Observing Supernovae 

Okay, so last time we got to the point of core collapse, rebound, and blast wave -- the explosion. This type of supernova is called a Type II supernova. (Type Ia supernova come from exploding white dwarfs -- we'll get to those soon...).

Historical naked eye supernovae:

Think about this: You study supernovae for a living. Where do you want to look for them? How do you know when a star is about to go supernova?


Type II Supernova Light Curves

 Let's look at the brightness of a supernova as a function of time -- a light curve.





Why is it shining? What provides the energy of a supernova?

Radioactive decay


Supernovae Remnants

   

The Crab Nebula


By age dating this nebula, we find that it is about 950 years old. The supernova was observed and noted by the Chinese (on July 4, 1054 AD), and rock paintings found in New Mexico suggest the Anasazi Indians also saw it. There is some debate as to whether or not the Europeans saw it, although it was so bright that it should have been observable in the day time!

The Crab has been found to be very rich in metals, like oxygen, carbon, iron, etc -- the products of nucleosynthesis. More interstellar recycling. 

What powers the Crab -- why does it shine? Certainly shock excitation plays a role, but that can't explain all the energy we see coming from the Crab. The supernova energy itself has been radiated away, so what else could be giving the Crab energy?? 


 

Supernova 1987A:


The nearest (d ~ 50 kpc) supernova in modern times:

It gives us a chance to observe a very young supernova remnant.

We see a very young remnant, surrounded by dust and gas (about 1/2 parsec in diameter) which has been lit up by the supernova.

We now see evidence that this ring is brightening, evidence that supernova ejecta is colliding with the ring.