in that system. Credit: NRAO/AUI/NSF

Explore further: ALMA discovers cold dust around nearest star

More information: Meredith A. MacGregor et al. Detection of a Millimeter Flare from Proxima Centauri, The Astrophysical Journal (2018). DOI: 10.3847/2041-8213/aaad6b

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17 comments

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gkam
3 / 5 (4) Feb 26, 2018
There goes my idea of owning land on that planet.
jonesdave
3 / 5 (2) Feb 26, 2018
There goes my idea of owning land on that planet.


Oh, it's still available at knock down prices. Just pm me for the price list. I've also got a bridge that I need to sell........
dfjohnsonphd
4.5 / 5 (2) Feb 26, 2018
Anybody know the dynamics of small stars? Are red dwarfs more likely to send off giant flares than larger stars? They certainly are right about it not being a good place to spend time developing an evolutionary ladder. Probably not possible if these flares have been going on for a long time. No life could survive such a blistering, much less even get started.

Does anyone know if Proxima Centauri is gravitationally bound to the A and B stars. I have read that it is not certain, and could simply be a red dwarf passing close to these two. Perhaps not enough time has passed for us to make this clear determination.
Anonym983715
4.3 / 5 (3) Feb 26, 2018
Wait... this event happened in March of Last year? so... around 11 months ago?

But proxima centauri is a little over 4 light years away... so how did they manage to detect it in only 11 months? :)

Unless they mean that it happened a little over five years ago (as of today), and the light waves arrived last March...

Just wondering.
carbon_unit
5 / 5 (4) Feb 26, 2018
Are red dwarfs more likely to send off giant flares than larger stars?
Seemingly yes. https://en.wikipe..._systems
Does anyone know if Proxima Centauri is gravitationally bound to the A and B stars.
The Wikipedia entry says it is bound. https://en.wikipe...Centauri

There goes the story line for Steven Baxter's "Proxima". (Still very a good read.)
Da Schneib
4.4 / 5 (7) Feb 26, 2018
@Anon, the timing of events in astronomy, particularly in popular science articles, is the observed time, not adjusted for distance. What they're saying is that the light from the flare arrived eleven months ago, and they didn't find out until they checked the data. Data analysis can take quite a while.
jonesdave
3 / 5 (2) Feb 26, 2018
There goes the story line for Steven Baxter's "Proxima". (Still very a good read.)


Agreed. Also enjoyed his 'Northland' trilogy. Alternate history stuff.
delkin1
5 / 5 (1) Feb 26, 2018
For fans of Chixin Liu's Three Body Problem SF trilogy: Wonder if the Trisolarans are ok?
(If you're not familiar with the series, it's relevant to the article and comments--and worth reading).
On a more scientific note, this article made me grateful that we are living in a solar system with a stable sun!
dfjohnsonphd
5 / 5 (2) Feb 26, 2018
Stable stars appear to be highly desirable for life. I have been looking at data on all different kinds of stars, from red dwarfs to hyper-giants. Most look like pretty nasty places for finding any "habitable zones".

Clearly stability needs to be very long term if you expect to find life, at least advanced life. (Not sure if that includes humans.) Models based on earth would likely require several billion years of stability at the very least. And that with all the mass extinction events for whatever reason.

Someone noted they were grateful to be near a stable star. From what I am reading, you wouldn't never have existed to express such a sentiment if you were not!
Da Schneib
3.7 / 5 (3) Feb 26, 2018
@drjohnson, seems like stars near the center of the HR main sequence are more stable than ones that aren't.
rubiks6
4 / 5 (1) Feb 26, 2018
Wait... this event happened in March of Last year? so... around 11 months ago?

But proxima centauri is a little over 4 light years away... so how did they manage to detect it in only 11 months? :)

Unless they mean that it happened a little over five years ago (as of today), and the light waves arrived last March...

Just wondering.

---
Dude - don't you know about simultaneity?
gkam
1 / 5 (2) Feb 27, 2018
How lucky can we be?
dfjohnsonphd
not rated yet Feb 27, 2018
How lucky can we be?

It isn't over yet, but when it is, we might not be so lucky.

rrwillsj
3.8 / 5 (4) Feb 27, 2018
Yep, stable star. Obediently orbiting planetary neighbors. A large protective and stimulating moo. All the necessary ingredients for this stewpot of life.

A chance in a qwazizillion to result in a Living Earth.

Lucky, lucky for us!

Except, at the pinnacle of evolution resulting in sentient, sapient life? The Trickster Coyote God is howling with laughter as we Crazy Apes. Fulfilling our destiny as Homo Anthropophagus. Have so thoroughly endeavored to murder the only biosphere in sight!
dfjohnsonphd
5 / 5 (3) Feb 27, 2018
"Have so thoroughly endeavored to murder the only biosphere in sight!"

This observation is precisely why we have seen no sign of intelligent life in the universe. Just because humans can build big telescopes and get some idea of what is going on, and create marvelous medicines etc. doesn't mean we are intelligent as we are destroying that wispy film of life, the biosphere. Without it, we are gone.

That we are destroying it at an increasing rate, and that we are doing nothing to stop, or even slow it down, provides empirical evidence that we are dumber than slugs. At least they know how to "get along".

Thanks for getting me going @rrwillsj!!

Let's hope we are not the pinnacle. Sadly, we won't be leaving them much, except a lot of long-lived radionuclides from all the nuke plants, and dead oceans, etc. Hey, that is better than nothing, right? Let's see how smart they are!!

Trickster Coyote God? Hmmmm......Yeah, sure, okay!
TrollBane
not rated yet Mar 01, 2018
"A large protective and stimulating moo" And that's no raging bull...
rrwillsj
1 / 5 (1) Mar 01, 2018
"A large protective and stimulating moo"

Sorry to horn in butt my 'end' is hanging out in the dark of the moon.

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