How can a type Ia supernovae be used a tracer of the distant universe?

Question

How can they be used this way??? I know how they are formed but I am drawing a blank, I dont understand how they could change our understanding of the universe either.... Please help!

Answer 1

To qualify for a signpost, you need two characteristics: bright (so it can be seen from great distances); and well understood (so we know its intrinsic brightness). Type Ia supernovae have both.

Answer 2

The nice thing about type Ia supernovae is that they all have (almost) the exact same luminosity.

By measuring the apparent brightness, we find the distance.

Having a way to accurately measure distances allows us to tell if a galaxy is young (very far away = very long time ago) or old (closer to us).

Being able to compare different galaxies at different ages allows us to better understand how the universe changes with time.

Answer 3

The amount of energy that a type Ia supernova releases is customarily consistent to any other type of Ia super nova. By the time the light from the supernova reaches us, it has been affected by everything in its way and around it..Based on what happens to the radiation from the supernova, certain things can be told like ho far away it is it, information about the area,  or possible desities of ddark matter in an area. As well as the fact that the supernova exlosion its self radiates all surrounding gases of things around it so we are able to map out certain things.

Answer 4

Type 1a supernovae are thought to be white dwarf stars that steal material from a companion.  When they get heavy enough, they detonate.  The thought is that such stars should all be about the same brightness, because the same threshold is reached in a fairly repeatable and precise way. So when they explode, they should be the same brightness.

One can tell a type 1a supernova from other supernovae through spectra features.

By comparing the brightness expected of the supernova with it's actual brightness, one can tell how far away it is.  It's a little more complicated, because you have to adjust for absorption of gas and dust. But this can be done by carefully looking at the spectrum too.

One expects a type 1a supernova to happen in the context of a galaxy.  So if you detect the supernova and can see the galaxy, you can get the red shift from the galaxy.  The red shift of the galaxy is related to the distance to the galaxy through the Hubble constant.  It should be noted that the Hubble constant isn't constant in time.  In any case, if you have good data for how far a galaxy is from the supernovae, then you can calibrate the red shift data.  This technique was used in 1998 to determine that the acceleration of the Universe is increasing - leading to the Dark Energy concept.