Eta Car: tick tock, tick tock

By Phil Plait | June 20, 2007 11:15 am

So when is the supermassive star Eta Carinae going to blow? No one knows. But at 100 – 150 times the Sun’s mass, it doesn’t have much time left. And the presence of lots of nitrogen in the gas surrounding it is a bad sign: that means that the star was making heavy elements in its core, then belching them up into space. By the time a star like Eta Car is making nitrogen, it doesn’t have long left to go. And when it goes, it’ll go.

The image above is from NASA’s Chandra X-ray observatory. The blue part is an optical image from Hubble, and shows the bipolar lobes of gas ejected when Eta Car had a coughing fit back in the 1840s. That’s 20 octillion tons of gas (20,000,000,000,000,000,000,000,000,000) it ejected at about a million miles per hour, in case you’re not getting enough awesome in your diet.

The yellowish ring is gas the star ejected long ago getting slammed by more recently blown out matter. The gas gets heated to a few million degrees by the impact, and gives off X-rays. By examining the energies of the X-rays, astronomers have found the ring is rich in nitrogen, and that’s the bad thing. Stars like the Sun fuse hydrogen into helium in their cores. If the star is really massive, then it can fuse helium into carbon once the hydrogen in the core is used up. Then it can fuse carbon into neon, and up the periodic table until it hits iron. Stars can’t fuse iron in their cores, which takes away the source of support for the zillions of tons of gas in the star. It collapses, and then complicated stuff happens (forgive me, I just wrote a long chapter for my next book about this, and I don’t wanna repeat myself right now… but I wrote a description of how this works on my Bitesize pages), and then the outer part of the star explodes. The inner part collapses down into a neutron star or a black hole.

Usually, a star like Eta Car can go through its hydrogen in a few million years. But each element fuses more quickly than the last, and by the time neon or oxygen is fusing, the star has literally centuries left at most. The presence of nitrogen in the gas means there was time to make that much of it, get it to the surface, expel it, and let it expand for a while.

So Eta Car is ticking bomb. It could go off tonight, or in the year 3000 (did Futurama ever cover this?), but it won’t be much longer than that.

Note that the lobes appear to be tilted away from us by about 40 degrees or so. That’s a good thing. When stars like Eta Carinae explode, they tend to shoot of beams of energy and matter that, at its distance of 7500 light years, could kill every living thing on Earth. But since it’s pointed away from us, all we’ll get is a spectacular light show. If you’re keeping score at home, gamma-ray burst aimed at you = bad, pretty supernova with no accompanying high energy radiation = good.

I just wrote a lot about Eta for my upcoming book, so if you like this kind of stuff you’ll love that chapter. It gave me the creeps, so I’m glad I’m done with it. Now I’m off to write about black holes devouring the Earth


Comments (159)

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  11. » Burn Notice | June 23, 2007
  12. » Eta Carinae pronta ad esplodere (well, actually happened 7500 years ago!) « Schininà.it - LogBook » Blog Archive | June 25, 2007
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  17. It’s Your Last Night On Earth | August 17, 2007
  18. CHROMEMUSIC » Scientific Update 2 | September 10, 2007
  19. Blog de Astronomia do astroPT » Eta Carinae | September 13, 2008
  20. Blog de Astronomia do astroPT » Carina | August 24, 2009
  21. Hubble. Is. Back! | Bad Astronomy | Discover Magazine | September 9, 2009
  22. Blog de Astronomia do astroPT » Eta Carinae | March 14, 2010
  23. Eta Carinae: una bomba sobre nuestras cabezas « La mentira está ahí fuera | October 24, 2011
  1. baric

    Eta Carinae is hot stuff right now.

    If it doesn’t blow in the next 10 years or so, people are going to want us to send a nuke over there to speed things up.

  2. SpikeNut

    Well said, Phil, and awesome picture.

  3. coolbreeze

    that is really is awesome stuff. I have heard about this star i did not know it was so Huge!!

  4. Sergeant Zim

    It’s pointed away from us at about 40 degrees – – or was, during the last blowup, but that was 170 years ago…

    Since this star rotates, does it also precess? And could the precession be enough to tilt the beam toward Earth? I’ll have to e-mail Hoagland about this, or maybe Jim McCanney… J/K, but it would be amusing, to see Nancy Leider claim that this is Nibiru she’s been talking about for so many years.

  5. Stars can’t fuse iron in their cores,…

    Why? I mean, why do they stop specifically at iron as opposed to some other element?

  6. Tankko

    So, if it’s going to blow in the next 1000 years, and it’s 7500 light years away, technically, it’s already blown. Is that correct?

  7. Tim G

    Since it is only 7000-8000 light-years away, when it goes supernova, it may appear one hundred times brighter than Venus, right? However, the star’s declination is -59° 41′ 04″. So it is only really visible from the southern hemisphere :-(

  8. JanieBelle, I’d answer that question, but then why would you buy my book next fall?

    OK, fine. Quick answer: it takes too much pressure and heat to fuse iron. And it takes more energy to fuse it than you get out of the fusion. Iron is just weird that way.

    There’s a lot more to it as well, but that’s the gist.

    Hmph. I need to add a “Death from the Skies” category.

  9. baric

    dead man watching?

  10. Indeed. At least if it’s done it within the last 7500 years.

    BA, has anyone ever done an animation of the past century of Eta Car observations, similar to the M2-9 animation featured by APOD/a> a couple of days ago?

  11. Heh. Local supernovae are one of those disasters that you just can’t do anything about. No last-minute space shuttle mission. No heroic mining team. No deflection by another passing celestial object. You are, quite simply, boned. Even being on the daylight side of the planet would only let you live another few seconds. 😀 I don’t know if the effects would be enough to melt the Earth’s crust, but by the time all life has been extinguished, who would be left to care?

  12. Gamma rays? Isn’t that what turned David Banner into The Incredible Hulk? *hee*

    I enjoy your blog even if I don’t pick up all the science on a quick read-thru.

