What method scientists use to tell how far a galaxy is?

Question

What method scientists use to tell how far a galaxy is?

Answer 1

Very large telosopes also they send signals like a microwave to see through all the debree and dust in space and the furthest they can see is to a wall of radiation so they assum this is the edge of the universe however they are unsure and are in the process of making better teckonogy so that they might see further the last bits of light that they see is are galaxies and are 13.7 billion light yrs awaythey use this as of now to tell how and how old our galaxy is large  

Answer 2

There are a few different methods, however one of the more reliable ones is the use of stars called Cepheid variables. Variable stars are stars (or sometimes star systems perceived to be one star) that change in luminosity over time. In some cases, this is due to the motion of a stars in a star system (as in 2 binary stars orbiting each other and periodically one eclipses the other). In the case of a Cepheid, the star itself goes through periodic physical changes in its atmosphere that alternatively make the atmosphere more or less transparent to light. Now that's all very well and good, but it doesn't explain why this is useful. It turns out that the relationship between a Cepheid's periodicity and its absolute luminosity is very tightly correlated. This means that if astronomers measure the period of the star's variability, they can calculate how luminous it actually is, compare that to how luminous it appears, and thus figure out how far away it is. A Cepheid in a star cluster, or even another galaxy, can be used to determine the object's distance.

Answer 3

We use the Cosmic Distance Ladder:

http://en.wikipedia.org/wiki/Cosmic_dist...

http://en.wikipedia.org/wiki/Extragalact...

Answer 4

The most common method is to observe a type of star in the galaxy called a Cepheid. These are variable stars with a definite relation between the rate at which they vary and their actual brightness. YOu can calculate how bright they look versus how bright they actually are and from this, how far away they must be.

For really far away galaxies, it is not possible to observe individual stars. They use the speed at which space is expanding between us and the galaxy to estimate how far away the galaxy is. THey measure the speed at which the galaxy is receding from us by examining the spectrum of the star. All the lines in the spectrum will be shifted towards red. This is called redshift. The greater the redshift, the fast the galaxy is going away from us, so the further away it must be.

Answer 5

First, you need to know the distance to nearby stars.  The Earth goes around the Sun at a known distance, and you observe a star, then do it again 6 months later.  With geometry, you can tell how far it is.

Do this for lots of stars, and study their spectra.  That way if you see a dimmer star with the same spectra, you can figure out how far away it is from how bright it is.  Some really bright stars, Cepheid variables, change brightness in a way that tells you how bright they are, so you can work out distances.  This works for nearby galaxies.

For distant galaxies, you need something brighter.  Type 1a supernovae work pretty good here.  Since we haven't had one in our own galaxy, you need to have seen one in a galaxy whose distance you already know, for calibration.

Answer 6

I believe it's done by the COLOR of the light coming from that galaxy.