AST1002 – Flashcard
102 test answers
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In the Figure below (Figure 0.20A - Parallax), a smaller Earth would result in
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a smaller parallax angle.
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How, and by roughly how much, would the length of the solar day change if Earth's rotation were suddenly to reverse direction?
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A solar day would be approximately 8 minutes shorter than the current one.
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If you watch Polaris all night, what does it do?
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Not much! It just sits there.
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When is the Earth closest to the Sun?
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In the winter in the northern hemisphere.
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What causes Earth's seasons?
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23.5° tilt of Earth's rotational axis
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The angle of parallax increases as
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the baseline gets larger.
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Why don't we have solar and lunar eclipses every month?
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ecause the Moon's orbit around Earth is tilted by about 5° out of the ecliptic.
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he average distance from the Earth to the Sun, 149,600,000 km, can be written in scientific notation as
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1.496 × 108 km.
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If there are about 6000 stars in the entire sky that can be seen by the unaided human eye, about how many stars would be seen at a particular instant on a given dark night from a single location with an uninterrupted distant horizon?
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3000
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Are the constellations seasonal?
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Yes. On a summer night many of the constellations you can see are different from the constellations you can see on a winter night. But there are some constellations you can see all year long.
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At what time of the year in the northern hemisphere will your shadow in sunlight at midday be shortest?
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first day of summer, about June 21
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How long does it take light to travel a distance of one light year?
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One year or about π×107 seconds.
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What is the unit that we use to measure distances in the solar system?
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The astronomical unit or AU is very convenient.
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The most southern location on Earth where the Sun can be seen directly overhead at noon is called
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the Tropic of Capricorn
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How long would a radar signal take to complete a round trip between Earth to Mars and back to Earth when the two planets are 0.7 AU apart
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about 11.6 minutes
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Mars, Jupiter, and Saturn show retrograde motion because
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Earth moves faster in its orbit.
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Epicycles were used in Ptolemy's model to explain
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why retrograde motion occurred.
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Copernicus' important contribution to astronomy was
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proposing a simpler model for the motions of planets in the solar system.
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Which of Galileo's initial observations was most challenging to established geocentric beliefs?
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moons of Jupiter
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Newton's law of gravity states that the force between two objects
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increases with mass.
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The word planet is derived from a Greek term meaning
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wanderer
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In the geocentric model of the solar system developed by Ptolemy, the planets move
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in circular epicycles while the centers of the epicycles move in circular orbits around the Earth.
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he major contribution of Tycho Brahe to the development of modern astronomy was
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measuring planetary positions very accurately.
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epler's second law states that a planet moves fastest when it
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is closest to the Sun.
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to which point in a planetary orbit does the word perihelion refer?
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point closest to the Sun
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hich of the following sentences correctly states the significance of Galileo's observation that Jupiter has satellites (moons)?
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The observation showed that bodies can orbit an object other than the Earth.
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Suppose that a planet of the same mass as the Earth were orbiting the Sun at a distance of 10 AU. The gravitational force on this planet due to the Sun would be
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1/100 of the gravitational force the Sun exerts on the Earth.
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stronomers analyze starlight to determine a star's
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motion, temp, composition, all of the above
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What is the wavelength of a 98-MHz ("FM 98") radio signal?
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3.1 m
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Rigel appears as a bright bluish star, whereas Betelgeuse appears as a bright reddish star. Rigel is
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hotter than Betelgeuse.
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the light from a distant star is approaching you, you will observe
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its spectral lines are shorter in wavelength.
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he wavelengths of emission lines produced by an element
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are identical to its absorption lines.
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What types of electromagnetic radiation from space will reach the surface of Earth without being significantly absorbed by the Earth's atmosphere?
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visible light and radio waves
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For lecture on "Waves", a sound wave can travel through ________.
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molten rock, solid rocks
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How many times lower would the intensity of light from a given star become if the star is 2 times farther away?
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4 times
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visible wavelengths of electromagnetic radiation have a range of wavelengths of
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400 nm to 700 nm.
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forms of light have what property in common? (Light in this case refers to the whole spectrum, not just the visible range.
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All forms of light are electromagnetic radiation.
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What is the one fundamental difference between X rays and radio waves?
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the wavelengths of X rays and radio waves are very different.
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ieces of metal are heated by varying amounts in a flame. The hottest of the pieces will be the one that shows most prominently which color?
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blue
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What changes would you expect to see in the resulting spectrum of emitted light from a piece of metal when it is heated slowly in an intense flame from 500 K to 1500 K?
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he intensity of radiation would increase greatly, and the color would change from red through white to blue.
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An ideal blackbody in physics and astronomy is an object that
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absorbs and emits electromagnetic radiation at all wavelengths.
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According to the Doppler effect
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the wavelength of light is shifted to a shorter wavelength if the source of light is moving nearer to the observer.
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The Doppler effect is the change in the wavelength of light caused by the source
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moving with respect to the observer.
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he dark absorption lines in the solar spectrum are caused by
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a cooler layer of gas overlying the hot solar surface, which contains many elements, including hydrogen, helium, magnesium, calcium, and iron.
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Atoms in a low-density, hot gas (e.g., in a fluorescent lamp or a neon tube) emit a spectrum that is
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a series of specific colors unique to the type of atom in the tube but fixed in position when the gas temperature changes.
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The main reason that most professional research telescopes are reflectors is that
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mirrors produce sharper images than lenses do since there is no chromatic aberration.
