Solar System Review Nebular Theory Eagle Nebula Solar

Solar System Review

Nebular Theory Eagle Nebula • Solar System formed through the collapse of a large cloud of gas under its own gravity Lagoon Nebula

Gravitational Collapse • Start out with a large cloud of gas – A few light years in size with a very low density – Very cold temperatures • Something triggers the collapse – Supernova explosion • Cloud can no longer support itself against its own gravity. Continues to collapse

More Gravitational Collapse

From Cloud to Solar System • Energy Conservation – Heats the cloud • Ang. Momentum – Causes the cloud to spin faster • Cloud Flattens – Mergers between particles average out the velocities

How do planets form? • Through accretion –Small particles are able to build larger complexes of particles –Eventually the complex becomes large enough to “attract” pieces through gravitation – planetesimals –Only the largest planetesimals survive to become planets

Planet Formation • Terrestrial planets (Mercury, Venus, Earth, and Mars) all formed beyond a distance of 0. 3 AU – Rock could not condense within this distance • Jovian planets (Jupiter, Saturn, Uranus, and Neptune) all formed beyond the frost line (3. 5 AU) – Hydrogen compounds formed the cores of these planets

Jovian Planets • Gravity of icy planetesimals was large enough to capture hydrogen and helium gas • Continued to grow larger as mass increased • Large masses also explain the large number of moons

How old is the Solar System? • Oldest Earth rocks found to be 4 billion years old • But this only tells us the time since rock last solidified, after the Heavy Bombardment • Solar System must be older than 4 billion years • Moon rocks give an age of 4. 4 billion years, but they also re-solidified at some point • Need objects that have not vaporized since the solar nebular collapsed – Meteorites! – Found to have an age of 4. 55 billion years

Astronomy • To the study of motion

The Planets of Our Solar System The Inner Planets Sizes to Scale Mercury Venus Earth and Moon Mars

Interior Components • The interiors of all the terrestrial bodies consist of the same components – Core – Highest density (iron, nickel) – Mantle – Rocky material, around core – Crust – Lowest density (granite, basalt) • Material separated when Earth was still molten – Densest material “sank” to the center

Interior Structure

Comparing Interiors Active geology Inactive geology

Changing Appearances • Before the Heavy Bombardment, the inner planets probably looked very similar, aside from size • Today we can see they look very different, but why? – Impacts – Asteroids/Comets striking – Volcanoes – lava flows – Tectonics – Formation of mountains – Erosion – Wears down structures

• Always circular in structure • Produce a large amount of debris that litters the surrounding area • Seen on all terrestrial planets Craters Left: A bowl shaped crater Top: Crater with a central peak; similar to dropping an object in water

Mercury • Heavily cratered appearance • 88 day orbit with a 59 day rotation rate (slow) • Temp ranges between 425°C and – 150°C • No atmosphere – Too close to the Sun – Too small in size

Activity on Mercury • Very little if any – Dead planet • Lava plains, although no where near as large as those found on the moon • Relatively few craters in Caloris Basin suggests volcanism after the Heavy Bombardment • Little or no erosion Caloris Basin

Venus • “Sister Planet” to Earth, but in fact is quite different • Thick cloud cover prevents an optical view of the planet • Use radar mapping by sending radio signals to “see” surface features – Mostly rolling plains – A few mountains

Venus Surface image from the Venera 13 spacecraft

Volcanism on Venus • Very few craters seen on Venus • Due to a combination of plate tectonics and volcanism • Few mountain ranges and deep trenches • Large number of shield volcanoes Sif Mons – Shield Volcano

Erosion on Venus • Nearly non-existent – No evidence of features eroding • Extremely hot temperatures exceeding 430°C – Water/Ice cannot exist • Very slow rotation rate of 243 days – No wind of any sort Ushas Mons

Radar image of the surface of Venus, assembled from Magellan data. Ganiki Chasma and Sapas Mons are shown in the white box -- possibly the sight of active volcanism. NASA/JPL

