My Dark Sky

In the previous posts, we talked about how gamma rays were first detected, how astronomers know that they were located far far away up to distances of billions of light-years, and also what are the types of gamma ray bursts and what causes them.

If we want to detect gamma ray bursts (GRBs), unfortunately, we can’t do it on the ground. Gamma rays coming to Earth cannot penetrate through our planet’s atmosphere and thus do not reach the ground. So, if we want “see” gamma rays, we have to go to space, up above the atmosphere, and this is why all our gamma-rays telescope are in space.

Currently, we have a few gamma-rays telescope around Earth. We have Swift Gamma Ray Burst Explorer, High Energy Transient Explorer 2 (HETE 2), International Gamma Ray Astrophysics Laboratory (INTEGRAL) and Astrorivelatore Gamma ad Immagini LEggero (AGILE). The latest addition to our list of gamma ray telescopes is Fermi (previously known as GLAST), launched just about half a year ago.

As we’ve mentioned before, afterglows are important for further analysis and understanding of GRBs. For example Swift, as it detected a GRB in the sky, it’ll quickly turns its X-ray camera to the source. The purpose is to get a more accurate position of the GRB. You see, gamma rays don’t like to be focused… so it’s hard to pinpoint exactly where a GRB came from. All we can get is the GRB came from somewhere there, and that “somewhere there” might be an area of the sky few degrees across; an area which is not small enough for some telescope to point at the sky and find something new and interesting.

So we use X-ray cameras to give us a more precise position. Once we have that, these coordinates will be sent down to Earth, allowing both ground-based and space-based telescopes around the world the opportunity to observe the burst’s afterglow. For Swift to detect, get the coordinates, and relay the information to Earth only took it less than a minute to finish; you don’t called it “Swift” for nothing…

Fermi, on the other hand, will provide detail observations of the burst over the gamma ray spectrum, giving scientists a complete view of the total energy released in these events.

With all these observatories, we hope to solve some of the GRB’s mystery. As the data keep pouring in, we may find ourselves in a situation where trying to solve one mystery, we end up with more mysteries… but then, isn’t that’s where all the fun lies?

Gamma rays bursts don’t give off their radiation uniformly in all direction. The energy were concentrated and funnelled out the two poles in narrow beams – we called them the jets.

We can only detect the burst if the jets are pointing at us, if not, they’ll go unnoticed. =>

Posted in General Astro Talk
Tags: gamma ray burst