Furthest Gamma-Ray Burst Ever Observed

jd writes "The SWIFT team have announced the furthest-ever observed super-massive gamma-ray burst (from 13 billion light years away). The burst was observed on the 6th of September and lasted for 3 minutes - long enough for a number of other telescopes to home in on the gigantic explosion. The distance is only barely within the reaches of the observable universe. The idea of the SWIFT telescope and follow-up observations is that they will discover both the cause of the bursts and the consequences to the star."

Comments

NOVA ran a program on gamma ray bursts...

[Propagandhi]

Imagine there are a few people rather lost at the headline (we're not all astronomers/cosmologists/whatever :) ). Anyway, NOVA ran an excellent show on this a couple years ago, and as usual there was an excellent companion website.

If that doesn't answer your questions, well... there's always Wikipedia. /I feel like a Karma whore linking to wikipedia, mod me as you see fit..

Re:NOVA ran a program on gamma ray bursts...

[Propagandhi]

The observable universe is the total volume of the universe from which light could have reached us since the beginning of said universe (the big bang or whatever).

In other words, as you get farther away from our point of observation (Earth and the area immediately around it) you eventually reach a point in space which is so far from us that light could not have reached us. Assuming that nothing can move faster than the speed of light, this sphere would include everything that could have possibly affected us since the beginning of the universe. Ugh. I hope that makes sense, and I hope I didn't screw that up.

As usual Wikipedia has more information: Cosmic Light Horizon and Obxervable Universe

Re:NOVA ran a program on gamma ray bursts...

[Michael Woodhams]

Here's the simple answer:

About 13.5 billion light years ago, the universe changed from being opaque to photons to being transparent (an event inappropriately called "recombination"). No photon emitted earlier than this time could reach us, so we cannot observe further than about 13.5 billion light years away. (The photons emitted at that time are the cosmic microwave background.) So the observable universe is 13.5 billion light years in radius. A billion years from now, it will be 14.5 billion light years in radius.

However, it gets more complicated: the universe is expanding, so the space that photon travelled through has got bigger in the meantime.

Imagine two points in the universe. Because the universe is expanding, the distance between them is increasing with time. The rate at which the distance increases is a velocity (which you can think of as causing the red shift of distant galaxies.) Hubble's law says this velocity is proportional to the distance between them. If they are sufficiently distant, the relative velocity is greater than the speed of light.

So (for example) imagine this is twice the speed of light. A photon emitted from one point travels towards the other. After one year, it has travelled one light-year, but the points have got two light-years further apart - clearly it will never arrive. These two points are not in each other's observable universes. The edge of our observable universe are the points which have a recession velocity equal to the speed of light.

The discussion above assumes no acceleration. Of course, astronomers from Hubble onwards knew there would be acceleration, but it wasn't until the mid 1990s that we could measure it.

It turns out, contrary to general expectation, that the expansion of the universe is now accelerating. This means that as time goes on, points don't have to be so far apart before their recession velocity exceeds the speed of light, so in a sense the observable universe is getting smaller. (In the sense that points that were within our observable universe in the past are no longer so. But remember that the points are always getting further apart - the radius of the obserable universe is increasing linearly with time.)

I am an ex-astronomer, not a cosmologist. There may be subtle errors in the above, but I hope not.

Re:An honest question...

[Peyna]

How do we know the universe is 13.7 billion years old? It was recently discovered that the universe's expansion is accelerating as time goes by. Assuming this change in acceleration has been the case all along, doesn't that really fudge with the numbers we used to estimate the universe's age?

There are many ways to estimate the age of the universe, not all of which involve calculating the expansion of the universe.

http://www.astro.ucla.edu/~wright/age.html

Re:light instead of gamma

[mbrother]

Well, the leading idea about (this type of) gamma ray burst says that they're associated with supernovas. So, they look like supernovas.

Quasars are the most luminous long-lived light sources. Gamma ray bursts can release more energy for short periods of time, but there are arguments about to what extent the energy is beamed in a preferred direction (complicating efforts to calculate total energy released).

I'm not sure what you mean by "alpha and beta?" Are you talking about alpha and beta radiation? Apples and oranges, although all are called "radiation". Gamma rays are a form of light (very high energy photons), while alpha and beta radiation isn't electromagnetic radiation at all, but rather particles (He nuclei and electrons).

Re:light instead of gamma

[UnrefinedLayman]

For being so feisty, are you quite sure there's no such thing as alpha and beta radiation?

http://www.orau.gov/reacts/alpha.htm

http://www.orau.gov/reacts/beta.htm

Both are particle radiation and both plentifully originate in stars. You can read more about them in Wikipedia also.

http://en.wikipedia.org/wiki/Particle_radiation

Grammar Whore

[Anonymous Coward]

ahem. Farthest Gamma-Ray... Farthest . 'Further' is a definition of degree. 'Farther' is a measure of distance.

Re:Blackhole Question...

[erichill]

If this massive gamma-ray burst resulted in a black hole, then how did the light escape enough to reach us here on earth, 13 billion light years away?

Someone or another asks something like this everytime anything related to black holes comes up on Slashdot.

The radiation emitted from black hole related events, such as quasars, gamma ray bursts, and Hawking radiation, for that matter, comes from processes near-sometimes very near, but still OUTSIDE, the event horizon. As long as you're outside the horizon, there are trajectories that escape.

As for,

Also, if a black hole was created at explosion, was this even more massive then we can see, yet the black hole swallowed up a majority of the explosion and what we see, is just a small glimpse of it?

According to the literature on very massive stars, there as mass ranges that results in the star collapsing completely into a black hole such that no significant amount of matter or radiation gets away at all.

Check out How Massive Single Stars End their Life. Figure 1 is particularly enlightening. It's a pretty math-free article, so I think anyone who's generally interested in this stuff can follow it, maybe with a bit of help from Wikipedia and Science World.