  13. JanieBelle;

    If you were to plot the available energy from the nuclear reactions (both fusion and fission) of various elements you would see a roughly parabolic curve with iron at the bottom of the curve. Iron is at the bottom of the energy valley for both fusion (light elements fusing to make heavier elements) and fission (heavy elements splitting to make lighter elements). Iron does not release energy when it fuses into heavier elements, it sucks in energy instead. So the fusion energy released is like a marble rolling down a slope. It stops when it gets to the bottom.

  14. RayCeeYa

    “did Futurama ever cover this?”

    As a matter of fact yes. It was the episode where they go back in time to Roswell and Fry becomes his own grandfather. The episode starts out with the group getting ready to watch a super nova. Unfortunately Fry puts aluminum foil in the microwave at the same time the super nova goes. This causes the microwave rays to mix with the supernova rays tearing a hole in space time and sending them back in time.

  15. did

    OK, additional life goal: live long enough to see Eta Car go kerfloofle.


  16. Tim G

    Oops. I just checked my estimate and realized it may not quite reach the brightness of Venus.

  17. Tim, I get it being very roughly -7 in magnitude. The absolute mag for a supernova is -19, that is, how bright it would be at 10 parsecs. Eta is 2000 pc away, so it’s 200x times farther away than 10 pc. That means it will be 200×200 times fainter, or 1/40,000th as bright as -19. That’s about 12 mags, more or less. -19 + 12 = -7.

    If it went GRB on us, and the jets were pointed at us, it would be about mag -16 or so, depending on how energetic it was. That’s only 0.0001 as bright as the Sun, but brighter than the Moon by a factor of about 15. But the optical light is no issue at all compared to what happens when the gamma rays would hit us…

    These numbers are very rough.

  18. so wait –
    “If you’re keeping score at home, gamma-ray burst aimed at you = bad, pretty supernova with no accompanying high energy radiation = good.”

    The first question that pops into MY head is “what stars ARE aimed this way?”

  19. Bad Astronomer, et al.:

    When this subject came up in my corner of the Net, a helpful commenter provided links to journal articles indicating that Eta Car’s rotation axis is tilted away from our line-of-sight. Consequently, the jets from a GRB wouldn’t come our way.

    The abstract of B. C. Thomas et al. (2007) reads as follows:

    Recently Supernova 2006gy was noted as the most luminous ever recorded, with a total radiated energy of ~10^44 Joules. It was proposed that the progenitor may have been a massive evolved star similar to Eta Carinae, which resides in our own galaxy at a (poorly determined) distance of ~2.5 kpc. Eta Carinae appears ready to detonate, and in fact had an outburst in 1843. Although it is too distant to pose a serious threat as a normal supernova, and given its rotation axis is unlikely to produce a Gamma Ray Burst oriented toward the Earth, Eta Carinae is about 30,000 times nearer than 2006gy, and we re-evaluate it as a potential superluminous supernova. We find that given the large ratio of emission in the optical to the X-ray, atmospheric effects are negligible. Ionization of the atmosphere and concomitant ozone depletion are unlikely to be important. Any cosmic ray effects should be spread out over ~10^4 y, and similarly unlikely to produce any serious perturbation to the biosphere. We also discuss a new possible effect of supernovae, endocrine disruption induced by blue light near the peak of the optical spectrum. This is a possibility for nearby supernovae at distances too large to be considered “dangerous” for other reasons. However, due to reddening and extinction by the interstellar medium, Eta Carinae is unlikely to trigger such effects to any significant degree.

    I’d link directly to it (the arXiv provides the paper for free) but I’m already living in mortal dread of the BA’s spam filter.

  20. I was going to ask something similar to what Tankko said above. If it’s 7500 light years away, then even if it did go supernova today, we wouldn’t see it or any gamma rays for 7500 years, right? I mean, what we see when we look at it in the sky right now isn’t the way it really is right now, we’re looking at the way the star was 7500 years back, so how do we know it hasn’t happened already? I might be just confusing myself, but it just seems odd to talk about what’s happening with the star in the present if we’re really just seeing what happened in the past… meaning gamma-rays could already be on the way?

  21. Bryan

    Iron just happens to be the element that sits at the turning point for energy in nuclear reactions. For elements heavier than Iron, like Uranium or Plutonium, splitting the atom (fission) releases energy, and combining atoms (fusion) takes in energy. For elements lighter than Iron, like Helium, splitting the atom takes in energy whereas combining atoms releases energy.

    But it’s kind of weird- to get something like hydrogen to fuse, you need a lot of energy to compress it enough and make it hot enough to provide the right conditions, because normally atoms don’t want to get that close together. In a star, this energy comes simply from the weight of all of the gas above it crushing down upon the core.

    So if you look at how hydrogen bombs work, they split a bunch of large atoms, like plutonium, in order to get the energy to create the kinds of pressures and temperatures that you normally only see inside of stars, which is what it takes to make the hydrogen (well, really an isotope of hydrogen: deuterium) fuse and release even MORE energy.

  22. Crux Australis

    Phil, with your permission, you are about to become a permanent fixture in my society’s monthly astronomy newsletter (with full credit of course). It’s all due to posts like this one, and one-liners like “in case you’re not getting enough awesome in your diet”. I am, however, going to blatantly plagiarise that particular one for my own use in class.

  23. Tim G


    Thanks. I did a quick comparison with 1987A (which I now realize may have been obscured by dust) and assumed it reached an apparent magnitude of -3 instead of the actual +3.

    So Eta Car could appear around ten times brighter than Venus.

  24. spacenaut

    I have a grandstand view here in southern Australia. The Eta Carina nebula sits halfway between the Southern Cross & the False Cross, shining much brighter than the Orion Nebula.

  25. Stark

    Meh… it’s 7500 LY away… so we have at least that long to get out of the neighborhood before the Gamma gets here… :) Or we could just empty out the meteor belts and build a really BIG radiation shield out beyond the moons orbit. Heck, that should be do-able in 6000 years I would think. I mean we only achieved flight 100 or so years ago and now we can land objects on other planets.

    Toungue firmly in cheek folks. I do realize, of course, that if a star goes nova and a GRB is pointed at us we’ll have a few seconds to go “Huh, that sure is a bright star!” before we were cooked like an egg in a microwave… and that would be the first warning we had of our impending doom.

