Uranus Neptune Discovery Uranus William Herschel in 1781

Uranus & Neptune

Discovery • Uranus – William Herschel in 1781 in the process of creating accurate star maps. • Neptune – In 1845 two mathematicians (John Adams and Urbain Leverrier) analyzed the orbital motions of Uranus and determined that there had to be a 8 th planet. The predictions of Leverrier were used by Johann Galle to find the planet in September 1845.

Interesting Facts: • Uranus: Obliquity is 97° and the rotation period is 17. 3 hours (retrograde!) • Uranus and Neptune: – – Total mass is about 15 earth masses apiece Mostly ices. Both have ring systems Both have lots of satellites all of which are essentially coplanar with the planetary equator. – Both have seasons. – Both have magnetic fields.

Uranus Properties Property Unit Uranus Average Distance from Sun AU 19. 22 Maximum Distance from Sun AU 20. 11 Minimum Distance from Sun AU 18. 33 Orbit Eccentricity 0. 046 Average Orbital Speed Km/s 6. 8 Revolution Period Years 83. 75 Rotation Period: Internal H: M: S 17. 24 Obliquity Degrees 97. 86 Orbit Inclination Degrees 2. 49 Diameter Km 51, 118 Mass Earth 14. 500 Average Density Kg/m^3 1290 Surface Gravity m/s^2 8. 82 Escape Velocity km/s 21. 3 Average T at Cloud top K 55

Uranus Seasons

Seasonal Heating

Changing Appearance of Uranus Voyager II 1986 HST - 1997

Uranus - The New View

Uranus • Became more active as it approached its Autumnal Equinox in 2007. • Has no internal heat source so the observed changes are due to the changing aspect of the planet with respect to the Sun. • Voyager found that the dark side of Uranus was actually warmer than the sunward side!

Sturcture of Uranus

Standard 3 Level Uranus – a rocky (silicate/iron-nickel) core in the center, • • The core is relatively small, with a mass of only 0. 55 Earth masses and a radius less than 20% of Uranus’s Uranus's core density is around 9 g/cm 3, with a pressure in the center of 8 million bars (800 GPa) and a temperature of about 5000 K – an icy mantle in the middle • the mantle comprises its bulk, with around 13. 4 Earth masses. The ice mantle is not in fact composed of ice in the conventional sense, but of a hot and dense fluid consisting of water, ammonia and other volatiles. This fluid, which has a high electrical conductivity, is sometimes called a water–ammonia ocean – an outer gaseous hydrogen/helium envelope • • the upper atmosphere is relatively insubstantial, weighing about 0. 5 Earth masses and extending for the last 20% of Uranus's radius. The composition of the Uranian atmosphere is different from its bulk, consisting mainly of molecular hydrogen and helium. The helium content of the atmosphere is very close to the protosolar helium mass fraction indicating that helium has not settled in its center like it has in the gas giants.

Uranus Atmosphere

Wind Speeds

Magnetic Field

Uranus in 2006 / 2007

Uranus Aurora - HST Images

Neptune Properties Property Unit Neptune Average Distance from Sun AU 30. 11 Maximum Distance from Sun AU 30. 38 Minimum Distance from Sun AU 29. 84 Orbit Eccentricity 0. 009 Average Orbital Speed Km/s 5. 5 Revolution Perid Years 163. 73 Rotation Period H: M: S 16. 11 Obliquity Degrees 29. 56 Orbit Inclination Degrees 1. 77 Diameter Km 49, 528 Mass Earth 17. 204 Average Density Kg/m^3 1640 Surface Gravity m/s^2 10. 8 Escape Velocity km/s 23. 5 Average T at Cloud top K 55

Neptune Appearance

Neptune • During the 1989 Voyager fly-by there was a prominent marking which was called the Great Dark Spot. By 1994 the Great Dark Spot was gone.

Neptune Views

Neptune Rotation

Neptune Interior 1. Upper atmosphere, top clouds. 2. Atmosphere consisting of hydrogen, helium, and methane gas. 3. Mantle consisting of water, ammonia, and methane ices. 4. Core consisting of rock (silicates and nickel-iron).

Magnetic Field Oddities

Tilt Comparison

Atmospheres

Pluto • Discovered in 1930 at Lowell Observatory by Clyde Tombaugh • It is not the planet that was being sought based on calculations of deviations in the orbit of Neptune. It is too small and in the wrong orbit. (The deviations turn out to be random measurement errors in Neptune’s position) • Mass = 0. 0021 Mass of the Earth • Quintet of Moons: Pluto & Charon, Nix, Hydra, Kerberos, Styx • Density = 2. 06 g/cm^3 • Eccentricity = 0. 249 : Inclination = 17. 15 degrees • Is it more related to Kuiper Belt Objects than the planets?

