1. Solar System Lecture

2. Standards Understand the scale and contents of the universe Understand the scale and contents of the universe Understand how advances in technology enable further advances in science (e.g., telescopes and understanding of the universe) Understand how advances in technology enable further advances in science (e.g., telescopes and understanding of the universe)

3. History Greeks & other ancient astronomers were aware of: The moon The moon Stars Stars Comets Comets Meteors Meteors And 5 planets: Mercury, Venus, Mars, Jupiter & Saturn And 5 planets: Mercury, Venus, Mars, Jupiter & Saturn

4. History Knowledge of the contents of the solar system remained unchanged until the early 17 th century when Galileo started using his telescope. Knowledge of the contents of the solar system remained unchanged until the early 17 th century when Galileo started using his telescope.

5. Technological advances have allowed astronomers to begin discovering objects invisible to the unaided eye: Rings of Saturn (1659) Rings of Saturn (1659) Uranus (1758) Uranus (1758) Pluto (1930) Pluto (1930) Moons Moons Asteroids (largest = Ceres [1801] (now considered a dwarf planet) Asteroids (largest = Ceres [1801] (now considered a dwarf planet) 2 moons of Pluto (2005) (for a total of 3) 2 moons of Pluto (2005) (for a total of 3) (4 th found in July, 2011 & 5 th found in July 2012) ~50 dwarf planets, including: ~50 dwarf planets, including: Quaoar (2002) Quaoar (2002) Sedna (2004) Sedna (2004) Eris (“10 th Planet”) (2005) Eris (“10 th Planet”) (2005)

6. Objects in our Solar System Our solar system contains:

7. 1 star (our sun)

8. 8 Planets

9. Objects in Solar System Several dwarf planets found in the last few years and several smaller Kuiper belt objects Several dwarf planets found in the last few years and several smaller Kuiper belt objects Kuiper belt = region beyond Neptune Kuiper belt = region beyond Neptune Eris - dwarf planet formerly known as the “10 th planet” or 2003UB313, larger than Pluto (30% wider and 27% more massive). Eris - dwarf planet formerly known as the “10 th planet” or 2003UB313, larger than Pluto (30% wider and 27% more massive).

10. Objects in Solar System Moons 176 moons so far (July 2013) 176 moons so far (July 2013) (including the moons of dwarf planets) This is up from 169 in 2008, 156 in 2005, 143 in 2004, 137 in 2003 This is up from 169 in 2008, 156 in 2005, 143 in 2004, 137 in 2003

11. Objects in Solar System 6 asteroids larger than 300 km in diameter 6 asteroids larger than 300 km in diameter 26 larger than 200 km in diameter 26 larger than 200 km in diameter Tens of thousands of smaller asteroids Tens of thousands of smaller asteroids Gaspra

12. Vesta. Photo by the Dawn Spacecraft

13. Objects in Solar System Myriad comets a few km in diameter Myriad comets a few km in diameter Nucleus of Comet Wild Comet Hale-Bopp

14. Comet 67P/Churyumov-Gerasimenko by Rosetta’s OSIRIS narrow-angle camera on 3 August, 2014 from a distance of 285 km.

15. Objects in Solar System Countless meteoroids less than 100 m across Countless meteoroids less than 100 m across Leonids Meteor Shower

16. Objects in Solar System Dust Dust Photo: 10 micron piece of dust from our solar system collected by high-flying, U2-type aircraft NASA: http://www.astronet.ru/db/xware/msg/1170762

17. Layout of Solar System All solar system objects lay very close to the sun relatively speaking All solar system objects lay very close to the sun relatively speaking Distance from sun to Pluto is 40 a.u., ~15,000 times the distance from Earth to the moon. Yet the diameter of Pluto’s orbit is less than 1/1000 of a light year (remember the next nearest star is 4.3 light years away) Distance from sun to Pluto is 40 a.u., ~15,000 times the distance from Earth to the moon. Yet the diameter of Pluto’s orbit is less than 1/1000 of a light year (remember the next nearest star is 4.3 light years away) Distance to Eris is 97 a.u. and to Sedna is 486 a.u. Distance to Eris is 97 a.u. and to Sedna is 486 a.u.

