Questions and Answers
In comparing first magnitude Deneb with second magnitude Polaris, how much brighter does Deneb appear to us than Polaris?
What is the motion of a star across the sky, perpendicular to our line of sight, called?
Proper motion
Why are astronomers much more interested in the luminosity of a star than its apparent brightness?
Because the luminosity tells us how bright a star really is, while apparent brightness only tells us how bright it happens to look from Earth.
What term is given to a pair of stars that appear to change positions in the sky, indicating that they are orbiting one another?
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Perhaps the greatest of the Greek astronomers, __________ compiled the first catalog of stars, accurately measured their positions, and defined the basic system of stellar brightnesses.
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How much electrical charge does an atom with 6 protons, 6 neutrons, and 5 electrons have?
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What will a star moving towards the Sun show?
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How did the astronomer measure the average speed of a star moving away from the Sun?
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What can we conclude if one object has a large redshift and another has a small redshift?
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Why do different types of atoms give off or absorb different spectral lines?
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What will the light from an object moving tangentially to your left or right exhibit?
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If an atom of iron has an atomic number of 26 and an atomic mass number of 56, how many protons, neutrons, and electrons does it have if it is neutral?
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If several lines in the spectrum of a distant star come from titanium oxide molecules, what spectral type is the star likely to be?
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What can be inferred if star A and star B have the same temperature, but star B is more luminous than star A?
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By which method can gas density, axial rotation, and the magnetic field of a star be deduced from its spectrum?
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The absolute magnitude of a star is its brightness as seen from a distance of how many parsecs?
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When an atom absorbs a photon containing energy, which of the following can happen except?
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What kind of instrument would it be smart to use to find type L stars, which are cooler than traditional spectral type M stars?
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In general, the narrower the spectral line of a star, what can be said about the star?
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What are we seeing when an electrified glass tube containing very thin neon gas glows with a rich red color?
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How do astronomers learn what elements are present in a given star?
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In a visual binary system with circular orbits, if the two stars' position angles have shifted by 30 degrees in 20 years, what must the pair's period be?
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Which of the following can astronomers NOT learn from studying the spectrum of a star?
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Study Notes
Stellar Magnitudes and Brightness
- Deneb is approximately 2.5 times brighter than Polaris, highlighting differences in first and second magnitude stars.
- Luminosity indicates a star's true brightness, while apparent brightness is how bright it appears from Earth.
Star Motion and Position
- Proper motion refers to a star's motion perpendicular to our line of sight.
- A star moving toward the Sun displays spectral lines shifted toward the blue end of the spectrum.
- The Doppler shift in a star's spectrum is used to measure its speed relative to the Sun.
Types of Star Systems
- Visual binaries are pairs of stars appearing to change positions as they orbit each other.
- The absolute magnitude of a star is measured from a distance of ten parsecs.
Elements and Atomic Structure
- An atom with 6 protons, 6 neutrons, and 5 electrons has a net positive charge of +1.
- An atom of iron (atomic number 26, atomic mass 56) contains 26 protons, 30 neutrons, and 26 electrons when neutral.
Spectroscopy and Star Characteristics
- Different atoms have distinct spectral lines due to varying energy levels.
- The presence of titanium oxide in a star's spectrum suggests it is of spectral type M.
- The line shape in a star's spectrum can provide insights into gas density, axial rotation, and magnetic fields.
- The narrower a star's spectral line, the larger the star is likely to be.
Star Discovery and Classification
- Astronomers have identified new spectral type L stars that are cooler than traditional type M, often requiring sensitive infrared telescopes for detection.
Emission and Absorption Spectra
- When energized neon gas in a glass tube glows red, it produces an emission spectrum.
- Astronomers determine the presence of elements in stars by analyzing absorption lines in their spectra.
Binary Systems and Orbital Mechanics
- In a visual binary with circular orbits, a 30-degree shift in position angles over 20 years indicates a period of 240 years for the pair.
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Description
Test your knowledge on essential concepts from chapter 3 of astronomy. This quiz covers topics such as star brightness and proper motion, offering a quick reference for key definitions. Perfect for students looking to enhance their understanding of astronomical principles.
