2006-07-19 10:30:56 · 7 answers · asked by ? 1 in Science & Mathematics ➔ Astronomy & Space
None of the answers given are correct. The Hubble used a class of stars called Cepheid Variables to find out how far away the Andromeda galaxy is. Cepheids are stars that reside in the "Instability Strip" on the H-R (Hertzsprung-Russell) Diagram of luminosity v temperature. The stars lie between F0 and G8 in the spectral sequence and are mostly supergiants. Now, the pulsations that are the hallmark of these star's instability are fundamentally tied in with their temperature and size.....i.e: the hotter, bigger and brighter the Cepheid, the longer it takes to pulsate. And the variations in the light output of the Cepheids follows a fairly nice and neat curve on a graph, such that they peak early and rather quickly, then slowly fade back to their original magnitude of brightness. Knowing the precise light output then, allows us to plug these variations into the distance modulus equation (u=m-M=5logd-5) to give us a distance to the galaxy.
Turns out the Andromeda Galaxy, from observations of its Cepheids, is about 2.4 million light years from us. Which agrees rather well with other methods of distance determination, such as the Tully-Fischer relationship (having been refined), recent doppler shift and parallax methods, and a few others.
2006-07-19 11:04:19 · answer #1 · answered by ozzie35au 3 · 6⤊ 2⤋
Hubble didn't determine it. The distance to the Andromeda Galaxy was figured out long before Hubble was put in space. Beyond that, Ozzie had a very good explanation of how galactic distances are determined using Cephied Variable stars. We've been doing it this way for decades with ground-based telescopes.
2006-07-19 12:09:04 · answer #2 · answered by Anonymous · 0⤊ 1⤋
He applied the period-luminosity relation to Cepheid variables.
2015-05-21 12:28:43 · answer #3 · answered by Anonymous · 1⤊ 0⤋
Cepheid variable period luminosity relationship.
M = -2.76 log(P) - 1.4
Distance modulus (solved for distance).
d = (32.61 lightyears) 10 ^ { 0.2 (m - M) }
M = abolute magnitude
m = apparent magnitude
P = cepheid period in days
d = distance in lightyears
2006-07-19 12:14:44 · answer #4 · answered by David S 5 · 0⤊ 1⤋
If this is a homework question, it's not fair to ask, it borders on cheating.
2006-07-19 10:34:48 · answer #5 · answered by Peach 4 · 0⤊ 2⤋
a really long ruler
2006-07-19 10:34:32 · answer #6 · answered by DainBramaged 3 · 1⤊ 0⤋
triangulation?
2006-07-19 10:32:41 · answer #7 · answered by habaceeba 3 · 0⤊ 0⤋