A supernova is reborn

By Phil Plait | June 9, 2011 6:30 am

A little over 24 years ago, light from the closest supernova in four centuries reached Earth. It was the first such supernova seen in 1987, so it was officially dubbed Supernova 1987A, or SN87A for short.

It was full of surprises: the star that blew up (Sanduleak -69 202) was the first blue supergiant ever seen to explode — most such supernovae progenitors are red supergiants. The intense ultraviolet flash from the explosion lit up a gigantic pre-existing hourglass-shaped shell of gas surrounding the star; over five light years long, nothing quite like it had ever been seen before. The hourglass had a thick ring around its middle, which to this day is still something of a mystery.

The expanding debris from the explosion itself has been growing for more than two decades as well. Screaming out at thousands of kilometers per second, it’s been getting less dense as it grows larger, and has been fading as well.

However, that appears to be changing now. The debris is getting brighter once again… which actually has been expected. The gas in the hourglass nebula surrounding the supernova was actually expelled by the star more than 20,000 years ago, and has been sitting there ever since. Inside the dense ring is a thin, hot gas, too faint to be seen directly, but inferred by various means. The debris from the explosion has been plowing into this gas for more than 20 years, but now the expanding material is starting to interact with the ring. Well, to be fair, it’s been doing that for a few years, but the real interaction is now starting in earnest.

The supernova material –the elongated fish-shaped thingy in the middle of the ring — is hitting the ring material, creating a massive shock wave. That wave is generating X-rays and other forms of light that have been slowly heating up the material from the supernova. The material is starting to glow once again in visible light, as can be seen in the photo above (the wider view here is from 2007). The odd shape is probably a combination of the explosion dynamics itself with the density profile of the gas through which it’s moving; there is more gas in the plane of the disk, so the supernova debris can’t move through it as quickly. This gives the debris that pinched shape in the middle, making it a smaller version of the giant hourglass around it.

The ring is not a smooth distribution of matter; it has bright knots where the density is higher. Funny — I studied this ring to get my PhD, and I observed it using a filter that lets through light from ionized oxygen. This peculiar flavor of oxygen actually fades faster the denser it is, so in the original images from 1992 or so, the densest material was actually the darkest! In the images above, though, we’re seeing light from hydrogen, which glows more brightly the denser it is. Looking at images like this is not at all straightforward, and you have to be careful when analyzing them.

Those knots are getting brighter too; a few years ago they had faded considerably, but the fast material from the supernova has been hitting the ring for some time, lighting them back up. The slower moving (but still mind-numbingly fast) gas that makes up the bulk of the explosion is right behind, and will slam into the ring in the next few years. When it does, it’ll tear the ring apart. But it won’t be overnight; some models indicate it will take decades for the ring to be destroyed.

What a sight that will be! An object over a light year across — 10 trillion kilometers — will be shredded by an octillion tons of matter moving outward and through it at a significant fraction of the speed of light. And we’ll have front-row seats to it; when the action really starts we’ll have a fleet of telescopes trained on it. Nothing like that has ever been seen before by human eyes, and I can’t wait for it to happen. That might seem weird; me wanting to see an object I spent five years studying destroyed. But c’mon, PhD research has been derailed by any number of mundane things; who can say theirs was ripped apart by a supernova blast?

Image credits: Pete Challis (CfA); NASA, ESA, P. Challis & R. Kirshner (Harvard-Smithsonian Center for Astrophysics)

Related posts:

20 years ago today (a history of SN87A)
One ring to rule them all
One ring to fool them all
Birth cry of a supernova
Anybody wanna peanut?
AAS Report 2: Things that go boom

CATEGORIZED UNDER: Astronomy, Pretty pictures

Comments (29)

  1. CJSF

    I am always excited by updates to SN1987A. I’ve been following along with the BA for years now. I am not sure what I like more – the awesome pics each time, or reading Phil’s excitement on what new things are going on each time!


  2. JEHermit

    Okay this has me wondering. Is what we are seeing herre a actual “ring”? Or is this just a ring slice of a “Sphere” that we can see? What I mean is this a giant doughnut of matter or a ball that we can only see part of? So are we just lucky this star exploded with one of its poles pointed at us?

  3. kevbo

    Is there a time-lapse video of this since 1987?

  4. Kevin Klein

    Is it just me or does that thing in the middle really look like a bust of Homer Simpson?
    Could this be the sign from God that we have all been waiting for?

  5. Funny, I was thinking it – the whole thing, ring and all – looks like the PBS logo.


    (Got held in moderation limbo – Phil, I repeated it without the link so feel free to delete this one.)

