Astronomy 101 Exam 3 questions and
Verified Answers
Wien's displacement law - ANSWER states that the black body radiation curve for
different temperatures peaks at a wavelength inversely proportional to the temperature.
Two stars same size and distance which is hotter - ANSWER Which peak is higher
Which of these stars in
Orion is most luminous?
star m M distance
1 Rigel 0.18 -6.69 773
2 Betelgeuse 0.42 -6.02 643
3 Bellatrix 1.64 -2.72 242
4 Alnilam 1.69 -6.38 - ANSWER 1. Rigel- Most negative=most luminous
Two stars at the same distance, which is more
luminous? - ANSWER Whichever is putting out more light at all wavelengths
Two stars at the same distance, which looks redder? - ANSWER Which peak is in the red
section 600-700nm
Two stars at the same distance, which emits more red
light? - ANSWER Which is higher in the red section
Which spectrum is from the
hottest object? - ANSWER peak furthest to the left
,Kirchhoff and Bunsen - ANSWER Study spectral lines. spectroscope- studied emission lines- took
advantage of a convenient industrial fire, and measured the amount of sodium burning
Spectral lines - ANSWER show atoms have high energy levels. Blue photons=more energy than
red
Kirchhoff's Laws: 3 kinds of spectra, 3 geometries - ANSWER 1) Continuous spectrum
2) Dark line (Absortion spectrum)
3) Bright line (Emission spectrum)
2+3 require thin cloud of cool gas
Types of Spectra - ANSWER • Emission: hot, thin gas makes a spectrum of bright lines.
• Continuous: any hot, opaque (even gas ) thing makes a continuous spectrum of color.
• Absorption: gas backlit by a continuous source can create dark absorption lines if the gas is
cooler than the source.
1. What kind of spectra is a prism photo?
2. What kind of spectrum is a Full rainbow spectrum rectangle w few black thin lines+ absortion
3.Which is caused by backlit gas? - ANSWER 1. Continuous
2. Absortion
3. Same as absortion- full rainbow rectangle
Harvard Observatory's "Computers" - (Women) - ANSWER Edward Pickering Director,
Harvard College Observatory
Williamina Fleming - ANSWER Worked for Edward Charles Pickering. • Devised a system of
classification based on the strength of the hydrogen lines. • A stars had the strongest H lines,
• B stars the next strongest, ↓ • O stars had the weakest.
, Annie Jump Cannon - ANSWER • Re-devised a system of classification based on temperature. •
Dropped many of Fleming's categories, leaving: O B A F G K M
The horizontal axis of these spectra is changing, 1. energy 2. temperature 3. luminosity -
ANSWER Answer: 1. energy. light's wavelength corresponds directly to its energy.
The spectra from these emission tubes are:
1. bright line emission spectra 2. dark line absorption spectra 3. continuous spectra
(1 red light tube line 1 blue) - ANSWER Answer: 1- bright line
Stellar spectra (like the negative images above) are:
1. emission spectra. 2. absorption spectra. 3. continuous spectra. - ANSWER 2- absortion
Electrons can absorb or emit a photon only if,
1. the thermal spectrum has the right peak wavelength. 2. the photon has sufficient intensity.
3. the photon is a certain wavelength. 4. the photon is at the correct speed. - ANSWER Answer:
3 the photon is a certain wavelength —wavelength corresponds to energy
Spectral Lines are caused by: - ANSWER Electron transitions
Nitrogen has strong spectral lines at 645 and 1200 nm. If a star has NO nitrogen, is it likely to
have lines in its spectrum at 645 and 1200 nm?
1. Very likely 2. Not very likely 3. Can't tell - ANSWER Answer: 2.Not very likely —unlikely that
other elements would cause lines in the exact same spots
Nitrogen has strong spectral lines at 645 and 1200 nm. If a star has abundant nitrogen, will
it have lines in its spectrum at 645 and 1200 nm?
