Supernova Secrets Seen In X-Rays

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."

Comments

Wilhelm Roentgen Would be Proud

[Publiu5]

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

Re:Wilhelm Roentgen Would be Proud

[daknapp]

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.

Re:Wilhelm Roentgen Would be Proud

[wonkey_monkey]

There is no universal consensus for a definition distinguishing between X-rays and gamma rays.

Re:Wilhelm Roentgen Would be Proud

[daknapp]

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."

Re:Wilhelm Roentgen Would be Proud

[Anonymous Coward]

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.

Re:Wilhelm Roentgen Would be Proud

[Anonymous Coward]

Electrons can just as well emit gamma rays, for example in inverse Compton scattering processes. And gamma rays are produced in inelastic proton scatterings.

In some sense, the GP was correct because in some subfields, the photons emitted by those processes would be labeled as x-rays. Where the GP failed was not for the distinction between x-rays and gamma rays by source process, but for insisting that those subfields are the only valid definition. For better or worse, there are several technical definitions/jargon words that change definition with field, although in this case it is a lot less confusion compared to say the definition of a metal being any element other than hydrogen or helium.

Re:Wilhelm Roentgen Would be Proud

[marcosdumay]

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

Looks like for astronomers, the correct name is "x-rays". At least, you said so. And that being an article about astronomy...

No model eh?

[Anonymous Coward]

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.

Re:No model?

[Urkki]

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?

Re:No comments in 1 hour

[Sepodati]

First comment was 8 minutes after the summary was posted.

Why are you still here? You know what's more annoying than beta? The kid that has to come around every day to tell you that he's leaving. This time for good. I mean it. I really do. I'm being serious here, guys. I'm out. I'm leaving.

Bah to slide shows!

[antdude]

One ugly web page showing thumbnails: http://deslide.clusterfake.net... OR http://desli.de/11IE ...

Wiki defn.

[justthinkit]

Wiki:

The distinction between X-rays and gamma rays has changed in recent decades. Originally, the electromagnetic radiation emitted by X-ray tubes almost invariably had a longer wavelength than the radiation (gamma rays) emitted by radioactive nuclei. Older literature distinguished between X- and gamma radiation on the basis of wavelength, with radiation shorter than some arbitrary wavelength, such as 10â'11 m, defined as gamma rays. However, with artificial sources now able to duplicate any electromagnetic radiation that originates in the nucleus, as well as far higher energies, the wavelengths characteristic of radioactive gamma ray sources vs. other types, now completely overlap. Thus, gamma rays are now usually distinguished by their origin: X-rays are emitted by definition by electrons outside the nucleus, while gamma rays are emitted by the nucleus.

Re:No model?

[jaharris87]

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.