AST PRACTICE EXAM 5 - Complete Verified Answer Set

AST PRACTICE EXAM 5 - Complete Verified Answer Set Which method could detect a planet in an orbit that is face-on to the Earth? - answer - astrometric method Which detection method or methods measure the gravitational tug of a planet on its star, allowing us to estimate planetary mass? - answer - astrometric and doppler methods Choose the correct statement describing the astrometric method and the GAIA mission. - answer - Astrometric method uses very precise measurements of stellar side-to-side positions in the sky to look for the slight motion caused by orbiting planets. The GAIA mission was launched by the European Space Agency with a goal of measuring the positions of a billion stars to unprecedented accuracy. Choose the correct statement describing the Doppler method. - answer - The Doppler technique watches for movement in stars by looking for periodic Doppler shifts. It's best for detecting massive planets with close-in orbits. It detects planets in all orbit orientations except face-on. It requires large telescopes, and it provides only minimum mass when orbital inclination to Earth is unknown. Choose the correct statement representing the evidence that the planet orbiting 51 Pegasi is a hot Jupiter. - answer - 51 Pegasi is a planet whose orbital period is so short (4 days) that it must lie incredibly close to its star. Furthermore, the size of the stellar Doppler wobble is so large that it must be caused by a planet with at least a mass of 0.6 MJMJ. Choose the correct statement representing how does the transit method work. - answer - We monitor the brightness of a star as the planet passes in front of the star's disk. The star's light dims slightly because the planet blocks some of the star's visible light. This technique works only in the rare cases when the planet's orbit is nearly edge-on as seen from Earth. So we can only detect a small fraction of the existing planets. Choose the correct statement explaing what was the Kepler mission? - answer - The Kepler mission uses the transit method to search for Earth-size planets in Earth-like orbits. Which one of the following can the transit method tell us about a planet? - answer - its size To determine a planet's average density, we can use - answer - transit and doppler methods together What are the strengths and limitations of the Doppler method? - answer - The Doppler method is able to detect planets in a wide range of orbits--as long as the orbit is not face-on. Its disadvantage is that it can yield only the orbital period and estimation of planet's mass. What are the strengths and limitations of the transit method? - answer - The transit method has the advantage of yielding a planet's size. Its disadvantage is that few planets have the necessary orbital alignment to even be detectable. What kinds of planets are easiest to detect with each method? - answer - Both techniques are most sensitive to large planets close to their stars. Are there certain planets that each method cannot detect, even if the planets are very large? - answer - Planets that do not have necessary orbital alignment cannot be detected. Choose the correct description of advantages gained if a planet can be detected by both transit and Doppler methods. - answer - If a planet can be detected by both methods, then we can find its density--an indication of its composition. The following images show four identical Sun-like stars and their companion planets, all traveling in circular orbits. In each case, the mass of the planet is given in Jupiter masses and the orbital distance is given in Astronomical Units (AU). Rank each case based on the strength of the gravitational force exerted by the extrasolar planet on its central star, from weakest to strongest. If you think that two (or more) diagrams should be ranked as equal, drag one on top of the other(s) to show this equality. (Not to scale) - answer - weakest one jupiter mass, 2 au four jupiter mass, 2 au one jupiter mass, 1 au two jupi