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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
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)
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, 2011...
–
The Terrestrial Planets
● Messenger (Mercury Surface Space Environment, Geochemistry, and Ranging) at Mercury
– Messenger is at Mercury now!
– New images everyday, check it out!
– http://www.nasa.gov/mission_pages/messenger/main/index.html
– http://messenger.jhuapl.edu
From APL
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
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)
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%
http://www.geo.umass.edu/courses/climat/radbal.html
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 http://www.astro-observers.com
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%
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
Vesta: Asteroids● Large asteroids Vesta
– 525 km diameter
– Minor planet “4 Vesta”
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
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
The Jovian Planets (Gas)● Jupiter
– Diameter: 142984 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
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!
Jupiter's Rings
● Very thin rings (3 main rings)– Gossamer– Halo– Thebe within ring
system, but Europa is not
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
Jupiter's Aurora
● The Sun extends out to all the planets and interacts with them like it does the earth
● Jupiter Aurora
Saturn● Diameter: ~120000 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 °
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)
Saturn’s Rings and Major Moons
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)
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)
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
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
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
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
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 blue-green clouds are an added ammonia and water clouds)
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
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
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)
Pluto, not that big
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 re-classification; however recent observation suggest it is smaller than Pluto
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
MakeMake (Easterbunny)
● MakeMake is an Easter Island Fertility God
● Where will it end?
Sedna
● Sedna (2003 VB 12)
– Plutoid??? Not yet
– Diameter: 1100-1600km
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)
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
– http://solarsystem.nasa.gov
