Birth cry of a supernova

By Phil Plait | May 21, 2008 11:00 am

Very, very cool news today: for the first time in history, astronomers have unambiguously observed the exact moment when a star explodes.


The Quick Version

NGC 2770 is a galaxy at the relatively close distance of 84 million light years away. On January 9, 2008, a massive star in it exploded, and instead of finding out days or weeks later, astronomers caught it in the act, right at the moment, in flagrante delicto. The image above, from the Gemini observatory, shows the galaxy and its new supernova.

We’ve seen lots of stars explode; thousands in fact. But because of the mechanics of how a star actually explodes, by the time we notice the light getting brighter, the explosion may be hours or even days old. This time, because it was caught so early, astronomers will learn a whole passel of new knowledge about supernovae.

That’s the brief summary… but this event has a rich back story. Pardon me the lengthy description, but this is very cool stuff, and I think you’ll enjoy having the details.

The Death of a Star

I’ve explained before how massive stars explode. After a few million years of generating energy by fusing light elements into heavier ones (hydrogen to helium, helium to carbon, and so on), the core runs out of fuel. Iron builds up in the very center of the star, and no star in the Universe has what it takes to fuse iron. It’s like ash piling up in a fireplace. At some point, so much iron builds up that it cannot support its own weight, and the ball of iron collapses.

In a millisecond, more than the mass of the Sun’s worth of iron collapses from an object the size of the Earth to a ball only about 20 kilometers across. Weirdly, it happens so quickly that the surrounding layers don’t have time to react, to fall down (think Wile E. Coyote running over a cliff’s edge). While they hesitate and just start to fall, all hell breaks loose below them.

Artist’s drawing of a supernova

The collapse of the core generates a vast explosion, a shock wave of incomprehensible power that moves out from the surface of the collapsed core into the layers of gas still surrounding it. Like a tsunami of energy, this shock wave works its way up to the surface of the star. The energy is so huge that the material it slams into gets heated to millions of degrees. When the shock wave breaks out through the surface, it bellows its freedom to the Universe with a flash of X-rays, a brief but incredibly brilliant release of high-energy light.

After that flash (what’s called the shock breakout), the explosion truly begins. The outer layers of the star — gas that can have many times the mass of the Sun, octillions of tons — blast outwards. The star tears itself apart, and becomes a supernova.

So — and this is important — the X-ray flash is emitted immediately, but the bright visible light follows it later.

Millions of light years away, astronomers on Earth patrol the sky with telescopes. We use ones that are sensitive to visible light, the kind we see with our eyes. They can see large parts of the sky easily, and that’s good since we never know where the next supernova will be. But that also means we don’t see the shock breakout; we notice the star exploding usually days after the actual event occurs.

We really want to see the supernova as early as possible; the physics, the mechanics of the explosion depend critically on what happens early on, so the younger we see the new supernova, the better we can tune our models and understand precisely how and why stars explode. An X-ray telescope would detect the first moments of the event, but they typically have too small a field of view to catch one as it occurs. The odds are simply way too small, and no one has ever actually witnessed the predicted X-ray flash from the shock breakout.

Until now.

Now, finally, we have seen a supernova go off right as the moment happened. And, ironically, it was an accident, an amazing coincidence, that allowed it to happen.

The Astronomer, the Coincidence, the Mobilization

NASA’s Swift satellite is sensitive to X-rays; it’s designed to detect the flash of light from gamma-ray bursts, which are a particular flavor of supernova. But Swift can also be used to observe older events, too. Alicia Soderberg, an astronomer at Princeton, had gotten time on Swift to observe SN2007uy, a supernova that had exploded the month before. This was a routine observation, and on January 9, 2008, she was actually on travel, ironically giving a talk about supernovae!

When she got back from her talk, she logged onto the Swift archive to look at the data as it came in, and got a huge surprise. There was a second, new source of X-rays in the field of view… and it was incredibly bright. She quickly realized what she was seeing: a new supernova caught in the act, the X-ray flash of the shock breakout detected for the first time. She realized Swift had caught the birth of supernova 2008D as it was happening.

The image above shows the pre- and post-discovery Swift images of the event. The upper images are in ultraviolet light, and show the galaxy NGC 2770. The bottom images show the same field, but in X-rays, where the galaxy itself is dim, but stars and star-forming gas clouds are bright. The images in the left column were taken on January 7, 2008 and the right column two days later, during the shock breakout. You can see how SN2008D is rather unremarkable in ultraviolet, but in X-rays is tremendously bright, washing out everything else in the galaxy.

Mind you, the X-ray flash from the supernova only lasted about five minutes. If Swift had not been looking right at the spot at right at that moment, this once-in-a-lifetime opportunity would have been lost.

That’s how cool this is.

