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Home , 243 Ida, 9969 Braille

Lattimer, AST 248, Lecture 17 – p.1/22 anets, not the s, rotate on their ’s Law, which is a tem. . ll . tilt between the e . , cloud around the Sun tend to be large, un tend to be small, ut 5 to 10 , unless planetary and lunar s.

Facts Concerning the rocks, but may be similar in composition to and sma simple geometric progression. All the planets roughly the SunThis in plane a is plane. roughly the same asPlanetary the rotational are, equator for of the th most part,The circular. planets all revolve in the sameThe direction Sun about and the the Sun. planets, with the exception of Venus and Uranu The planets differ in composition: the planets nearest the S differ in chemical and geologic properties from Planets and most asteroids rotate with similar periods, abo The distances of the planets from the Sun generally obey Bode Planet-satellite systems resemble miniature solar system Cometary orbits, as a group, define a large, almost spherical The Sun contains 99% of the in the Solar System, but the pl axis in the same direction.equator With and the the exception orbital of plane Uranus, of the the Sun and planets isdense small. and metal-rich, whereas thelight planets and farthest hydrogen-rich. from the obvious tidal forces slow them, as in the case of the and Solar System. Sun, contain nearly all the angular momentum of the Solar Sys • • • • • • • • • • • • Law as times Lattimer, AST 248, Lecture 17 – p.2/22 1–2–3 ocus is at th s transits; pernican theory nd Earth; le) explain its orbit ubed; shadow it cast es better estimate of tive distances and 3 om northern locations a 2 π = 4 2 P 1 ) planet m + ⊙ M ( G Copernicus – Earth and planets orbitTycho Sun Brahe – Measured detailed planetary positions Kepler – Analyzed Brahe data and deduced 3 Laws of Motion: – Laws of motion; telescopic observations proved Co Newton – Law of gravity and derivationHalley of – Kepler’s First 3 good laws estimate of size of solar system from Venu Roemer – Measured light speed using ’s moons corrected by Newton: Each planet moves in an ellipse with Sun atA one line focus (Wrong: between Sun f andOrbital a period planet squared sweeps is out proportional equal to areas semi-major in axis equal c center-of-masss) Ptolemy – Proposed Earth to be at center of Universe (Aristot Aristotle – argued the Earth is round because of the circular Aristarchus – Earth revolves around Sun; revolves arou Eratosthenes – Measured shape & size ofHipparchus Earth – Discovers precession of the equinoxes; provid • • • the Moon’s distance; rejects notion that Earth orbited Sun. during lunar eclipses, and that some stars are not visible fr estimated size of the Moonsizes from of lunar Sun eclipse; & measured Moon; rela concluded Sun was much bigger than the Ear showed that Halley’s is periodic and prodded Newton to 100 AD 1546–1604 1571–1630 1473–1542 300 BC 1564–1642 270 BC 250 BC 135 BC 1656–1742 1642–1727 1644–1710

A Brief History of Solar System Discoveries Lattimer, AST 248, Lecture 17 – p.3/22 Hale-Bopp Hally’s nucleus from Giotto Shoemaker-Levy 9 before Jupiter impact and other gases 2 O, CO 2 vaporized from nucleus during close passage to Sun “Dirty snowballs”, a mixture ofejected ices from and solar dust, system when planets formed Mass mostly contained in asnowball) nucleus with (solid km-sized dirty diameter Coma, a cloud of H Hydrogen cloud, a huge but sparse neutralDust H tail, cloud 1–10 million kmoff long, nucleus composed by of escaping dust gases driven when closeIon to tail, Sun 100’s of millionsdriven of off km by long, solar composed wind of plasma, Most reside far outsideare the occasionally orbit perturbed of into Pluto, orbitsthe but that a Sun; take few some them are near in elliptical orbitsAfter and a reappear few hundred passagesis near lost, the leaving Sun, a icy dead material for comet an which can be mistaken • • • • • • • •

Debris in the Solar System Comets Comet Holmes, Halloween, 2007 V. Peris and J. L. Lamadrid

Fragment G HST 7/18/1994

Shoemaker-Levy 9 HST 7/7/1994

Lattimer, AST 248, Lecture 17 – p.4/22 Lattimer, AST 248, Lecture 17 – p.5/22

Comets comets, 30,000 AU–1 lt. yr. 12 10 Records of comets exist at leastBrahe to observed 1140 comet BC of 1577, proved they are extraterrestrial Halley: some comets are periodic (1531, 1607, 1682) Halley’s Comet: 2467 BC (?), 240 BC (China), 1066 (Bayeux Tapestry) Motivated Newton to develop gravity theory Hyperbolic: pass Sun once, depart forever Elliptical: periodic Peri-/Aphelion: closest/farthest solar approach Short-period come from ,icy 35,000 bodies larger than 100 km, 30-100Long-period AU come from Oort comet∼ cloud, Most formed within inner solarpushed system, outwards then by repeated near encounters • • • • • • • • • • • History Orbits Origin ◦ 60 Lattimer, AST 248, Lecture 17 – p.6/22 out 32% of this. imilar orbits. he discoverer or the bserved proportions; bjects, centaurs or ds. They last for about to gravitational Earth and Venus. in the orbits of and itational minima) carbonaceous, 75% silicaceous, 17% metallic, 8%

Asteroids Jupiter (main ). These percentages do not reflect true proportions, but only o Probably they form as aa result billion of years. collisions between asteroi encounters that eject them from solar system. Also called minor planets or planetoids, largely lying with Objects lying outside Neptune are called trans-Neptunian o The first asteroid to be discovered wasTotal asteroid Ceres mass on is Jan about 1, 4% 1801. of the Moon’s mass. CeresCan is be ab roughly classified by spectralC-type type: S-type L-type About a third of asteroids are members of families that have s Asteroids are slowly lost due to collisions with planets and Trojan asteroids collect in Lagrangian points (stable grav Asteroids are given a number in order of their discovery and t Kuiper-Belt objects. The first 4 asteroids have 51% of the total. some are easier to see than others. IAU may name them. ahead of and behind Jupiter in its orbit. Similarly for Mars, • • • • • • • • • Lattimer, AST 248, Lecture 17 – p.7/22 Lattimer, AST 248, Lecture 17 – p.8/22

243 Ida

433 Eros

Lattimer, AST 248, Lecture 17 – p.9/22 Lattimer, AST 248, Lecture 17 – p.10/22 solarviews.com

What is a Kuiper-Belt Object? The Kuiper Belt is a disk- shaped region past the orbit of Neptune extending roughly from 30 to 50 AU fromcontaining the many Sun small icy bodies. It is now considered to be the source of the short-period comets. About 1000 are known, and many (like Pluto) are in a 3:2 orbital resonance with Neptune. Centaur objects, of which 9 are known, orbit between Jupiter and Neptune. Their orbits are unstable, and are probably displaced from the Kuiper Belt. Lattimer, AST 248, Lecture 17 – p.11/22 100 200 165 120 140 ± ± ± ? ? ± ± 1500? 1500 Diameter (km) 2400 2320 1200 1250 1270 < ∼ 1200 1065 890 900

Kuiper Belt Objects Name 2003 UB313 Pluto 2003 EL61 2005 FY9 Sedna 2004 DW Quaoar Ixion 2002 AW197 Varuna solarviews.com Lattimer, AST 248, Lecture 17 – p.12/22 solarviews.com

They Have Moons! AU 0 . 1 Lattimer, AST 248, Lecture 17 – p.13/22 a < , AU 0 . 1 3 AU . 1 a > AU 3 . < q < 1 q < 1 AU AU and 0 . 1 Closest approach to EarthAbsolute less magnitude than less 0.05 than AU 22.0 Assuming is 13%, thisgreater means than diameter 150 m (500There ft) are currently 773 known PHAs • • • • Atens - Earth-crossing, semi-major axis Apollos - Earth-crossing, Amors - Earth-approaching but interiora > to Mars, PHAs - Potentially Hazardous Asteroids

What are Near-Earth Objects? • • • • Comets and asteroids deflectedperihelion into distance orbits with Made of water ice plus embeddedOriginated dust in cold outer solar system Primordial, leftover building blocks of planets Classes of Near-Earth Asteroids: • • • • • Lattimer, AST 248, Lecture 17 – p.14/22 Lattimer, AST 248, Lecture 17 – p.15/22 km within 10 1 > % of NEAs 90 > Lincon Near-Earth Asteroid Research (LINEAR) Near-Earth Asteroid Tracking (NEAT) Spacewatch Lowell Observatory Near-Earth Object Search (LONEOS) Catalina Sky Survey Japanese Spaceguard Association (JSGA) Asiago DLR Asteroid Survey (ADAS)

How Do We Find Near-Earth Objects? • • • • • • • years Early efforts relied onseveral comparison minutes photographs apart taken Vast majority of objects recordedgalaxies, were which stars don’t and move Special stereo viewing microscopes pick outCurrent NEOs efforts use CCD cameras Computer-aided comparisons of digital images NASA’s goal: Find Total population estimated to be about 1000 • • • • • • • Lattimer, AST 248, Lecture 17 – p.16/22 Lattimer, AST 248, Lecture 17 – p.17/22 X-ray spectrometers to infer -rays from cosmic rays, γ α -ray and γ -particles from a spacecraft Curium source chemical/elemental composition of surfae. X-rays come from Sun, α Imager: Camcorder IR and UV spectrometers toand infer gaseous mineralocgical compositions Lidar: Optical equivalent ofshape radar, useful of to target define and aidsX-ray, in navigation Dust mass spectrometer detects high-velocitywhose dust impacts produce ions Magnetometer to infer magnetic fieldPackage of to target measure temperatures/ of plasma clouds created as sun’scometary radiation atmosphere. ionizes Also usedspacecraft to ion monitor engine DS1 drive

Studying Near-Earth Objects in Space • • • • • • • Typical instruments: • Lattimer, AST 248, Lecture 17 – p.18/22 of 243 Mathilde and433 433 Eros Eros, touchdown on Study and excavate a crater on Comet Tempel 1 Flyby of 9969 Braille andTested Comet new Borrelly technology – ionconcentrating drive solar rocket, panel, auto navigationusing system asteroids

Spacecraft Missions • • • • Near-Earth Asteroid Rendezvous (NEAR) 2/17/962/12/01 - Deep Impact 11/1/99 - 7/4/05 (DS1) 10/25/98 - 9/22/01 • • • Lattimer, AST 248, Lecture 17 – p.19/22 Lattimer, AST 248, Lecture 17 – p.20/22 Lattimer, AST 248, Lecture 17 – p.21/22 Flyby of 243 Mathilde and433 433 Eros Eros, touchdown on Study and excavate a crater on Comet Tempel 1 Flyby of 9969 Braille andTested Comet new Borrelly technology – ionconcentrating drive solar rocket, panel, auto navigationusing system asteroids 2 interstellar dust collections, flybyAnnefrank, of encounter 5535 with Comet WildDiscovery 2 of and otherCa, minerals Al containing and Ti, all hi-T condensates, in comet dust

Spacecraft Missions • • • • • • Near-Earth Asteroid Rendezvous (NEAR) 2/17/962/12/01 - Deep Impact 11/1/99 - 7/4/05 Deep Space 1 (DS1) 10/25/98 - 9/22/01 Stardust 2/7/99 - 1/15/06 • • • • Lattimer, AST 248, Lecture 17 – p.22/22 Lattimer, AST 248, Lecture 17 – p.23/22 landing on 25143 Itokawa (diameterplanned = sample 600 return m), to EarthSuffered in fuel summer leak 2007 after successfulprevents second communications to landing, direct rocket’s return Investigate in detail Ceres andOriginally Vesta planned to launch May"stood 2006, down" but for is budgetary now reasons ESA probe to Comet 67utilizing Churyumov-Gerasimenko, 3 Earth and 1To Mars orbit gravity comet assist toward mvrs. its perihelionIncludes for lander 17 named months Philae,containing island obelisk in with River bilingual Nile inscriptions providing Champollion with final cluesdecipher needed hieroglyphs to of Rosetta Stone Flyby 2867 Steins (5/9/08), 21 Lutetia (7/10/2010)

More Spacecraft Missions • • • • • • • • Hayabusa 5/9/03 - 9/12/05 Rosetta 3/2/04 - 2015 • • •