stars - Test #2 results Clicker Question: CB Grades posted...

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1 Test #2 results Grades posted in Mastering Astronomy A B C D F Clicker Question: If the mass of Hydrogen fusing into helium in the Sun suddenly dropped by a factor of 3, how would the energy production change? A: go down by a factor of 3 B: go up by a factor of 3 C: go down by a factor of 9 D: go up by a factor of 9 Clicker Question: If the Earth had no Moon then what would happen to the tides? A: The tides would not be as strong but would occur with the same frequency B: There would be no tides C: The tides would occur less often D: The tides would occur more often Clicker Question: Earth’s rotation is slowing down because of the tidal interaction between Earth and the Moon at a rate of 2 milliseconds/century. If this rate remains constant at the present value, how long will it take for one day on Earth to become 2 seconds longer than it is now: A: 1000 years B: 100,000 years C: 1 million years D: 100 million years Measuring the Stars How big are stars? How far away are they? How bright are they? How hot? How old, and how long do they live? What is their chemical composition? How are they moving? Are they isolated or in clusters? By answering these questions, we not only learn about stars, but about the structure and evolution of galaxies they live in, and the Universe. How Far Away are the Stars? Earth-baseline parallax - useful in Solar System Earth-orbit parallax - useful for nearest stars Parallax demo
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2 New distance unit: the parsec (pc). Using Earth-orbit parallax, if a star has a parallactic angle of 1", it is 1 pc away. Remember 1" (arcsecond) = 1/60 arcmin = 1/3600 degrees Distance (pc) = 1 Parallactic angle (arcsec) 1 pc = 3.3 light years = 3.1 x 10 18 cm = 206,000 AU 1 kiloparsec (kpc) = 1000 pc 1 Megaparsec (Mpc) = 10 6 pc Closest star to Sun is Proxima Centauri. Parallactic angle is 0.7”, so distance is 1.3 pc. If the angle is 0.5", the distance is 2 pc. Earth-orbit parallax using ground-based optical telescopes is good for stars within 30 pc (1000 or so). Tiny volume of Milky Way galaxy. Other methods later. Our nearest stellar neighbors (to 4 pc)
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stars - Test #2 results Clicker Question: CB Grades posted...

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