# Measuring distances to stars

#1
I know of these:
-Trigonometry parallex for close stars
-Kepler's law for planets within our solar system
-Standard candles for distant stars
-Hubble and Doppler for distant galaxies

Also I'm not sure how to phrase my q but can someone please tell me how close is close enough? At what distance does a star or galaxy become distant? What's the limit or range of distances for all these?
0
3 years ago
#2
(Original post by Presto)
I know of these:
-Trigonometry parallex for close stars
-Kepler's law for planets within our solar system
-Standard candles for distant stars
-Hubble and Doppler for distant galaxies

Also I'm not sure how to phrase my q but can someone please tell me how close is close enough? At what distance does a star or galaxy become distant? What's the limit or range of distances for all these?
A distant star may be something farther than the closest starts, i.e. beyond a couple tens of parsecs. Proxima centauri is something like 4.2 ly away, if I remember correctly. That's pretty close. The stars in the LMC are tens of thousands of parsecs away. The supernova (not stars) used in the High-Z project are literally millions away. Putting a limit on what's close or far is hard so it probably depends on your exam board/etc, but I'd say beyond 30 Pc is far away.

If I remember correctly there is an angular resolution limit on the order of 1/1000th of an arc second for space-based optical telescopes with parallax capabilities, and based on possible targets about which you can accurately measure parallax that takes you to a max of ~100 pc. The pc is 3.26 ly... the ly is a light year.

Kepler's law is as it sounds, the solar system. You can reliably use it and it has been reliably used for the entirety of it, to my awareness.

Standard candles for distant stars can give you a range on the scale of mega pc, i.e. 1 x 10 ^ 6. Cepheids and RR Lyrae can act as those candles, just for note, I mean I assume its noted but it's worth noting that I'm talking about them.

Hubble/Doppler have a range that goes into the billions of light years, you can find the reddest faintest galaxies out there like this.
0
#3
(Original post by Callicious)
A distant star may be something farther than the closest starts, i.e. beyond a couple tens of parsecs. Proxima centauri is something like 4.2 ly away, if I remember correctly. That's pretty close. The stars in the LMC are tens of thousands of parsecs away. The supernova (not stars) used in the High-Z project are literally millions away. Putting a limit on what's close or far is hard so it probably depends on your exam board/etc, but I'd say beyond 30 Pc is far away.

If I remember correctly there is an angular resolution limit on the order of 1/1000th of an arc second for space-based optical telescopes with parallax capabilities, and based on possible targets about which you can accurately measure parallax that takes you to a max of ~100 pc. The pc is 3.26 ly... the ly is a light year.

Kepler's law is as it sounds, the solar system. You can reliably use it and it has been reliably used for the entirety of it, to my awareness.

Standard candles for distant stars can give you a range on the scale of mega pc, i.e. 1 x 10 ^ 6. Cepheids and RR Lyrae can act as those candles, just for note, I mean I assume its noted but it's worth noting that I'm talking about them.

Hubble/Doppler have a range that goes into the billions of light years, you can find the reddest faintest galaxies out there like this.
Thank you soo much!
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