The red dwarf that roared

By Phil Plait | May 19, 2008 11:03 am

EV Lacertae is a dinky star, a cool red dwarf about 16 light years away. It really is small; its diameter is about 0.4 times that of the Sun, and it’s so faint that if it weren’t one of the closest stars to us we wouldn’t be able to see it at all. Even though it’s a close neighbor, it’s still too faint to see with the naked eye, and is tough even in binoculars.

So it’s not very interesting, right? Heh. Bzzzzt.

EV Lac is almost fully convective, which means that the heat from hydrogen fusion in its core is transported upwards almost entirely due to hot gas rising. In more massive stars like the Sun, that heat is transported through radiation, literally through light. What this means is that almost all the gas inside EV Lac is moving up and down, rising and falling like water boiling in a pot.

The gas is ionized, meaning it has an electric charge. Moving electric charges generate magnetic fields, so little red dwarfs like EV Lac can have pretty strong magnetic fields.

Bear with me. We’re almost there…

EV Lac is also rapid rotator; literally, it spins quickly, taking only about 4 days to rotate once (the Sun, for comparison, takes a month). This means the gas inside it doesn’t just rise and fall in beautiful convection cells; it gets twisted up, tangled like a mass of string. But the magnetic fields hold a huge amount of energy. Twisting them up builds that energy, and eventually something’s gotta give. On the surface of the star the field lines suddenly reconnect, and the energy stored inside is released.

A lot of energy.

BANG.

The energy erupts out in the form of a flare: heat, light, particles all flash out of the reconnecting regions. On the Sun these flares can release as much as 10% of the Sun’s total energy — the equivalent of 15 billion one-megaton bombs — all concentrated in one spot. But on EV Lac, the flares get even bigger…

On April 25, several satellites detected a huge flash of X-rays. WIND was the first, but NASA’s Swift mission picked up on the flare two minutes after it erupted. The flare was so bright that Swift’s UV/Optical Telescope actually shut down to protect itself! The flare continued for eight hours, pouring energy from this tiny star into the cosmos.

The energy of the flare was immense, thousands of times more powerful than a normal solar flare on the Sun. To put this in scale, that means that the flare from this tiny red dwarf star was actually more luminous than the Sun. If you had been looking at the right spot in the sky, you would have been able to actually see the normally invisible red dwarf, it got so much brighter than usual.

This is the brightest flare ever seen from EV Lac, even though it’s been monitored for a long time — it’s a known flare source, blasting them out all the time, but none has ever been detected like this one. For astronomers, it’s a boon. EV Lac is young (less than half a billion years old) which gives us insight into how stars behave when they’re still fresh off the vine. It’s a testbed for models of magnetically active stars, and bright flares are good for pushing the limits of both what the star can do and how our physics can model them.

Plus, it’s just cool. A flare this big on the Sun — which, as far was we know, is currently impossible — would do some major hurt on the Earth. It would blast away our ozone layer, fry our satellites, create electromagnetic pulses that would take down our power grids and wipe out electronics, and cause all sorts of havoc on Earth… and maybe even a mass extinction*. Mind you, the Sun can’t put out flares like the one from EV Lac, because the Sun is in middle age and has a more settled magnetic field (despite sometimes acting up). But when it was younger flares like that may have been common, sending out particle and electromagnetic radiation which slammed into the planets. Studying stars like EV Lac give us a handle on what our own star was like back in its raucous youth.



*… so of course this is a topic of a chapter in my upcoming book, Death from the Skies!

Comments (61)

  1. Quiet_Desperation

    It would blast away our ozone layer, fry our satellites, create electromagnetic pulses that would take down our power grids and wipe out electronics, and cause all sorts of havoc on Earth… and maybe even a mass extinction

    What’s the downside?

    Hmph.

    Sorry. I’ve a touch of the rotten mood today. :-(

  2. zeb

    “If you had been looking at the right spot in the sky, you would have been able to actually see the normally invisible red dwarf, it got so much brighter than usual.”

    You mean in X-Rays, right? Not visible light.

