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!

Welcome to the BAUT Forum.

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.

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0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0....

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.

Very Minor nitpick in the BAUT tradition:
LMC and SMC

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

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WANTED:

Schroedinger's Cat

Dead And Alive

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..

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

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If everyone had even a basic grasp of scientific principles, this planet would be a better place (Phil Plait)

Die Lücke, die wir hinterlassen, ersetzt uns vollkommen (Carl Heinz Schroth)

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

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"As truth is gathered, I rearrange,
Inside out, outside in - Perpetual change." - A British rock band

Of course! , thanks

__________________
If everyone had even a basic grasp of scientific principles, this planet would be a better place (Phil Plait)

Die Lücke, die wir hinterlassen, ersetzt uns vollkommen (Carl Heinz Schroth)

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

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I am Mugs, of the Alien clan of Usa, Nordamerica, a Terran, of Sol.

Perception isn't reality. It's merely an abstraction thereof, and quite often not a very good one at that.

I am human. Fully human.

Ysat.

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.

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.

__________________
I am Mugs, of the Alien clan of Usa, Nordamerica, a Terran, of Sol.

Perception isn't reality. It's merely an abstraction thereof, and quite often not a very good one at that.

I am human. Fully human.

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

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http://www.FreeMars.org/jeff/

"The other planets?
Well, they just happen to be there, but the point of rockets is to explore them!"
-- Kai Yeves

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

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

Try it yourself, or did you mean et voilá ?

__________________
If everyone had even a basic grasp of scientific principles, this planet would be a better place (Phil Plait)

Die Lücke, die wir hinterlassen, ersetzt uns vollkommen (Carl Heinz Schroth)

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

Nothing to do with measuring distances in Space.

-- Jeff, in Minneapolis

__________________
http://www.FreeMars.org/jeff/

"The other planets?
Well, they just happen to be there, but the point of rockets is to explore them!"
-- Kai Yeves