Honors Astronomy Final Exam 1 – Flashcards
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Where is the Sun on September 23?
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12 hours RA, 0 degrees declination
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Where is the Sun on June 21st?
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None of these is correct.
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Which statement about Right Ascension is false?
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It is most like latitude in geography.
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Which statements about the day are TRUE?
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The sidereal day is four minutes longer due to our revolution around the Sun.
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Where would you be on the Earth if the noon Sun passed through your zenith on June 21?
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Tropics of Cancer
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Where would you be if Polaris was directly at your zenith?
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North pole
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Where on Earth can you observe all the stars in the whole sky over the entire year?
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Equator
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What phenomena accounts for the 26,000 year wobble which shifts poles and equinoxes?
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precession
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What celestial line is created by our Earth's rotation?
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equator
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What celestial line is created by the Earth's revolution around the Sun?
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Ecliptic
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What conditions are necessary for an annular solar eclipse?
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new moon on ecliptic near apogee
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What conditions are necessary for a total solar eclipse?
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new moon on ecliptic near perigee
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What conditions are necessary for a partial solar eclipse?
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new moon near ecliptic, with us in its penumbral shadow
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Why is there a two day difference in the sidereal and synodic months?
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The Earth has also revolved around the Sun, so the Moon must "catch up."
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A solar eclipse can only happen during a ______ moon.
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new
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A lunar eclipse can only happen during a ______ moon.
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full
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Which statement about the length of the day is FALSE?
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The sidereal day is four minutes longer due to our revolution around the Sun.
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Which statement about the first quarter moon is FALSE?
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To us, it appears one quarter lit.
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Parallax is described as
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inversely proportional to the object's distance
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If the Moon rose tonight about 6 PM, then tomorrow it will rise about ____.
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7 PM
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Right ascension and declination are both
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A means of specifying stars' locations on the celestial sphere and analogs of latitude and longitude on Earth's surface
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What is the range of values that the coordinate declination can have?
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-90 to +90 degrees
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How many stars are visible on a clear, dark night with the naked eye alone?
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a few thousand
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Scientists today do not believe the Ptolemaic model because:
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it has been proven incorrect
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Indicate which one of the assumptions or statements below is part of the both the Ptolemaic and Copernican hypotheses.
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the moon orbits the earth in a month
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What was one of the contributions made by Copernicus to astronomy?
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He said that the Earth is not the center of the universe.
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Which of the following is one of the many contributions made by Galileo to astronomy?
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He used a telescope to observe sunspots and the rotation of the Sun.
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Which of these concepts was NOT part of Ptolemy's model?
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Planets moved in ellipses.
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Which concept below was NOT part of Kepler's Laws?
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Retrograde motion requires epicycles when the planet lies at opposition, closest to us.
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The force of gravity between two objects:
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Increases with the mass of the objects and decreases with the distance between them.
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Geosynchronous satellites orbit about four earth radii above our equator. There the earth's gravitational force is how many g's?
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1/16 g
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Which of these was not telescopically observed by Galileo?
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saturns rings
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What was one of Newton's contributions to astronomy?
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He developed a theory of gravity that could explain orbital motion.
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On what did Copernicus and Ptolemy agree?
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All orbits are circular.
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The Ptolemaic model of the universe:
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Explained and predicted the motions of the planets with deferents and epicycles.
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As Saturn lies at about 10 AU from the Sun, out there the Sun's gravity would be:
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100 times weaker
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Which of these concepts was not part of the Copernican theory?
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Venus must always lie between the Earth and Sun on its epicycle.
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What contribution to astronomy was made by Tycho Brahe?
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He made extensive and detailed observations of the positions of the planets.
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Upon which point did Kepler and Copernicus disagree?
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All planetary orbits must be circular.
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By combining Newton's and Kepler's Laws, we can weigh the Sun, provided we know:
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the size of the AU and the exact length of the year.
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Stefan's Law says:
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that the energy radiated by a black body is proportional to T4.
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At which of these Kelvin temperatures is water a liquid?
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300 K
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The frequency at which the intensity of a star's light peaks depends on the _____ of the star.
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temperature
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The fact that doubling the star's surface temperature will halve its peak wavelength is:
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Wein's Law
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What does Wien's Law reveal?
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the hotter the object, the bluer the radiation
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According to Wein's Law, if the Sun's surface temperature of 5,800 K were doubled:
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the peak of its energy would now fall in the ultraviolet part of the spectrum.
