Lecture- Chapter 7 .docx

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Astronomy & Astrophysics
Michael Reid

Lecture- Chapter 7 10/16/2012 10:16:00 AM  A solar system consists of a star orbited by planets, moons, and lots of debris (comets, asteroids, dust)  all planets orbit counterclockwise (prograde)  most planets rotate prograde (except Venus and Uranus)  outer solar system:  Jupiter, Saturn, Neptune, Uranus  Terrestrial planets: o small, rocky, thin or no atmosphere, few moons o M, V, E, Mars  Jovian- Jupiter-like o Large, liquid + gas, small rocky core, many moons o ‘Gas giants’ is not correct term o J, S, U, N o all have rings  Mercury:  No atmosphere, highly cratered  rocky exterior with a huge iron core  temperatures fluctuate between -170 C and 425 C (lead melts at 327 C)  no moons  has magnetic field, don’t know why  currently being explored by MESSENGER probe  craters have terraces and uplifts  Venus:  Thick CO a2mosphere, lots of possibly active volcanoes  about the same size as Earth  runaway greenhouse effect makes it even hotter than Mercury: 460 C everywhere all the time (lead melts at 327 C)  really hot due to its atmosphere  rains acid  no moons  rotates very slowly and backwards  takes 243 Earth days to rotate once on its axis, does so clockwise  probes now  Earth:  Wet planet  unusually big moon o our moon vs planet size ratio is the greatest compared to any other planet moon relationship o only planet  Mars:  Very thin CO a2mosphere  less gravity than Earth  many huge, extinct volcanoes  was probably Earth-like in distant past (wet, warmish)  many surface features to be carved by water  lots of sub-surface water  no life known to date  both Mars and Venus both have atmospheres made up of completely CO2 and but Venus’ concentration of CO2 is much more thick  has some of the largest volcanoes in the solar system o Olympus Mods (big as France or Arizona)  Lots of canyons, and many believed to be formed by water o Its is said that the deeper you go into a canyon, the more atmosphere you would find  Great range in elevation o One point, ranges from -9 km to +21 km in elevation  Asteroid Belt  Between Mars and Jupiter’s’ orbits  many thousands or millions of rubble piles  asteroids are metal and rock  material left over from formation of solar system prevented from turning into a planet by tides from Jupiter o Eros  Jupiter  Largest planet in the solar system  Juno sent out to Jupiter  Io is the most volcanically active body in the solar system, thanks to tides from Jupiter  Saturn:  Cassini studies Saturn, especially its rings  Saturn’s rings are incredibly thin, and made up of many tiny particles of ice (small, size of tip of finger)  Uranus and Neptune:  Both more appropriate to be called ‘ice giants’  Uranus is tipped over! , its pole is tipped toward the Sun  Uranus would have very extreme seasonal changes as a result Main Difference between Terrestrial and Jovian Planets:  Terrestrial- mainly rock and metal, but also has some gas and liquid  Jovian- mainly gas, but also somewhat rock, ice, and liquid  Trans-Neptunian Objects  Beyond Neptune, there are many dwarf planets  Small, like Pluto  Eris, Makemake, Haumea, Sedna, Orcus, Quaoar, Varuna  Kuiper Belt: ring of comets orbiting just beyond Neptune o Consists of debris left over from the formation of the solar system, and this creates many comets o Comets are ice-rich o New Horiz
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