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Supernova Secrets Seen In X-Rays

Posted by samzenpus on from the check-it-out dept.

wjcofkc writes "CNN reports that astronomers using NASA's NuSTAR telescope have for the first time mapped deep within the radioactive material from a supernova. The light from the originating star, Cassiopeia A, located about 11,000 light-years away and having had about eight time the mass of our sun, first reached Earth about 350 years ago. But that does not mean there still isn't a lot to study. Scientists using the NuSTAR, which stands for Nuclear Spectroscopic Telescope Array, launched in June 2012 and consisting of an instrument with two telescopes that focus high energy X-ray light, were able to peer deep within the cataclysmic aftermath. While there is currently no model for how the process of a supernova works, the findings in the study are a big step forward. 'Until we had NuSTAR, we couldn't see down to the core of the explosion,' Brian Grefenstette, lead author and research scientist at the California Institute of Technology, said at a news conference Wednesday."

7 of 23 comments (clear)

  1. Wilhelm Roentgen Would be Proud by Publiu5 · · Score: 2

    The marvels of x-ray radiation: not only can they shed light in the inner workings of humans, but also the stars themselves...

    1. Re:Wilhelm Roentgen Would be Proud by daknapp · · Score: 4, Informative

      Unfortunately, in this case the observed photons were actually low-energy gamma rays. I guess they are called "x-rays" in the article because they fall into the region of the electromagnetic spectrum that is usually associated with x-rays. Ti-44 undergoes electron capture to Sc-44, which emits the two gamma rays at 78 and 68 keV, and then the Sc-44 decays (again by electron capture) to Ca-44.

      But they are not true x-rays.

    2. Re:Wilhelm Roentgen Would be Proud by daknapp · · Score: 4, Interesting

      Universal, no, but physicists agree, and, really, who else matters? X-rays are emitted by electrons (atomic transitions or bremsstrahlung); gamma rays by nuclear transitions. Those definitions have been pretty well agreed upon by physicists for at least the last 15 years.

      Astronomers, however, seem to characterize photons only by energy, which kind of makes sense if you realize that they frequently don't know the origin of the observed photons and build instruments for energy ranges instead.

      But nonetheless it is still incorrect to characterize these photons as "x-rays."

    3. Re:Wilhelm Roentgen Would be Proud by Anonymous Coward · · Score: 5, Informative

      No it is not incorrect. Your definition comes from nuclear physics but X-rays and gamma rays can and are produced in other ways too. Electrons can just as well emit gamma rays, for example in inverse Compton scattering processes. And gamma rays are produced in inelastic proton scatterings. As you say, in astrophysics we classify based on energy and typically keV photons are X-rays and MeV photons and up are gamma rays.

  2. No model eh? by Anonymous Coward · · Score: 2, Informative

    http://en.wikipedia.org/wiki/Supernova#Current_models
    http://arxiv.org/find/all/1/all:+AND+modelling+supernova/0/1/0/all/0/1

    Slashdot editing at it's finest.

  3. Re:No model? by Urkki · · Score: 2

    I Think it means, no working model, which would match observations. In current models supernovas do not happen reliably, the stars fail to actually go supernova. Is it a supernova model, if there's no supernova happening according to the model?

  4. Re:No model? by jaharris87 · · Score: 2

    State-of-the-art models produce reliable explosions in 2D with a neutrino heating mechanism, but given the extraordinary computational cost of three-dimensional simulations (one model costs ~100 million hours of total compute time), the jury is still out on if these models will explode with no imposed spatial symmetry. Despite this, it's looking more and more like we understand the fundamental principles of the mechanism, and a lack of a supernova in one of these 3D supernova models is more likely to be the result of an unjustified approximation or technical oversight in the numerical analysis.