18. Layout of Solar System Except for Mercury, the planets’ orbits are nearly circular (i.e., low eccentricities). Except for Mercury, the planets’ orbits are nearly circular (i.e., low eccentricities). Pluto, and the other dwarf planets, have very eccentric orbits Pluto, and the other dwarf planets, have very eccentric orbits

19. Layout of Solar System All planets orbit the sun counterclockwise as seen from above Earth’s N pole, and in nearly the same plane as the Earth – the ecliptic plane (Mercury & the dwarf planets deviate slightly) All planets orbit the sun counterclockwise as seen from above Earth’s N pole, and in nearly the same plane as the Earth – the ecliptic plane (Mercury & the dwarf planets deviate slightly)

20. Layout of Solar System We can think of the solar system as being flat. It’s “thickness” perpendicular to the plane of the ecliptic is less than 1/50 the diameter of Pluto’s orbit. We can think of the solar system as being flat. It’s “thickness” perpendicular to the plane of the ecliptic is less than 1/50 the diameter of Pluto’s orbit.

21. Layout of Solar System The orbits of the planets are not evenly spaced. The planets get farther and farther apart the farther they are from the sun, but there is a regularity to their spacing. The orbits of the planets are not evenly spaced. The planets get farther and farther apart the farther they are from the sun, but there is a regularity to their spacing.

22. Terrestrial and Jovian Planets Comparative planetology – compares and contrasts the properties of the planets and moons. Comparative planetology – compares and contrasts the properties of the planets and moons. 1. Helps us understand how planets form and evolve. 2. Gives us knowledge about the nature of other planetary systems.

23. Inner Planets All within 5 a.u. of sun All within 5 a.u. of sun Mercury, Venus, Earth and Mars Mercury, Venus, Earth and Mars Small, dense and rocky in composition Small, dense and rocky in composition Called terrestrial because similar to Earth Called terrestrial because similar to Earth

24. Inner Planets All of relatively low mass, and all have solid surfaces. All of relatively low mass, and all have solid surfaces. After this, similarities end. After this, similarities end.

25. Inner Planets Uncompressed densities decrease steadily as move farther from the sun, therefore their overall composition differs. Uncompressed densities decrease steadily as move farther from the sun, therefore their overall composition differs. All have atmospheres, But dissimilar: All have atmospheres, But dissimilar: Near vacuum on Mercury Near vacuum on Mercury Hot, dense inferno on Venus Hot, dense inferno on Venus Earth alone has oxygen (as well as liquid water) Earth alone has oxygen (as well as liquid water)

26. Inner Planets Rotations Rotations Earth and Mars similar: one rotation every 24 (Earth) hours. Earth and Mars similar: one rotation every 24 (Earth) hours. Mercury and Venus: months to rotate once, Venus rotates in opposite direction. Mercury and Venus: months to rotate once, Venus rotates in opposite direction.

27. Inner Planets Moons on Earth and Mars, none on Mercury or Venus Moons on Earth and Mars, none on Mercury or Venus Magnetic Fields: Magnetic Fields: Earth and Mercury: measurable, but weak Earth and Mercury: measurable, but weak Venus and Mars: none Venus and Mars: none

28. Inner Planets Surface conditions distinct: barren, heavily cratered on Mercury to widespread volcanic activity on Venus to craters, canyons and volcanoes on Mars. Surface conditions distinct: barren, heavily cratered on Mercury to widespread volcanic activity on Venus to craters, canyons and volcanoes on Mars.

29. Mercury Mariner 10 1974 Only part of Mercury Photographed until 2008

30. Mercury Messenger January 2008

31. Venus

32. Earth

33. Mars

34. Outer Planets Jupiter, Saturn, Uranus and Neptune Jupiter, Saturn, Uranus and Neptune Large, low density and gaseous. Large, low density and gaseous. Similar to one another chemically and physically. Similar to one another chemically and physically. Called Jovian after Jupiter. Called Jovian after Jupiter.

