How astronomer measure the distance between galaxies?

Question

If a galaxy is 50 million light years from earth, it means it takes 50 years for light to travel from the galaxy to earth. How astronomer knows the light from a galaxy is 50 million years old?

Answer 1

By the red shifts of the measurement. Or to make a short story long it's the displacement of features in the spectra of astronomical objects, such as galaxies and quasars, towards the longer wavelengths, generally interpreted as a result of the Doppler effect due to their recessional velocities (i.e. how fast they're moving away from something) The expansion of the universe means that all but the nearest galaxies have redshifted spectra (in fact this is what led to the discovery of the expanding universe back in the 1920's). Hubble first described this back in 1925 that the redshift or recession velocity of a galaxy is proportional to the distance in relationship with the viewer. All that means is that by this redshift they were able to approximate the distance of these galaxies, and since they had these distances they could state them in light years (since light years is a distance, not necessarily a time)

Answer 2

Astronomers estimate distances by comparing the brightness or sizes of objects in the unknown galaxy with those in Earth’s galaxy. The brightest stars, supernovas, star clusters, and gas clouds have been used for this purpose. Cepheid variables, stars the brightness of which varies periodically, are especially valuable because the period of pulsation is related to the intrinsic brightness of the star. By observing periodicity, the true brightness can be computed and compared with the apparent brightness; distance can then be inferred. Astronomers have learned that the speed of the stars as they orbit the center of their galaxy depends on the intrinsic brightness and mass of that galaxy. Rapidly rotating galaxies are extremely luminous; slowly rotating ones are intrinsically faint. If the orbital velocities of stars in a galaxy can be determined, then the distance of that galaxy can be inferred.

Answer 3

By the Doppler shift of the light. One thing to remember though, these distances aren't static. Many galaxies are moving away from each other as the universe expands so the distances are increasing.

Answer 4

i know 2 ways.. first is by the illuminosity method... they compare the illuminosity of a ster with respect to refrence star assumed at a fixed distance... and what would be its brightness if it were at that distance... second is the angle cone method.. first measure the angle what the star makes at one of the equinox then again measure at the next exiunox... now you wil get a cone in which you know the semi vertical angle and the base length so you can get the height that is the distance of the star....

Answer 5

light years

Answer 6

Measured in light years... !!!!!

Answer 7

simple method that u can try is the parallex method
related with trigonomatry

Answer 8

fiona is 3 things. smart. right. and HOT (being the other two also helped)

Answer 9

hygrometre

Answer 10

http://www.astro.ucla.edu/~wright/distance.htm

http://www.astronomynotes.com/galaxy/s16.htm

Knock yourself out.