I can only imagine what Soderberg was thinking when she saw that image on the lower right. Wow. But she acted quickly. She and her colleagues immediately mobilized a team of astronomers using telescopes across the world — and above it — to observe the newly born supernova. Using the Gemini telescope (the same one that made the beautiful picture at the top of this post) they quickly got spectra of the event, and it confirmed the event: she had bagged an exploding star. The energies of a supernova are so great that the outer layers explode outwards at a fraction of the speed of light, and velocities measured from SN2008D indicated expansion rates of more than 10,000 kilometers per second — fast enough to cross the entire Earth in just over one second, and faster than the expansion in a typical supernova.

The Aftermath

Because so many people observed this supernova from so early on, a vast wealth of knowledge was collected. The progenitor star probably started out life with about 30 times the mass of the Sun. Over a few million years, it shed quite a bit of its mass through a dense, super-solar wind, blowing off most (but probably not all) of its outer layers. When the core collapsed, the shock wave tore through what was left of the star’s envelope. Because there wasn’t as much material as usual surrounding the core, the energy of the blast could accelerate the gas outward at an unusually high speed. It’s also been determined that the explosion wasn’t symmetric: it wasn’t a perfect sphere, with the gas expanding in every direction equally. Instead it was off-center, with gas on one side of the explosion moving outward faster than on the other. This has been seen before, but never so early on.

All of this adds up to an incredible boon for astronomers. The observations collected are yielding a huge amount of information not just on this particular event, but on the basic parameters of supernova explosions themselves. Because of this happy coincidence — a new supernova occurring near an older one, and just as a powerful and sensitive X-ray observatory was pointed in the right direction, and with attentive scientists keeping an eye on their data — astronomers will take a huge step forward in understanding these tremendous explosions.

The Importance

You should understand something else here, too. As the blast wave moves through the gas of the star, the elements in that gas undergo an explosive fusion, creating new, heavier elements. Elements like iron, calcium, and gold. The hemoglobin in your blood, the bones in your body, and the wedding ring on your finger — all of these can trace their lineage back to a star that exploded like SN2008D. Every heavy element in the Universe was created in such an event, in the heart and fury of a supernova.

We owe our very existence to stars that explode.

That’s why work like this is important. Through science like this we can determine our own origins, from the hydrogen that formed a millisecond after the Big Bang, through elements built up in normal stars like the Sun, through heavy elements created in supernovae… to us.

That’s where science leads. We look out to the farthest reaches of the Universe, and we wind up seeing ourselves.


Comments (125)

  1. Michelle

    Woah! That’s just AWESOME! Talk about a bunch of luck right there. The chances of this happening right in your face are stunningly low.

  2. zach

    I’ve only been reading this blog regularly for a couple weeks now, so i gotta ask: is this much awesome astronomy stuff always happening? because you never really hear about it in mainstream news, I’d always kind of had the impression that new and exciting things from space happened few and far between. it seems, though, that cool things happen pretty frequently; is that true or has this been an exceptional few months so far?

  3. Wow. How freakin’ cool is that!

  4. serenity

    Freaking cool, and very well written! *applause*

  5. Michael Campbell

    “In a millisecond, more than the mass of the Sun’s worth of iron collapses from an object the size of the Earth to a ball only about 20 kilometers across.”

    My math is obviously wrong here, or I’m misunderstanding something.

    If something collapses from earth size (12756 km diameter) to 20 km diameter in a millisecond, the outermost shell of “stuff” is travelling inward for

    [(12756 km diameter – 20 km final diameter)/2] km

    in .001 seconds?

    That works out to be:

    [12_736 / 2] km / .001 sec =
    6_368 km / .001 sec =
    6_368_000 km/sec

    Which seems a tad > c by a factor of around 20. So either my math is faulty, or not all of it collapses in that time, or something else I’m obviously not cognizant of.

    Where’d I go wrong?

  6. Gnat

    I love the fact that she was able to mobilize astronomers world-wide! How cool is that? No governments, no red tape…just scientists coming together for science that they will all use. *happy sigh*

    Thanks, I needed that “utopian” moment today.

    And the supernova is cool too!


  7. Michael, the actual size of the iron core is somewhat smaller than the Earth. I wasn’t trying to be perfectly accurate, I was giving an idea of the range. The whole core is roughly Earth-sized, but doesn’t all collapse down. The details get muddy, and I didn’t want to overwrite that part. I suppose I could just talk about the iron part of the core, but the post was already getting too long. :)

  8. Fauxnetikz

    Freakin AWESOME. I bet she’ll be just floating off the ground for the next month.

  9. TravisM

    No doubt! And this gets a tag for Women in Science too! Un-freaking-believable coincidence… Well worded supernova narrative as well, I will use that when a certain friend of mine wants to gab science again.

  10. Well… if you put there 25 milliseconds instead of one, the speed is lower than c. I think he was giving the order of magnitude.