  26. If it does go off in my lifetime, I’ll just *have* to fly to Australia to see it.

  27. Rowsdower

    Okay, I get that stars can’t fuse iron, but where do heavier elements come from? There’s more heavier elements than lighter, and that’s not even counting transuranic elements. (Fe = 27, U = 92.)

  28. If it’s 7500 light years away, then even if it did go supernova today, we wouldn’t see it or any gamma rays for 7500 years, right?

    We talk about stars as being how we view them because we are essentially talking about them from our own frame of reference. It is nearly a 100% certainty that, in reality, Eta Car has long since blown…probably 6000 years ago or more, but the light hasn’t reached us yet. When we see the first light from the supernova, we will reference the supernova as having happened on that date, not 7500 years prior.

  29. Rowsdower:

    Heavier elements are formed during supernovae!

    There are probably many good resources about this; one which springs to mind is Evelyn’s “Origin of the Earth” series at the Skepchick blog.

  30. Why do the jets follow the rotation axis?

  31. DenverAstro

    All the really cool stuff is south of the border dangit. Them folks down there got the Megellanics, they got the Centaurus group, the got Tarantula…
    Right, thats it. Im moving to the Shire, Bag End, you folks in New Zealand just got fair warning.

    (now they’re gonna lock every door and window on the whole island)

  32. Kelfazin;

    The short answer is “we don’t know for sure”.

    A longer version is here:

  33. How close would a supernova have to be in order to boil off a coma & tail from everything in the Kupier belt? That would be worth seeing, even if it did turn the stratosphere into NOx for a while.

  34. has

    “When stars like Eta Carinae explode, they tend to shoot of beams of energy and matter that, at its distance of 7500 light years, could kill every living thing on Earth. But since it’s pointed away from us, all we’ll get is a spectacular light show.”

    Whee for us (this time…), but I can’t help feeling it’s still going to put a real damper on some poor sod’s day. Imagine: it’s a lovely day out, the suns are shining, and you’re feeling pretty dang pleased with yourself having evolved your first prehensile toe just that very morning, when “What the F…” – along comes one of Eta Car’s silent-but-deadlies and turns you and yours to a sad little puff of loosely dissociated hydrocarbons without so much as a “sorry”.

    Man, talk about bad gas. Somebody pass the Glade.

  35. has

    (But on the bright side: “Oooh, teh pretty!”)

  36. Skepterist

    Fry: “I’ve never seen a supernova blow up, but if it’s anything like my old Chevy Nova, it’ll light up the night sky”

    It took me a long time to start to wrap my brain around the whole time/distance thing, and I’m sure I still don’t have a firm grasp of it. They say the light that we see from Eta Carinae today is from about 7500 years ago. Whether you are using a giant telescope or your own eyes, that light is still 7500 years old. If Eta Carinae did suddenly blow, and if it were pointed in our direction, then we would have almost no warning before the gamma rays hit us, since the gamma rays would also be traveling at the speed of light. In other words, by the time we see the explosion, it would be too late.

    I don’t know for sure, so someone correct me if I am wrong, but I imagine there could be a brief period of time from the initial explosion to the actual burst of gamma rays. I think that is on the order of seconds or minutes, not years…

    Its hard for me to comprehend time frames of thousands or millions or billions of years, unless its when I’m waiting for the next Harry Potter book/movie.


  37. Bad Albert

    Is an octillion more or less than a gazillion?

  38. Folcrom

    As a rule of thumb
    All elements from Helium through to Iron are created during fusion processes in the cores of stars.
    The more massive the star, the heavier the elements the star core can fuse.
    Supermassive go all the way to and stop at iron.
    Elelments heavier than iron are created during the violent supernova explosion.
    The core implodes, the outer shells explodes, heavier elements are produced.
    In short:-
    Elements Helium through Iron are created during the life of a star.
    Elements heavier than Iron are created during a supermassives stars death.

  39. Sergeant Zim

    Octillion is the SI unit of measure. Gazillion is the old ‘standard’ unit.

    Of course the Engineers in the group will recognize the more accurate unit, “A Whole $hitload”.

    Still reminds me of the morning Presidental Briefing last year, when one of Dubya’s advisors told him that 3 Brazilian soldiers had been killed in Iraq.

    Dubya shook his head sadly, and commented on how terrible that was, then turned to Carl Rove and said, “How many is a Brazillion?”

  40. Crux Australis

    DenverAstro, I guess you mean the North Island. There are 3 islands in the New Zealand mainland, Bag End is in the North one. My grandparents live a few minutes’ drive from there. No, they are not hobbits.

  41. Heather S

    Well silly me. I saw the headline in my reader and thought you’d suddenly started writing about Basque separartists. Neato. Now I really have to save up to go visit my brother in Kiwistan…

  42. Lo'ihi

    Stuff happens.

  43. Grand Lunar

    Not sure how to check, but is Eta Car visible from South Florida? Hate to have it go BOOM and not be in a place where I can’t see it.

    Also, is there any way to detirmine it’s exact mass? Or at least narrow it down further?

  44. (quote)# Bad Albert Says:
    June 20th, 2007 at 4:56 pm

    Is an octillion more or less than a gazillion?(/quote)

    Only if you put your little finger to the corner of your mouth, and say it ala Dr. Evil. 😉

  45. Brian

    Gadzooks! Prepare the neutrino detectors.

  46. So could something that is 7,500 light years from Earth
    do us any real harm, even if it were aimed at us?

  47. Bean Counter

    “in case you’re not getting enough awesome in your diet”


  48. The Tarrkid

    The other cool thing about you guys making a SWAG on the magnitude…

    Since Venus is visible during the daytime, and you’re saying this bad boy will be about 10x brighter…

    It should be easy for most Below-Average Joes to spot during the daytime (if we can just get them to look UP every now and then)

    So with all due respect to anything living near Eta Carinae…


  49. Dom

    Its crazy to me that its actually already blown and we are just waiting for the particles to get here.

