HOW ASTRONEMERS COME TO KNOW THE DISTANCE OF GALAXY?

Question

HOW ASTRONEMERS COME TO KNOW THE DISTANCE OF GALAXY?

Answer 1

Finding out the distance to anything outside our own planet is a very complex question. For galaxies, astronomers use a wide variety of techniques.

First are the type I supernovae, which are a special type of nova explosions that happen at the end of a star's life. As our understanding has it, these events always have the same brightness, and by comparing the observed brightness, it is possible to calculate how far away the event happened. If you find one of these events in a distant galaxy, it gives you a figure for how far away the whole galaxy is. Similar methods that observe other kinds of events also exist.

For more distant galaxies, even these events are too dim to be seen, so instead the Hubble relationship of redshift and distance is used, meaning that the faster a galaxy is moving away from us, the farther away it is. Since we can measure a galaxy's redshift more or less directly, this then gives an estimate of how far away it is.

Naturally, none of these methods gives you an exact number, so astronomers constantly work at improving the figures, and any conclusions drawn from the distances must consider how large the error margins are.

Answer 2

The initial evidence that convinced astronomers that spiral nebulae like the Great Nebula in Andromeda were their own "island universes" (galaxies) separated from ours by a lot of mostly empty space was the detection and analysis of Cepheid variable stars in the Andromeda nebula.  With the 100-inch Hooker telescope on Mt Wilson the nebula could be resolved into individual stars.  Cepheid variables found within the Milky Way had shown that their brightness was a function of the period of their variability.  By observing Cepheid variables in Andromeda and measuring their period their instrinsic brightness could be calculated and a comparison with the observed brightness gives the distance modulus, which is principally governed by the inverse square law.  This established that the Andromeda Galaxy is around 2.5 million light years away.  These observations were made during the 1920s.  As data were gathered on other galaxies, astronomers realised that the spectra of galaxies further away from us were shifted further to the red end of the spectrum and that, especially for the more distant galaxies, the amount of red-shift was a measure of the distance.

Answer 3

I think through the trigonometric ratios because astronomy is based on trigonometry largely.

Answer 4

with the hubble telescope

Answer 5

by carbon dating

Answer 6

They major through applying amathamatical formulas of physics

Answer 7

calculating the time the light takes to reach us