An octillion ton cannonball

By Phil Plait | November 30, 2007 8:58 am

Astronomers using the Chandra X-ray telescope made a pretty nifty observation of the supernova remnant Puppis A.

This pretty picture (click to embiggen) is a combination of X-ray and optical observations, and it shows just how impressively huge a supernova event can be. Attend:

Puppis A formed more than three millennia ago when a massive star exploded at the end of its life. Over time the cloud of debris expanded, forming this intricately woven web of filaments of gas.

Only the outer layers of the star exploded outwards, though. The core of the star collapsed to form a neutron star, an ultradense object with the mass of a star like the Sun, but squeezed into a ball only a few kilometers across.

Neutron stars are funny beasts. Some of them are seen to be screaming across the sky at fantastic speeds, up to hundreds of kilometers per second (fast enough to circle the Earth in a few minutes). What could possibly toss around an object of that mass so quickly?

There are two ways, in fact. The star could have been in a tight binary orbit around another massive star. When it exploded, it loses most of its mass. The sudden drop in mass lowers the gravity of the system, and its the gravity holding the two stars together. When the gravity lets go, the two stars slingshot away from each other at high speed.

Another way is for the explosion itself to be off-center. When the core of the star collapses, triggering the explosion, there are several complicated processes that can make the explosion asymmetric. This acts like a rocket, kicking the new neutron star in one direction while the ejected matter goes off in the other.

Usually, it’s not easy to figure out which scenario took place in a given supernova. But in Puppis A, using Chandra, the astronomers found massive blobs of oxygen created in the explosion all moving in roughly the same direction. The neutron star that was once the core of the star that exploded was found to be moving in the opposite direction! When they added up the velocities and masses of the blobs, they matched those of the neutron star: but in the opposite direction. So the forces all balance out, indicating it was an off-kilter explosion that blasted the star off at high speeds. In the picture inset, you can actually see the motion of the neutron star over the six years between observations.

From the images, the astronomers figured the neutron star is moving at at least 5 million kilometers per hour. That’s fast. In the 3700 years since it formed, it’s moved about 20 light years, or 200 trillion kilometers.

I study this kind of thing all the time, and in fact I researched this very topic for my second book (to see how fast I could get a black hole to move, so that I could work out the math of what would happen if one approached the Earth… yikes!). And yet the sheer size and scale of events like these never ceases to give me a chill down my spine. The Universe is such an amazing place. I’m really glad we’re here.


Comments (28)

  1. Coo, but what’s that little spindle in the direction of motion of that x-ray source?


    Oh, it’s an arrow. An Astral Arrow of Arjuna the Archer.

    That or it was photochopped on. Whatever.

    Lessee… 20 c*yrs / 3700 yrs means 0.0054c. That’s a damn good clip. Is it fast enough when, combined with the gravitational force of the star, to start getting large relativistic effects (like compression and embiggened tau fields) around it?

  2. If the moving chunk runs into anything, it would presumably be bad. Is there anything obvious in its way? I would guess that would make quite a light show.

  3. It’d put the Deep Impact copper impactor to shame, at the very least.

    Although that brings up a good point. It’s going 0.005c through interstellar dust. Wouldn’t that have some effect? I’d love to see some star-asploding action myself, although waiting a few more millenia to see it would be problematic.

  4. bigjohn

    Phil, you insist on using the term ’embiggen’ which, as every one knows, is not a real word. I wish that you would use a proper word. In this case the proper term should be “unsmallify’. Thank you.

  5. Gary Ansorge

    Isn’t it amazing that a three pound chunk of wetware has the potential to understand these complex phenomena?

    I have high hopes that our currently unknown(intellectual) inadequacies will be supplemented/compensated for by our development of alternative mechanisms of thinking, (ie, Artificial Intelligence) and we will continue to grow in our understanding of the complexity of this marvelous reality.

    WAY cool pics, Phil.

    GAry 7

  6. Ken B

    “Embiggen”, “unsmallify”, who cares? It’s just 72 of one, half a gross of another.

  7. DrFlimmer

    I haven’t checked your results, but if the neutron star really moves with 0.005c than there is no real relativistic effect. you can do the calculations still in the “classical” way and will fit very good. Relativistic calculations start at about 10%c, I think.
    But the damn thing is still VERY fast and rushing into a star would be a very nice fireworks. But, sadly, such crashes are very unlikely. There is too much space between the stars, so the chances are really low (when 2 galaxies collide, there is almost no star-crash!), except it will run into a star cluster, but I don’t think that we are lucky.

    Btw: I’ve read on that a new record of the mass of a stellar-mass Black Hole (not the big ones in the cores of galaxies!) has been established: 24 times the mass of the sun. That’s quite heavy!

