Astr 1504/1514 midterm
A spectral line associated with a particular element is measured in the lab to be at a wavelength of 570.2 nm. An astronomer measures it in Star Y's spectrum at a wavelength of 571.0 nm, and in Star Z's spectrum at a wavelength of 570.6 nm. Which statement best describes what is happening?
Both stars are moving away from us, with Star Y receding faster.
Why is an absorption spectrum especially useful for astronomers?
It has dark lines in it that allow astronomers to determine what elements are in the star
Suppose you observe a star whose spectrum exhibited neither a redshift nor a blueshift. What could you conclude about this star?
The star has no radial motion with respect to us
What happens as an electron falls from a higher level to a lower level in an atom?
a photon is given off
To go from a lower level in an atom to a higher level, an electron must
absorb a photon of energy
Why do different types of atoms (elements) give off or absorb different spectral lines?
because the spacing of the energy levels is different in different atoms
The red color we see on a lot of photographs of nebulae comes from which element?
hydrogen
How do astronomers learn what elements are present in a given star?
look at the absorption lines in its spectrum
When a star or galaxy is moving away from us, we observe the Doppler effect by seeing the lines in its spectrum
redshifted (shifted toward the red end of the light spectrum)
The ground state in an atom is
the electron orbit with the lowest possible amount of energy
Analyzing the light in the spectrum of a star can tell astronomers the star's temperature, what elements are in it, and its speed in a direction toward us or away from us.
true or false