1. Very likely 2. Not very likely 3. Can't tell - ANSWER Answer: 3. Cant tell —the star also has
to be at the right temperature
Verified Answers
Wien's displacement law - ANSWER states that the black body radiation curve for
different temperatures peaks at a wavelength inversely proportional to the temperature.
Two stars same size and distance which is hotter - ANSWER Which peak is higher
Which of these stars in
Orion is most luminous?
star m M distance
1 Rigel 0.18 -6.69 773
2 Betelgeuse 0.42 -6.02 643
3 Bellatrix 1.64 -2.72 242
4 Alnilam 1.69 -6.38 - ANSWER 1. Rigel- Most negative=most luminous
Two stars at the same distance, which is more
luminous? - ANSWER Whichever is putting out more light at all wavelengths
Two stars at the same distance, which looks redder? - ANSWER Which peak is in the red
section 600-700nm
Two stars at the same distance, which emits more red
light? - ANSWER Which is higher in the red section
Which spectrum is from the
hottest object? - ANSWER peak furthest to the left
,Kirchhoff and Bunsen - ANSWER Study spectral lines. spectroscope- studied emission lines- took
advantage of a convenient industrial fire, and measured the amount of sodium burning
Spectral lines - ANSWER show atoms have high energy levels. Blue photons=more energy than
red
Kirchhoff's Laws: 3 kinds of spectra, 3 geometries - ANSWER 1) Continuous spectrum
2) Dark line (Absortion spectrum)
3) Bright line (Emission spectrum)
2+3 require thin cloud of cool gas
Types of Spectra - ANSWER • Emission: hot, thin gas makes a spectrum of bright lines.
• Continuous: any hot, opaque (even gas ) thing makes a continuous spectrum of color.
• Absorption: gas backlit by a continuous source can create dark absorption lines if the gas is
cooler than the source.
1. What kind of spectra is a prism photo?
2. What kind of spectrum is a Full rainbow spectrum rectangle w few black thin lines+ absortion
3.Which is caused by backlit gas? - ANSWER 1. Continuous
2. Absortion
3. Same as absortion- full rainbow rectangle
Harvard Observatory's "Computers" - (Women) - ANSWER Edward Pickering Director,
Harvard College Observatory
Williamina Fleming - ANSWER Worked for Edward Charles Pickering. • Devised a system of
classification based on the strength of the hydrogen lines. • A stars had the strongest H lines,
• B stars the next strongest, ↓ • O stars had the weakest.
, Annie Jump Cannon - ANSWER • Re-devised a system of classification based on temperature. •
Dropped many of Fleming's categories, leaving: O B A F G K M
The horizontal axis of these spectra is changing, 1. energy 2. temperature 3. luminosity -
ANSWER Answer: 1. energy. light's wavelength corresponds directly to its energy.
The spectra from these emission tubes are:
1. bright line emission spectra 2. dark line absorption spectra 3. continuous spectra
(1 red light tube line 1 blue) - ANSWER Answer: 1- bright line
Stellar spectra (like the negative images above) are:
1. emission spectra. 2. absorption spectra. 3. continuous spectra. - ANSWER 2- absortion
Electrons can absorb or emit a photon only if,
1. the thermal spectrum has the right peak wavelength. 2. the photon has sufficient intensity.
3. the photon is a certain wavelength. 4. the photon is at the correct speed. - ANSWER Answer:
3 the photon is a certain wavelength —wavelength corresponds to energy
Spectral Lines are caused by: - ANSWER Electron transitions
Nitrogen has strong spectral lines at 645 and 1200 nm. If a star has NO nitrogen, is it likely to
have lines in its spectrum at 645 and 1200 nm?
1. Very likely 2. Not very likely 3. Can't tell - ANSWER Answer: 2.Not very likely —unlikely that
other elements would cause lines in the exact same spots
Nitrogen has strong spectral lines at 645 and 1200 nm. If a star has abundant nitrogen, will
it have lines in its spectrum at 645 and 1200 nm?
1. Very likely 2. Not very likely 3. Can't tell - ANSWER Answer: 3. Cant tell —the star also has
to be at the right temperature