    And Phil, in the phrase “After a few million years of generating energy by fusing light elements into heavier ones”, at first I was going to say if you wanted to write “billion” instead of “million”, but now I’m not sure. ¿Is the star so massive that only lasts that little time? I think 30 solar masses could be enough, but just in case…

    I think I’ll translate this post into Spanish for my local astronomy club if you don’t mind. I can put the link here later if you want to.

    This is an AMAZING article. Very well explained. Thanks.

  11. Beth Katz

    How wonderfully serendipitous that Swift was pointed there. And kudos to Dr. Alicia Soderberg for the discovery and spreading the word.

    Why isn’t 2007uy still visible in the lower right photo? Is it a different field of view?

    Where can we read more about this?

  12. sirjonsnow

    Silly BA, you can’t fool us – that’s not an artist’s drawing of a supernova, that’s God’s eye!

    Very cool article.

  13. TomG

    At the end of the day, we are all the stuff of stars and are alike in more ways than we are different. This is an awesome event to have observed and that we will be able to learn from for probably years. Very nicely reported and explained. Good job!

  14. Stark

    DarkSapiens – Yep, It’s millions, not billions. Massive stars have very short lives on the cosmic timescale. They burn bright and die young – that’s good for us though or there wouldn’t be enough of the heavier elements in the universe for us to form! Supernovae are the begining of the life cycle for us carbon based critters!

  15. For the past month or so, i’ve been blogging with brief notes about astronomy events, about once a week, with links to articles. Last week bagged 14 articles, depending on how you count them. A slow week has two or three. When there’s an astronomy conference, there can be a dozen stories all at once just from the conference.

    This event took place in January, and we’re just hearing about it. That’s actually faster than usual. Many interesting articles are just coming out – used the ACS camera on the Hubble Space Telescope. This instrument has been broken for a year or so. Analysis can take awhile. But note: This was SN2008D – the 4th supernova in 2008, took place on the 9th of January. That’s a star exploding (and we notice) every couple days. Not all of them are news.

  16. Phil,

    Clicking on the image at the top of the article takes me to a login page at Is there a publicly-accessible site?

  17. Andre


    You got it right. Astronomy actually IS that cool!

  18. rob

    joni mitchell knew about nucleosynthesis and even sang about it at woodstock:

    “We are stardust, we are golden, We are billion year old carbon… And we got to get ourselves back to the garden”

  19. Stark

    Beth – most likely the x-ray burst of the new supernova was so bright it literaly drowned out the other dimmer source. It’s still there – it’s just lost in the background glow. Also, you have to remember that these are artificially colored images and the colors represent intensities of the x-rays – in order to represent the vastly “brighter” x-rays of 2008d I’m assuming that they would have had to shift the scale up a bit. This means that 2007uy probably dropped off the bottom end of the visible scale.

  20. Michael Campbell

    Fair enough – thanks BA and DarkSapiens. I was just practicing my skepticability, and these numbers immediately felt wrong, so wanted to know what the story was.

  21. phunk

    DarkSapiens: a 30 solar mass star will only live about 10 million years

  22. Naked Bunny with a Whip

    Birth pangs? So who’s gonna change this baby’s diapers, huh, did you ever think of that before your irresponsible nucleosynthetic fling?

  23. Togan

    “Iron builds up in the very center of the star, and no star in the Universe has what it takes to fuse iron.”

    If I remember correctly from my physics classes, iron can still be fused, it just takes more energy than it releases (otherwise we wouldn’t have heavier elements, right?) thus, if the star has still enough fusion of lighter materials going on, it should be able to fuse iron into those heavier elements as well.

    Please correct me if I remember wrong :)

  24. Togan,

    Re-read the part about supernovae creating heavier-than-iron elements in the explosions. I think Phil meant no *active* star has the energy required to fuse iron.

  25. BMcP

    I am curious to hear the reasons behind the knowledge that stars cannot fusion elements past iron no matter how powerful they are. Also, how were they able to figure out that process that leads up to the iron core. I understand through observations of our own sun, we know of hydrogen fusing to helium. How was it discovered that after the helium is all used up, that fusion into elements such as Oxygen, Carbon and so forth occur. Also, what happens to the iron core after the explosion, is it compressed further (and thus we get neutron stars or black holes)?

  26. slang

    Wow… you had an early supernova story earlier (even though to me it seemed the story wasn’t exactly right).. and now I can finally use the comment I had then for a *real* early supernova …. AWESOME! Keep us posted on any suprising results from this event, please!

  27. Thanks to all of you that clarified the million years thing :)


    You’re right, iron can be fused, but as BA says in the phrase you quote, a star can’t do that, or perhaps not in large quantities. The stability of the star depends on the pressure from energy coming from fusion reactions in the core to balance the heavy and large amount of material pushing from above due to gravity. Since iron takes more energy than it releases in fusion, it becomes insufficient, the equilibrium is broken, and the core collapses.

