astr 11-14 test4

astr 11-14 test4 - Sun-Scorched Mercury 1. Closest planet...

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Sun-Scorched Mercury 1. Closest planet to the sun a. Mercury looks similar to our moon b. Mercury has an eccentric orbit (most eccentric planet) i. Its greatest elongations are very different by 10 degrees 1. Eastern elongation- planet is farther east than the sun 2. Western elongation- planet is farther west than the sun 3. Favorable elongation- maximum possible elongation at 28 degrees and its orbital plane is inclined at a large angle to the observer’s horizon 4. Unfavorable elongation- minimum possible elongation at 18 degrees and its orbital plane is inclined at only a shallow angle to the observer’s horizon ii. Time to think 1. It is possible to see Mercury in the night sky a. At any time during the night. b. Just before sunrise or just after sunset c. At midnight directly overhead d. At midnight toward the south iii. Time to think 1. At greatest eastern elongation (see diagram) Mercury is visible a. Just before sunrise b. Just after sunset c. At midnight directly overhead d. At midnight toward the south c. The orbital period is 88 days but the rotational period is about 59 days d. Made of mostly metals i. The temperatures are either incredibly hot or insanely cold e. We cannot see much, but we can still get information i. There is literally a hole in the ground that accepts photons. If something doesn’t cross over it, then it cannot collect information. This device is a receiver and a transmitter. 1. A radio signal was sent toward Mercury. It hit the surface and bounced back 2. Reflected waves from Mercury’s receding side are Doppler shifted to longer wavelength ii. Mercury has a tidal bulge that constantly faces the sun 1. The mass of Mercury is less than that of the sun, so we would think that the Earth- moon thing would apply 2. In fact Mercury is an elliptical orbit, and its long axis only points toward the sun at perihelion: Mercury spins on its axis 1.5 times during each complete orbit (3-to-2 spin-orbit coupling). a. This is because the tidal bulge only lines up with the sun at perihelion and the eccentric orbit causes this because of tidal forces iii. Time to think 1. What is the cause of the 3:2 orbit-spin coupling? a. Spin of the solar nebula b. Tidal forces c. Collision d. Interactions with Venus 2. Missions to Mercury a. One mission did a fly-by, not a land i. Usually you do a fly-by of both Venus and Mercury at the same time. The Mariner is still out there but only flew by Mercury 3 times.
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b. Messenger will enter Mercury’s orbit in March 2011 and carry out comprehensive measurements for one Earth year i. It moves at 100,000 K an hour, which is really fast. 3. Surface a. Mercury is heavily cratered i. Inter Crater plains 1. This is similar to the moons maria. 2.
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This note was uploaded on 04/28/2008 for the course ASTR 1101 taught by Professor Campbell during the Spring '08 term at LSU.

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astr 11-14 test4 - Sun-Scorched Mercury 1. Closest planet...

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