35. Outer Planets Are everything the terrestrial planets are not. Are everything the terrestrial planets are not. Widely spaced through outer solar system. Widely spaced through outer solar system. Predominantly hydrogen & helium, the lightest elements (rare on terrestrial planets). Predominantly hydrogen & helium, the lightest elements (rare on terrestrial planets). No solid surface: dense atmospheres thicken with depth, and merge with liquid interiors. No solid surface: dense atmospheres thicken with depth, and merge with liquid interiors.

36. Outer Planets All have strong magnetic fields. All have strong magnetic fields. Many moons each, no two alike. Many moons each, no two alike. All have rings. All have rings. All rotate much faster than terrestrial planets. All rotate much faster than terrestrial planets.

37. Jupiter

38. Saturn

39. Uranus

40. Neptune

41. Dwarf Planets: Pluto In mass and composition, more in common with icy jovian moons than terrestrial or jovian planets. In mass and composition, more in common with icy jovian moons than terrestrial or jovian planets.

42. Pluto Hubble Photograph – highest resolution photo before New Horizons flyby

43. Pluto New Horizons July 14, 2015

44. Dwarf Planets: Eris Largest object found since Neptune & Triton were discovered in 1846. Largest object found since Neptune & Triton were discovered in 1846. Discovery redefined solar system (Pluto no longer a planet) Discovery redefined solar system (Pluto no longer a planet) Named after the Greek goddess of discord and strife (aptly so since this is the discovery that brought about the much argued change in the definition of a planet). Named after the Greek goddess of discord and strife (aptly so since this is the discovery that brought about the much argued change in the definition of a planet). One moon – Dysnomia (daughter of Eris) One moon – Dysnomia (daughter of Eris)

45. Dwarf Planets: Eris Located 10 billion miles from sun Located 10 billion miles from sun 97 a.u. from the sun (Pluto is 40 a.u.) 97 a.u. from the sun (Pluto is 40 a.u.) 560 year orbit, very eccentric (97 a.u. at furthest point in orbit and 38 a.u. at closest approach to sun) 560 year orbit, very eccentric (97 a.u. at furthest point in orbit and 38 a.u. at closest approach to sun) Surface of frozen methane Surface of frozen methane Interior likely rock and ice Interior likely rock and ice

46. Eris and Dysnomia

47. Hubble photo of Eris (highest resolution photo available)

48. Interplanetary Debris There are countless chunks of rock and ice in space between planets, in highly eccentric orbits around the sun – interplanetary matter. There are countless chunks of rock and ice in space between planets, in highly eccentric orbits around the sun – interplanetary matter. These have a large range in size. These have a large range in size.

49. Interplanetary Debris 1. Dust: difficult to see in visible wavelengths, can see in IR. Solar system is dirty compared to interstellar or intergalactic space.

50. Interplanetary Debris 2. Asteroids and meteoroids: rocky in composition, similar to outer layers of terrestrial planets. a. Anything larger than 100 m diameter (mass ~10,000 tons) is an asteroid; smaller is a meteoroid. b. Total mass is less than Earth’s moon c. Help us understand early solar system (made of material that has not evolved much since beginning of solar system).

51. Interplanetary Debris 3. Comets: icy (contain some rocky material), 1 – 10 km diameter. a. Similar in composition to some of the icy jovian moons. b. Even more than asteroids & meteoroids, represent truly ancient material. c. Vaporize and emit radiation as they near the sun, so use spectroscopy to determine composition.

52. Spacecraft Exploration of Solar System Have greatly improved images and understanding of the planets. Have greatly improved images and understanding of the planets. All planets have been visited, starting in 1960’s. All planets have been visited, starting in 1960’s. New Horizons mission launched January 19, 2006 to study dwarf planets in Kuiper Belt. New Horizons mission launched January 19, 2006 to study dwarf planets in Kuiper Belt. Flew by Pluto on July 14, 2015, and will fly by Kuiper Belt Objects from 2016 - 2020. Flew by Pluto on July 14, 2015, and will fly by Kuiper Belt Objects from 2016 - 2020.

53. Launch of New Horizons