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Which of the following is constant for all types of electromagnetic waves in space?
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speed
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High-energy astronomers study:
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X-rays and gamma rays.
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Which of the following types of visible light has the highest energy?
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violet
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Light waves differ fundamentally from either water waves or sound waves because:
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They do not require a material medium.
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Which of the following statements is true regarding the Kelvin temperature scale?
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Water freezes at 273 K.
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If an object is moving toward you, what effect do you observe in the spectrum of that object?
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It appears blue-shifted.
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You go to a physician who is also really into physics. If your body temperature is normal, his Kelvin thermometer should read:
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310 K
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Two forms of electromagnetic radiation that penetrate Earth's atmosphere are:
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Visible light and radio waves.
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Space travelers looking out from the front of their spacecraft would note that the light emitted from the star system toward which they were moving seemed to be:
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Getting bluer.
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What is spectroscopy?
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An analysis of the way in which atoms absorb and emit light.
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In the atom, what type of particle determines the element that atom represents?
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protons
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Spectral lines are sometimes referred to as the stars' "fingerprints" because:
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all of these
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Line broadening is caused by:
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all of these
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The part of the atom responsible for its chemical reactions is the:
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electron
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A hydrogen atom consists of:
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One electron orbiting a proton.
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What is emitted from an atom when one of its electrons makes a transition from a higher energy state to a lower energy state?
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photon
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What discovery resulted from the photoelectric effect?
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The particle nature of light.
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The particle which adds mass but no charge to the atomic nucleus is the:
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neutron
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If you view a hot star through a cool cloud of gas, what sort of spectrum are you likely to see?
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Absorption.
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Which of these is the classic continuous spectrum?
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a rainbow
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An incandescent light bulb (glowing hot tungsten filament) produces which spectrum?
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continous
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A neon light (thin hot neon gas in a vacuum tube) produces which type of spectrum?
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emission
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The Orion Nebula is a hot, thin cloud of glowing gas. Which best describes its spectrum?
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a few bright lines on a dark background
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Typical stellar spectra appear as:
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a rainbow with dark lines mixed in
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Why are most large telescopes reflectors, not refractors?
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Large lenses deform under their own weight, while large mirrors can be supported.
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-uses a lens to collect light; subject to chromatic aberration -combines light from two different telescopes to greatly enhance resolution -the convex secondary bounces light down hole to focus behind hole in main mirror -its flat secondary mirror, tilted 45°, focuses the image to the front side of the tube
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-refractor -interferometer -casserigan reflector -newtonian reflector
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The telescope has a 60 mm diameter achromatic objective with a 200 mm focal length. How much better RESOLUTION does this lens yield than your eye's 6 mm exit pupil?
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10✕
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A telescope has a 60 mm diameter achromatic objective with a 200 mm focal length. Compared to your eye's 6 mm exit pupil, how much fainter stars (better light grasp) does it show than your eye alone?
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100✕
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Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes?
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It is larger than any Earth-based instrument.
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What is the primary advantage of the Hubble Space Telescope over ground-based telescopes?
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It is above the atmosphere.
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What problem is adaptive optics used to correct?
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effects of atmospheric turbulence
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Diffraction is the tendency of light to:
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spread around corners.
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It is diffraction that limits the _________ of a telescope, given its objective's aperture.
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resolution
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Which statement best express the advantages of large telescopes over small ones?
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Large telescopes collect more light than small ones and they bring the light to a sharper focus.
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What is the resolving power of a telescope?
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its ability to distinguish two adjacent objects in the sky
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Contrast the resolving power of a Celestron C-8 with its finder, given the main scope has an aperture eight times larger than its finder lens.
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8✕ better detail
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Contrast the light grasp of a Celestron C-8 with its finder, given the main scope has an aperture eight times larger than its finder.
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64✕ fainter stars
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What is the primary advantage of CCDs over the photographic plate?
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They record up to 75 percent of the light instead of only 5 percent.
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What is the primary purpose of an astronomical telescope?
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to collect a large amount of light and bring it to a focus
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In which part of the spectrum is there no information coming to us from space and is therefore not observed by astronomers?
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none of these
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Which of the following is a problem inherent to all large radio telescopes?
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They have poor angular resolution.
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A mountain top is a good location for optical and infrared telescopes because the site:
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is above much of the atmosphere.