  50. Stark


    If the gamma ray burst of the impending Eta Car supernova was pointed directly at us – even at 7500 LY distance – it would mean the end of all life on Earth. We’re basically talking about the galactic equivalent of a microwave oven here. Boiling oceans, everything taht can be on fire is on fire, crust of the planet metling… generally a VERY bad day. It’s possible that the crust of the planet may not melt (due to the distance involved – I’ve not doen the math on that) but still, everything dies. You end up with a nice sterile piece of rock in orbit around the sun.

    There is good news though. The odds this ever occuring are vanishingly small. Teh small number of supernova in our galctic neigbhborhood, combined with the vastness of space means that a GRB pointed right at us is a VERY unlikely occurance. A besides, if it did happen we’d probably never even know what hit us. We’d certainly have no warning that it was coming and all human life would be snuffed out pretty darned quick when it hit.

  51. Thanks for the quick answer, Dr. BA.

    And I’d buy your book anyway, even if I already knew all about every subject in it.

    Just so y’know.



  52. Astrogeek, thanks for furthering my understanding. I think I get what you’re saying, and it relates back to what Dr. BA said, right?


  53. Further thanks to Bryan, Blake and Folcrom. I didn’t mean to leave you out, I just hadn’t gotten that far yet.

    With Kate’s help, I think I’ve got a handle on it now.

    Kisses to you all,

  54. JanieBelle;

    Yep. Same stuff as what Phil (and several others) said. Iron builds up in the core of these super-massive stars but doesn’t burn (fuse). It just sits there until it reaches a certain critical mass, at which point it collapses under its own weight, setting off the supernova.

  55. Chip

    Wikipedia offers a more refined and a slightly less alarming view of GRBs with regard to mass extinctions on Earth. The article also differentiates between an early-Universe, very distant extra-galactic burst of which there are many, and a different kind of burst theorized to be much rarer within our more metal rich galaxy.

  56. Tim G

    Grand Lunar,

    At 26 degrees north latitude, Eta Car should be above the horizon for only a few hours every day, reaching a maximum angle of about four degrees.

    The time of day of visibility shifts throughout the year. Eta Car could go supernova at a time of year when it is above the horizon in south Florida only during daylight.

  57. [Beavis] heh heh…car bomb…heh heh [beavis]

    You’re starting to give me headaches on a regular basis. One of these days it may stop hurting and start firing on all cyclinders again!

  58. Ok, so here’s an astro-geometry question then.

    Is Eta Car ever directly behind the sun? I don’t think it is, because Carina is outside the twelve zodiac constellations through which the sun appears to travel, but if I’m mistaken feel free to correct me.

    So here’s the hypothetical question…

    Just for argument’s sake, let’s suppose that Eta Car were directly behind the sun from our vantage point when the gamma ray burst came crashing through our system. Since I believe I read somewhere that the gamma ray burst only lasts a very brief time (seconds or minutes?), would the sun protect us from utter annihilation, or would the gamma rays pass right through the sun unaffected and turn us to cinders anyway?

    My guess is that it wouldn’t matter, right? Even in its plasma state at the core, I wouldn’t think the density of the sun would be enough to stop the enormous energy of the gamma rays, would it?

    …or am I talking out of my very cute little butt?

  59. JanieBelle:
    Gamma Rays can’t even penetrate the atmosphere. You won’t get irradiated by them, especially if you live in the Northern Hemisphere- eta Carinae is next to the Southern Cross, so to get to the North they would have to pass through the Earth.

    What a gamma ray burst would do is to ionize the upper atmosphere, which would then recombine to form nitrous oxides. These nitrous oxides would eventually form nitric acid and rain out, but only after eating most of the stratosphere’s ozone. Depending on the energy, there might be a bit of 14-C or 10-Be produced as well, but it is mostly the ozone depletion coupled with solar UV that is the main risk factor from gamma irradiation.

  60. Thanks Lab Lemming.

    I knew Carina was in the southern hemisphere, but wasn’t sure of the exact position/geometry of the earth/sun/eta car setup. D***ed astronomers refuse to draw nice, neat little squares on the sky so I can visualize them better. No, they gotta have irregular boxes, size and shape arbitrary, wherever they feel like it. And what’s with the 88 thing? Hello? Metric system anyone? And what about Aries? Does anyone see a ram in …

    uh… sorry. Where was I?

    oh yeah. Death from above.

    So the gamma rays are not the direct cause of our incineration, but because such a concentrated burst would wipe out the ozone layer, we would basically die of severe sunburn?

    Further, if the gamma rays can’t even get through our atmosphere, in my previous scenario they wouldn’t be able to get through the sun, either?

  61. Ken G

    To the BA– I have noticed a certain misconception that creeps at times into your descriptions of the luminosity of massive stars, and it exists in spades in the Nick Strobel web notes you link to at . Here are some quotes from those notes, and I will explain why they are drastically inaccurate:

    “Massive stars have greater gravitational compression in their cores because of the larger weight of the overlying layers than that found in low-mass stars. The massive stars need greater thermal and radiation pressure pushing outward to balance the greater gravitational compression. The greater thermal pressure is provided by the higher temperatures in the massive star’s core than those found in low-mass stars…

    The nuclear reaction rate is very sensitive to temperature so that even a slight
    increase in temperature makes the nuclear reactions occur at a MUCH higher rate. This means that a star’s luminosity increases a lot if the temperature is higher. This also means that a slight increase in the mass of the star produces a large increase in the star’s luminosity.”

    There are two significant misconceptions in this quote that you see in a lot of places. It is time to stamp this out once and for all! First of all, massive stars have *weak* gravities, not strong– that’s why they are not degenerate. So Nick is just completely wrong there, it is not the strong gravity that causes their cores to be at somewhat higher temperatures– the gravity is *weaker* than in a low-mass core. Which leads us to the second paragraph and the really insidious falsity: that the need for higher temperature is the *cause* of the higher luminosity. That exactly reverses the correct logic– more massive stars need higher luminosity simply because they are very *large* leaky buckets of bright radiation– end of story. Given this need, such stars must leak out a huge luminosity, and *that’s* what forces the core temperature to be high. The core temperature will simply be whatever it needs to be to supply the needed luminosity, not the other way around! This correct logic is expressed in just a handful of places– it is remarkable how often you will find authoritative books and websites that get this wrong. I’m sure Nick’s notes are excellent in many ways, but he has fallen victim to this phenomenon in a big way.