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he PRIMARY reason professional observatories are built on the highest mountain tops is to
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reduce atmospheric blurring
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the Spitzer Space Telescope is stationed far from Earth because
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This infrared telescope actually does not orbit the Earth, but follows our planet around the Sun, reducing the heat interference from Earth
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The best way to study young stars hidden behind interstellar dust clouds would be to use
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infrared light
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An FSU student is observing the phases of Venus with his 16 inch reflector telescope, and a UF student is doing the same with a 8 inch reflector telescope. How much more light gathering power does the FSU telescope have?
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4 times more
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again, an FSU student is observing the phases of Venus with his 16 inch reflector telescope, and a UF student is doing the same with an 8 inch reflector telescope. How much "more" resolving power (i.e. angular resolution) does the FSU telescope have?
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Twice as much.
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Seeing in astronomy is a measurement of
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the image quality due to air stability.
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Resolution is improved by using
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larger telescopes and shorter wavelengths.
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an advantage of CCDs over photographic film is
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they don't require chemical development,digital data is easily store and transmitted, CCDs are more light sensitive than film, CCD images can be developed faster. All of the above are true.
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Radio dishes are large in order to
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improve angular resolution.
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adaptive optics refers to
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reducing atmospheric blurring using computer control.
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Radio telescopes are useful because
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observations can be made day and night, radio waves are not blocked by interstellar dust, we can see objects that don't emit visible light, they can be linked to form interferometers. Correct: All of the above are true.
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The Hubble Space Telescope (HST) offers sharper images than ground telescopes primarily because
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HST orbits above the atmosphere.
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the light-gathering power of a telescope depends directly on the
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area of its primary mirror or lens.
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What is the main reason for placing astronomical telescopes and detectors on satellites?
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to get above the absorption in the Earth's atmosphere
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The major difference(s) between the terrestrial and jovian planets involve(s)
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mass and density.
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The asteroid belt is evidence of
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ancient material from the formation of the solar system.
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Pluto seems to be more similar to
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the moons of jovian planets.
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What causes a meteor shower?
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Earth runs into the debris of an old comet littering its orbit.
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Any theory of the origin of the solar system must explain all of these EXCEPT
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the direction that planets orbit the Sun is opposite to the Sun's spin.
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The condensation sequence theory explains why
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terrestrial planets are different from jovian planets.
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xtrasolar planets the size of Earth have NOT been seen yet with current techniques because
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large planets orbiting near to their stars are more easily detected.
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s a rotating gas cloud contracts, it spins faster.
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True
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In the solar nebular theory, the dusty disk condensing around the Sun's equator became the ecliptic plane in which the planets then formed.
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true
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Due to their great masses, all four Jovian worlds are much denser than the earth.
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false
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the temperature in the solar nebula at the location now at the center of the asteroid belt is
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400k
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Strong evidence for the existence of planetary systems in the process of formation around other stars comes from
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photographs and infrared observations of disks of dust.
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The Moon's internal structure is similar to Earth's, but the Moon lacks
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a hydrosphere. a magnetosphere. an atmosphere. Correct: It lacks all of the above
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The principal greenhouse gases in our present atmosphere are
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water vapor and carbon dioxide.
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At what lunar phase would the variation between high and low tides be greatest?
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both new and full moon
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What is true of the Moon's orbital and rotational periods?
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They are equal.
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he magnetic field of the Earth probably arises from what process or condition?
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A dynamo effect due to the motion of the electrically conducting molten iron core.
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Without the greenhouse effect operating in our atmosphere,
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Earth would have an average temperature of -23 degrees Celsius.
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The Moon's near side always faces Earth due to
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Earth's tidal force.
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What are the two most abundant gases in the Earth's atmosphere
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Nitrogen and Oxygen
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Why did Earth's earliest atmosphere, composed primarily of hydrogen and helium, not last long?
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Hydrogen and helium are light gases, and they soon escaped into space.
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What is the distribution of maria on the Moon's surface?
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Maria are largely confined to the hemisphere facing Earth; there is only one small mare on the distant side.
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How do the atmospheres of the Moon and Mercury compare?
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Neither body has a permanent atmosphere.
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Mercury has extreme high and low temperatures between night and day because
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it has no atmosphere to moderate temperatures over the globe.
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hich of the following inner solar system bodies has the densest atmosphere?
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venus
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he greenhouse effect on Venus is due to carbon dioxide in its atmosphere.
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carbon dioxide
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enus' surface shows all of the following EXCEPT
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many impact craters of all sizes.
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Venus and Mars probably evolved differently from Earth because
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they orbit at different distances from the Sun.
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How does Mercury's rotation rate relate to its orbit around the Sun?
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Its rotation rate is 2× as long as its year, due to tidal resonances.
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Venus' rotation once about its axis
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takes longer than its orbit around the Sun.
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The chief gas in the martian atmosphere is
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carbon dioxide.
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Why are Mars's seasons more extreme than those of the Earth?
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weather is driven by evaporation from the polar ice in its summer. orbit is more eccentric than our almost circular one. seas dried up long ago. axial tilt is slightly more than our 23.5 degrees. Correct: All of the above contribute to the huge barometric changes that Mars experiences.
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Why doesn't Venus have a magnetic field?
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Its extremely slow rotation doesn't produce a significant dynamo effect.
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The craters on the Moon and on Mercury surfaces are due to
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impacts from meteorites and asteroids.
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The surface temperature on Venus is
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much higher than that on the surface of the Earth.
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Mercury can be seen easily from the Earth only
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when Mercury is near the Sun, just after sunset or just before sunrise.
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the best images of the overall topology of Venus have been produced by
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reflection of microwave and short radio wave radiation from the surface by an orbiting spacecraft.
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The most likely explanation for the retrograde rotation (rotation in a direction opposite that of most other planets) of Venus is the
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impact of a massive object on it early in its history
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