Using Supernovae in Cosmology

Figure 1: How standard candles allow us to measure distances
Credit: R. Nave (Hyper Physics)

Core-collapse supernovae involve the death of a massive star. The mass of this star is the main factor that determines how big the explosion is. Einstein's famous equations suggests that       E (energy) = m (mass) c2, then we can imagine more energetic explosions coming from more massive stars.

However, for Type Ia supernovae, the situation is a little different. We believe these always occur when the mass of the white dwarf is around 1.44 solar masses. This allows us to assume that each will have a similar brightness when they explode. This similarity means that astronomers can describe Type Ia supernovae as 'standard candles' (see Figure 1). How bright they appear to us on Earth is only determined by how far away they are. 

There are lots of objects in astronomy that we can think of as standard candles such as variable stars and some types of galaxies. Supernovae are particularly useful as they can be detected and analyzed even when they occur in galaxies that are far, far away.

This type of work was first demonstrated by the famous American astronomer, Edwin Hubble in the 1930s (using variable stars) but in 2011, the Nobel Prize in Physics was awarded for the use of Type Ia supernovae in understanding and measuring the expansion and history of the Universe. It is some aspects of this work that we try to replicate in this activity.

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