  62. A chicken passeth by

    But even if it does blow in our direction, won’t it still take 7500 years for the gravity wave to get here?

    (Judging from the state of the world right now, I’d say we need all the time we can get. >_>)

  63. is your measurement of the explosion (roughly a thousand yrs.) a measurement of the actual explosion, or a measurement of when we’ll experience it on earth…

    if it actually blows in a thousand yrs., earthlings wont experience it for another 7500 yrs…

    well, let me take that back.. the measurement is done with the statistics and evidence taken from the observatory so technically, this star may have already lived it’s last days, huh?

    anyway, nice blog man.. i like it..

  64. Ed

    Wow, this is some impressive stuff.

  65. Cool

    “I’d just like to say here, that this is my only line….”

  66. Chip, the Wiki article is OK, but doesn’t talk about distances. A GRB at a distance of about 7000 light years could still do serious damage to the Earth, as it says. I am writing about this for my book, and have a stack of journal papers three inches high on the topic. :-) One paper calculated that even at that distance, secondary particles (muons) created in our air from the gamma rays could do devastating damage to life on Earth. I’m hoping to get more info on that soon.

    Either way, Eta isn’t pointed at us, so I’m not concerned. I don’t think it can precess that way either. It’s a massive star and probably a binary, so the angular momentum will keep it pointed in the same direction.

  67. Narky

    How long would the super-nova last?

    I realise the explosion itself would be over in mere moments, but how long would we have to see the visuals ?

    Is this something that we’d see as a bright flash in the sky? Or something that would remain burning brightly for quite some time?

  68. Adam


    “A supernova may briefly out-shine its entire host galaxy before fading from view over several weeks or months.”

    So we’d be able to see it for awhile. Also in the wikipedia entry on Eta Car:
    “At least one scientist has claimed that if the star were to explode, “it would be so bright that you would see it during the day, and you could even read a book by its light at night””

  69. John

    Is the shockwave of particles distributed in any manner like a sandslide or mudslide.. smaller swifter particles riding the surf ahead of the larger stuff?

    I’m just speculating.. but over 7500 light years it seems there would be practically a rainbow of distribution.

    And not that I’m a crack pot physicist or anything, but wouldn’t this be an awesome laboratory instrument for detecting all sorts of off exotic particles, I mean line up several particle detectors in solar space and aim them at Eta Carina.. maybe we could start by looking for Cherenkov radiation ? Tachyons ?

    I doubt we’ll ever be able to build a particle accelerator with as much Umph.. at least in our lifetimes.

    Of course maybe the scale precludes what we can do in a laboratory.. but there’s an awful lotta mass doing some wicket particle experiments just for the looking.

  70. bushcheney1984

    I’d be interested to hear a bit more about the interaction of GRB’s and other radiation fronts interacting with planets (my favorite is Earth, because I live there) and the various scenarios for doom. All the “but if it exploded 1000 years ago, and light takes, um, 7500, uh…” is getting old in this chain.

  71. Well, bc1984, I *am* writing a chapter about this in my book… but that won’t be out until next Fall. I’ll be doing a series of podcast interviews with astronomers for each chapter, and those’ll start coming out probably next year sometime, though maybe sooner.

  72. Mikeinjapan

    Congrats on the front page of Digg! When this thing blows will we see awesome beams flashing out of both ends, or just a brightening of the star?

  73. Roman

    Thanks for the article and for the great comments!

  74. David Winter

    In case there are SF readers in these scientific circles … :) Greg Egan explored the idea of a gamma ray burst wiping out all life on Earth ca 3000 AD in his novel “Diaspora”. Luckily, at this time most of mankind has already transformed into robots and pure software intelligences … It’s a great novel, although it uses the radiation burst only as a plot device, indicating that transforming our species into a space-faring software intelligence might be a pretty good safeguard against large-scale catastrophes, as it allows backups/copies of individuals and groups to travel to other parts of the galaxy.

  75. John Magee

    Given that its 7500 light years away, it probably doesn’t exist anymore! we’re just awaiting the light show! :-)

  76. Bob

    You have a great way of explaining things. Much better than NOVA or Discovery channel.

  77. Alex

    Oh growup guys its just the cloking device for the vogon ship 😛

  78. btw what is … ‘tronomy’? must be good for it be badas@

  79. Alex;

    They’re parked there for the Carina Invitational Poetry Contest?

  80. Suppose Eta Car is a superweapon made by an alien race
    that doesn’t like to share the galaxy with others. Maybe
    they are getting it ramped up and ready to turn at the
    next civilization they find. Oh, say, one that has been
    broadcasting into space for about 100 years.

    So we’ve got about 7,400 to get ready before they find us
    and put Earth in their sights. And then another 7,500 years
    before the blast hits us. You think in 18,000 years or so
    we’ll be able to shield maybe the whole Solar System?
    Would a Dyson Sphere do the trick too? Maybe they
    are the only type of galactic civ that survives.

  81. Cassandra12:

    To paraphrase the Geico cave man: “Buhhh… *WHAT*????”

  82. What if Eta Car is a weapon being used by an advanced alien
    race to get rid of the competition?

  83. I guess I should have checked your home page before I expressed my disbelief. It’s obvious you live in a different reality. However, taking your question at face value:

    1) If an alien race was A) advanced enough and B) mad at us, sure, I suppose they could make Eta. Car go ‘boom’, but why do that to Eta Car (7500ly) when Antares is much closer (604ly)? Heck, if they can do that to Eta Carinae, why not just do it to our own sun… that would be much more effective.

    2) We have no evidence of advanced alien races, despite what Hoagland, Art Bell, or anyone else you link to on your home page says.

    3) There is no evidence that Eta Car is doing anything other than following its normal, predicted path of stellar evolution.

    In the end, you’re left with a big bag of nothing, while the real astronomers, who do real science, are looking at Eta Carinae as a huge opportunity to see a Type II supernovae close up, and from relative safety.

