Sun and Planets. Sun and planets formed around 4.55 billion years ago Planets are by-products of star formation. Images: NASA

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1 Sun and Planets Sun and planets formed around 4.55 billion years ago Planets are by-products of star formation Lots of them initially Mercury, Mars may be a single formation Venus and Earth are numerous collisions One of those collisions (with Theia) formed the Moon Images: NASA

2 The Terrestrial Planets Mercury About the size of the Moon (~4800 km diameter compared to ~3500 km diameter) Craters like the Moon, but... Dipolar magnetic field suggests iron core Iron core that is actually about the size of the Moon (which the Moon does not have)

3 The Terrestrial Planets Mercury Known to exist since at least 3000 BCE In the epic of Gilgamesh Does not have a significant tilt, therefore poles are not exposed to sun...hence cold (and ice?) Density like the Earth Mariner 10 in 1974 Messenger just arrived March,

4 The Terrestrial Planets Messenger (Mercury Surface Space Environment, Geochemistry, and Ranging) at Mercury Messenger is at Mercury now! New images everyday, check it out! From APL

5 The Terrestrial Planets Venus ~12000 km diameter (similar to Earth) Hotter than Mercury because of greenhouse effect (mean surface temperature 480 C) Retrograde rotation Atmosphere Carbon Dioxide 96% Nitrogen ~3% Venera (16 official missions, many more duds) missions from the USSR most important Pioneer and Magellan from the US added some additional knowledge

6 The Terrestrial Planets Venus ESA's Venus Express at Venus now gather new data Water boiled away Earth's future? ESA and Russia contributed to this experiment Venus Express is a twin of the Mars Express ASPERA (Analyser of Space Plasma and Energetic Atoms) MAG (Venus Express Magnetometer) PFS (Planetary Fourier Spectrometer) SPICAV/SOIR (Ultraviolet and Infrared Atmospheric Spectrometer) VeRa (Venus Radio Science Experiment) VIRTIS (Visible and Infrared Thermal Imaging Spectrometer) VMC (Venus Monitoring Camera)

7 The Terrestrial Planets Earth Largest terrestrial planet About the size of Venus Larger than Mars Mean surface temperature ~15 C Atmosphere Nitrogen ~78% Oxygen ~21% Argon ~1%

8 The Terrestrial Planets Earth The Moon is fifth largest moon behind Ganymede (Jupiter), Callisto (Jupiter), Titan (Saturn), and Io (Jupiter) The Moon (r~1735 km) is larger then Pluto (r~1195 km) Image from

9 The Terrestrial Planets Mars ~-140 C to 20 C with a mean surface temperature of -63 C Has polar caps South (Carbon Dioxide) North (Water) Moons: Phobos and Deimos Atmosphere (thin) Carbon Dioxide 95% Nitrogen ~3% Argon ~2% Oxygen ~0.1%

10 The Terrestrial Planets Mars is on google!

11 The Asteroids The Minor Planets Main belt between Mars and Jupiter Destroyed or failed planet? Some asteroids have moons Planets downgraded Ceres Has atmosphere? Dwarf planet (so planet again) Vesta Had volcanic activity Piece of it fell to Earth Protoplanet? Pallas, Juno, Eros, Kleopatra Present Mission: Dawn

12 Vesta: Asteroids Large asteroids Vesta 525 km diameter Minor planet 4 Vesta

13 Ceres: Dwarf Planet Ceres 932 km diameter Thin atmosphere Water vapor recently detected in atmosphere Originally classified as an asteroid, then a planet, than an asteroid, now a dwarf planet Dwarf planet in the asteroid belt

14 The Asteroids Types C-Type Carbon 75% of asteroids S-type (Stony or Silicate type) Nickel-iron Some iron and magnesium silicates 17% of asteroids Many sub-types under this type M-type (Metallic type) Nickel-iron

15 The Jovian Planets (Gas) Jupiter Diameter: km Atmosphere (similar to Sun) Hydrogen 90% Helium 10% Mean cloud temperature -121 C 67 known moons (53 confirmed and named, 14 pending confirmation) Very thin rings Differential rotation Galilean satellites are the largest moons of Jupiter: Io, Europa, Ganymede, and Callisto The observatory satellite Juno reached Jupiter in July 2016

16 Jupiter's Moons Ganymede (largest moon) Diameter: 5262 km Small atmosphere Europa Brightest object Smooth surface Crust over water, very active 670,900 km from Jupiter (compared to 150,000,000 km for the Earth from the Sun) Heated by gravitational stresses (tidal forces) and radioactive decay May harbor life!