  3. I think red dwarfs are interesting because they are the most common, and oldest lived stars in the universe. I love them they’re so cool! (sorry that was a bad one) :)

  4. Kaptain K

    “…the Sun can’t put out flares like the one from EV Lac, because the Sun is in middle age and has a more settled magnetic field.”

    And, as you said earlier in the article, the Sun is not fully convective like EV Lac, nor is it a rapid rotator.

  5. Zeb, flares emit light across the EM spectrum. This star would’ve been bright enough to see in visible light. Had you been looking, you would’ve seen it.

  6. Jeffersonian

    When our sun was at this stage (capable of flares of this scale), what stage was the Earth in atmosphere-wise?

  7. Volatile little bugger, that. :)

  8. Steve G

    “A flare this big on the Sun — which, as far was we know, is currently impossible — would do some major hurt on the Earth”…and maybe even a mass extinction”

    Sounds like a new chapter for the book!

  9. Chip

    Proxima Centauri, the closest star to our Sun, is also a Red Dwarf, and a flare star as well as too dim to be seen naked eye. But I wonder if it can be spotted when flaring up.

  10. “To put this in scale, that means that the flare from this tiny red dwarf star was actually more luminous than the Sun. If you had been looking at the right spot in the sky, you would have been able to actually see the normally invisible red dwarf, it got so much brighter than usual.”

    Well, not quite. You still have this problem that your eyes can only see visible light, so no, you wouldn’t have been able to see it.

  11. Here, this is from the press release itself:

    “The flare, an explosive release of energy from a star, packed the power of thousands of solar flares. It would have been visible to the naked eye if the star had been easily observable in the night sky at the time.”

    Now, it wasn’t easily observable in the night sky at the time. What does this mean? Would we have been able to see it if the star was closer? If there was better seeing/visibility at the time? Or if the wavelengths of light were those we could see?

    Either way, I think it’s jumping the gun to say “we could have seen it with our naked eyes if we were looking.”

  12. andy

    It would blast away our ozone layer, fry our satellites, create electromagnetic pulses that would take down our power grids and wipe out electronics, and cause all sorts of havoc on Earth… and maybe even a mass extinction.

    Of course, the situation for any planets in the “habitable zone” around EV Lacertae would be far worse, given that they would be much, much closer to the star than Earth is to the Sun.

  13. Chris B.

    … except that the BA just said the thing was kicking out light all across the spectrum, so we could have seen it.

  14. SteveG, yes, it would. That’s why I put the footnote in the blog post when I wrote it. :-)

    Ethan, as I mentioned in the post, the UVOT actually shut itself down because the flare was so bright. Flares emit across the EM spectrum, so yes, this star would have been visible to the naked eye.

  15. Nice photo. What telescope took that picture?

  16. Nice photo. What telescope took that picture?

    If you hover your mouse pointer over the pic you get to see its description.

  17. Len Bonacci

    On the surface of the star the field lines suddenly reconnect, and the energy stored inside is released… BANG.

    Why am I reminded of Ghostbusters? Don’t cross the streams! :D

  18. Mike R

    Wow, I think I found my new desktop background. Awesome image.

  19. andy

    In fact, just how bad would this be for a planet in EV Lac’s HZ? Putting out 1% of the Sun’s total luminosity at normal times, the HZ would be at about 0.1 AU.

    Now if we set off a flare with the same luminosity as the Sun, and assuming the energy does not get distributed very much around the planet, the dayside shoots up to temperatures of about 1000 degrees C, which is enough to melt (some kinds of) rock. With that kind of thing happening, it is doubtful that EV Lac has anything approximating a habitable zone (or maybe life could survive on outer icy planets which get periodically melted by large flares).

    If all red dwarfs pass through an EV Lac-type stage of their evolution, it’s doubtful that the habitable zones of such stars contain planets which actually support life.

  20. If a sun flare “releases” up to 10% of its energy and as often as there are sun flares, how can it not be getting smaller very fast?

    My assumption is that “releases” is the wrong word in that most of the energy is actually retained.

    Am I missing something?

