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What is a standard candle?

Answer 1

Astronomers use standard candle to calculate the distance to stars.

If we know the luminosity of a star (Brightness )we can calculate its distance. THe light intensity reduces by inverse square law. as distances increase. Si if you find a known intensity star in a galaxy by this law we can calculate the distance/.THere are some stars called variable star. They change their luminosity at a particular period..Some of these stars called periodic variables act as standard candles.there is a relation between the period and the brightness of variable stars.stars. Delta Cepheid is an example.So,use of such stars is a method to determine distance to stars and galaxies.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.