  84. Rick

    For those of us well up in the northern hemisphere, would there be any observable Eta-glow on the lunar surface? I’m guessing that Earthshine would overwhelm any shadow Eta would cast.

  85. Mallorn

    […] And not that I’m a crack pot physicist or anything, but wouldn’t this be an awesome laboratory instrument for detecting all sorts of off exotic particles…
    I doubt we’ll ever be able to build a particle accelerator with as much Umph.. at least in our lifetimes. […]

    Current particle accelerators provide far more “umph” than a supernova which only goes up to MeV energies while current accelerators are at TeV energies i.e. 1,000,000 times larger. Of course supernovae heat up a LOT more material than an accelerator but us particle physicists are a lot more interested in energy per particle than total energy.

  86. CFTeague

    Not 7500 years from now… it’s “soon”.

    While, true, if it actually blows up tommorrow, it would take 7500 years, but it’s not going to blow up tommorrow. They are guessing that it’s blowing up soon, based on the light that we can see now; so thats 7500 year old news.

    It’s (almost certainly) already blown up, probably 7450 years ago. So it’s only 50 years more to wait…

  87. Sam-Hec

    Cassandra12 said:
    “What if Eta Car is a weapon being used by an advanced alien
    race to get rid of the competition?”

    There was an anime to that effect not long ago, complete with the requisite annoying teenieboppers, and giant mecha.

    Contemplating moving to Australia…

  88. Neil

    Is it just me that’s pedantic enough to be annoyed by all the people saying “well, maybe it’s already happened, we just haven’t seen it yet”? I thought that the convention was that we speak of stuff happening _when we see it_ – and we do not talk about possible events currently outside our light cone as if they have already happened.

  89. Nathan Myers

    I wonder if anybody understands supernovae as well as is claimed. Did anybody predict supernovae would not be spherically symmetric? Does anybody have an explanation why they are so perfectly axial? Is the X-radiation from the “gas” (which we know to be completely ionized, therefore not gas at all, but low-density plasma) really thermal, or is it synchrotron radiation?

  90. Raph Hix

    Phil, you’re certainly having fun with this. It’s good to see stellar astrophysics draw a crowd. It certainly would be a good show if Eta Carinae went off. Should make getting supernova proposals funded easier too.

    I wanted to clear up a couple misconceptions that have crept into the discussion.

    1) While the discussion of the burning stages is correct, it’s important to note that nitrogen is not produced with carbon and oxygen. Nitrogen is actually a by-product of hydrogen burning. In hot stars, 2 solar masses and more, hydrogen burns via the CNO cycle, a series of catalytic reactions on carbon, nitrogen and oxygen that converts hydrogen to helium and leaves the carbon and oxygen as nitrogen. So the presence of nitrogen in the circumstellar matter means the envelope mixed down to the hydrogen burning shell, not into the core. Still a sign of advanced evolution, but not of mixing beyond the helium layer.

    2) If Eta Carina really has a mass of 100+ solar masses then it probably will explode well before it produces iron in the core. When its core is composed of oxygen, it will undergo a “pair-production” supernova. Now, during the explosion, 20+ solar masses of radioactive nickel will be produced. Note that until the recent observations of supernova 2006gy, these pair supernovae existed only in computer simulations, so we’re not on the firmest ground here. But if it is like 2006gy, the absolute magnitude is more like -22.

    3) While half of the isotopes heavier than iron are made in the “rapid neutron capture process” or r-process, which we think (but can’t prove) happens in supernovae, the other half are made in “plain” giant stars. The “slow neutron capture process” or s-process works in the hydrogen and helium burning shells of asymptotic giant branch stars, adding neutrons to pre-existing iron to build up things like lead, etc.

    Whew, that was a lot to type in the little comment box.

  91. Ralph, good comment!

    1) I was not too clear on the nitrogen production in the article, true. As a matter of fact, I think, when I wrote it, I was mixing up the CNO cycle with a later process. Nuts. So nitrogen is made pretty much immediately in the star. Then my basic premise, that Eta may blow very soon, may be off. It depends on the convection cycle and stellar wind timescales.

    2) I don’t think we know enough about this, as you point out, to make solid claims yet. One supernova does not a pair-production model prove. But as far as timing goes, I wonder how much of a lifetime difference it would make; it’s not like 100 solar mass stars live a longtime. Five million years? Less?

  92. Ralph mentioned in passing

    20+ solar masses of radioactive nickel will be produced.

    Can you buy radioactive shoes with those? I need some shoes that sizzle!

    Sorry, those two glasses of wine that I drank while watching the Stargate series finale that I didn’t drink because I’m underage have kicked in would have kicked in about now.


  93. Byron Clarke

    So you mean to say that if this star were oriented in a different way it could have wiped out all of humanity from 7,500 light years away? That’s an incredibly scary thought!!

  94. timo

    Cool… Though my guess is that it is gone already, we will just see it bit later.
    Anybody to track it for me during the next 7500 (or half of it) years, please jump
    back in time and tell me how it was:-)

    Anyway, the thing I am wondering is… With these american vs. european
    notations of large numbers, which is the correct one? I mean that one would
    expect physics to have an agreed definition, right?

    From an european background the value 20 octillion tons is something different
    than the one presented here. No complains about the article, really, bus just an
    attempt to find out what is the “real” naming. The best rule I ever learned was
    the “1 illion”, “2 illion”, “3 illion” – where one is supposed to replace the “1”, “2”,
    etc by “mono”, “bi”, “tri” and so on. With this it suddenly makes sense that
    “illion” is 1000000 – and the number of zeroes is multiplied.
    Thus million has 6, billion 12, trillion 13 zeroes and so on. Octillion would have 48, not 24.
    [ But even for 24 there seems to be disagreement, whether octillion is 24 or 27 zeroes. ]

    But I would really like to know whether there is an agreement on these in the
    (astro)physics, and if so, why is this not pushed for by articles? Whatever the
    definition (IMHO european makes more sense) the scientist would then have
    a way to educate a common agreement on the one they use. I doubt they need
    to convert it between the two.