Our Moon • Only terrestrial planet with a large moon. • Collision with a Mars sized object – Moon has a similar composition to that of Earth’s surface – Smaller proportion of vaporized materials (water)

Our Moon • Very similar in appearance to Mercury • Much larger lava basins • During differentiation, magma rose to the surface, creating magma oceans • Must have a low viscosity due to their large size

History of Mars An actual image of Mars. As you can see, Lowell had quite the imagination Percival Lowell’s drawings showing regions of lush vegetation and canals to transport water

Mars Image of Mars from NASA’s Mars Exploration Rover Spirit

History of Mars • One of the better studied planets. Multiple spacecraft have landed on Mars and taken images and data samples – Vikings Missions (1976) – Mars Pathfinder (1997) – Spirit and Opportunity -Curiosity (2012) (2004)

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• The only other planet Erosion on Mars that shows significant erosion – Wind/Dust Storms – Rotation rate similar to Earth’s (1 day) – Water – Numerous images showing features believed to be created by running water

An artist’s impression of the ancient ocean on Mars, which lasted for billions of years more than was previously thought. Credits: Mars Geronimo Villanueva/Nasa

Impact Craters on Mars • Shows numerous craters – The northern hemisphere contains few craters and filled in with lava plains – The southern hemisphere is at a higher elevation and contains many more craters

Mars and Volcanoes • Mars has the largest volcano in the solar system • Volcanoes on Mars should be dead based on size – Recent analysis finds volcanic rock at an age of only 180 million years! – May become active again, but should die out within the next 1 -2 billion years as the interior continues to cool

Life on Mars? • No Martians! • Continuing to search for past life on Mars • Best bet is to look for microbes • Look ahead to future missions

Asteroids Ida

Ceres

Asteroids • Rocky leftover planetesimals – Pieces that were not picked up by the inner planets • Where are they? – Most are in the Asteroid Belt between Mars and Jupiter – Trojan Asteroids – in Jupiter’s orbit – Near Earth Objects (NEO’s) – those that are close to Earth

The Outer Solar System Neptune Uranus Saturn Jupiter Orbital radii: Jupiter 5. 2 A. U. Saturn 9. 5 A. U. Uranus 19 A. U. Neptune 30 A. U.

The Planets of Our Solar System The Outer Planets Jupiter Saturn Earth Included for Scale. Uranus Pluto Neptune

Jupiter • 11 times Earth’s diameter (1/10 sun’s) • 300 times Earth’s mass (1/1000 sun’s mass) • Visible surface is gas (mostly hydrogen); interior must be mostly liquid, with solid core • Fascinating banded patterns, hurricanes, great red spot

24 Jupiter rotations from Oct. 31 st to November 9 th, 2000.

Moons of Jupiter (Galilean) • Io: volcanically active, covered with sulfur • Europa: Covered with ice, with liquid ocean underneath • Ganymede: Bigger than Mercury, icy and cratered • Callisto: Also big, icy, cratered • Many smaller moons (chunks of rock)

Io: Heated by tidal friction

Europa: Water beneath ice Water is probably kept warm by tidal friction. Could this be a place to look for life?

Moons of Jupiter

Saturn • Prettiest planet in small telescopes • 9 times Earth’s diameter • 100 times Earth’s mass (1/3 Jupiter) • Gaseous surface, liquid interior, solid core (like Jupiter) • Rings! • Many moons

Saturn’s rings Rings are mostly ice particles, from tiny grains to boulder-sized chunks. Gaps are created by tug of nearby moons.

Cassini Mission

Titan (Saturn’s largest moon) Opaque atmosphere of nitrogen, methane, smog. Surface (cold!) could have liquid methane, other hydrocarbons.

