Astronomers measure the spectrum of light coming to Earth from a distant star. Explain how they might...?

Question

Astronomers measure the spectrum of light coming to Earth from a distant star. Explain how they might determine if the star is moving towards or away from the earth.

ty for your help!

Answer 1

OK this looks like a homework problem but I'll answer it if you remember it for the next time. You obviously know what a spectrum is ... the rainbow from star (sun) light. If you look at it closely, you will see little gaps in the spectrum caused by absorption of light by specific elements in the sun. The same happens with stars. Now because of a thing called the Doppler shift ( yep, the train whistle sound as it goes by) those gaps in the light are shifted lower in frequency ( red shift) or higher (blue shift) if the star is moving away or toward us. That's how they can measure the star's motion. Red shift (away) blue shift (towards us) tell all there is to know about motion.

Answer 2

It's called doppler or red shift.

You know how when a car comes towards you it sounds higher and when it passes you it sounds lower?

Well light from something is coming towards the Earth has a redder spectrum and a something moving away has a bluer spectrum. The farther to one side the faster it is moving.

Answer 3

Gather light in a telescope.
Put light through a prism and spread the spectrum.
Look for telltale absorption lines
See how much those lines have moved relative to where they should be.
use the wavelength that they've moved to determine the velocity.

If it moves to the red, longer wavelength, it's moving away from you, and vice versa.

Answer 4

Doppler shift will tell them if the star is moving toward or away, and how fast. But it will not tell them the "transverse" velocity -- also called "proper motion". For that, they use other methods.

Answer 5

go get a degree in aerospace