Questions and Answers
Which color star emits mostly low energy light?
Which color of star gives off more light at short wavelengths than long wavelengths?
Which color star is hotter?
Blue
Betelgeuse and Rigel have the same luminosity, but Rigel is much hotter. Which one is bigger?
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Bellatrix and Sirius B have the same temperature. Bellatrix is much larger than Sirius B. Which star is more luminous?
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You observe three stars, one red, one white, and one blue. The white one is the brightest and the blue is the faintest. Which of the following is true?
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The color of a black body object tells you its:
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The stars Rigel and Sirius B have the same color. Rigel is much larger than Sirius B. Which star is more luminous?
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Betelgeuse and Rigel have the same luminosity, but Rigel is much hotter. Which is bigger?
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Spica is a blue star and Pollux is an orange star. Spica is brighter than Pollux. Which one is larger?
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What will a second observer see if they have to look through an atom with its electrons in the ground state to see the black body object?
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What will a third observer see if they can observe the atom without the black body being anywhere in their field of view?
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Using your spectrograph, you observe a low density cloud of gas floating in space. Which kind of spectrum will you see?
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Imagine that an astronaut in space, floating high above the Earth's atmosphere, is holding on to an incandescent light bulb. If you could observe that light bulb from BR using your spectrograph, which kind of spectrum would you see?
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Energy is released from atoms in the form of light when electrons
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If an electron moves from an orbit with an energy of 5 to an orbit with an energy of 10, what happens?
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When a source is moving away from you, the Doppler effect causes the light to
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A bright star is moving towards Earth. If you were to look at the spectrum of this star, what would it look like?
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You observe the two red-shifted spectra shown below. Which of the following statements best describes the motions of the two sources?
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What do your pupils do when you walk into a dark room?
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Which wavelength is most effectively blocked out by Earth's atmosphere?
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Some telescopes are placed in space above Earth's atmosphere primarily for which reasons?
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Why do we care about light other than visible?
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Using parallax, you determine that the star Pollux is 10 pc away. Dr. Landlot measures the apparent brightness of Pollux at 1.16. What is Pollux's absolute magnitude?
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Your friend discovers they have super powers and uses those powers to move Pollux closer to Earth. How would Pollux's absolute magnitude change?
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Your friend discovers they have super powers and uses those super powers to move Pollux closer to Earth. How would Pollux's apparent magnitude change?
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Your friend discovers they have super powers and uses those powers to move Pollux closer to Earth. How would Pollux's apparent magnitude number change?
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Study Notes
Star Colors and Properties
- Red Stars: Emit mostly low energy light, indicating a cooler temperature.
- Blue Stars: Emit more light at shorter wavelengths, indicating higher temperatures; they are generally hotter than other stars.
Luminosity and Size
- Betelgeuse and Rigel: Have the same luminosity; however, Betelgeuse is larger due to its cooler temperature.
- Bellatrix vs. Sirius B: Both stars share the same temperature; Bellatrix is larger, making it more luminous.
- Rigel and Sirius B: Both exhibit the same color, but Rigel's larger size results in higher luminosity.
Black Body Radiation
- The color of a black body object is indicative of its temperature, with color changing based on energy levels of emitted light.
Spectroscopy Observations
- Low Density Gas Cloud: Observed with a bright line emission spectrum.
- Incandescent Light Bulb: Viewed from space produces a dark line absorption spectrum, indicating the presence of elements absorbing certain wavelengths.
- Photon Absorption: Occurs when electrons move from a higher energy level to a lower level.
Doppler Effect and Spectrum Shifts
- When an object moves away, its light shifts toward longer wavelengths (redshift).
- A bright star moving toward Earth shows an absorption spectrum that is blue-shifted.
Motion and Redshift
- Comparing two red-shifted sources indicates that greater redshift implies faster relative motion; source B moves faster than source A.
Human Perception of Light
- Pupils dilate in dark environments to allow more light in for better visibility.
Atmospheric Effects on Light
- Gamma Rays: Most effectively blocked by Earth's atmosphere, hence some telescopes are placed in space to avoid this issue.
Importance of Non-Visible Light
- Non-visible light provides critical information about celestial objects that is not observable in the visible spectrum.
Distance Measurements and Magnitudes
- Using parallax, Pollux determined to be 10 parsecs away has an absolute magnitude equal to its apparent brightness (1.16).
- Absolute Magnitude: Remains unchanged regardless of distance from Earth.
- Apparent Magnitude: Increases in brightness as an object approaches Earth, leading to a decrease in its apparent magnitude number.
Potential Changes in Celestial Position
- Moving Pollux beyond 10 parsecs would impact its apparent brightness without altering its absolute magnitude.
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Description
Prepare for your ASTR Test 2 with these comprehensive flashcards. Explore key concepts like stellar color, luminosity, and temperature differences among stars. This quiz will help reinforce your understanding of fundamental astrophysical principles.