  21. Michael

    Ok so I am a little confused on one point. If the star is 16 light years away, then wouldn’t the event have to occured 16 years ago for us to see the light? Sorry is this is an easy question I am just a bit confused.

  22. ChrisP

    “On the Sun these flares can release as much as 10% of the Sun’s total energy…”

    Do you really mean to say “energy” here? Maybe power rather than energy?

  23. Vlad

    CafeenMan:

    I think you have a misconception. Do you think that a flare releases 10% of total energy [i]Sun will ever have[/i]? Because it is very much not the case. An extremely powerful flare on the Sun gets [i]as bright[/i] as 10% of Sun’s normal luminosity. So for the few minutes the flare is active, it releases 10% as much energy as the rest of the Sun does — during the same few minutes. All in all, Sun gets 1.1 times brighter for a few minutes.

    Keep in mind that “10% of the Sun’s total energy” is an unusually powerful flare. Most solar flares are weaker than that.

  24. Vlad

    If the star is 16 light years away, then wouldn’t the event have to occured 16 years ago for us to see the light?

    Yes. But astronomers usually do not mention this, as self-evident. Few days ago the “youngest supernova in Mily Way” was announced. As we see it, it exploded 140 years ago. It is also 25,000 light years away, so it is not actually the youngest supernova in the Mily Way — Crab Nebula exploded “in 1054″ and is 6500 light-years away, so it actually happened 7500 years ago. But as I said, astronomers tend to say events happen “as we see them”.

  25. Irishman

    The Bad Astronomer wrote:

    The energy of the flare was immense, thousands of times more powerful than a normal solar flare on the Sun. To put this in scale, that means that the flare from this tiny red dwarf star was actually more luminous than the Sun. If you had been looking at the right spot in the sky, you would have been able to actually see the normally invisible red dwarf, it got so much brighter than usual.

    I assume by that you mean the intrinsic brightness was greater than the Sun, but that our local brightness was not because of geometry (i.e. distance)? Or are you implying it was visible in daylight?

    And I agree with ChrisP, I think perhaps you meant instantaneous energy rather than sum total energy.

    Ethan said:
    >Here, this is from the press release itself:

    >â??The flare, an explosive release of energy from a star, packed the power of thousands of solar flares. It would have been visible to the naked eye if the star had been easily observable in the night sky at the time.â??

    >Now, it wasnâ??t easily observable in the night sky at the time. What does this mean? Would we have been able to see it if the star was closer? If there was better seeing/visibility at the time? Or if the wavelengths of light were those we could see?

    >Either way, I think itâ??s jumping the gun to say â??we could have seen it with our naked eyes if we were looking.â??

    Ethan, digging in to the matter, Wikipedia has this to say:

    Lacerta is located between Cygnus, Cassiopeia and Andromeda on the northern celestial sphere. It looks like a ‘little Cassiopeia’ as it is W shaped as well.

    http://en.wikipedia.org/wiki/Lacerta

    Cassiopeia is visible in the early night sky in mid to late fall.

    This link states:

    The constellation of Lacerta is best viewed during the month of October for mid-Northern latitudes.

    http://www.go-astronomy.com/constellations.php?Name=Lacerta

    What that tells me is that Lacerta is in the sky during daylight hours. The remaining question is whether it was bright enough to be seen during daylight. The press release suggests it would have been naked eye visible for the very short time it was in the night sky, but the wording suggests it was not bright enough for daylight viewing.

  26. Dave C

    Do these red dwarf stars calm down as they grow older? (If not, then we can forget about finding intelligent life around these stars.)

  27. Michael

    Thanks for the explanation Vlad.

  28. That makes me think back to Stanly Miller’s experiment. Lightning has usually been the suggested energy source for zapping the primordial soup, but perhaps solar flares played a role in that process.

  29. Chip

    Vlad: “…Crab Nebula exploded “in 1054″ and is 6500 light-years away, so it actually happened 7500 years ago. But as I said, astronomers tend to say events happen “as we see them.”

    Yes, and though descriptions of events can sometimes become contentious with those who insist that the universe must have only one universal time scale, it is actually just as correct to say “The star exploded 140 years ago” as it is to say “The star exploded just now, as we see it.”

