Jovian Wrapup Uranus and Neptune. Uranus was discovered by accident Neptune was found via predictions from gravitational physics.

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1 1 Jovian Wrapup Uranus and Neptune Uranus was discovered by accident Neptune was found via predictions from gravitational physics. Uranus Neptune

2 2 William Herschel's Discovery of Uranus In 1781 William Herschel noticed a moving object (moving night-to-night) that he supposed was a comet. He reported the comet and people around the world began to observe it. They soon realized that the object was in a circular orbit around the Sun beyond Saturn a new planet!

3 3 Neptune's Discovery By the mid-1800's Uranus had completed an orbit around the Sun since its discovery. Astronomers noted that it was not quite following the path predicted by Newton's physics and gravitation It was likely that a massive unknown planet beyond Uranus was tugging Uranus off of its expected path. Working backwards English mathematician Adams and French mathematician LeVerrier independently calculated the location of the unknown planet. LeVerrier contacted astronomers in Berlin who found Neptune within an hour of the start of the search (only a finger's width away from the predicted position). Adams LeVerrier

4 4 Uranus and Neptune Uranus and Neptune are Jovian worlds dominated by Hydrogen/Helium mantles.

5 5 Uranus and Neptune Jupiter and Saturn have solar composition. Uranus and Neptune are more dominated by ice (and rock).

6 6 Uranus and Neptune Jupiter and Saturn have solar composition. Uranus and Neptune are more dominated by ice (and rock).

7 7 Uranus and Neptune Methane gas absorbs red light but lets blue light pass into the atmosphere, off the particulates, and back to us giving them their blue-green color. Since they are colder than Jupiter and Saturn the high white clouds are made of methane ice crystals.

8 8 Uranus and Neptune

9 9 Uranus and Neptune Uranus and Neptune both have systems of thin rings Infrared views reveal/exaggerate the Uranian rings since the planet is quite dark at these wavelengths. Visible light views hardly show them at all.

10 10 Uranus and Neptune Uranus and Neptune both have systems of thin rings

11 11 Uranus and Neptune Uranus and Neptune both have systems of thin rings Neptune's Rings

12 12 Uranus/Neptune Wrapup Uranus and Neptune both have systems of icy moons

13 13 Uranus/Neptune Wrapup Uranus and Neptune both have systems of icy moons

14 14 Triton Triton is a Pluto-sized world with a youthful icy surface. It holds on to a thin nitrogen atmosphere. It orbits Neptune backwards and is likely a captured cousin of Pluto

15 15 Triton Like Enceladus and the Uranian satellites, Triton is dominated by water/ice and is rich in volatiles like ammonia, nitrogen and methane. This mix enables geological activity at the frigid temperatures of the outer Solar System with only modest interior warmth. Triton is likely to be representative to what we will find when we arrive at Pluto in Frozen lakes on Triton?

16 16 Triton's Atmosphere, Ice Caps and Geysers Triton's south pole is just coming out of a decades-long winter where it is so cold the thin nitrogen atmosphere has frozen solid on the surface. The dark streaks arise from nitrogen/ice geysers that shoot material into the atmosphere. The nitrogen atmosphere freezes out at the poles in winter. Warmed in the summer, the gas bursts out from below the frozen surface layers.

17 17 The dark streaks arise from nitrogen/water/ice geysers that shoot material into the atmosphere.

18 18 Pluto: Major Planet or Minor Nuisance? Pluto/Charon is a double world at the outskirts of the Jovian Planet region of the Solar System

19 19 Pluto: Major Planet or Minor Nuisance? Smaller than the Earth's Moon, it's status as a major planet, secure for 70 years, was recently lost.

20 20 Pluto: Major Planet or Minor Nuisance? From its discovery in 1930 until its demotion in 2006 Pluto was regarded as one of nine major planets in the Solar System. Pluto and its satellite Charon

21 21 Pluto: Major Planet or Minor Nuisance? The formal definition of Pluto as a dwarf planet by the International Astronomical Union in 2006 brought strong reaction from both astronomers and nonscientists.

22 22 Pluto: Major Planet or Minor Nuisance? The formal definition of Pluto as a dwarf planet by the International Astronomical Union in 2006 brought strong reaction from both astronomers and nonscientists.

23 23 If you want to understand the issues surrounding Pluto's planetary status, then you first must understand... Solar System Debris: Comets and Asteroids Primarily found in two zones in the solar system. The Asteroid Belt (rocky, between Jupiter and Mars) The Edgeworth/Kuiper Belt (beyond Neptune) and Oort Cloud (way out there) sources of comets (icy)

24 24 Solar System Debris Why do comets and asteroids exist?... Solar system formation is a messy process.

25 25 Solar System Debris During the accretion of the planets, the planets sweep up and fling out most of the debris but stable/protected zones remain.