  28. SteveT

    I hope this one gets named the “Soderberg Supernova,” even if only in general usage. She deserves it just for being that lucky! Plus, it sounds really cool!

    I will always feel that the most mind-blowingest concept I have ever learned is the “humans=stardust” one. Thanks for reminding me, Phil!

  29. Conan

    Iron in the core fuses, into Nickel, and consumes energy, this cools the core very rapidly when this starts, and the outer shells of the star are no longer held by the heat and energy being radiated, and collapse at high-fraction-of-c speeds towards the core, then rebound off of it, causing the supernova explosion that we observe.

  30. Woweee. I wish I could see a supernova explosion in our own galaxy within our lifetimes….not the life-threatening ones you know…

    Incredibly well written Phil!!

  31. Iron can’t be fused in the core during the normal life of the star. In the blast of a supernova, though, it can be part of the fusion process to heavier elements.

  32. Dutch

    Thanks for the very cool story and explanation.

  33. Beth Katz

    Stark, looking at the pictures in the paper to appear in Nature May 22, Soderberg does make clear that SN2007uy is in that second x-ray photo. Those photos also show the scale which clarifies (even though Phil said so) that the photos are the same scale.

    This is so cool. I’m having fun describing it to my kids as they come home from school.

  34. Great article, saw it posted via Facebook!

  35. Benjamin Franz

    “The hemoglobin in your blood, the bones in your body, and the wedding ring on your finger — all of these can trace their lineage back to a star that exploded like SN2008D.”

    I remember reading that gold is probably more easily formed in gamma ray bursts when two compact objects (say, two neutron stars) collide. Additionally, the unusually high percentage of gold in the solar system compared with galactic abundances suggests that the majority of the gold here on earth was formed in just such a collision rather than in an ordinary supernova.

  36. Amazing luck, very exciting stuff!

  37. Chip

    Supernovae are amazing events. The calcium in our bones can trace its origin to such events. In many ways we’re truly children of the stars. In a sense we’re the universe looking at itself. Thanks for writing to inform and inspire as well.

  38. Colin J

    “That’s where science leads. We look out to the farthest reaches of the Universe, and we wind up seeing ourselves.”

    Well said. Could someone forward that to Ben?

    Great reporting BA!!

  39. PerryG

    Just adding a few more details as I understand them to an already great explanation: There are neutron-capture reactions that convert iron into something heavier, but as was stated, this actually consumes energy (they are “endothermic” or more accurately “endoergic”). I’m not 100% sure, but I think they would happen if there were enough neutrons and other particles called neutrinos around in the core, but there aren’t. These reactions later are driven by the energy created in the blast to create elements heavier than iron (when there are a lot of neutrons and neutrinos around to react with).

    With no more energy being produced in the core to hold itself up, the iron core collapses, an the atoms themselves are destroyed by the intense heat built up during the gravitational collapse. Since sub-atomic particles can get closer together than atoms can, the core collapses some something Earth-sized to something city-sized… The electrons and protons from the broken atoms react to create huge amount of neutrinos, too.

    And yes, cool things happen in astronomy every day that the general media doesn’t hear about! (And when they do, they can’t explain it nearly as well as someone like Phil can.)

  40. Keanu Reeves
  41. Togan

    Thanks Ryan, I must have missed that part :/

  42. Chris B.

    In my undergrad astronomy classes, I was taught (20 years ago) that the trans-iron elements are formed in the outer layers of the explosion as the shock wave expands through the star’s remains. Did I hear it that way? If so, is this still how we understand it?


  43. Chris

    Gnat said “No governments, no red tape…just scientists coming together for science that they will all use. *happy sigh*”

    I’ve had the same thought many times. Scientists from all over the world collaborate on the Large Hadron Collider, for instance, while their countrymen slaughter each other in pointless wars of religion and tribal vengeance.

    I read today a mob in Kenya burned 11 people for being witches, as the ISS glides overhead!

  44. Beth Katz

    These supernovae (SN 2007uy and SN 2008d) were observed on Earth within a month of each other. The galaxy containing them, NGC 2770, is 84 million light years away. For reference, the Milky Way is about 100,00 light years in diameter.

    Can we say definitively which star exploded first? Are there locations where each of the explosions would be observed before the other? How about SN 1999eh which is the other one we’ve observed in that galaxy?

  45. Stark

    Beth –
    Good question. I’m not sure on the exact distances of the 2 former stars (and don’t have time to look it up) but it is certainly feasible that 2008d exploded “before” 2007uy… however, from our local frame of reference we go with 2007uy happened first. It’s an accepted method to say that something happened “now” in astronomy when we know that in reality it occured 84 million years ago and the light from the event is only just reaching us. Using the relative timing of our local frame of reference makes keeping track of events much easier than if we were to use absolute measures that adjust for the distance to the object in question. As for could it appear elsewhere in the universe that 2008d came first : absolutely! It’s all a matter of location in relation to the events.

