Distances

[cylindrical_puppy]

Hi

I'm a compelte noob, so sorry if this has been answered and beaten to death so many times its corpse has turned into something martian (or terran) bacteria might not be able to decompose into food.

How do astronomers know how far away stars are?

thanks!

[01101001]

Welcome to the BAUT Forum.

How do astronomers know how far away stars are?

Many ways. Many methods for different distances. They complement and verify each other.

UCLA: ABCs of Distances

The collection is often called the Cosmic Distance Ladder (Wikipedia), for thinking of the different methods as rungs of a ladder.

[alainprice]

A quick summary:

For very close stars(our neighboors), we use parallax. Which is the same as having 2 eyes instead of one to see in 3D. You take 2 pictures 6 months apart of the same spot and use the earth's orbit to create the distance to get angles. From there, it's just trigonometry.

Another method is predictable stars. For certain types of stars and events, the brightness and color is well known. We can compare the brightness to get an idea of distance.

And then there's redshift. The universe is expanding, everywhere, all the time. This causes far away objects to appear as if they're moving away. The farther away, the faster it fades away. This would cause a blue light to look green, or even red, or even infrared. The amount of shift tells a speed. Hubble is famous for this work. Using Hubble's constant, it's easy to relate the speed with distance. This is going to work best with far away galaxies, since the closest major galaxy to us is blueshifted as we approach on a near collision course.

[Neverfly]

This is going to work best with far away galaxies, since the closest major galaxy to us is blueshifted as we approach on a near collision course.

Very Minor nitpick in the BAUT tradition:
LMC and SMC

[cjl]

Well, he did say closest major galaxy. I wouldn't consider that to be in error.

[Neverfly]

Well, he did say closest major galaxy. I wouldn't consider that to be in error.

Yeah neither would I. That's why I said "very minor nitpick."

Now if the Ambassador from LMC/SMC comes on to post- there might be a heated exchange..

[dhd40]

Very Minor nitpick in the BAUT tradition:
LMC and SMC

From ToSeek´s "dictionary": LM= lunar module, SM=service module, C=?

[Argos]

Large Magellanic Cloud/Small Magellanic Cloud. Our neighbor galaxies.

[dhd40]

Large Magellanic Cloud/Small Magellanic Cloud. Our neighbor galaxies.

Of course! , thanks

[mugaliens]

Thanks, Argos. For a moment I thought the modules had passed through a wormhole.

[Neverfly]

Ysat.

[astromark]

LMC-smc. Lunar modules.... I worry about some of you.
As for the distance confirmation; It is obtainable by interrogation of the photon stream. Detain and do not feed until they tell all...or... All you need to know is how long its been since lunch or breakfast. Simply multiply by the first inverse law and the velocity of light and there you have it.... Ummm... what was the question...Mark.

[mugaliens]

I thought it was multiply by the inverse of the imaginary cube root of c... Someone help me out, here - I haven't had breakfast.

[Jeff Root]

I haven't been able to figure out the meaning of "Ysat", though "you should"
seems likely for the first two letters if it is an ETLA.

-- Jeff, in Minneapolis

[Neverfly]

I haven't been able to figure out the meaning of "Ysat", though "you should"
seems likely for the first two letters if it is an ETLA.

-- Jeff, in Minneapolis

Oh.,
Mugs complained about the abbr. LMC/SMC, so I replied "Yeah, Sorry About That"

[dhd40]

I haven't been able to figure out the meaning of "Ysat", though "you should"
seems likely for the first two letters if it is an ETLA.

-- Jeff, in Minneapolis

Interesting. Googling for ETLA I found: Harry Potter 4 et la coupe de feu

Try it yourself, or did you mean et voilá ?

[Jeff Root]

"ETLA" is a joke. It stands for "extended three-letter acronym".

Nothing to do with measuring distances in Space.

-- Jeff, in Minneapolis