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The amount of diffraction depends on what factor or factors?
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the wavelength used and the telescope size
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For what is an interferometer used?
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to improve the angular resolution of radio telescopes
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This type of telescope has its focus is behind the back of the hole in the main mirror.
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Cassegrain
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Refracting telescopes suffer from this type of defect. Light of different wavelengths is focused at different positions and focal points.
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Chromatic aberration
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What is "seeing"?
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It is a measure of the image quality due to the stability of the air.
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Why are CCDs, or charge-coupled devices, so useful to astronomical research?
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All of these.
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Radio dishes must be large in order to:
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detect the small amount of radio energy reading Earth.
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What is the name of the effect when an electromagnetic wave is bent as it passes from one material into another?
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refraction
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Which statement about planet orbits is incorrect?
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Most stay close to the Earth's equatorial plane.
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Which of these statements is not true of all the jovians?
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They all have their poles pointing approximately perpendicular to the ecliptic.
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Which of the following falls into the category of interplanetary debris?
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Large and small asteroids, comets, and grains of dust.
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Which of the following defines density?
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mass divided by volume
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Which statement about density is not correct?
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All planets have densities greater than water, at 1 gram/cc.
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What is the goal of comparative planetology?
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To determine the origin and evolution of the solar system.
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Our understanding of the solar system has come in a way that can best be described as:
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We have learned more in the past few decades than during all of previous history.
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Which of the following are the jovian planets?
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Jupiter, Neptune, Saturn, Uranus
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A gravitational "sling-shot"
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changes the speed and direction of planetary spacecraft as they pass near a planet or moon.
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Which of the following are the terrestrial planets?
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Earth, Mars, Mercury, Venus
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Which of the following is NOT a way in which the terrestrial and jovian planets differ?
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The jovian planets have orbits that are highly inclined to the ecliptic and do not revolve in the same direction as the terrestrial planets.
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Which of the following has an icy composition?
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comets
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Where are the asteroids generally found in the solar system?
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between the orbits of Mars and Jupiter
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What is the name of the NASA probe visiting Comet Wild and returning a sample to Earth?
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Stardust
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The ESA probe which came the closest to Comet Halley's nucleus in 1986 was:
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Giotto
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The NASA orbiter that ultimately landed on the surface of the asteroid Eros was:
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NEAR Shoemaker
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On its way to Jupiter, Galileo also gave us close-ups of:
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Gaspra and Ida
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Before it arrived in orbit about Eros, the NEAR spacecraft also flew past:
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Mathilde
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Large meteoroids are thought to collide with Earth:
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A few times in every million-year period.
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Iron meteorites are believed to come from:
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the core of a differentiated asteroid, now broken up.
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Meteor shower debris is believed to come from:
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a broken up cometary nucleus.
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What part of a comet has only been seen by a space probe?
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nucleus
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Compared to Ida, Eros, and Gaspra, what was odd about the density of Mathilde?
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It was less dense than rock, but more than ice, suggesting a porous structure.
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What are comets made of?
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All of these.
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The Kuiper Belt objects have orbits that:
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Stay out beyond Neptune.
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The Trojan asteroids have orbits that:
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Stay sixty degrees ahead of or behind Jupiter.
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The Apollo and Aten asteroids have orbits that:
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Cross the orbit of Earth at perihelion.
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Long period comets are thought to reside mainly in:
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The Oort Cloud
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Which of the following objects would be found on the Moon's surface?
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Meteorites.
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The Oort Cloud is thought to be:
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A cloud of comets surrounding the solar system.
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The orbits of most asteroids:
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Lie entirely beyond the orbit of Mars.
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The orbits of most comets:
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Lie almost entirely beyond the orbit of Neptune.
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Which of the following gives direct information about the age of the solar system?
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Meteorites.
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Which of the following objects never collide with the Earth?
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All of these can collide with us
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What causes a meteor shower?
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Earth crosses the orbit of a comet, and this orbit is littered with debris.
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Meteorites are valuable to astronomers because:
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They may provide evidence about the process in which the solar system was born.
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What are Gaspra, Mathilde, Eros, and Ida?
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asteroids
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The nucleus, or main solid body, of a comet has a typical size of
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a few kilometers.
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What is the defining property of the Trojan asteroids?
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They have orbits at the distance of Jupiter and 60 degrees ahead of or behind it.