  30. zeb

    Oh dang. Wish I had been looking.

  31. Jonas Engelhardt

    I want that picture as my background. Does anyone have a link to a higher-res version?

  32. Any planet within .1 AU of a star is going to be tidally locked fairly quickly, so what happens on the abused side will be oblivious to the dark side. Assuming there is an atmosphere, some IR may be conducted past the terminator.

    The habitable zone of a “habitable” planet of a red dwarf would have to be near the poles, I think. Red dwarfs (dwarves?) burn a log time, and convection continues throughout its lifetime, and flares are common. Maybe inhabitants take shelter behind a large mountain or underwater (!)

    BTW, hovering does nothing (Mac w/Firefox) There has to be an artist.

  33. Any planet within .1 AU of a star is going to be tidally locked fairly quickly, so what happens on the abused side will be oblivious to the dark side. Assuming there is an atmosphere, some IR may be conducted past the terminator.

    The habitable zone of a “habitable” planet of a red dwarf would have to be near the poles, I think. Red dwarfs (dwarves?) burn a log time, and convection continues throughout its lifetime, and flares are common. Maybe inhabitants take shelter behind a large mountain or underwater (!)

    BTW, hovering does nothing (Mac w/Firefox) There has to be an artist.

    KP

  34. Chip

    On a hypothetical planet with an atmosphere, tidally locked in close around a red dwarf, the heated side would likely produce high winds whipping around to the dark side. Also, due to much of the light being in the infrared, the daylight side would not necessarily have a blue sky (assuming its an Earth-like world.) Probably a dark daytime sky with a wild blazing red dwarf hanging in it.

  35. Jim Baerg

    So normally EV Lac is radiating much less power than our sun. Where did Andy get that 1% figure? Is it accurate.

    During the flare it was briefly over 10x brighter that our sun. So a hypothetical planet of EV Lac that normally gets about as much heat as earth would briefly get much more energy from its star.

    But how long is that pulse? How many days (months? year?) of normal irradiation would the planet get from the flare?

    If the flare is short enough that the energy released is a few days of normal stellar output, then the atmosphere & ocean of the planet can absorb the excess energy without heating up very much & a habitable planet would still be habitable after the flare.

    If the flare is equivalent to several years of normal stellar output, that planet will be thoroughly toasted.

    So how many days of normal stellar output would be equivalent to the energy released in the flare?

  36. kebsis

    Are there any actual pictures of this event available?

  37. Natalie

    If you don’t stop it I ‘m going to have to buy your book!!! grrrr…. October?……grrrr…. my dad might like one too…. grrrr….. oh, and my brother….. grrrr…..
    Well, I guess you’ve done it! Some of your coolest posts in a book!!!
    Nice! I’m looking forward to it, despite the frustration.

  38. Buzz Parsec

    Jim Baerg, solar flares typically last just a fraction of a minute. I don’t know how long the flares last on a red dwarf, but I would be surprised if they last more than a few minutes, with the brightness exponentially declining as it fades.

    Think of it as a minute or two at maximum brightness, and maybe 10 to 20 minutes at 10% of maximum, and another hour or two at 1%, and faded to invisibility after that. This is going to blast ozone layers, cause sunburns, etc., but it won’t melt lead!

  39. Tod

    @ Kim Poor:
    WRT the plural of dwarf, you were right the first time – it’s dwarfs. However, the Wikipedia entry has this to say “…both dwarfs and dwarves are in current use. Many grammarians prefer dwarfs, many fantasist prefer dwarves. The form dwarfs is generally used for real people affected by dwarfism; the form dwarves is used for the mythical people described by Tolkien and others.” So WRT dwarf stars, who knows? Six of one, half a dozen of the other.

    Regarding the image, I’m on a Mac using Safari and hovering shows the link to be: http://www.nasa.gov/centers/goddard/images/content/226765main_pipsqueak.jpg

    @ Phil: Thanks for yet another well-written and equally well-explained in layman’s terms a post about an interesting stellar neighbor.

    I love this blog!