  46. a particular flavor of supernova

    Chocolate, butterscotch or Rocky Rocco… Road?

    that’s not an artist’s drawing of a supernova, that’s God’s eye!

    Is there a Mote in it?

    So who’s gonna change this baby’s diapers, huh, did you ever think of that before your irresponsible nucleosynthetic fling?

    Time to buy some Stellar-size Pampers[TM]?


  47. Doug Little

    The heavier elements created in supernovae are due to another process. You can read about it here.

  48. Axel

    Amazing. Your writing style is absolutly amazing! I am no star geezer and all that astonomer-lingo is nearly all gobble-di-gook to me. Not until I read your page, and I read all of it, and I did understand all of it as well. It is not that I am such a dummy, it is your wonderful style of writing which dilutes that highly condensed sci-talk to the “language of the common man”, so to speak. Thank you very much, and keep going, you are doing well!!!

  49. BaldApe


    Apparently Crosby Stills Nash and Young added the “billion year old carbon” line. It’s not in the Joni Mitchell lyrics.

    I have heard the Joni Mitchell version of that song only once. It is very different, in a good way, not to criticize the CSNY version either.

  50. carbonUnit

    Um, would it be fair to say this was a bad month for any lifeforms in that galaxy? Guess it’s not really a month, given the novas are more than a light month apart, right? That being the case, I guess there are places there where the x-ray bursts would have arrived simultaneously from both sides! How far out would those blasts be lethal to Earth like planets?

    An incredible and luck discovery!

  51. Chas

    As long as we’re picking nits on Phil….

    “84 million light years away. On January 9, 2008, a massive star in it exploded…”

    Don’t you mean, Phil, that the star went nova 84 million, 298 thousand, 364 years, and 3 months ago. Tuesday.

    Rather a lot of science involves looking at the right place at the right time (think fossils). But kewl!

  52. Chas

    That’s why we need more scientists, to look in more directions

  53. DuddleyFuddle

    If a supernova collapsed to a black hole, wouldn’t it suck in the explosion and the star stuff before it had a chance to get out. Maybe black hole supernova are never seen???

  54. Tom Marking

    “I am curious to hear the reasons behind the knowledge that stars cannot fusion elements past iron no matter how powerful they are. Also, how were they able to figure out that process that leads up to the iron core.”

    It has to with the nuclear binding energy per nucleon. If you check out:

    and scroll down they have a nice little chart in red plotting nuclear binding energy per nucleon versus atomic mass. The curve has a maximum of about 9 MeV per nucleon at about an atomic mass in the mid-50’s which would be iron.

    So nuclear fusion (combining nuclei together) occurs exothermincally on the left side of the chart from hydrogen up to iron, and nuclear fission (splitting nuclei) occurs exothermincally on the right side of the chart from uranium down to iron.

    Fusion from iron on up to uranium actually costs energy and is therefore endothermic. It occurs in supernova explosions where there’s a lot of excess energy available.

  55. Lies! Kent Hovind says you just can’t fuse past iron, and he taught high school science for 15 years. Are you saying that you’re smarter than Kent Hovind?

    Get a real education:

    Hahaha. Kent Hovind pwns all of Astronomy in 20 minutes.

    Are you sure this guy isn’t your anti-particle Phil? He sure likes simplifying science for kids. Well … oversimplifying actually.

  56. Tom Marking

    I’ve always been curious about the explanation for the actual explosion. One version is that the exterior layers of the star collapse upon the collapsed core and then rebound outward. I wonder if there is any actual evidence of this happening. I’m not sure it’s necessary since you can think of the central core shrinking as a sudden reduction in its potential energy which must be compensated by a sudden increase in the kinetic energy of the outer layers of the star.

    Also, how long before they can tell if this is a type I supernova or a type II supernova?

  57. Tom Marking


    has a way cool chart where they show how long the different fusion processes last:

    Hydrogen burning into helium – 10 million years
    Helium burning into carbon and oxygen – 1 million years
    Carbon burning into neon, sodium, magnesium, and aluminum – 1,000 years
    Neon burning into magnesium – 3 years
    Oxygen burning into silicon, sulfur, argon, and calcium – 0.3 years
    Silicon burning into iron – 5 days

    So the last fuel stage only lasts a few days before the star has exhausted all of its silicon and then the supernova happens.

  58. Alex Besogonov

    You can fuse iron and heavier elements, but it _requires_ energy input (that’s why we can get energy by _splitting_ uranium atoms).

    So when the iron core gets heavy enough it can’t support its own weight by radiation pressure from fusion.

  59. Fred Doutish

    Sorry, I don’t believe this.


  60. That’s some great astronomizing there Phil. I could pick your post apart like some of the other commenters but I’ll let it slide this time. Right now I think I am going to go and fuse a pint of beer to my liver. Cheers.

