Type Ia supernovae are extremely useful in measuring the distance of remote galaxies. It is known that type Ia supernovae always reach the same brilliance at their peak. Like Cepheid variables, they can be used as “standard candles” to determine distances. What type/sub-type of supernovae can be used to measure distances to a nearby galaxy?


1 Answer 1


There seems to be a misconception. You can use type 1a supernovae as standard candles for nearby and distant galaxies.

But nearby galaxies have individual stars visible and resolvable, and these include Cepheid variables which can also be used as standard candles. Moreover, supernovae only occur rarely, so if no supernova occurs, you have to wait, whereas Cepheids are always visible in nearby galaxies, and so are a much more convenient "standard candle".

In distant galaxies, individual stars are not resolvable, so Cepheid variables can't be used as standard candles, and you have to use something else, such as type 1a supernovae.

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    $\begingroup$ BTW, if a type Ia supernova is caused by a merger, rather than by accretion, it will be brighter than a standard candle. But such mergers are rare. $\endgroup$
    – PM 2Ring
    Jun 4, 2021 at 21:50

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