This Just Out.Key

This just out….. Enceladus • With ice volcanoes!

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This just out…. (Sept 30) This just out (Oct 3):

• Organic molecules (Building blocks for amino acids) found in vents on Enceladus

NASA PW Peter Watson

Note most of them are This just out (Oct 7): retrograde (i.e. orbit backwards • 2019 Nobel Prize in Physics • and you can name them! • now 82 altogether • probably originally part of one large moon • Saturn now has more moons than Jupiter! (79!) PW PW The solar system looks so Cosmogony: Origins of the simple Solar System • So where did the solar system come from....?

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What we Thought we Knew (~1960) Nebular Hypothesis.

• Age ~4.5 billion years • A rotating gas cloud, probably compressed • All planets orbit in almost the same plane. by a nearby supernova shock wave, starts to Orbit shapes are nearly circular • collapse. Most of mass the of solar system is in the sun. • • The central part • Inner planets are small and rocky (terrestrial) collapses to the sun. • outer planets are large cold gas giants (jovian) • moons are rocky and bare

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•The outer planets condense ﬁrst. •Solar winds removes hydrogen and helium •Gas and dust particles out of the plane collide more from the inner planets. often and get forced into plane •Terrestrial planets form from the left over refractory materials.

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•The orbits are circularized by collisions and tidal effects.

Peter Watson Peter Watson If we are lucky, we can see them directly How many?

• 6 planets known since pre-history • Uranus: 1781 e.g β-Pictoris • Neptune: 1846 • 51 Pegasus

≤ •Young star β • Pluto: 1931

•dust clouds

•giant planet Note: even this is an underestimate: Kepler has 2321 candidates, 61 74 conﬁrmed

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Michel Mayor and Didier Queloz Doppler shift

• Universal for all waves, including sound • Wave gets “stretched out” by motion • Can measure how fast something is moving by looking at the light

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Cna measure the shift on Planet 51 Pegasus b lines in the spectrum of a star • Star is sun-like • Can use these spectral lines since they all get shifted by • Planet orbits 8000000 km from star (1/4 the same amount distance of Mercury, 4.2 day orbit (!) • Makes star “wobble” with change in speed of 70 m/s, • about 1/2 mass of Jupiter

ESO/M. Kornmesser/Nick PW Risinger (skysurvey.org) This just out… Cosmic Microwave Background Radiation Jim Peebles • Early universe must have been very simple: no stars • Winnipeg, University of Manitoba or galaxies. • Princeton • However, it was very hot: hot things radiate.... • Universe is "full" of light: fossil light from Big Bang, discovered accidentally by Penzias and Wilson (1964)

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Where does it come from? • Gamow (1948) discussed Hot Big Bang for ﬁrst time, suggested that radiation might be observable. • Peebles (1964) found T ~ 10°K (and everyone had general feeling that it would be unobservable). • Note we are measuring temperature on the absolute scale or Kelvin scale • T (°K) = T (°C) + 273 • 0 °K is lowest possible temp. ~ -273 °C

Peter Watson