What's the method astronomers use to tell how far galaxies are is called, what?

Answer 1

Hi Tina!

Three methods are used:

1) For nearby galaxies, they measure an unusual kind of star called the Cepheid variable. These stars brighten and fade over regular periods, with the exact time based on their brilliance. If you pick an individual Cepheid out in a nearby galaxy, such the Andromeda galaxy, and see how long it takes to brighten and fade, you can quickly do the math to determine how far away it is. It was the Cepheids that astronomers used to first discover that Andromeda was not just a star cloud in the Milky Way, but a galaxy of its own.

2) Cepheids are the not the brightest possible stars. For galaxies farther away, where a Cepheid would be too dim to make out individually, we can still pick out the very brightest stars. Since there is an absolute limit to how luminous a star can get before blowing apart, we can calculate distances by gauging the brightness of the most brilliant stars we can see.

3) Astronomer Edwin Hubble proved that almost all galaxies are moving away from us, and the more distant they are, the faster they are receding. When an object is moving away from you, the light of its spectrum will shift redward, so that radiation in the red part of the spectrum becomes infrared, violet moves toward the red, and so on. We can measure the shift in the spectrum lines to show how far redward the lines have been shifted by receding. The greater the shift, the father away the object is.

Using all three of these, it is possible to calibrate the scale so we can estimate how far away galaxies are.

Answer 2

It was noticed that on certain type of vairable star called a Cepheid Variable, the timeing of the maximun and minunium could be use to tell the absolute brightness. If you know the absolute brightness of a star, you could tell the distance.

Now, these stars are fairly common and could be islolated and measured in some of the closer galaxies.

Then, Edwin Hubble noticed that further away a galaxy was the greater the red shift, and from that determined that the faster the further away it was, and using red shift could determine the distance to the galaxies.

Answer 3

The latest and most accurate method is looking for type 1a supernovas. They all have almost the exact same brightness, so measuring how bright they look from here tells you how far away they are.

Answer 4

There are three types of methods
1) parallax
2) spectroscopic parallax
3) ceiphid variables

Answer 5

It's called the SWAG Method. Scientific Wild-A s s Guess.


;-0

Answer 6

Light years.

Answer 7

they use the doppler effect and measure the grvitational red-blue shift.