Mini-flares potentially jeopardize habitability of planets circling red dwarf stars

June 6, 2017
This illustration shows a red dwarf star orbited by a hypothetical exoplanet. Red dwarfs tend to be magnetically active, displaying gigantic arcing prominences and a wealth of dark sunspots. Red dwarfs also erupt with intense flares that could strip a nearby planet’s atmosphere over time, or make the surface inhospitable to life as we know it. By mining data from the Galaxy Evolution Explorer spacecraft, a team of astronomers identified dozens of flares at a range of durations and strengths. The team measured events with less total energy than many previously detected flares from red dwarfs. This is important because, although individually less energetic and therefore less hostile to life, smaller flares might be much more frequent and add up over time to produce a cumulative effect on an orbiting planet. Credit: NASA, ESA, and G. Bacon (STScI)

Cool dwarf stars are hot targets for exoplanet hunting right now. The discoveries of planets in the habitable zones of the TRAPPIST-1 and LHS 1140 systems, for example, suggest that Earth-sized worlds might circle billions of red dwarf stars, the most common type of star in our galaxy. But, like our own sun, many of these stars erupt with intense flares. Are red dwarfs really as friendly to life as they appear, or do these flares make the surfaces of any orbiting planets inhospitable?

To address this question, a team of scientists has combed 10 years of ultraviolet observations by the Galaxy Evolution Explorer (GALEX) spacecraft looking for rapid increases in the brightnesses of stars due to flares. Flares emit radiation across a wide swath of wavelengths, with a significant fraction of their total energy released in the ultraviolet bands where GALEX observed. At the same time, the from which the flares arise are relatively dim in the ultraviolet. This contrast, combined with the time resolution of the GALEX detectors, allowed the team to measure events with less total energy than many previously detected flares. This is important because, although individually less energetic and therefore less hostile to life, smaller flares might be much more frequent and add up over time to produce an inhospitable environment.

"What if planets are constantly bathed by these smaller, but still significant, flares?" asked Scott Fleming of the Space Telescope Science Institute (STScI) in Baltimore, Maryland. "There could be a cumulative effect."

To detect and accurately measure these flares, the team had to slice the GALEX data into very high time resolution. From images with exposure times of nearly half an hour, the team was able to reveal stellar variations lasting just seconds.

First author Chase Million of Million Concepts in State College, Pennsylvania, led a project called gPhoton that reprocessed more than 100 terabytes of GALEX data held at the Mikulski Archive for Space Telescopes (MAST), located at STScI. The team then used custom software developed by Million and Clara Brasseur (STScI) to search several hundred red dwarf stars and detected dozens of flares.

"We have found dwarf star flares in the whole range that we expected GALEX to be sensitive to, from itty bitty baby flares that last a few seconds, to monster flares that make a star hundreds of times brighter for a few minutes," said Million.

The flares GALEX detected are similar in strength to flares produced by our own sun. However, because a planet would have to orbit much closer to a cool, to maintain a temperature friendly to life as we know it, such planets would be subjected to more of a flare's energy than Earth.

Large flares can strip away a planet's atmosphere. Strong ultraviolet light from flares that penetrates to a planet's surface could damage organisms or prevent life from arising.

Currently, team members Rachel Osten (STScI) and Brasseur are examining stars observed by both the GALEX and Kepler missions to look for similar flares. The team expects to eventually find hundreds of thousands of hidden in the GALEX data.

"These results show the value of a survey mission like GALEX, which was instigated to study the evolution of galaxies across cosmic time and is now having an impact on the study of nearby habitable planets," said Don Neill, research scientist at Caltech in Pasadena, California, who was part of the GALEX collaboration. "We did not anticipate that GALEX would be used for exoplanets when the mission was designed."

New and powerful instruments like the James Webb Space Telescope, scheduled for launch in 2018, ultimately will be needed to study atmospheres of planets orbiting nearby red dwarf and search for signs of life. But as researchers pose new questions about the cosmos, archives of data from past projects and missions, like those held at MAST, continue to produce exciting new scientific results.

These results were presented in a press conference at a meeting of the American Astronomical Society in Austin, Texas.

The GALEX mission, which ended in 2013 after more than a decade of scanning the skies in , was led by scientists at Caltech. NASA's Jet Propulsion Laboratory, also in Pasadena, California, managed the mission and built the science instrument. JPL is managed by Caltech for NASA.

Explore further: Frequent flaring on TRAPPIST-1—unsuited for habitability?

