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Birth of a Supernova

If the pace of discovery seems to be accelerating, that’s surely because of the network of tools we’re putting into place, able to work with each other both in space and on the ground to ferret out new information. Thus the collaborative effort that followed the remarkable observation of a new supernova, one caught so early in the process that it was found before visible light from the blast had begun to become apparent.

We have such tools as the Swift satellite to thank for this. Its ongoing observations of a supernova in the spiral galaxy NGC 2770, ninety million light years from Earth in the constellation called the Lynx, caught a three-minute, 40 second x-ray burst from the same galaxy, another supernova in the process of happening. What Swift seems to have uncovered was the shock wave of kinetic energy heating gas in the star’s outer layers to the temperatures that produce X-ray emissions. Such an event would be undetectable at optical wavelengths, which is where most supernovae have thus far been discovered.

Swift’s job is to use its wide-angle instruments to target interesting phenomena like the supernova now known as SN 2008D, at which point it puts other, more sensitive instruments on the alert. Both Hubble and the Chandra X-ray Observatory went to work, but so did numerous sites on Earth, including the Very Large Array, the Palomar Observatory, the Keck I telescope in Hawaii and too many others to list here.

Birth of a supernova

Image: Scientists had planned on studying Supernova 2007uy in the galaxy NGC2770, which was already several weeks old when seen in this visual, ultraviolet image (upper left) taken on January 7, 2008, by NASA’s Swift satellite. A close-up, X-ray image of that supernova is beneath. At the right, you can see SN 2008D, shown in ultraviolet imagery (top) and at X-ray wavelengths (below). Credit: NASA Swift team.

Alicia Soderberg (Princeton University), leader of the team studying this event, calls the new supernova “…the Rosetta stone of supernova studies for years to come,” a reasonable statement given that the ‘shock breakout’ of X-rays, triggered by the compression and ensuing rebound of the newly formed neutron star produced by the massive star’s collapse, has never been observed before. The team’s paper on the event shows that the energy and pattern of the X-ray burst are consistent with its origin in the exploding star. And note this:

“A fascinating conclusion from the theoretical modeling of this outburst is that a thin outer layer must have been ejected at velocities up to about 70-percent the speed of light. This speed is much higher than previously known for the bulk of the stellar envelope, which moves at only up to 10-percent the speed of light,” said Peter Meszaros, Holder of the Eberly Family Chair in Astronomy and Astrophysics and Professor of Physics at Penn State and leader of the theory team for Swift. “The relatively higher-energy X-rays observed can now be understood as the usual optical photons emitted by the supernova being boosted up to X-ray energies as they are batted back and forth between the slower envelope and the faster outer shell.”

Thus we gain plentiful data about how supernovae occur, which should help us tune the existing model. Current thinking is that stars far more massive than the Sun produce supernova explosions when they exhaust their resources for thermonuclear reactions. When the core of the star stops producing the needed energy, the core collapses, causing the rebound that blasts stellar materials into space. Either a neutron star or a black hole is left behind. If most supernovae show an X-ray outburst like this one, hundreds should be detectable per year with the space-based instruments we currently have in the planning stage.

And here’s something I didn’t know: Ninety-nine percent of the energy of a supernova is carried away in the form of neutrinos (this is from David Pooley at the University of Wisconsin-Madison). Pooley leads a quick-reaction team for the Chandra X-ray Observatory program and is one of the authors of the paper on this work. He sees our ability to study future supernovae as useful for future instruments like the IceCube neutrino detector being built at the South Pole. “If we have better and more accurate knowledge of when and where these happen, that would let an instrument like IceCube be more sensitive,” says Pooley.

Which could offer a natural segue into the uses of neutrinos, but I’ll put that discussion off until tomorrow. For now, the supernova paper is Soderberg et al., “An extremely luminous X-ray outburst at the birth of a supernova,” Nature 453 (22 May 2008), pp. 469-474. Available online.

Comments on this entry are closed.

  • James M. Essig May 21, 2008, 15:56

    Hi Paul;

    I also did not know that 99 percent of the energy of a super nova is carried away in the form of neutrinos. In a way, this is exotic physics itself, for we have yet to produce any exotic macroscopic explosion on Earth that produces 99 percent of its energy in the form of neutrinos. I am looking forward to tomorrow’s discussion on neutrinos.

