Determining Distances to Galaxies

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In summary, the conversation discusses different methods of determining a galaxy's distance, such as using standard candles or redshift. It also mentions the difficulties in obtaining the actual size of a galaxy and suggests using a galaxy's rotation curve as a possible method.
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sderamus
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Is there anyway to determine a galaxy's distance by figuring out its actual size (or the visual portion) and then reverse triangulate to us? All I hear is about standard candles as the source for determining galactic distances - either Cepheid variables or Supernovae.

We have of course reverse triangulated to the LMC using the famous SN 1987A shockwave. Reading about that made me wonder if we have other ways of independently determining the actual galaxy size. Perhaps we could use a galaxy's rotation curve to determine a distance? Or at least be able to compare similar galaxies and determine a relative distance.

Thanks!

sderamus
 
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  • #2
For galaxies not in our local group, we can use redshift to estimate a distance (via, Hubble's law).

Uhm...trying to get the actual size of a galaxy is tough. You can try using doppler shifts on the edges to obtain a rotation curve, but that would require the galaxy to be relatively edge on...
 

Related to Determining Distances to Galaxies

1. How do scientists determine the distance to a galaxy?

Scientists use a variety of methods to determine the distance to a galaxy, including using the redshift of light, the brightness of certain stars, and the period-luminosity relationship of certain types of stars.

2. What is redshift and how does it help determine distance to galaxies?

Redshift is the displacement of spectral lines towards the longer (red) end of the spectrum, indicating that the light source is moving away from us. By measuring the redshift of light from a galaxy, scientists can calculate its distance using the Hubble constant.

3. How do scientists use the brightness of stars to determine distance to galaxies?

Scientists use the concept of standard candles, which are objects with known intrinsic brightness, to determine the distance to a galaxy. By comparing the intrinsic brightness of a standard candle (such as Cepheid variable stars) to its apparent brightness, scientists can calculate the distance to the galaxy.

4. What is the period-luminosity relationship and how is it used to determine distance to galaxies?

The period-luminosity relationship is a relationship between the period (time between peaks) of a pulsating star and its intrinsic brightness. By measuring the period of certain types of pulsating stars, such as RR Lyrae or Cepheid variables, scientists can calculate their intrinsic brightness and use it to determine the distance to a galaxy.

5. Are there any other methods used to determine distance to galaxies?

Yes, scientists also use a technique called parallax, which measures the apparent shift of a star's position as the Earth orbits the Sun. This method is typically used for nearby galaxies and is less accurate for more distant galaxies. Additionally, scientists may use the Tully-Fisher relation, which relates the rotational velocity of a galaxy to its intrinsic brightness, to estimate the distance to a galaxy.

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