More information: "gPhoton: The GALEX Photon Data Archive," Chase Million et al., 2016 Dec. 20, Astrophysical Journal, 2016 Dec. 20. iopscience.iop.org/article/10. … -4357/833/2/292/meta , Arxiv: arxiv.org/abs/1609.09492

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tblakely1357
3.3 / 5 (3) Jun 06, 2017
This is too bad, in one fell swoop astronomers have eliminated the vast majority of stars from being able to support complex lifeforms. Since massive stars are also poor candidates, I wonder what percentage of stars out there have a reasonable possibility of supporting complex lifeforms?
Jonseer
3.4 / 5 (5) Jun 06, 2017
This is too bad, in one fell swoop astronomers have eliminated the vast majority of stars....


Uh no "they" haven't.

This is barely a hypothesis. It isn't proved. In fact the information we have currently is so scant that it can't be disproved either.

Papers come out all the time disproving these sorts of nonsense papers the moment our tech. becomes good enough to find more solid information to make disproving possible.

Europeans announced they discovered a planet on Proxima Centari years ago only to be humiliated by American astronomers who mocked their work and procedures.

Then a few years later, the Europeans won the argument with hard to refute proof. For stars much further away the facts are far more dubious.

That's the beauty of working in Astronomy, everyone thinks you are talking cold, hard facts when in reality most are farting out their latest brainstorm to a public that believes them, because they have no choice.

somefingguy
3 / 5 (1) Jun 07, 2017
This is too bad, in one fell swoop astronomers have eliminated the vast majority of stars from being able to support complex lifeforms.


Your ignorance is truly astounding. First of all, an atmosphere similar to Earth's would protect quite a bit from those smaller solar flares. Look at Mars, it took ionizing winds from the sun millions of years to strip off its atmosphere and turn the surface into a dust-bowl. So unless we know that those surrounding planets do not have an atmosphere at all, it is very presumptuous to claim that habitable star systems dropped to almost zero.

Also, you are very narrow minded in your presumption that complex life cannot arise under more hostile conditions. There could be life in the oceans of Europa, under the planets surface; or there could be life unlike anything we can imagine which thrives under intense solar radiation.

But hey, better spout some BS to tell yourself you have something interesting to say.

bobbysius
not rated yet Jun 07, 2017
Well, this doesn't really rule out anything. For instance UV flux doesn't really matter since most red dwarf planets in the habitable zone will be tidally locked and thus at least half of the planet isn't exposed to this UV or exposed minimally in the terminator zones. As for stripping the atmosphere, this would happen in the absence of a strong magnetic field, which models have shown can exist even in tidally locked planets. Red dwarf flaring has been evaluated for its impact on habitability before, and hasn't ruled anything out. This study just suggests flaring is more prevalent than we thought.
bobbysius
not rated yet Jun 07, 2017
Since massive stars are also poor candidates, I wonder what percentage of stars out there have a reasonable possibility of supporting complex lifeforms?


It really depends on your definition of massive. Late type F main sequence stars are generally regarded as habitable, and I would argue for the habitability of early F and even A type stars. With those you have higher UV flux and stronger stellar wind, but you also have a MUCH wider habitable zone for planets to form in. Their short lifetimes might constrain complex life, but (based on our own history) life is able to form as early as a billion years after solar system formation and possibly even earlier. All that said, it looks more and more like early K main sequence stars are the sweet spot with minimal flaring, long lifetimes, and reasonable luminosity to host planets that don't necessarily need to be tidally locked.
AGreatWhopper
not rated yet Jun 07, 2017
Dr Who has posited for years that humanity's spread into the cosmos was precipitated by our own sun's red stage and its flares making life on earth inhabitable.

Point being, maybe this is an event that spurs ancient civs around these stars to branch out?

Just a thought.
tblakely1357
not rated yet Jun 07, 2017
"Also, you are very narrow minded in your presumption that complex life cannot arise under more hostile conditions."

Lol, the number of narrow minded @ssholes who post on this site are astounding. My presumption that complex life is unlikely to arise under more hostile conditions is based on our own planet's history. Maybe it can, maybe it can't, but until we actually look and see it's safer (ie, more scientific) to assume not based on our current knowledge of biology.
somefingguy
not rated yet Jun 08, 2017
"Also, you are very narrow minded in your presumption that complex life cannot arise under more hostile conditions."

Lol, the number of narrow minded @ssholes who post on this site are astounding. My presumption that complex life is unlikely to arise under more hostile conditions is based on our own planet's history. Maybe it can, maybe it can't, but until we actually look and see it's safer (ie, more scientific) to assume not based on our current knowledge of biology.


Working with the assumption that our set of variables is the only plausible one is, in this case, the definition of narrow minded (rather the application of the definition in context to what we're discussing)...? I'm not sure if that went straight over your head or you realized it after typing it. Regardless, you're pretty stupid,

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