Cephid Variable

[ronniemonda9]

How do you work out their absolute luminance?

[Buenchico]

The answer you require is contained within this discussion but it's not exactly light reading! :
http://uplink.space.com/printthread.php?Cat=&Board=a skastronomer&main=67942&type=thread

Chris

(Er, I think there's an unintentional pun there somewhere :-) )

[jake-the-peg]

OOh you got in there just before me

Cephid variables are really cool. They gave us the first measurements of distance for extra galactic objects. It was found that their light output could be deduced from the period of their variability.

So by measuing the time between darkest and brightese you could calculate how much light they were putting out and if you know that you can calculate their distance.

And bang! in 1932 Hubble found one in the Andromeda galaxy and we got the first distance of over a million light years - From this we got the red shift and the ability to measure distant galaxies.

All from a little pusing star

[jake-the-peg]

er pulsing (must get a new keyboard)