  61. Sudro

    Carrying on with the point that Gnat made way above, here’s a paragraph from Reuter’s article about the supernova:

    “The 38-member international scientific team rushed to have a look with both orbiting and ground-based telescopes including the Chandra X-ray Observatory, Hubble Space Telescope, Keck I telescope in Hawaii, Palomar Observatory in California and National Science Foundation’s Very Large Array and Very Long Baseline Array radio telescopes.”

    What strikes me here is the selflessness involved. From what I’ve heard about the scheduling for time on any of these major astronomical observation instruments, they sure weren’t sitting idle when news of the supernova started to spread. And they probably weren’t all coincidentally pointed at the same part of the sky, either. A lot of people gave up time on their own research to better everyone’s knowledge, with no apparent regard about whether it benefited them immediately and directly.

    Proof that scientists are cool people.

  62. Excellent and very cool description. This is the stuff that makes space science FUN!

  63. slang

    Thinking about this some more, and with all due respect for miss Soderberg (and with the caveat of not having read all articles linked) … doesn’t the Swift system itself (automatically?) send out a notice of a detected x-ray burst to other observers? That’s its normal mode of operations, right? Detect X-ray burst, send notice, slew spacecraft, start observing? (Obviously no slew needed this time).

    I like the suggestion of naming this the Soderberg nova, or something with her name in it. It is a truly significant event, and whether luck is involved or not, this researcher deserves some big kudos.

  64. Ken

    Mind blowing.

    Also, I didn’t really appreciate or realise that heavier elements come from supernova. No wonder Delenn thinks we are star stuff.

  65. Wow. I just saw this on PBS. Fascinating. First thing I did was click over here to see if you had any info and I found this great explanation.

    Thank you.

  66. Nathan Myers

    I will only note here that there was nothing at all ironic about either coincidence. The word just doesn’t mean that, fluffy Alanis Morisette lyrics notwithstanding.

    By the way, as I understand it the theory of supernova process predicts a more or less spherical remnant, but what we seem to find uncomfortably often is the hourglass shape consistent with a monstrously powerful example of the Z-pinch plasma instability readily obtained in laboratory experiments. It’s a spectacular show either way, and well worth recording.

  67. Darth Robo

    “No wonder Delenn thinks we are star stuff.”

    Yup. We are born of stars…


  68. Brouha

    Incredible blog post BA. Just amazing!

    This is one I’m sharing with the kids. Sadly (well, maybe not!) they probably will understand the physics of it better than me.

    It’s a big beautiful sky out there, especially at night, and your posts help us understand it just a little bit more. Keep it man, pretty impressive.

  69. Delenn

    It is a curious habit of the humans, to mistake the obvious for the profound. Of course we are made of stars for they came first.

    (Damn you, 177069, for making the reference first…. :))

  70. Bruce

    She can thank her lucky stars!

    (Someone had to say it)

  71. MandyDax

    BA, that is… wow, I need a tmesis in the midst of incredible, but I’ll keep it family friendly for ya. 😉 Alicia Soderberg has got to be feeling like the luckiest person on Earth.

    @Tom Marking

    Hydrogen burning into helium – 10 million years
    Helium burning into carbon and oxygen – 1 million years
    Carbon burning into neon, sodium, magnesium, and aluminum – 1,000 years
    Neon burning into magnesium – 3 years
    Oxygen burning into silicon, sulfur, argon, and calcium – 0.3 years
    Silicon burning into iron – 5 days

    Catching a Type II Supernova in the shock breakout – Priceless


  72. lars

    That’s clever! kudos to you MandyDax

  73. Tim Leonard

    Sure it’s a surprising coincidence that Swift was pointing the right way at the right time. But just how surprising is it?

    How much of the sky is covered by sensors that would detect the X-ray flash? How long does it typically take before a sensed flash is reported? How often do supernovae occur? Given those numbers, what’s the likelihood of such a timely detection this year? (The likelihood will change over time as the telescope population changes and as reporting procedures change, so its current value seems the easiest number to figure.) One in a hundred? One in a million? I’m curious, but don’t have the data needed to figure it myself.

  74. Michael Llaneza

    Let there be light !

  75. Tom Marking

    “Catching a Type II Supernova in the shock breakout – Priceless”

    LOL. That’s a good one.