Saturn’s other moons…

Uranus • At the threshold of naked -eye visibility • Less than half the size of Saturn, and nearly twice as far • Another gas giant planet with rings (faint), many moons • Spin axis is tipped sideways

Uranus • Discovered by William Herschel, 1781 • At the threshold of naked-eye visibility • Less than half the size of Saturn, and nearly twice as far • Another gas giant planet with rings (faint), many moons • Spin axis is tipped sideways

Moons of Uranus All are icy, smaller than our own moon.

Neptune • Discovered by mathematics (anomaly in orbit of Uranus) in 1845 -46. • Can be seen in binoculars (looks like a faint star) • About the same size as Uranus, but 60% farther away • Voyager 2 discovered a cool blue spot, which has since disappeared • Largest moon, Triton

Pluto • At 2300 km, Pluto is a dwarf planet • Has most elliptical orbit: ranges from 4. 4 to 7. 4 billion km from Sun (2. 8 -4. 5 billion miles) • Actually crosses orbit of Neptune • Orbits in 248 years, 1. 5 times Neptune

Properties of Pluto • Discovered in 1930 by Clyde Tombaugh Hubble ST image of Pluto & Charon

Pluto and Charon • Pluto’s large moon Charon is almost half as big as Pluto (1100 km) • Orbits only 20, 000 km away • Pluto and Charon always keep same face to each other (rotation locked) • Pluto rotates, and Charon revolves, in 6. 4 days • Pluto has 4 additional moons

More on Pluto’s • Moon Charon has about 1/8 the mass of Pluto – Compared to our moon which has 1/80 th the mass of Earth • Charon also orbits at a small distance of only 20, 000 km – Our moon orbits at 400, 000 km

• A very thin Pluto’s Atmosphere atmosphere of nitrogen gasses • Atmosphere thins as Pluto approaches aphelion – Gas refreezes onto the surface • Atmosphere will rethicken when Pluto makes its way back to the Sun

Pluto Mission • Close-up images would improve upon our current knowledge of Pluto’s surface features • Mission to Pluto (New Horizons) to reach Pluto/Charon in 2015

Pictures reveal diverse new features: • Possible dunes • Nitrogen ice flows that apparently oozed out of mountainous regions onto plains • A networks of valleys that may have been carved by material flowing over Pluto’s surface. • Large regions that display chaotically jumbled mountains reminiscent of disrupted terrains on Jupiter’s icy moon Europa.

The planets, to scale

Kuiper Belt Objects • http: //www. msn. com/en-us/video/wonder/billions-of-milesaway-from-earth-new-horizons-spots-a-wandering-object/vi. AAg 34 Dl? ocid=se • Scientists Discover Pluto's 'Little Sister' Makemake Has Its Own Moon

• Icy leftovers • Two locations – Kuiper Belt – Oort Cloud Comets

• Its existence was predicted with mathematical modeling and computer simulations, and was said to exactly explain the strange clumping behavior of a group of dwarf planets in the Kuiper Belt, a field of icy objects and debris beyond Neptune. • http: //www. msn. com/en-us/video/wonder/planet-9 -just-got-weirder/vi -BBs. Gb. ES

Other Solar Systems? • Detected 3, 264 planets (5 -10 -2016) • Difficult to detect directly – Even for the largest planets, light from the star overwhelms any light from the planet • Use indirect evidence to search for planets – Gravitational tugs – Transits

• Trio of Earth-like planets found near ultracool star may have the right conditions for life

• http: //www. msn. co m/enus/news/world/trioof-earth-likeplanets-found-near -ultra-cool-star-may -have-the-rightconditions-forlife/ar. BBsw. IIE? li=BBnbfc

A Closer Look at Our Solar System http: //www. astro. umn. edu/courses/1001/prevsem/summer 104/lecnotes/256, 1, Astronomy 1001 http: //departments. weber. edu/physics/schroeder/astro/lectureslides/352, 9, The Outer Solar System http: //www. uwgb. edu/dutchs/Cosmos. Power. Point/277, 18, Pluto http: //www. astro. umn. edu/courses/1001/prevsem/summer 204/lecnotes/256, 1, Pluto and Earth