Supernova's Gamma Rays and Comets

**crays** · Nov6-09, 07:49 AM

Hi guys, me again, with two questions. Just saw a documentation about supernova, when supernova happens, a huge amount of gamma ray is emitted since it is vacuum in space, why wouldn't the gamma ray hit us? Even if its far and takes a few thousand years for it to reach us, it would eventually reach us right?

About comets, i know it is composed of ice, but what actually propel it? The comets need a force to act on it so that it could move :o?

Thanks in advance and sorry for my poor english.

**Janus** · Nov6-09, 08:26 AM

Yes we get gamma rays from Supernovae. There is a whole field called Gamma Ray Astronomy that deals with detecting gamma radiation from space.

Comets, just like any other body in the Solar system travel in orbits around the Sun, they don't need propulsion any more than the Earth does.

**twofish-quant** · Nov6-09, 10:27 AM

Originally Posted by crays

Hi guys, me again, with two questions. Just saw a documentation about supernova, when supernova happens, a huge amount of gamma ray is emitted since it is vacuum in space, why wouldn't the gamma ray hit us?

Most supernova don't produce particularly large amounts of gamma rays. Apparently, some of them do, for reasons which we don't completely understand. Also space is big so by the time the gamma rays get to earth, they are weak enough so that you only see them with special satellites and the atmosphere blocks them out.

Also, the satellites that originally found gamma ray sources from space were designed to look for gamma bursts from earth, to detect nuclear explosions and make sure that no one was cheating on arms control treaties.

About comets, i know it is composed of ice, but what actually propel it? The comets need a force to act on it so that it could move :o?

Nope. In space, there is no friction and things keep moving unless something stops it.

**crays** · Nov7-09, 06:11 AM

Thanks for the reply.
But the gamma ray is a ray, the energy level of the gamma ray would decreases?

About the comets, what initiate it? I mean when it started to form, it doesn't have a force that acts on it right?

**twofish-quant** · Nov7-09, 12:16 PM

Originally Posted by crays

But the gamma ray is a ray, the energy level of the gamma ray would decreases?

Gamma rays are high energy radiation.

About the comets, what initiate it? I mean when it started to form, it doesn't have a force that acts on it right?

The natural state of things in space is for things to move. There's no need to have any sort of initial force.

**Ophiolite** · Nov11-09, 07:27 AM

Originally Posted by crays

But the gamma ray is a ray, the energy level of the gamma ray would decreases?

Imagine you have a very bright light. So bright that even standing one hundred feet away it is painful to look at. Now go a mile away and look at the light. Ten miles. One hundred miles.
Do you get the point?

**Sorry!** · Nov11-09, 11:58 AM

Originally Posted by crays

Thanks for the reply.
But the gamma ray is a ray, the energy level of the gamma ray would decreases?

About the comets, what initiate it? I mean when it started to form, it doesn't have a force that acts on it right?

Gamma rays as already been mentioned are high energy radiation. Here's a little image to help you understand what radiation is and where gamma rays fit in: