Today s Class: Pluto & The Kuiper Belt 1. Reading: Chapter 13, Sections 13.1-13.2 on Extrasolar Planets. 2. Meet next class at Fiske Planetarium for show on Einstein & Interstellar Travel 3. FCQs open Dec. 8-15. On-line at colorado.campuslabs.com/courseeval. If class reaches 80% completion, I will award everyone clicker bonus points! Exam 3 Results Average 83 Median 85 Stand. Dev. 10 Min 52 Max 101 Earth, Moon & Pluto Space in the News: JPSS-1 to Provide More Accurate Environmental Forecasts Presenter: Katherine Lof This illustration depicts the Joint Polar Satellite System-1, or JPSS-1, spacecraft designed to provide forecasters with crucial environmental science data to provide a better understanding of changes in the Earth's weather, oceans and climate. Last Class Overview of Uranus & Neptune. Densities & Interiors of jovian planets. Atmospheres of Ice Giants compared to Gas Giants. The moons of Uranus & Neptune Triton Overview of asteroids Asteroid moons & calculating densities Orbits & Locations of asteroids Origin of the asteroid belt Class Exercise Suppose the asteroid impact from 65 million years ago had not occurred. How do you think the Earth would be different today? Would mammals still dominate the planet? This Class Overview of Pluto & the Kuiper Belt Pluto & dwarf planets The New Horizons Mission to Pluto Science goals Trajectory & closest approach Spacecraft & instruments What have we learned about Pluto? 1
Pluto's Orbit Kuiper Belt Objects Pluto will never hit Neptune, even though their orbits cross, because of their 3:2 orbital resonance. Neptune orbits three times during the time Pluto orbits twice. These large, icy objects have orbits similar to the smaller objects in the Kuiper belt that become short period comets. So are they very large comets or very small planets? Pluto is one of the largest members of the Kuiper Belt. What is Pluto like? Its moon Charon is nearly as large as Pluto itself (probably made by a major impact). Pluto is very cold (40 K). Pluto s density is only 2 gm/cm 3 whereas as Mercury is 5.4 gm/cm 3. Pluto has a thin nitrogen atmosphere Clyde Tombaugh discovered that will refreeze onto the surface as Pluto in 1930 Pluto's orbit takes it farther from the Sun. New Horizons has revealed a surprisingly active geology. Hubble's View of Pluto and its moons Pluto and Eris Pluto's size was overestimated after its discovery in 1930, and nothing of similar size was discovered for several decades. Now other large objects have been discovered in Kuiper belt, including Eris. The International Astronomical Union (IAU) now classifies Pluto and Eris as dwarf planets. Dwarf planets have not cleared most other objects from their orbital paths. Is Pluto a Planet? Much smaller than the terrestrial or Jovian planets Not a gas giant like other outer planets Has an icy composition like a comet Has a very elliptical, inclined orbit Has more in common with comets than with the eight major planets 2
Clicker Question: Which of the following Pluto observations did NOT help convince scientists to change Pluto's status from that of a planet? a) discovery of the Kuiper Belt b) discovery of seasonal atmosphere, similar to comets c) discovery of large Kuiper Belt Objects d) discovery of Pluto's 5 moons Clicker Question: Which of the following Pluto observations did NOT help convince scientists to change Pluto's status from that of a planet? a) discovery of the Kuiper Belt b) discovery of seasonal atmosphere, similar to comets c) discovery of large Kuiper Belt Objects d) discovery of Pluto's 5 moons Other Icy Bodies New Horizons Team (2004) There are many icy objects like Pluto on elliptical, inclined orbits beyond Neptune. The largest of these, Eris, was discovered in summer 2005, and is even larger than Pluto. Before NASA s New Horizons New Horizons PLUTO CHARON 11 KG PLUTONIUM: 200 WATTS 1000 BPS BANDWIDTH HYDRAZINE FUEL: (POST-PLUTO ~30 KG LEFT) 7 SCIENCE INSTRUMENTS 2X8 GB ONBOARD SOLID-STATE STORAGE 3
New Horizons at the Cape After NASA s New Horizons Launch video Closest Approach 2015 July 14 Charon-Earth Occultation 14:17:50 Pluto-Earth Occultation 12:49:50 13:40 Charon Charon-Sun Occultation 14:15:41 12:40 Pluto Sun Earth 0.24 S/C trajectory time ticks: 10 min Charon orbit time ticks: 12 hr Occultation: center time Position and lighting at Pluto C/A Distance relative to body center Pluto-Sun Occultation 12:49:00 Charon C/A 12:12:52 26,937 km Pluto C/A 13.87 km/s 11:59:00 31,000 mile/hr 11,095 km 13.77 km/s 11:40 New Horizons at Charon Pluto's thin atmosphere 4
What have we learned? What is Pluto like? An icy world with mysterious active geology. Why is there a Kuiper belt? Made up of leftovers from planet formation era. Shaped by interactions with jovian planets. 5