New Horizons PLUTO - NEW HORIZONS - July 14, 2015 ORIGINAL IMAGE DESCRIPTION: Four images from New Horizons’ Long Range Reconnaissance Imager (LORRI) were combined with color data from the Ralph instrument to create this global view of Pluto. (The lower right edge of Pluto in this view currently lacks high-resolution color coverage. ) The images, taken when the spacecraft was 280, 000 miles (450, 000 kilometers) away, show features as small as 1. 4 miles (2. 2 kilometers), twice the resolution of the singleimage view taken on July 13 [2015]. NOTES: The north polar region is at top, with bright Tombaugh Regio to the lower right of center and part of the dark Cthulhu Regio at lower left. Part of the dark Krun Regio is also visible at extreme lower right. The original NASA image has been modified by doubling the linear pixel density and cropping.

Pluto and its Moons Charon, Nix, Hydra, Kerberos, Styx

HST Image of the Pluto System

Orbit of Pluto and Charon are members of Kuiper belt of small, icy objects, caught in orbital resonances with Neptune (“Plutinos”). Neptune and Pluto are in a 3: 2 resonance. The period of Neptune is 165 years and Pluto is 248 years. Even though the orbits “cross”, Pluto and Neptune never get close to one another. http: //www. compadre. org/osp/items/detail. cfm? ID=9757

Origin of Pluto Like other members of the Kuiper belt, Pluto is thought to be a residual planetesimal; a component of the original protoplanetary disc around the Sun that failed to fully coalesce into a full-fledged planet. Most astronomers agree that Pluto owes its current position to a sudden migration undergone by Neptune early in the Solar System's formation. As Neptune migrated outward, it approached the objects in the proto-Kuiper belt, setting one in orbit around itself (Triton), locking others into resonances, and knocking others into chaotic orbits. The objects in the scattered disc, a dynamically unstable region overlapping the Kuiper belt, are thought to have been placed in their current positions by interactions with Neptune's migrating resonances. [Wikipedia]

Origin of Pluto Collision between Pluto and Charon may have caused the peculiar orbital patterns and large inclination of Pluto’s rotation axis Because of its different origin from the planets, Pluto is no longer considered a planet, but is the prototype of a new class of “Dwarf Planets”.

New Horizon Images Spherical mosaic of New Horizons images showing the expanse of Sputnik Planum (released September 10, 2015

New Horizon Images View of the Norgay Montes (left-foreground), Hillary Montes (left-skyline), and Sputnik Planum (right). Near-sunset view includes several layers of atmospheric haze.

Flyovers Flyover 1 Flyover 2

KBO/TNOs

Extreme Trans-Neptunian objects with perihelion greater than 30 AU and a semi-major axis greater than 250 AU[50] Orbit Object Orbital period (years) Semim aj. (AU) Peri. (AU) Aphel. (AU) Orbital plane Current Long. inclinatio distance Arg. peri asc Eccen. n from Sun ω (°) ☊ or Ω i (°) (AU) (°) Body Long. peri Current ϖ=ω+Ω mag. (°) Diam. (km) 2007 TG 422 11, 200 501 36 967 37 0. 93 285. 8 18. 6 113. 0 38. 8 21. 9 200 2012 VP 113 4, 300 263 80 450 83 0. 70 292. 9 24. 0 90. 8 23. 7 23. 4 600 90377 Sedna 11, 400 506 76 936 86 0. 86 311. 5 11. 9 144. 5 96. 0 21. 0 1, 000 2013 RF 98 5, 600 317 36 600 36. 5 0. 88 316. 5 29. 6 67. 6 24. 1 24. 4 80 2004 VN 112 5, 850 327 47 607 48 0. 85 327. 2 25. 6 66. 0 33. 2 23. 3 200 2010 GB 174 6, 600 351 48 650 71 0. 87 347. 7 21. 5 130. 6 118. 3 25. 2 200 ~1, 000? ~0. 6 ~150 ~30 ~102? ~252? Hypothe sized Planet Nine ~15, 000 ~700 Wikipedia quoting IAU Minor Planet Center >22 ~40, 000

Sedna Orbit HST Image of Sedna The orbit of Sedna (red) set against the orbits of outer Solar System objects (Pluto's orbit is purple). Szczureq/kheider/NASA | Wikipedia

The Outer Solar System

Planet 9 https: //www. youtube. com/watch? v=6 po. HQ 2 h 00 ZA&feature=youtu. be

Planet 9 Not Plan 9 From Outer Space

Last Frame