Astronomy Chapter 10 Practice Questions – Flashcards
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What is an extrasolar planet?
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A planet that orbits a star that is not our own Sun
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The first confirmed detections of extrasolar planets occurred in ____________.
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the 1990's
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What do the astrometric, Doppler, and transit methods share in common?
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They all search for planets by measuring properties of a star rather than of the planets themselves.
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The astrometric method looks for planets with careful measurements of a star's _________.
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position in the sky
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In essence, the Kepler mission searched for extrasolar planets by ____________.
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monitoring stars for slight dimming that might occur as unseen planets pass in front of them
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Can we determine orbital distances for extrasolar planets using the astrometric, Doppler, or transit methods?
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Yes: All three methods give us direct information about a planet's orbital period, from which we can use Newton's version of Kepler's third law to calculate the planet's distance.
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Why do we say that the Doppler method gives a planet's "minimum mass"?
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The size of the Doppler shift that we detect depends on the tilt of a planet's orbit.
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Which of the following statements is not true about the planets so far discovered around other stars?
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Photographs reveal that most of them have atmospheres much like that of Jupiter.
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What do we mean by a "hot Jupiter"?
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a planet that is Jupiter-like in size but orbits very close to its star
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Overall, what do current data suggest about planetary types in other planetary systems?
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Planets come in a wider range of types than the planets in our solar system.
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Based on current data, about what fraction of stars have one or more planets?
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at least about 70%
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Which new idea has been added into our theory of solar system formation as a result of the discoveries of extrasolar planets?
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Jovian planets can migrate from the orbits in which they are born.
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Which of the following might explain the lack of "water worlds" —small planets made mostly of water or other hydrogen compounds—in our own solar system?
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In our solar system, the solar wind did not clear out gas until relatively late.
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How is the GAIA mission relevant to the search for extrasolar planets?
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It can detect planets through the astrometric method.
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From the viewpoint of an alien astronomer, how does Jupiter affect observations of our Sun?
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It causes the Sun to move in a small ellipse with an orbital period of about 12 years.
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Suppose you are using the Doppler method to look for planets around another star. What must you do?
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Compare many spectra of the star taken over a period of many months or years.
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In general, which type of planet would you expect to cause the largest Doppler shift in the spectrum of its star?
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a massive planet that is close to its star
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Suppose a planet is discovered by the Doppler method and is then discovered to have transits. In that case, we can determine all the following about the planet except ______________.
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its rotation period
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The transit method allows us in principle to find planets around __________.
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only a small fraction of stars that have planets
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You observe a star very similar to our own Sun in size and mass. This star moves very slightly back and forth in the sky once every 4 months, and you attribute this motion to the effect of an orbiting planet. What can you conclude about the orbiting planet?
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The planet must be closer to the star than Earth is to the Sun.
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Which of the following will allow you to learn something about a transiting planet's atmospheric composition?
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Compare spectra obtained before and during an eclipse.
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Very few of the known extrasolar planets have sizes as small as Earth. The most likely reason for this fact is that ________.
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small planets are more difficult to detect than larger planets
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Based on everything you have learned about the formation of our solar system, which of the following statements is probably not true?
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Only a tiny percentage of stars are surrounded by spinning disks of gas during their formation.
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To date, we've found very few planets orbiting their stars at distances comparable to the distances of the jovian planets in our solar system. Why do astronomers think this is the case?
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We have not yet been searching for planets at such distances for a long enough time.
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Current evidence suggests that some massive jovian planets orbit at very close orbital distances to their stars. How do we think these planets ended up on these close orbits?
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These planets migrated inward after being born on orbits much farther from their stars.
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Assuming that our ideas about how "hot Jupiters" ended up on their current orbits are correct, why didn't our own solar system end up with any hot Jupiters?
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Our solar nebula must have been blown into space shortly after the formation of the jovian planets.
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When is the soonest we are likely to have moderate-resolution images and spectra of Earthlike planets around other stars?
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In a decade or two, through space observatories now in the early planning stages.