26 26 Solar System Debris: Asteroids Jupiter interfered with the formation of a planet between Mars and Jupiter. Some fraction of the debris remains today as the asteroid belt. Jupiter stirred up the planetesimals so that collisions were violent rather than gentle.

27 27 Asteroids Asteroids are small, rocky, cratered and irregularly shaped. They are the collisionally modified remains of leftover planetesimals between the orbits of Mars and Jupiter.

28 28 Asteroids Asteroids are small, rocky, cratered and irregularly shaped. They are the collisionally modified remains of leftover planetesimals between the orbits of Mars and Jupiter.

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30 30 Asteroids Asteroids are small, rocky, cratered and irregularly shaped. They are the collisionally modified remains of leftover planetesimals between the orbits of Mars and Jupiter.

31 31 Asteroids Millions of these objects orbit in the Asteroid belt staying between Mars and Jupiter. Some have orbits that cross the inner planets.

32 32 Asteroids Millions of these objects orbit in the Asteroid belt staying between Mars and Jupiter. Some have orbits that cross the inner planets.

33 33 Asteroids Some asteroids are binary objects.

34 34 Asteroids The original parent bodies that were the predecessors of the asteroids were large enough to differentiate. some asteroids are metallic, consisting of the core fragments of a large parent body. the largest asteroids may be intact parent bodies. The DAWN mission, now in orbit around Ceres targets two of the largest Ceres and Vesta.

35 35 The Dawn Mission The Dawn spacecraft, launched in 2007, arrived at Ceres (2011) and will travel on to Vesta (arriving in 2015).

36 36 The Dawn Mission Ceres and Vesta are thought to represent substantially intact planetesimals from the early Solar System.

37 37 Vesta from Dawn Click on the image for a movie of Vesta's rotation

38 38 Vesta from Dawn

39 39 Asteroids and Meteorites Meteorites that fall to Earth are just small asteroids. They tell the story of the differentiation and fragmentation of the asteroids. Some are entirely metallic, some are stony, some appear to come from unmodified undifferentiated objects.

40 40 Asteroids and Meteorites Meteorites that fall to Earth are just small asteroids. They tell the story of the differentiation and fragmentation of the asteroids. Some are entirely metallic, some are stony, some appear to come from unmodified undifferentiated objects.

41 41 Meteorites If you want to find a meteorite, go to a place on Earth where Earth-rocks are rare. Antartica and the Sahara Desert are good choices.

42 42 Asteroids and Meteorites Meteorites that fall to Earth are just small asteroids. They tell the story of the differentiation and fragmentation of the asteroids. Meteorites are often spectral fingerprint matches to distant asteroids. You can hold a piece of Vesta in your hand with certainty.

43 43 Meteorites There are four major classes of meteorites Stones: rocky meteorites with iron flecks. Stones represent the majority of falls but are found in equal numbers with iron meteorites.

44 44 Meteorites There are four major classes of meteorites Stones tend to be composed of chondrules glassy beads making up most of the mass of the rock. Astronomers still argue about the origin of chondrules how did these glassy beads form during the formation of the Solar System?

45 45 Meteorites There are four major classes of meteorites Irons represent the other significant type of meteorite. Only about 6% of falls are irons, but they represent the majority of finds because they are so recognizable as something completely odd.

46 46 Meteorites There are four major classes of meteorites Irons represent the other significant type of meteorite. When etched with nitric acid a crystalline patter appears in cross sections of iron meteorites. This pattern can only arise from the slow cooling of molten iron (one degree every million years) consistent with formation in the center of a huge differentiated asteroid!

47 47 Meteorites There are four major classes of meteorites Stony-iron meteorites (a.k.a. Pallasites) appear to have come from the core-mantle boundary in a differentiated asteroid. They are quite rare.

48 48 Meteorites There are four major classes of meteorites Carbonaceous chondrites are possibly the most interesting of meteorites of all. They represent about 1% of falls. Carbonaceous chondrites are undifferentiated and largely unprocessed. They must come from small parent objects too small to become hot and melt and differentiate. Some carbonaceous chondrites contain amino acids formed in the Solar Nebula the building blocks of protiens.

49 49 Meteorites Meteorites are important astronomically because they represent material preserved from the time of the origin of the Solar System. Recall that radioactive dating uniformly finds an age of 4.56 billion years for all of these objects.

50 50 Pluto: Major Planet or Minor Nuisance? The formal definition of Pluto as a dwarf planet by the International Astronomical Union in 2006 brought strong reaction from both astronomers and nonscientists.