    Big numbers anyway – and beyond my understanding surely…

  95. charles

    A rough equivalent of the earth being struck by a Carinae-style gamma-ray burst would be if you detonated a one-kiloton nuclear weapon for every cubic kilometer of atmosphere on the side of the world facing the beam. Everything on that side would instantly receive about 50x the lethal dose of muon radiation streaming down from the stratosphere as it was essentially reduced to plasma. The fireball would reach all the way around the other side of the world, and fry everything there, too.

  96. Tom

    Thanks for this blog post. It was interesting. My question is, if a star goes boom in the middle of a forest, er, I mean, Space, will anyone hear it?

  97. Anonymous Coward

    Sorry, but I have questions about this whole “GRB” thang. Since gamma rays are only energy (photons/quanta(!), they are subject to the “square law” of dissipation, and we *are* throwing around a distance of 75K *light years*, at which point, Car is only a “point source”.

    Unless some sort of natural “graser” (visible light makes lasers, gamma rays make grasers(?)) is being postulated, I don’t see how the “destroy all life on earth” bit is correct. Gamma rays emit from the source in a nice spherical distribution, 360 random degrees in every direction, *normally*. So how/where is this here “GRB” being forced into coherency? That’s what would be required for such an effect. or so a very casual inspection of the numbers seems to show.

    Further, not to throw TOO much cold water on all this, what prevents molar disruption of our whole exploding star’s gas shells, once they are clear of the exploding solar mass, perhaps turning them into on-site shielding (or at least gamma ray disruption/defraction) mechanisms?

    Lastly, at the range of 7500 light years, there is a very good chance of intervening clouds of gas, dust, and other interstellar materials/medium, up to and including water-ice crystals, ammonia , and other “heavy” atoms, which would also tend to be gamma-ray disrupters/defractors/shielding………

  98. borderinsanity

    Dumb Question of the Day: Let’s suppose that one could engineer living conditions near the Earth’s core; would the ~3000 km of Earth between the core and the GRB allow one to survive?

    Dumb Question of the Day follow-up: How about living ~2500 km under the surface of the Moon?

  99. RME

    I’m confused.

    If time is measured by the speed of light then is it correct to say this has already happened? Or is it more correct to say it is happening now? It seems awkward to say it happened 7500 years ago when time is measured by the light we are seeing.

    Oh, there it goes. My brain just jumped out of my skull. Gar, relativity.

  100. llewelly

    Dumb Question of the Day follow-up: How about living ~2500 km under the surface of the Moon?

    I think the moon is only about 1,738 km in radius. So 2500 km down puts you 762 km from the surface on the other side.

  101. Carinae

    Anonymous Coward, The Gamma rays are indeed focused out the rotational poles of hypernova. The core of the star collapses into a Black Hole, which forms an event horizon, an accretion disk and begins ‘eating’ the star from the inside out.

    The accretion disk gathers around the solar equator. It is VERY dense and very energetic. Gamma Rays cannot penetrate it. But they CAN penetrate through at the solar poles, where the density is lowest.

    It’s not a coherent beam, but it is highly focused. If we lie in the path of that beam, we’re literally toast.

  102. Nell, I think people are talking like that because Cassandra12 is talking about it taking 18000 years to destroy us, when “if it’s already happened” it would be more like 50. Though of course Cassandra12’s hypothesis requires it to have happened no more than 100 years ago, which doesn’t match the observations…

    Unless the aliens took a look at us 7 millennia ago and predicted our rise.

    Which would make them pretty damned prescient, and yet pretty slow to react.

  103. Carinae

    Ok, now I have a question myself. How do we know where Eta Car’s rotational axis lies? We see the twin gas lobes, but I thought the prevailing theory on the lobes requires that there be a companion star to focus the lobes. ie: the companion star orbits perpendicularly to the axis of the lobes, and NO information is given on the orientation of the primary star.

    Furthermore, we KNOW that supernova can reorient a stars rotational axis. See: Pulsars. So it’s within the realm of possibility….

  104. Romulan Ghost

    No one has answered the question of whether or not the calculations of when the star will supernova are based on when we will be able to see the light from the event or on real time estimates. B.A. the photo shows us an event that happened roughly 7500 earth years ago, so did the star supernova 3000 years after that and we need to wait 3000 more years to see it?

  105. DWC

    Could our sun protect us from the worst of such an event if we were to place it between us and the source of the burst?

    What about heavy water?

  106. Romulan Ghost

    “DWC Says:
    June 23rd, 2007 at 2:14 pm

    Could our sun protect us from the worst of such an event if we were to place it between us and the source of the burst?

    What about heavy water?”

    What about little, pointy aluminum hats?

  107. AH, Charles, it looks like you have been reading the same papers I have. yes, I saw that exact number in a paper. I wrote that up for my chapter in the book, too. I’m wondering, though, if that number is actually accurate? I haven’t been able to corroborate it thoroughly yet.

  108. To be fair to DWC, yes, that’s correct. The Sun is much larger than the Earth, so if it just so happened that a burst occurred with the Sun between us and it, we’d get no effects (at least none I can think of off the top of my head).

    Note, though, that that Sun’s area is about 1/50000th the area of the sky, so the odds of the Sun blocking a GRB are 1 in 50,000.

  109. chronusmcgee

    Actually a star of that size can fuse anything on the periodic table, and a few things not on that table. When it comes to iron, which the write said cannot be fused, for instance. That is actually an error. When Iron is fused the net energy of the reaction is negative, instead of positive for lighter elements. Nonetheless, if the core of the star is fusing other lighter elements as well, there is still enough energy to form iron as well as the heavier elements. In reality, there is always a small but distinct probability that any star capable of fusion can produce heavier elements not normally on the menu. These elements won’t be found in very high quantities, but they will be produced.

    Any collision between lighter elemental nuclei has a chance to form a larger nucleus, it’s just not very probable for lower temperatures and pressures. A star with a highly turbulent atmosphere could stir up the heavier elements from the core, while one with more laminar flow would appear pristine in a spectrograph.

  110. Koliedrus

    This sort of thing fascinates me to no end. Not just the subject of the post but the questions asked and the answers given. My mind has been taken on a 7500 light year journey and back from the top of the page to the end.