  6. Funny, I was thinking it – the whole thing, ring and all – looks like the PBS logo…

  7. Messier Tidy Upper

    Any sign of the central pulsar or black hole? Has anybody calculated what the mass of Sanduleak -69 202’s core was (ie over or under the neutron star limit) & thus what the core remnant should be? Any news on that front – or should I say centre?

    EDIT : The B3 Ia-Ib blue supergiant star & Luminous Blue Variable itself had a mass of 20 suns according to Wikipedia if that helps at all.

    If only we could see a bright, nearby, (but not *too* close!!!) supernova occur in our Milky Way sometime soon .. Sigh.

    @3. Kevin Klein : That’s definitely Homer Simpson’s head, I agree. ūüėČ

  8. Messier Tidy Upper

    @2. kevbo : “Is there a time-lapse video of this since 1987?”

    See : http://www.youtube.com/watch?v=t-Mj0XGHlX8

    for one very short 4 second one via Youtube. Don’t blink or you’ll miss it.

    This Youtube clip :


    has a good discussion and series of images showing SN 1987 A evolve and there’s apparently more videos linked from there in the info box.

    Plus there’s this one :


    Which has an animation of the (possible) history of the star and how it evolved and got to where it is along with actual images. Not sure whether it’s exactly what you’re after but hope it helps. :-)

    PS. Warning tho’ the initial beeping intro is a bit shrill and you may want to mute the first second and turn the sound back on once the supernova picture appears.

  9. Markk

    Surely this is a sign to us people of Wisconsin. There is a definite neon Wisconsin in that SN most in the smaller last picture. I wonder what they are advertising? Agricultural products? New posts for our retiring teachers? There is something there all right.

  10. Kyle

    Reminds me of the “Red Ring of Death” that once appeared on my Xbox. Seems fitting as this is a dead star, as opposed to a dead console.

  11. Nigel Depledge

    The BA said:

    That might seem weird; me wanting to see an object I spent five years studying destroyed.

    Perfectly natural, I would say! ūüėČ

  12. Nigel Depledge

    The BA said:

    And we’ll have front-row seats to it

    Don’t sit in the front three rows – you’ll get soaked!

  13. Messier Tidy Upper

    Link for my source @ #7 on the mass and spectral class of the former star Sanduleak -69 202 here :


    Google images search list results for “SN1987A Time Lapse” here :


    and here :


    is the space-dot-com search results if these help which hopefully they will. Plenty of links from there to choose from. :-)

  14. Messier Tidy Upper

    @4. Kevin Klein : “Is it just me or does that thing in the middle really look like a bust of Homer Simpson?”

    Kind of apt that Homer’s “head” is full of hot dense radioactive gas isn’t it? ūüėČ

  15. Messier Tidy Upper

    Aha! Wikipedia has a (brief again) time lapse animation here :


    via it’s entry on Supernova 1987A :


    while for another perspective check out this :


    3D model of the supernova remnant on Youtube courtesy of the ESO, VLT & HST. :-)

    BTW. When does a “supernova” officially end and a “supernova remnant” officially start? Anyone?

  16. BigBadSis

    “the elongated fish-shaped thingy”

    Thanks. It’s those types of interjections that keep my layman’s eyes from glazing over. :-)

  17. Jeremy

    I think that thing in the middle looks like goldfish cracker. Probably because I’m hungry.

  18. @Kevin Klein

    I thought the same thing. Homer’s head surrounded by a giant, disco-sparkly doughnut. Mmmm….doughnuts….

  19. Sili

    the elongated fish-shaped thingy in the middle of the ring

    Don’t be silly.

    It’s clearly a bluebeaked chicken.

  20. CB

    Wait, so some people see a fish, others see Homer Simpson… It’s Mr. Sparkle!

    But really, cool picture and story. It’s kinda cool to think that in a universe where a human lifespan is so tiny and short that very little changes in such an eye-blink, nevertheless it is dynamic to the point where sights like this can be created and then destroyed in just a few decades. Awesome.

  21. Old Geezer

    How long have you guys been reading BA? Its gotta be Jesus or the Virgin Mary (or is that only on toast).

  22. Crudely Wrott

    I feel a little less insignificant when I can observe such a huge, distant event taking place in real time and see it changing withing my own memory!

    So many astronomical events are on scales slower and longer lasting than any individual’s attention or lifespan.

    To watch, and to be informed not only by watching but by a multi-voiced narrative (you too, Phil) makes me and all of us just a little bit more aware, better informed, perhaps a bit wiser. Maybe even larger and older.

    Please promote the joy of astronomy everywhere you go, people. All one has to do is look.

  23. Gavin Flower

    Thing in the centre, is clearly an arrow pointing the direction we should look for something important.

  24. Wzrd1

    Gavin, it’s not where to LOOK. It’s a detour sign.

  25. Enema Cowboy

    It’s a goldfish cracker!


Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!


See More

Collapse bottom bar