51 51 The Discovery of the Asteroids (ca. 1800) On January 1, 1801 an object (Ceres), much smaller than the Earth's Moon, was discovered orbiting the Sun between the orbits of Mars and Jupiter. At first it was thought to be the 8th planet (only 7 were known at the time), but... On March 28, 1802 another object (Pallas) was discovered in nearly the same orbit, and another (Juno) in 1804, and yet another (Vesta) in In 1828 textbooks listed 11 planets, however by 1851 twelve(!) more of these objects had been found. Finally, in 1852, astronomers recognized these asteroids as a separate class of object and went back to a Solar System with eight planets (Neptune having been discovered in 1846). The asteroids were tiny compared with the classical planets See

52 52

53 53 The Discovery of Pluto in 1930 Pluto was discovered in 1930 during a deliberate search for a planet beyond Neptune. When it was discovered it was thought to be larger than the planet Mercury. All hailed it as the Ninth Planet in the Solar System. That designation stuck until 1992 when the first of hundreds of similar objects were found orbiting the Sun beyond Neptune.

54 54 Pluto's Stock Plummets By 2000 it was apparent that Pluto was simply the largest object yet discovered in an outer (icy) asteroid belt. Astronomers counted the days until an object larger than Pluto was discovered in this region. It happened with the discovery of 2003UB313 (now Eris) in Astronomers now had to cope with the issue. Was 2003UB313 Planet 10, or was it time to demote Pluto to non-planetary status? In 2006 the vote was official The Solar System has Eight planets. Eris and Dysnomia

55 55 Pluto's Demotion The Solar System now officially contains 8 major planets. Pluto, along with Ceres and Eris are dwarf planets. The body that governs the naming of astronomical objects has officially decided: "A planet is a celestial body that (a) has sufficient mass for its selfgravity to overcome rigid-body forces so that it assumes a hydrostaticequilibrium (nearly round) shape, and (b) is the dominant object in its local population zone, and (c) is in orbit around the Sun."

56 56 Why Pluto Never Had a Chance Bottom line the Solar System has Four well defined zones The rocky terrestrial planets Mercury, Venus, Earth, Mars The asteroid belt The immense gas giant worlds Jupiter, Saturn, Uranus, Neptune. The outer icy asteroid (Kuiper) belt containing Pluto and hundreds of thousands of other objects.

57 But Pluto's Status as an Interesting World has not Changed Pluto has a large moon, Charon, and an atmosphere. Two new smaller moons were discovered in One or maybe even two even smaller ones turned up recently. The New Horizons spacecraft (the fastest thing ever launched by Humans) will arrive in Pluto is getting farther from the Sun at present New Horizons hopes to arrive before the atmosphere freezes out. 57

58 58 Detecting Pluto's Atmosphere How do you tell that a world that is just a dot in a telescope has an atmosphere? Watch it pass in front of a star...

59 59 Spending on Space Guiding principle: All federal investments should maximize societal benefit Direct return The information returned may directly benefit us all Protection against rogue asteroids Perspective on Earth climate Finding resources or a future refuge... unfortunately not. Exploration for exploration's sake... the data themselves are worth the cost. Earth orbit is the ideal platform for Earth monitoring. Products of space exploration (pictures of Titan) are of intrinsic worth equal to expenditure. A definition/expectation of a great civilization.

60 60 Spending on Space Guiding principle: All federal investments should maximize societal benefit Indirect return Economic stimulus on steroids Note that NASA does not launch gold bars into space valued at billions of dollars Funding spent on NASA ( ½ a percent of the federal budget) gets spent here on the ground employing people and developing our high-technology infrastructure. 100 times more than the NASA budget is already spent on social programs. Savaging NASA would make the smallest dent here on Earth. Of the $4 billion spent on the Cassini mission, the salvage value of the spacecraft is maybe $100,000 the rest went into jobs and technology development in the US. Even spectacular NASA failures (e.g. the recent Orbiting Carbon Observatory) are economic successes.

61 We Should Solve Our Problems Here on Earth First This is exactly the outcome of spending on space exploration. Development of new practical technologies (why do you think you have an iphone?) High quality highest-technology jobs here in the U.S. Significant budgetary multiplier Every dollar of NASA spending is estimated to provide several dollars of return to the economy. Inspiration Fostering the next generation of scientists is possibly the most important outcome of NASA spending Astronomy is the most visually compelling and thus instantly inspiring of the sciences. If you want to lift a child out of poverty make him/her want to be a scientist (and provide the opportunities to pursue that goal maybe the hardest part, back to social programs...). 61

62 62 Investing in the Future Today's high-tech society and its resultant wealth-generating power can be tied in many ways to the significant investment made in space exploration in the 1960s. How can we afford not to take as aggressive an approach to science today??? We're not...

63 63 Bottom Line(s) Investment in Space drives technology innovation benefiting all of society. Technology is the ultimate engine of our economy in the present era. World leadership is the outcome. Space Exploration, in many ways is the ultimate economic stimulus. How can we afford NOT to invest in space exploration in the midst of a recession or at any other time???