New observations from two Arizona State University astronomers using the Hubble Space Telescope have caught a red dwarf in a violent eruption or superflare. The blast of radiation was stronger than any such eruption ever discovered by the sun, and would likely affect the stability of planets orbiting it.
In addition, such superflares in younger red dwarfs that erupt, appear to arrive more frequently 100 to 1000 times more powerful than they will when they age.
The Superflare was discovered as part of a Hubble Space Telescope Observation Program called HAZMAT, which stands for "HAbitable Zones and Mdwarf Activity across Time". The program examines red dwarves (also known as M dwarves) at three different ages ̵
"Red dwarf stars are the least common and longest living stars in the galaxy," says Evgenya Shkolnik, assistant professor at the ASU School of Earth and Space Research and principal applicant for the HAZMAT program. "Besides, we think that most red dwarf stars have systems of planets orbiting them."
The Hubble telescope's orbit above Earth's atmosphere gives it clear, unobstructed views at ultraviolet wavelengths. It is believed that the torches are driven by strong magnetic fields that are caught by the surging movements of the stellar atmosphere. When the tangle becomes too intense, the fields break and reconnect, releasing huge amounts of energy.
ASU postdoctoral fellow Parke Loyd is the first author of the article (published in the Astrophysical Journal) reporting the stellar outbreaks.
He says, "When I realized how much light the Superflare emitted, I sat on my computer screen for a while and just thought, Whoa & # 39 ;.
Loyd states, "Gathering data on young red dwarfs was particularly important because we suspected that these stars would be quite unruly in their youth, which is the first hundred million years or so after they have formed.
He adds, "Most of the potentially habitable planets in our galaxy have withstood strong shocks, as we've seen at some point in their lives." This is a sobering thought. "
Rough environment for Planets
About three quarters of the stars in our Milky Way are red dwarfs. Most planets in the galaxy's "habitable zone" – planets that surround their stars at a distance where temperatures are so moderate that liquid water can exist on their surface – orbiting around red dwarfs. In fact, the next star of our Sun, a red dwarf called Proxima Centauri, has a planet of earth in its habitable zone.
However, red dwarfs – especially young red dwarfs – are active stars that produce torches that can explode so much energy that it interrupts and potentially detracts from the atmospheres of these young planets.
"The goal of the HAZMAT program is to understand the habitability of planets around low-mass stars," explains Shkolnik. "These low-mass stars are critical to understanding planetary atmospheres." Ultraviolet radiation can alter the chemistry in the atmosphere of a planet or possibly remove that atmosphere.
The observations, published in the Astrophysical Journal, examined the flare frequency of 12 young (40 million year old) red dwarfs and represent only the first part of the HAZMAT program. These stars show that young low-mass stars light up much more often and energetically than old stars and middle-aged stars like our Sun – as the Superflor shows.
"With the sun we have a hundred years of good observations," says Loyd. "And in that time, we've seen one, maybe two, flares that have energy close to that of the superflare."
However, he says, "In less than a day, Hubble observations of these boys were stars, we caught the Superflor, which means we observe superflares every day or even a few times a day."
Could be superflares such frequency and intensity bathe young planets in so much ultraviolet radiation that they forever rule no chance of livability?
According to Loyd, "Flares, as we've seen them, have the ability to remove the atmosphere from a planet, but that does not necessarily mean a mood of subversion for life on the planet, it could be a different life from us or there may be other processes that could freshen up the planet's atmosphere, it is certainly a harsh environment, but I would hesitate to call it a sterile environment. "
The next part of the HAZMAT study will be To study red middle-aged dwarfs who are 650 million years old. Then the oldest red dwarfs are analyzed and compared with the young and middle stars to understand the evolution of the high-energy radiation environment for planets around these low-mass stars.
Red Dwarfs, estimated to burn for so long As a trillion years, they have a vast amount of time to eventually host evolving, habitable planets.
"They simply have many more opportunities for life to develop, given their longevity," says Shkolnik. "I do not think we know for sure, in one way or another, whether planets orbiting red dwarfs are still habitable, but I think time will tell."
She says, "It's great that we live in a time when we have the technology to actually answer these kinds of questions rather than just philosophize about them."
Arizona State University
Stellar chemistry, the universe and everything in it
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