  76. Buzz Parsec

    Slang, SWIFT has wide-angle gamma-ray detectors that cover most of the sky and very narrow-angle UV and X-ray telescopes. It’s designed to rapidly slew around to point at a gamma-ray burst and observe the source with the narrow-angle detectors. GRBs happen once a day or so, and when there aren’t any to observe, the telescopes don’t just sit idle. Telescope time in orbit is far to valuable to waste. Instead astronomers use the telescope to study interesting things, knowing that at any second the gamma-ray detectors could see something and steal the telescopes back for its primary mission. Soderberg was using it to observe a recent supernova when a 2nd supernova went off in the same galaxy. Supernovae occur once every few years in a typical galaxy, so watching one for a few days or a few weeks, the chances of a second one are probably about 1 in 100 or 1 in 1000, so it’s lucky but not something wildly improbable. Spotting the 2nd supernova very quickly, instead of months later while looking at the recorded data, and then getting lots of other astronomers to look at it also, using many different instruments while it was still happening, was the real heads-up play. Way to Go!!!!

  77. wright

    Wonderful writing as usual, Phil. Concise, easy to understand and full to bursting with your enthusiasm and wonder.

    Chas: “That’s why we need more scientists, to look in more directions.”

    Chas, that is a beautiful summation of Why Science Matters.

  78. slang

    Thank you mr. Parsec, can’t believe I forgot that GRBs are the main mission focus. Whiskey and thinking don’t always mix well, I guess :)

  79. You may be interested to look at this … check the image, then check the dates. Nice, ain’t it? 😉


  80. MarkW

    Long-ish time reader, (I first found the site while attempting to debunk a moon-hoaxer) first time commenter:

    That is freaking awesome. 😀

    I reckon that ~10% of a human (by mass) is hydrogen, that means the other 90% must come from stars. (I can safely ignore big bang nucleosynthesis; ain’t much He or Li in a human!)

    In fact not just from stars, from supernovae; there’s no other way heavy elements can get out of the star is there?


  81. Jeff Sonas

    Could someone please clarify the timing for me? I don’t quite understand how much time there was between the X-Ray detection and being able to see the supernova by visible light. I’m trying to get a sense of whether people could leisurely point their telescopes and see the very start of the supernova, or was it that we just got to join it in progress much earlier than usual, but not quite from the start? The “five minutes” is just how long it stood out on the X-Ray detection, right? But on the one hand we’re talking about things propagating at significant fractions of lightspeed, and on the other hand the AP article I just read seemed to imply that astronomers had a month’s warning of where to look to witness the supernova.

  82. MarijnS

    What are the odds of that happening? No, seriously, what ARE they?

    I suppose you’d need to know at least 4 things:
    -how many telescopes are on average looking at the universe?
    -how many stars are on average in the field of view?
    -how many of these stars are close enough to gather useful data (maybe for simplicity define this as <= 84 million light years)
    -what’s the average lifetime of a star that goes supernova

    Of course this is a very rough estimate, but anyone any ideas about what the odds are or how to calculate that?


    P.S. WOW, cool, amazinggg!!!!! this is really exciting. I am excited, honestly, I just though I wouldn’t start my post out with that because everyone else already did that :p

  83. Jonas Engelhardt

    That was a very well-written and informative. Keep up the good work, Phil :-)

  84. DLC

    Okay, so. . . today in history, Jan 9 83997992 BCE.
    A star in galaxy NGC 2770 exploded.
    (complete with a sticking out of the tongue at the Bad Astronomer)

  85. Way cool indeed, and it’s amazing that they managed to catch it when they happened to be looking the right way. I’ll have to second Michael Campbell, though; you should correct the math error in the core collapse time you stated. It’s the kind of error you see all the time in science popularizations, of course, but since your blog is titled “bad astronomy,” you have set yourself a high bar.

  86. Michael Giorew

    Hi Phil!

    My name is Michael, I’m from Poland.
    I heard the news about the SN2008D on the radio, I googlesearched some information about it and I found this page. The way You wrote that article/news/blog… whatever… was very clear and easy to understand, even for someone unexperienced. Congratulations! I bet a lot of people will more easily understand the importance of the finding of Alicia Soderberg, thanx to Your way of writing about it… :)

    Keep on the good work!

    Regards from Poland!

  87. In the future, maybe we could avoid luck.

    I am thinking of a “fly eye” xray camera, that has the ability to look at a thousand galaxies all at once. Now a supernova goes off, and the CCDs get a dose of X-rays. Now close off half the eyes. If the signal goes away, the supernova is in the set that closed off. Keep up this binary process 10 times, and you have the source of the signal. Now point the telescope at the target, using the main camera/lens.

    Lots of engineering problems – like x-rays are a pain to deal with so it might not be possible to look at a thousand sources at once. How long each step takes matters because there is only a 5 minute window to work, and pointing at a galaxy with precision might take too much time.

    Perhaps you guys do something like this already.

  88. Tom Marking

    “there’s no other way heavy elements can get out of the star is there?”

    Stars lose mass everyday. For example, our sun has a steady solar wind in which protons and other nuclei are ejected into outer space.

    When a star of roughly one solar mass reaches the end of its life it forms a red giant. Ultimately most of the outer layers of the star are ejected into space (becoming what we call a planetary nebula – it has nothing to do with planets, that’s just what it’s called) and the remnant becomes a white dwarf (no supernova takes place for a 1 solar mass star).

