ASTR Notes 3

# ASTR Notes 3 - lines which are shifted from their usual...

This preview shows page 1. Sign up to view the full content.

The Power of Starlight We have seen that by analyzing starlight we can determine 1. Temperature – from Wien’s Law 2. Composition – From spectral lines 3. Next: Motion- From Doppler Effect Doppler Effect Sound waves: Ex. - As the train approaches, the sound waves get crunched together. The wavelength gets shorter . (Higher pitches) - As the train recedes, the sound waves get stretched apart. The wavelength gets longer (lower pitch) Light Waves: - if a source of light is approaching, the waves of light will be crunched, and smaller. - Smaller wavelength (Lambda) = blue - This is called blueshift. - If a source of light is receding away, the waves will be stretched and the light will become redder. - Longer wavelength (Lambda) = red - This is called redshift. Doppler Shift of Spectral Lines We can determine if a star is moving toward us or away from us based on its spectral
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: lines, which are shifted from their usual “rest wavelength” lambda 0. (Lambda= Wavelength) Doppler Effect Calculation The faster something moves, the bigger the change in wavelength Lambda 0 = rest wavelength emitted by the source Delta (triangle thing) lambda = wavelength change due to Doppler effect Vr= radial velocity (speed) The light of a moving source is blueshifted or redshifted by [Delta lambda/lambda 0 = Vr/C] (c = speed of light) Ex. A certain spectral line (Hcx) has a rest wavelength of 656 nm Suppose we observe a stars spectrum with the Hcx line at (Lambda) = 658 nm. Question: how fast is this star moving? Is it moving toward us or away? (Lambda 0) = 656 nm (rest wavelength)...
View Full Document

{[ snackBarMessage ]}

Ask a homework question - tutors are online