Calculating the Distance to Supernovae

Astronomers use a relationship called the distance modulus to calculate the distance to a supernova. The distance modulus (DM) is the difference between the peak apparent magnitude (m) and the peak absolute magnitude (M). For most Type Ia supernovae, the corrected peak absolute magnitude (M) is always the same value: -19.4.

So the DM = (m - M)
= (m - (-19.4))
= (m + 19.4)

In order to calculate the actual distance from Earth, the value of the distance modulus (DM) is inserted into the equation below:

d = 10 ^ ((DM+5)/5)

Where distance (d) is expressed in parsecs*, and DM is your value for the distance modulus.

*1 parsec = 3.26 light-years

Does this look complicated? Don’t worry- we’ll do the calculations for you! All you have to do is enter the peak apparent magnitudes you determined. The calculated distances will be added to the table, reported in megalight-years (Mly). One Mly is equal to one million light-years