    The material that is ejected in the red giant phase may contain carbon and even silicate particles. So it’s a good bet that most of the material that formed our planet came from red giant ejection and not a supernova. It is only the elements heavier than iron that necessarily came from supernovae but they are a trivial percentage of the total mass of the earth.

    Here’s a good URL talking about it:

  89. Am I missing something or isn’t it true that this actually happened 84 million years ago? Since that’s how far it is, it takes that long for the image of it (light) to get to us. We didn’t watch this show live, we just happened to catch the episode as it aired.

    First sentence in article:

    “NGC 2770 is a galaxy at the relatively close distance of 84 million light years away”

  90. MojoJoeJoe

    # Alanon 22 May 2008 at 10:44 am

    You’re exactly right. This occurred roughly 84 million years ago, local time.

  91. William Raphael Hix

    Since I work on supernovae and nucleosynthesis professionally, I thought I’d clear up a couple points that have arisen in the comments.

    1) The carbon in the Solar System was probably made in Red Giants, but any silicon observed in a Red Giant was made in a prior star.

    2) Core collapse supernovae are responsible for the Solar System composition of Oxygen, Magnesium, Silicon, Sulfur, Calcium and their neighbors. CC SN are also responsible for roughly half of all Iron-Nickel-Cobalt elements in the solar system. These are all observed in supernova remnants.

    3) Elements heavier that iron are made in two processes, the s-process, which occurs in Red Giants, and the r-process. In both cases, these heavy fusion reactions require energy input, thus they can not provide energy to the hydrostatic stellar core. In both cases, these heavy elements are made in small amounts in regions dominated by helium and other light elements.

    4) While we understand the r-process pretty well on a microscopic level, we have quite a few potential places this could occur, including merging neutron stars and several variations of supernovae. All of these scenarios currently have significant problems, so there is room to argue in favor of your favorite. Unfortunately, the r-process represents such a small part of the ejected mass, it’s very unlikely to directly observe r-process elements in any of these events.

    5) If current simulations are to be believed, the core collapse timescale is more like a couple tenths of a second, however by the end, just before the bounce, the matter is falling in as fast as 20% of the speed of light.

  92. David P.

    Commenting on William R. Hix’s comment above:

    “5) If current simulations are to be believed, the core collapse timescale is more like a couple tenths of a second, however by the end, just before the bounce, the matter is falling in as fast as 20% of the speed of light.”

    That much matter going from essentially motionless to 20% of the speed of light, in that tiny time scale… is simply incomprehensible to my tiny mind. The energy that has to be involved is just… amazing. No other word for it.

    It’s things like this that I think can make science so awe-inspiring, independent of one’s personal philosophies and religious beliefs. The universe is simply stunning, regardless of what (or who) we think brought it about in the first place.

    I am feeling very, very tiny right now as I eat my lunchtime salad and read all this, but very, very big as I feel privileged that I/we can observe and appreciate what’s happening.

  93. jim

    We only just had astronomical confirmation of new supernovae in the 1970s, & someone’s already gotten shots of one taken right at the moment of its origin?!

    Very cool indeed … & Alicia Soderberg definitely won the Astronomy Lottery. With bells on.

    I think it’ll be quite a while before anyone gets this lucky again – although there may be new arrays that can stack the probability deck in our favour in years to come.

  94. Jackie


    Thanks for making the comment for me, so I didn’t have to.


  95. Stark

    OK, just a thing for a few of the folks who are confused about when the supernova happened : yes, it happended 84 million years ago in local time – that is time near the star that exploded. Now, we do not refer to it that way from here. From here we say it happened last Tuesday. The reason for this is simple – it would be much too confusing to refrence things by their absolute ages – especially when those ages don’t mean anyhting particularly useful to us. It’s far easier for our minds to refrence astronmical phenomena and ojects by their discovery date.

  96. FFPF

    Fantastic read. Thanks for writing it so well!

  97. flo

    wow. fascinating.
    10,000 km/sec- i feel so insignificant

  98. MarkW

    Thanks for the nucleosynthesis explanations people. 8) I clean forgot about solar (stellar) winds. D’oh!

  99. Sam
  100. Elizabeth

    re: other scientists turning over their telescopes…

    Don’t worry, they are very likely listed as co-authors on the paper.

  101. C is variable !

    No really it is, Einstein was wrong which is why we have so much trouble with quantum mechanics and no GUT that works.

    Take the tokamak for instance, how many stars look like a donut?

  102. sebas

    Hi. (great blog, thanks!)
    I’d like to know if the “5 minutes” are the time that usually lasts the x-rays emission (I mean if the x-rays are that instantaneous), or if it is the detection time length?

  103. rgyoegf

    Amazing. Do any of you think a creator made that.


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