Supernova Light

Hi everyone. I've gathered a few facts on supernovas, namely:
(A) When these things blow, they can briefly outshine a galaxy.
(B) Before fading from view, they can put out more energy than our sun does over its entire lifetime.
(C) The shockwave from these explosions can reach .10c.

Now, for A&B, how is this possible? How can a single exploding star generate enough energy to outshine an entire galaxy, let alone put out more juice than our sun does over its lifetime? Our sun's been around for a long time, and the light from billions of stars, in any given galxay, seems a bit much to overcome in an instant. So what's happening in these explosions? What makes them so powerful?

For (C): If some of the shockwaves can reach .10c, is this the kind of energy that we need to propel a spaceship to .10C?

Can anyone help me out?

okeeft01 wrote:

Hi everyone. I've gathered a few facts on supernovas, namely:
(A) When these things blow, they can briefly outshine a galaxy.
(B) Before fading from view, they can put out more energy than our sun does over its entire lifetime.
(C) The shockwave from these explosions can reach .10c.

Now, for A&B, how is this possible? How can a single exploding star generate enough energy to outshine an entire galaxy, let alone put out more juice than our sun does over its lifetime? Our sun's been around for a long time, and the light from billions of stars, in any given galxay, seems a bit much to overcome in an instant. So what's happening in these explosions? What makes them so powerful?

The short answer is that in a supernova, dramatic changes in the entire body of the star release a lot of energy in a short period of time. In the case of thermonuclear supernovae (type Ia), the entire body of a white dwarf star -- about 1.4 solar masses of carbon and oxygen -- undergoes nuclear fusion within a few seconds. The Sun and other stars have fusion reactions at their centers, but only teeny-tiny fractions of the star's entire mass is fused each second; hence, ordinary stars take millions or billions of years to radiate the energy released by fusion. In the case of core-collapse supernovae (types Ib/Ic/II), the core of the star collapses from the size of roughly the earth to the size of roughly New York City. This change causes a very large amount of gravitational potential energy to be converted into various types of radiation, and it also takes only a few seconds.

I'm sure there are many, many, many good books and websites which describe these processes in much greater detail.

Quote :

For (C): If some of the shockwaves can reach .10c, is this the kind of energy that we need to propel a spaceship to .10C?

Can anyone help me out?

No, this would be a poor method to choose for two reasons. First, the eject are moving very quickly, yes, but they have very low density. That means that the amount of mass striking the area of a ship would be very small, so little momentum could be transferred. Second, the environment would be filled with radiation of very high energy, and lots of it, which would likely destroy any ship in the neighborhood.

Oh, and if you are planning to use this mechanism to accelerate your ship to high speed, it implies that you don't have another method of reaching high speeds. In that case, how do you get your ship to the region of a supernova in time to catch the wave?

scopeman wrote:

No, this would be a poor method to choose for two reasons. First, the eject are moving very quickly, yes, but they have very low density. That means that the amount of mass striking the area of a ship would be very small, so little momentum could be transferred. Second, the environment would be filled with radiation of very high energy, and lots of it, which would likely destroy any ship in the neighborhood.

Oh, and if you are planning to use this mechanism to accelerate your ship to high speed, it implies that you don't have another method of reaching high speeds. In that case, how do you get your ship to the region of a supernova in time to catch the wave?

There is also the problem that getting to 0.1c in 5 seconds is an acceleration of about 600,000g. I doubt the crew would be feeling too good after that.

AstroJunkie wrote:

scopeman wrote:

No, this would be a poor method to choose for two reasons. First, the eject are moving very quickly, yes, but they have very low density. That means that the amount of mass striking the area of a ship would be very small, so little momentum could be transferred. Second, the environment would be filled with radiation of very high energy, and lots of it, which would likely destroy any ship in the neighborhood.

Oh, and if you are planning to use this mechanism to accelerate your ship to high speed, it implies that you don't have another method of reaching high speeds. In that case, how do you get your ship to the region of a supernova in time to catch the wave?

There is also the problem that getting to 0.1c in 5 seconds is an acceleration of about 600,000g. I doubt the crew would be feeling too good after that.

They would be a little worse for wear