  40. andy

    Jim Baerg: I got the 1% figure from the press release itself. I don’t know how accurate it is, but it seems consistent with the luminosities of other red dwarfs like Gliese 581. The press release states the flare lasted for about 8 hours.

  41. Grand Lunar

    Flare stars seem so often ignored. Glad to see this one gets attention, “speaking” for other flare stars. :)

  42. #
    # Vladon 19 May 2008 at 2:39 pm

    CafeenMan:

    I think you have a misconception. Do you think that a flare releases 10% of total energy [i]Sun will ever have[/i]?

    =================================

    That’s what I heard being said. Thanks for the explanation. I do understand that while the sun is sending mass into space, it’s also collecting the mass of things it captures. I figured this didn’t make much a difference in the overall mass of the sun.

    But if 10% of the mass is being released in big flares and maybe only 0.5% is being released in small flares, the sun would be gone really fast. So I knew I didn’t get it but I wasn’t sure if it was me or if it was the way it was stated.

    Thanks again!

  43. Victor Bogado

    The image is an artistic rendition, as the ‘alt’ tag shows “Artist’s drawing of a flare from the red dwarf star EV Lacertae”.

    The problem is that the alt tag is defined to be used by a browser that cannot, or will not, show images as an alternative text. This is very useful for accessible browsers that read the content to blind people for instance.

    But ie uses the alt tag also to show a tool-tip, that is not the intention of the alt property but I would argue that it does make some sense. But since there is a property that is designed with that intention, ‘title’, other browsers follow the recommended behavior and pop a tool-tip only for title tags, and show the ‘alt’ text when they can’t load the image. That’s why people with firefox and maybe other browsers can’t see the hover text.

  44. andy

    As for the image credit, the NASA press release the BA linked to lists “Credit: Casey Reed/NASA”. There’s also a print resolution 2000×1335 pixel image available there.

  45. Steve G

    â??I do understand that while the sun is sending mass into space, itâ??s also collecting the mass of things it captures. I figured this didnâ??t make much a difference in the overall mass of the sun.â??

    Actually the sun loses mass constantly by three methods:

    Fusion â?? the direct conversion of mass to energy (about 77,000 billion tons per year) http://www.astronomycafe.net/qadir/q1491.html

    Solar wind â?? the constant outflow of charged particles (1 million tons of material per second!) http://csep10.phys.utk.edu/astr162/lect/sun/wind.html

    CMEâ??s – coronal mass ejections (each of which can carry up to 10 billion tons of mass) http://science.nasa.gov/headlines/y2000/ast07jun_1m.htm

    Iâ??ve listed my sources here in case there are better or more accurate figuresâ?¦

    One more site that discusses the sunâ??s mass loss:
    http://www.universetoday.com/2008/02/07/the-astronomical-unit-may-need-an-upgrade-as-the-sun-loses-mass/

  46. SM

    For future reference, if for some reason you can’t see the “hover text” of a picture or other web page object, you can usually right-click it and select “Properties” to see the alt-text or whatever it is.

  47. Max Fagin

    I don’t know, does anyone else here smell a plot by the Firstborn to wipe out a dangerous species? ;)

  48. StevoR

    # andy on 19 May 2008 at 1:23 pm
    “In fact, just how bad would this be for a planet in EV Lac’s HZ? Putting out 1% of the Sun’s total luminosity at normal times, the HZ would be at about 0.1 AU.

    Now if we set off a flare with the same luminosity as the Sun, and assuming the energy does not get distributed very much around the planet, the dayside shoots up to temperatures of about 1000 degrees C, which is enough to melt (some kinds of) rock. With that kind of thing happening, it is doubtful that EV Lac has anything approximating a habitable zone (or maybe life could survive on outer icy planets which get periodically melted by large flares).

    If all red dwarfs pass through an EV Lac-type stage of their evolution, it’s doubtful that the habitable zones of such stars contain planets which actually support life.

    Remember though Andy & others that this is a very young star at the start of a trillion year lifespan.

    It may just be beginning to form a planetary system and any potentially inhabitable exoplanet there would probably be at a stage of its existence where it’s still too hot & too pummelled to have formed life yet anyway. Think Earth just after the Big Splash impact that formed the Moon …

    Given time, both the star and any hypothetical exoplanet may well settle down. 8)

    BA : (If you – or others who know are still reading on this thread) Any idea what magnitude EV Lacertae would reached at maximum for the mega-flare? Any chance of it repeating so massive a flare perhaps even at semi-regular~ish intervals and is it thus worth still keeping an eye out for?

  49. StevoR

    Hmmm .. wecould use this image in a cartoon see the roundabout linking :

    http://www.badastronomy.com/bablog/2008/05/21/science-cartoons-for-freedom/#comment-177170

    That now links to this links to that links to this ..

    Aha! My evil trap is working Bwhahaa haaaa haa! I’m now getting myself dizzy! Very dizzy! I’ll look into my eyes … Hey, tell me again, do evil hyponists really practice on themselves in the mirror!? Uh oh! ;-)

  50. andy

    StevoR: the issue is whether the flares are sufficient to deplete a close-orbiting planet of its volatiles (by atmospheric evaporation, etc.), or even preventing their delivery in the first place by pushing the snowline sufficiently far out relative to the HZ that the delivery of volatiles is inhibited, before the star settles down.

    (Even then there is still the small matter that at the fast orbital speeds, collisions between planets and water-rich asteroids/comets would be sufficiently violent to remove volatiles rather than result in accretion)

  51. StevoR

    Thanks Andy :-)

    I appreciate your response & I see what you mean but I’m not so sure …

    Given enough time and the possible inward migration and warming up of exoplanets from further out … who knows what might be possible?

    To some extent, I think we have to concede that until we actually explore such systems – whether from a vast distance via super-advanced telescope or, if possible, one day through interstellar spacecraft (with or without human crews aboard) then we really just don’t know for sure … do we?

  52. andy

    StevoR: definitely we don’t… in any case, it is almost certainly possible to migrate planets inwards from water-rich regions beyond the snowline: without that happening it is very difficult to explain the “hot Neptune” planets detected around such stars, and also it seems difficult under standard theories to grow inner-system super-Earths like the outer two planets of Gliese 581 in situ, which makes it seem likely that those two planets are icy in composition (i.e. ocean planets).

  53. Rachel

    some background on previous flares from EV Lac:

    It can produce huge flares in the optical/ultraviolet — two previously observed/studied flares in the 70’s/early 80s had an increase of more than 6 magnitudes from the quiescent state of the star.

    It can also produce huge X-ray flares, although none quite as big as this one. The Japanese X-ray satellite ASCA observed a flare from EV Lac in the late 90s large enough that it completely saturated two of its four X-ray detectors.

    It has a reputation among those who study flare stars for being “a good producer”; i.e. a high flaring rate. Most of its flares are much smaller than this one, and happen several times a day, however.

  54. Spectroscope

    Deleted post – sorry. Stuffed up. Mea culpa.

  55. Spectroscope

    Superb work by the space artist there – I love the painting of EV Lacertae flaring. Congratulations to whoever created that picture. :-)

    Link back to the connected “Unlocking the Jewel box” BA blog thread where flaring EV Lacertae gets a mention in terms of stellar ages :

    http://blogs.discovermagazine.com/badastronomy/2009/10/29/unlocking-the-jewel-box/

    Has it flared again so bright since this? Does anyone still reading here know & care to comment?

  56. Ali

    Inspiring – Flaring Article with a great Magnetic Attraction —- Excuse my Cosmic Language-
    ;)

    gotta a question for ya—

    “The gas is ionized, meaning it has an electric charge. Moving electric charges generate magnetic fields, so little red dwarfs like EV Lac can have pretty strong magnetic fields”

    Can you pls. mention if EV Lac’s Magnetic Field is Stronger than our Sun ?

    if Yes — could you also tell — how much stronger on a Scale if we compare it with other Magnetic Fields in the Universe e.g. Black hole

    Another question Can we Compare the Fast Rotation of Red Dwarf with that of a Black hole ?

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