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Any alien living on a planet huddled near a red dwarf star can breathe a sigh of relief (assuming they are breathing, and can sigh and feel relief): it’s possible that extremely powerful explosive stellar eruptions not sterilize the planets as previously thought.
Perhaps.
Red dwarf stars are much smaller, cooler, and darker than the Sun. Also, unlike the Sun, red dwarfs are fully convective, which means that hot plasma rises from their core to their surface (in the Sun, the convective region is much smaller). It may sound a bit esoteric, but it is of crucial importance: the rising and falling ionized gas generates a magnetic field, and whether a star is fully convective from top to bottom (or really from the inside to the outside) ), this means that it can generate very strong magnetic fields.
A star’s magnetic field is what powers explosive events on their surfaces like stellar flares and coronal mass ejections (or CMEs). Magnetic field lines store immense amounts of energy – like eclipsing all nuclear weapons on Earth by thousands or millions of times immense – and when they get tangled up, they can, in a sense, bypass and release that energy in one overwhelming blast. A solar flare on the Sun can emit a decent fraction of the Sun’s total energy and it does so in X-rays and a stream of subatomic particles, both of which can bypass our satellites, threaten orbiting astronauts and cause earthquakes. widespread power outages on Earth.
Coronal mass ejections are similar and can be triggered by flares, but lean more toward the stream of subatomic particles than light emission. A billion tonnes (!!) of hydrogen can be blown away from the Sun at a million kilometers per hour. An event like this is colossal and can once again cause a lot of damage here on Earth.
This could be a much bigger problem for the red dwarf planets. Red dwarfs are much more magnetically active than the Sun and can produce superfused which can go up to ten thousand times more powerful that all the sun produces. Worse yet, for a red dwarf planet to be habitable, it has to huddle closer to the colder star to support life, which means it really does experience such eruptions.
It’s such a big deal that astronomers believe stellar activity can not only sterilize a planet but also strip its atmosphere after a while.
Are the aliens inhabiting the red dwarf planet doomed?
Maybe not, according to new research. A team of astronomers used the Transiting Exoplanet Survey Satellite, or TESS, to examine the light of more than 3,000 very cold, fully convective red dwarfs. TESS observes the same part of the sky over and over again, making it ideal for looking for changes in starlight brightness. They found over 17,000 flares of these stars and narrowed it down to 343 super flare events.
What they wanted to find is what is called rotation modulation: An eruption that lasted long enough for the rotation of the star itself to sweep it in or out of our field of vision, altering the brightness of the eruption. They found four of these events from four different stars ranging from 36 to 150 light years from Earth. All four turn quickly, from 2.7 to 8.4 hours. Remember, it takes a month for the Sun to rotate once, so these stars turn on their own (rapid rotation also helps fuel magnetic fields, so since they are prone to super-eruptions, it not surprisingly, all of these stars are spinning quickly).
They found the signature of the rotational modulation in all of these flares, meaning their brightness changed due to the star’s rotation moving the flare in and out of our field of view. This is the cool and important part: From there they were able to determine at what latitude the eruption occurred on the star, i.e. whether it was near the equator or near. from the pole.
What they found is that all four super eruptions occurred at high latitudes, closer to the pole than to the equator, ranging from 55 ° to 81 ° (the pole is at 90 °, the equator at 0 °).
It is very interesting indeed. Most sunspots and associated flare activity on the Sun occur near the equator, rarely above about 35 °. But all of those flares were much further from the equator than that.
And maybe that’s what saves all potentially habitable planets. Planets tend to orbit around the equator of their host star, and this will be especially true for red dwarf star planets, which experience stronger tides from their stars due to their proximity; this will force the planets to be above the equator.
But flares occur closer to the poles of the stars, reducing their impact. Well, a bit: high energy x-rays and ultraviolet rays tend to be thrown in all directions, but it still reduces the effect somewhat. On the other hand, coronal mass ejections (which may be associated with rashes) are directional and tend to concentrate above the rash. A high latitude eruption would therefore move the CME away from the planets.
If this is true, it means that these planets are not hit as hard or as often as previously thought.
Be careful, this conclusion is still a bit broad given the data. For example, CMEs expand as they move away from a star, so those not directly aimed at a planet can still affect it. Additionally, it is not clear how CMEs actually work from red dwarf stars, as we cannot really detect them; we can only infer it from the way they work with the Sun. So there is more to discover here.
But it is full of hope. Red dwarf stars are by far the most common in the galaxy, accounting for 80% of all stars, and they preferentially form small, rocky planets like Earth. Statistically, these are the star types most likely to have habitable planets (although the devil is in the details, as usual). The idea that they can be erased from life by their host stars is a little depressing, so this conclusion, however preliminary, is – forgive the expression – a ray of sunshine.
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