Doppler shift question (galaxy movement)

In summary, the galaxy is observed to have an emission line of hydrogen with a shifted wavelength of 662.6 nm, compared to its rest wavelength of 656 nm. Using the equation for velocity, the calculated speed is 3018 km/sec, indicating that the galaxy is moving away from us. This answer has been verified and can be used for both homework and quiz questions.
  • #1
psych2012
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Homework Statement



In a distant galaxy, an emission line of hydrogen that has a rest wavelength of 656 nm has an observed wavelength of 662.6 nm. Is the galaxy moving away from us or toward us? How fast is it moving in (km/sec)?


Homework Equations



velocity = ((shifted wavelength - rest wavelength)(c)) / rest wavelength

The Attempt at a Solution



velocity = ((6.626 x 10^-10 km - 6.56 x 10^-10 km)(3 x 10^5 km)) / 6.56 x 10^-10 km = 3018 km/sec

My answer is: the galaxy is moving away from us at 3018 km/sec. I'm hoping someone can tell me if this answer is correct. My instructor assigned this as a homework question and will be using it as a quiz question as well, so it's a double whammy if I don't have the right answer.
 
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  • #2
Correct!
 

1. What is the Doppler effect?

The Doppler effect is a phenomenon where the frequency of a wave, such as sound or light, appears to change when the source of the wave is in motion relative to an observer. This effect is commonly observed in everyday life, such as when a siren from an ambulance sounds higher in pitch as it approaches and lower in pitch as it moves away.

2. How does the Doppler effect apply to the movement of galaxies?

The Doppler effect can also be observed in the movement of galaxies. As galaxies move through space, their light waves are stretched or compressed depending on their direction of motion. This results in a shift in the wavelength of light that is emitted from the galaxy, which can be measured and used to determine the speed and direction of the galaxy's movement.

3. What is redshift and blueshift?

Redshift and blueshift are terms used to describe the Doppler shift of light from a moving source. Redshift occurs when the source is moving away from the observer, causing the wavelength of light to appear longer (shifted towards the red end of the spectrum). Blueshift occurs when the source is moving towards the observer, causing the wavelength of light to appear shorter (shifted towards the blue end of the spectrum).

4. How is the Doppler shift used to measure the expansion of the universe?

The Doppler shift of light from galaxies is one of the key pieces of evidence used to support the theory of the expanding universe. By measuring the redshift of light from distant galaxies, scientists can determine the speed at which these galaxies are moving away from us. This information, along with other data, has led to the conclusion that the universe is expanding at an accelerating rate.

5. Can the Doppler shift be used to measure the movement of objects within our own galaxy?

Yes, the Doppler shift can be used to measure the movement of objects within our own galaxy. This technique is commonly used in astronomy to study the movement of stars, planets, and other celestial bodies. By analyzing the Doppler shift of light from these objects, scientists can determine their speed and direction of motion relative to Earth.

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