17 Jupiter's Rings Very thin rings (3 main rings) Gossamer Halo Thebe within ring system, but Europa is not

18 Jupiter's Spot Great Red Spot In this infrared picture you can see the spot in the lower right hand corner An asteroid (that hit Jupiter on July 16, 2009) breaking up can be see in each picture in the lower left First picture is from July 20,2009 Second picture is from August 16, 2009 IMAGE: NASA's Infrared Telescope in Mauna Kea, HI

19 Jupiter's Aurora The Sun extends out to all the planets and interacts with them like it does the earth Jupiter Aurora

20 Saturn Diameter: ~ km Atmosphere (similar to Sun) Hydrogen 97% Helium 3% Mean cloud temperature -125 C 62 known moons (53 confirmed, 9 pending confirmation) No rings Differential rotation Tilt ~27

21 Saturn's Rings Ring Divisions (9 MAJOR rings) Ring A, B Brightest Separated by Cassini Division (Gap) Ring C - dimmer Other rings: D to G Outer Halo Made up of ice and rock (Wall-E is essentially correct)

22 Saturn s Rings and Major Moons

23 Saturn's Ring A Ring A has a resonance pattern that might be explained by density wave theory (used for spiral galaxy theory as well)

24 Saturn's Aurora Aurora has hexagon feature Deep into cloud layer Unusually strong polar circulation Still somewhat of a mystery Red here represents 5 um wavelength (IR) First discovered by Voyager (1980s) but not very good images Many images from Cassini (as in here)

25 Saturn's Moons Titan Diameter: 2576 km Interesting similarity to Earth Water exists in three phases on Earth Methane exists in three phases on Titan which produces similar effects that water does on Earth

26 Uranus Diameter: ~51000 km Atmosphere (similar to Sun) Hydrogen 83% Helium 15% Methane 2% Mean cloud temperature -193 C 27 known moons (named after Shakespeare characters and Pope characters) Tilt 98 Rings (13 in all now) Retrograde rotation

27 Neptune Diameter: ~49500 km Atmosphere (similar to Uranus) Hydrogen 85% Helium 13% Methane 2% Mean cloud temperature -193 C 13 known moons (six discovered by Voyager) Tilt 30 Rings: 9 rings, very faint Image: HST, NASA

28 Neptune s Largest Moon: Triton Discovered in 1846 by William Lassel Financed his telescopy hobby with the money he made from his brewry Discovered 17 days after Neptune was discovered Triton (as are all of Neptune s moons) is named after minor Greek sea gods and nymphs (since Neptune is the god of the sea...duh!) Triton has retrograde motion compared to Neptune; they only moon that exhibits this behavior Triton s fate is eventually to be pulled apart by Neptune and become a ring (maybe)...but don t worry it will happen a long time from now Image: NASA

29 Neptune Why is Neptune blue? The clouds of Neptune are mostly frozen Methane which absorb red light and reflect blue light Same reason Uranus is mostly blue (the bluegreen clouds are an added ammonia and water clouds)

30 Neptune s Rings Rings 9 rings, very faint Outermost ring is named Adams with three bright arcs (see image Liberty, Equality, and Fraternity) Voyager observed first, though there was speculation before especially given the discovery of rings around Uranus

31 Pluto (Not planet, tis a dwarf planet or Plutoid) Diameter: ~2300 km Frozen solid (rock mixed with ices?) Icy surface ~98% Nitrogen Atmosphere Methane 0.3% 5 known moons Charon (1978), Hydra and Nix (2005), Kerberos (HST 2011), and Styx (HST 2012) Possible rings Pluto Express (canceled) New Horizons Launched 2006!!! with a 2015 arrival date

32 Pluto (Not planet, not dwarf, but Plutoid) Orbit actually goes inside orbit of Neptune periodically Tilted on it side like Uranus Retrograde rotation like Venus and Uranus Charon is not the same surface composition of Pluto (unlike our Moon and our Earth)

33 Pluto, not that big

34 Eris (Xena, Lila) Eris (2003 UB313) Originally named Xena as in Xena: Warrior Princess (Note: Eris was a recurring character on the show in the Latin name of Discordia) Plutoid Diameter: 3000 km +/- 400 km Moon: Dysnomia (Eris' daughter demon goddess mean lawlessness, original name was Gabrielle, of course) This object caused the reclassification; however recent observation suggest it is smaller than Pluto

35 Haumea (Santa) Haumea (2003 EL61) Haumea is the Hawaiian goddess of fertility Plutoid (pending) About the size of Pluto Moons: Hi'aka and Namaka Artist conception of Haumea on right; kinda of an odd shape isn't it

36 MakeMake (Easterbunny) MakeMake is an Easter Island Fertility God Where will it end?

37 Sedna Sedna (2003 VB 12) Plutoid??? Not yet Diameter: km

38 Dwarf planets/plutoids Dwarf planets are inside Neptune's orbit and Plutoids are outside of Neptune's orbit Dwarf Planet: Ceres Plutoids: Pluto, Eris, Makemake (pending), Haumea (pending)

39 Numbers game (from NASA) Numbers from 2017 Planets: 8 Dwarf planets: 5 (with many pending) One Dwarf Planet Four Plutoids Moons: 178 Asteroids: 732,315 Comets: 3,463 (estimate: 1 billion) To learn more about the planets go to