    A really neat nuclear fusion research facility being built in the U.S. is the National Ignition Facility which will use 192 laser beams of high power wherein various optical flux compression techniques will result in an ultra temporally short pulse of UV light blasting a pellet containing fusion fuel. Although the device is designed to model nuclear weapons explosions for purposes of refining and developing advanced nuclear weapons, I can see that the device might also be useful in modeling shock-wave fronts in supernova in 4-D space time, 3 spatial dimensions and in time. The device will deliver about 1.8 MJ to the target.

    The facility will have x-ray cameras that are capable of taking a billion x-ray photos per second. I can see that the supernova researchers are going to want to use this facility to produce 4-D models of the supernova shockwave fronts surface breakthrough patterns etc. It will be nice to actually be able to produce laboratory physical supernova simulations.



  • forrest noble May 23, 2008, 0:53

    OK Jim, found you. Yeah Jim, I never heard of the asserted 99% factor either.

    Would like to find another mechanism to create heavy matter other than supernovae. So far stellar fusion has been ruled out. But it seems to me even though the percentages are small there’s a lot of “heavy atoms” out there for just the single source of creation by supernovae. But even in my theories I’ve conceived of no other reasonable possibility, as yet.

    That work they are doing with lasers on your reply I never heard of either. Sounds cool.

    your friend forrest

  • James M. Essig May 23, 2008, 22:18

    Hi Forrest;

    Perhaps even more powerful laser systems that dwarf the NITF would be able to produce super heavy elements in macroscopic rest-mass mass quantities via fusion processes. I can imagine blasting pellets of Lead, Gold, Uranium, Hafnium, Plutonium, Americium etc. with super intense burst of laser light to produce temperatures perhaps as high as 100 billion K or greater.

    We might even discover some important physics regarding the interaction of such an intense photon energy field and the decay processes of ultra short lived nuclei or other particles that decay through the weak force through the electroweak unification. Perhaps even novel photon effects involving electro-strong physics in terms of theories such as G.U.T.s might be unveiled.

    Either way, because the NITF opens up the field of nuclear physics with concentrated laser light, I can see no reason why high energy and sub-nuclear physics cannot be done in high enough energy density photon fields.

    As usual, I say let the fun begin. I can’t wait until the NITF lasers see first light. Knowledge gained in fusion research should help us get (in the spirit of Tau Zero) “To The Stars”.


    Your Friend Jim

  • ljk May 28, 2008, 14:15

    Around the Pair Instability Valley – Massive SN Progenitors

    Authors: Roni Waldman

    (Submitted on 26 May 2008)

    Abstract: The discovery of the extremely luminous supernova SN 2006gy, possibly interpreted as a pair instability supernova, renewed the interest in very massive stars. We explore the evolution of these objects, which end their life as pair instability supernovae or as core collapse supernovae with relatively massive iron cores, up to about $3 M_\odot$.

    Comments: 4 pages, 3 figures, to appear in proceedings of IAU symp. no. 252 – The art of modeling stars in the 21st century, Sanya, China 2008

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0805.3874v1 [astro-ph]

    Submission history

    From: Roni Waldman [view email]

    [v1] Mon, 26 May 2008 05:40:21 GMT (115kb)


  • ljk June 3, 2008, 16:49

    Shock Breakout Emission from a Type Ib/c Supernova: XRF 080109/SN 2008D

    Authors: Roger A. Chevalier, Claes Fransson

    (Submitted on 2 Jun 2008)

    Abstract: The X-ray flash 080109, associated with SN 2008D, can be attributed to the shock breakout emission from a normal Type Ib/c supernova. If the observed emission is interpreted as blackbody emission, the temperature and radiated energy are close to expectations, considering that scattering dominates absorption processes so that spectrum formation occurs deep within the photosphere. The X-ray emission observed at ~10 days is attributed to inverse Compton scattering of photospheric photons with relativistic electrons produced in the interaction of the supernova with the progenitor wind.

    A simple model for the optical/ultraviolet emission from shock breakout is developed and applied to SN 1987A, SN 1999ex, SN 2008D, and SN 2006aj, all of which have optical emission observed at t~1 day. The emission from the first three can plausibly be attributed to shock breakout emission. The photospheric temperature is most sensitive to the radius of the progenitor star core and the radii in these cases are in line with expectations from stellar evolution. The early optical/ultraviolet observations of SN 2006aj cannot be accommodated by a shock breakout model in a straightforward way.

    Comments: 11 pages, 1 figure, submitted to ApJL 4/30/08

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0806.0371v1 [astro-ph]

    Submission history

    From: Roger A. Chevalier [view email]

    [v1] Mon, 2 Jun 2008 19:48:56 GMT (14kb)