  8. I wonder if the blue parts of the ROSAT/optical image are the x-ray and represent that expelled oxygen? The overall shape of the SNR is amazingly symmetrical for an off-center event…

  9. OneHotJupiter

    THIS has got to be one of the coolest stories in quite some time , diggin’ it!

  10. Justin

    Woohoo! I finally read something on my own research before finding it here!!

    I’m stealing your sources, Phil!

    But I’m still reading it here because you use small words that people like me can understand.

  11. Navneeth

    This post is a couple of days late! 😛

  12. DrFlimmer:

    I did make sure to post my math. 😉 I know relativistic effects only occur at about 0.1c normally, but also it’s not usually considered that an extremely high-mass high-density object like, say, a neutron star is going anywhere near that fast. One already gets relativistic space-bending around neutron stars orders of magnitude greater than around normal stars (gravitational lensing due to the whole ‘high mass high density’ part) and so I’m wondering if that combined with velocity effects in relativity make that fraction of c truly non-negligible.

  13. Gary Ansorge

    Hey folks, check out this article on proto-galaxies from

    Way cool insight into the presence of dark matter in the early Universe.

    Gary 7

  14. DrFlimmer

    The Centipede:

    Well, I forgot about the general-relativistic effects and then you’re right, I was just thinking about special relativity. Could be very interesting if we really can see such effects – fast moving gravitational lenses, sounds like a fascinating object 😉

  15. Jack

    Forgive me for not understanding astrophysics properly, but – traveling at 5 million kph relative to what?

  16. Raymer

    Hey, out of curiosity, I decided to figure out what percent of the speed of light this star is moving. I did some math and came up with 0.4% of the speed of light. Can anyone confirm my math? Doesn’t seem so fast now does it!

  17. DrFlimmer:

    > sounds like a fascinating object

    Hells yeah. I’ll admit my knowledge of general and special relativity is that of the dilettante, but this pretender to knowledge is very, very interested in what studying something this massive going this fast could yield.


    > Hey, out of curiosity, I decided to figure out what percent of the speed of light this star is moving. I did some math and came up with 0.4% of the speed of light. Can anyone confirm my math? Doesn’t seem so fast now does it!

    It went 20 light years in 3700 years. From me, in the first reply,

    > Lessee… 20 c*yrs / 3700 yrs means 0.0054c.

    You’re off by three orders of magnitude.


    > traveling at 5 million kph relative to what?

    Your mom.

    Meaning probably us here on Earth, and, as local variations in orbital and rotational speeds are relatively negligible next to 5 x 10^6 km/hr, equivalently relative to your mom.

    The Centipede: Bringing ‘your mom’ not-exactly-comebacks to the comments since… well… right now.

  18. Raymer

    Yeah, using that math I think I’m still pretty close. I mean, talking percents here, 1C would be 100% of the speed of light, of course. So 0.0054c would be 0.54% of the speed of light. Or am I wrong on how to figure percentages? It’s been a while.

  19. Raymer said:

    Doesn’t seem so fast now does it!

    5,000,000 km/hr – approx. velocity of the neutron star

    107,000 km/hr – approx. orbital velocity of Earth

    The neutron star is moving at approx. 46.7 times the speed that the Earth orbits the sun, and has a much greater mass. Does it seem faster now?

  20. *sees the decimal point*

    Hm, yes. Forget the three orders of magnitude bit. For some reason, every time I look at less-than-single percents my brain goes “DECIMAL POINT IS FALSE DATA.” Mea culpa.

  21. Less-than-one percents. Argh. It’s Friday, I’m tired, I wanna go home, and I wanna take a nap. :(

  22. Raymer

    Haha, it’s alright. Was just curious, I like to think of things in percents. I’m weird like that.

  23. Ted

    “Embiggen” is a perfectly cromulent word. I wouldn’t use it in a professional journal, but it’s fine on the web.

  24. > Haha, it’s alright. Was just curious, I like to think of things in percents. I’m weird like that.

    Just don’t come down with a case of accountancy. I hear it’s terminal[ly dull].

  25. John Phillips

    bigjohn, should we then call you unsmalljohn :) Conversely, I Myself am an unbigjohn

  26. Sergeant Zim

    “Enbiggen”, “Unsmallify”
    This just goes to show that if you give some people an attoparsec, they’ll take 1.61 terra-angsroms…

  27. Joules

    >I wonder if the blue parts of the ROSAT/optical image are the x-ray and represent that expelled oxygen? The overall shape of the SNR is amazingly symmetrical for an off-center event…

    the link says that the blue-ish purple clumps are indeed oxygen.


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