Galaxy A has an apparent velocity of 5,000 km/sec, and Galaxy B has a velocity of 2,500 km/sec..?

Question

Which of the following is true:

A standard candle in Galaxy A will have a higher luminosity than the same type of standard candle in Galaxy B.

A standard candle in Galaxy A will appear fainter than the same type of standard candle in Galaxy B.

A standard candle in Galaxy A will appear brighter than the same type of standard candle in Galaxy B.

A standard candle in Galaxy A will have a smaller luminosity than the same type of standard candle in Galaxy B.

Answer 1

1. False. Standard candles have the same luminosity everywhere. That's why they are "standard."

2. True. I assume the velocities in question are recession velocities, so, in general, A is further away than B, so its apparent magnitude will be larger, hence fainter. This is why standard candles are important, and that one distinguish between apparent magnitude and absolute magnitude.

3. False, A is further away, hence dimmer.

4. False. The luminosity of standard candles is the same everywhere.

HTH

Charles

Answer 2

ALL the candles would have a steady 'luminosity'.

the wavelength of light emitted would change slightly relative to the velocity.red shift if receding,blue shift if approaching.

This is known as 'Doppler shift'

Answer 3

A standard candle in Galaxy A will appear fainter than the same type of standard candle in Galaxy B.

Because...

The faster a galaxy is moving away the more distant it is.

and

The more distant the galaxy, the fainter the same standard candle in it appears to us.