    Some were asking questions regarding things like the Sun’s ability to deflect a GRB from the blast. The answer in this instance is “no”.

    Keep in mind that my official designation in the astronomy field is most aptly entitled “armchair” but given the number of tools available to the likes of me, I can cross-reference in order to come to certain conclusions.

    The plane of the Solar System is tilted in a way that has Eta hanging below us in the sky. Consider a string tied to the center of a Frisbee with a rock tied to the other end of the string. I gladly use the reference “below” since the bulk of our galaxy’s mass is located in roughly the same direction.

    From the perspective of the upcoming supernova, most of the radiation will impact the Earth’s south polar region.

    I invite climatologists to go to town with that information. The internet allows me to be an “armchair” one of those so I’ll keep my theories about outcomes regarding this particular set of parameters to a minimum. That is, until I turn my gaze in that direction.

    I can make guesses about what a relatively close supernova burst of gamma would do to Antarctica and move forward in time to describe localized effects. Instead, I propose getting Larry Niven and Steven King in the same room and just mention the subject. Hopefully they could hammer something out before a point in the southern sky goes “POP!”

  111. Stenny Hoyo

    What is the average degree of spread for a GRB and were one with a point of origin 7,500 light years away to occur, how broad would the beam be by the time it reached our solar system?

  112. DWC

    Fair enough, and getting a little roughed up, is fine.
    I am thinking more along the lines of moving off of the earth, and drifting around the sun in an attitude that would put out us out of harm’s way.

    Yes it is reminiscent of the Ark.

    Yet, by the same token, learning to drift for a long time independently of the earth could allow us to eventually return to our planet and pickup where we left off.

    This is probably not going to be the first time a blast of high energy particles has cleansed the earth of complex life – genetically orchestrated complex life.

    Nor would this likely deprive the earth of its freely available sources of energy.
    AS long as we have access to freely available sources of energy then we can rebuild.

    The need would be to explore space first by developing technologies that allow us to spend long long periods of time in space while in relative proximity to both the earth, and the inexhaustible source of energy provided by the sun.

    Space exploration gradually closer to the sun has an imperative that moving away from the sun lacks.

  113. bsingle


    When you wrote “20 octillion tons” above, what did you mean by a “ton,” since that is a weight and not a mass? Eta Car would have stronger gravity than the earth, and so that might lop off a lot of zeros. I’m not being facetious, I’ve just been trying to figure it out.

  114. Phil T.

    The QT column in today’s Chicago Sun-Times featured this page as its lead item. This is not the first time QT has featured BA. You can read it at,CST-NWS-qt24.article

  115. Big Star Girl

    I hope medical science advances fast enough for me to live to see it!

  116. DWC

    It is looking like a lot of people are making demands on your time.
    This was a very interesting
    thanks for your response you were able to offer me.

    God Bless

  117. DWC

    It is looking like a lot of people are making demands on your time.
    This was very interesting
    thanks for your response you were able to offer me.

    God Bless

  118. DMH

    What I would like to know is how much warning or lead time would we get from the released Neutrinos prior to the ‘main event’ of the protosphere torching off Eta Carinae? From what I understand the shockwave of the explosion would be outraced by our friendly neutrinos giving us some lead time to point the instruments that way. But how much time?

  119. Carinae

    DMH, during the supernova 1987A, a 12 second burst of neutrinos was received just before the supernova was detected. 1987A was 20x the distance of Eta Car, which might reduce the warning time somewhat.

    12s warning at best.

  120. Dwayne Hicks

    “Eta Carinae might be pretty again if it were properly back-lit”:

  121. make

    Would be absolutely fantastic if it went hypernova, those supposedly happen once in a 200 million years. Nice time to be alive, to see the millenium change and possibly a hypernova.

  122. Hm. Maybe I should make some bumper stickers that say “My other car is Eta Car”.

  123. Eta is getting dimmer:

    This is a bit confusing. More to come!

  124. Romulan Ghost

    So, has this event already happened and we are seeing 300 year old light? Are we waiting to see if any of the effects will reach us? Will it be another 300 years before it nova’s and another 300 before it is seen on earth?

  125. TAMU Student

    Now, I’m no physicist, but wouldn’t Eddington pressures prevent a star from over 60 Solar Masses from forming?

  126. Paul

    I am completely ignorant when it comes to astronomy but I am trying to do some research and I need a little succor from those who are not:

    Do supernovas create shockwaves, or anything that we could feel besides the deadly gamma rays you guys are talking about- like a tremble or something?

    What other kinds of radiation are dispersed during supernovae and what are their effects?

  127. why do the jets follow the axis?

  128. wow that’s pretty scary if the explosion could blow the earth.. since hubble was launced ppl has new perspective on outer space

  129. Den

    Terrific story here, but your blog is worth to read for some general information about our crazy world

  130. MikePacasi

    Mr. john Says: The “path” oriented thorough the two mutually opposed axis are created by the “last” minute dynamical deformation of space-time due to the formation of a black hole. That “path” is the only “corridor” left for the gamma ray to scape from the black hole field of attraction just before the singularity forms, or just out of the horizon of events, I think…Please correct me who know a better explanation..

  131. MikePacasi

    To Mr. john: The black hole has a spinning momentum related to the rotation of the star which originated it. I think that a theoretical black hole with a zero angular momentum would not produce the GRB jets but rather it would spread out the GRB in a spherical 3D pattern..

  132. Mikolaj O'Brien

    it will be inpossible to send a nuke to a star so far away. the reason for this is because the original plan for defence of the earth from asteroids is to nuke the incimng asteroid but the main reason why this wouldn’t work even if it was a little as 100,000miles incoming the nuke wouldn’t have enough fuel to get to the star. And also, the nuke would have to be about the size of our earth to destroy a sypermassive star.

  133. sometimes I think it’s necessary to keep a few people, including young women, of cause, in space. Maybe they can land after a planet crash and start producing new people again :)

  134. And then you just realize how small and unimportant we are….

  135. It probably wont blow, at least not in my life time. At least I hope so! 😀


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