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Planet Formation

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Planet Formation ƴÚˎ͛́ɓ (planet formation) ́D͟ ȓȓȓȓ 1111 þþþþ ĭĭĭĭ ɋɋɋɋ IIII ĤĤĤĤ ͓͓͓͓ &&&& ̤̤̤̤ The Solar System Planets are almost on the same plane. Planets orbit the Sun in the same direction. The Sun is rotating in the same direction as the planets’ orbital movement. Planets form in a disk! 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 2 SScceennaarriioo ooff SSttaarr && PPllaanneett ffoorrmmaattiioonn ƉƉƉƉ ͭͭͭͭ ǥǥǥǥ DDDD ³³³³ ǟǟǟǟ ΩΩΩΩ ³³³³ šššš ³³³³ ɋɋɋɋ ÕÕÕÕ Molecular Cloud 3̮ NJNJNJNJ ˠˠˠˠ ³³³³ ƦÀ͌ ʴʴʴʴ ÜÜÜÜ A star is made of gas star formation needs gas a star forming region is full of dense gas and dust (NJNJ ɁɁ ). Formation of the Solar System 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 4 Formation of planetesimals 20 micron 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 5 Formation of planets closer to the Sun, warm, no ice Far from the Sun, cold, Ice helps to grow a big solid core gas accretion 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 6 -³ j É ϕ ƴ Ú ƽ > ³ ɷ > ³ The Solar System ȳ ȳ ȳ ȳ ˚ ˚ ˚ ˚ ǯ ǯ ǯ ǯ Ω Ω Ω Ω Ź Ź Ź Ź ˙ǚ@ƍ: Ð Ð Ð Ð http://www.gps.caltech.edu/ ~mbrown/ ͧ΋I2Ω006̛ /11ʍ /1 ̮ ¹Ǥėɓ ɓ nj ƭ ƴ Ú 7 PPlluuttoo:: tthhee 99tthh ppllaanneett?? by Hubble Space telescope 1 AU (astronomical unit) Distance to Sun =earth-to-Sun distance 39.5 AU Eris (satellite: Dysnomia) 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 8 Orbit of Eris side view top view http://bobthealien.co.uk/eris.htm 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 9 NNeeww PPllaanneett DDeeffiinniittiioonn http://www.iau2006.org/mirror/www.iau.org/iau0603/index.html © orbit a star (upper mass limit: brown dwarf Υǖɓ, no nuclear fusion?) © massive enough to keep a round shape (lower mass limit: about 5x1023 g or ȂȂȂȂ ιιιι >400 km ?) © has cleared the neighborhood around its orbit. Pluto, Eris, and Ceres (͜͜͜͜ ˃˃˃˃ ³³³³ ) are now classified as “dwarf planets”. They are the same as “planets” except that firstly they can’t clear the neighborhood & secondly they are not satellites. Other Important Issues: • thermal view: small planets may preserve the raw materials of planet formation • formation view: Ceres & KBOs may fail to form an “original planet” in the past. • twin view: what about if the planet mass is comparable to its satellite mass? 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 10 note In the outskirt of the Solar System, Pluto is accompanied with a group of comet-like bodies at the similar orbital radii. This group is called the Kuiper Belt. The discovery of Eris and the continuous size distribution among largest Kuiper Belt objects suggest that we need to revise the definition of a “planet”. After the IAU (International Astronomical Union) general meeting held this August, astronomers have voted to re-define a “planet”. According to the new definition, now we have only 8 planets. Pluto and Eris are dwarf planets. The number of dwarf planets will increase. 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 11 Ultra-low mass stars & Brown dwarfs ȅȅȅȅ 6666 ³³³³ [[[[ ͅͅͅͅ ³³³³ ˁˁˁˁ šššš ³³³³ ΩΩΩΩ ßßßß Star: mass > Brown dwarf: 0.08 solar masses between nuclear fusion 13 Jupiter masses & 0.08 solar masses Planet: (very faint, difficult to no nuclear detect! Using infrared) fusion 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 12 CCoonnddeennssaattiioonn sseeqquueennccee ((ǡǡHHͿͿʀʀ) 273K=0oC http://ircamera.as.arizona.edu/astr_250/Lectures/Lec_21sml.htm http://inverse.astro.uwo.ca/ast21/slides20/slide2.html Planets form in a proto-stellar disk around a protostar. 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 13 SSnnooww LLiinnee oonn aa pprroottoo--sstteellllaarr ddiisskk Micron-size dust planetesimals (comets or asteroids) Kuiper planets snow line Belt objects gaseous (source of short-period comets) or giant planet terrestrial ice + dust grains or rocky core (more than 10 earth masses) planets Gas accretion Giant planet CCoommeett ((ƗƗɓɓ)):: ddiirrttyy ssnnoowwbbaallll water ice dry ice clay PAH olivine iron Fred Whipple http://www.spitzer.caltech.edu/Media/releases/ssc2005-18/ssc2005-18b.shtm proposed comets are dirty snowballs In 1950. 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 15 AAsstteerrooiidd:: mmiinnoorr ppllaanneett ųų́́ɓɓ ((cc..ff.. ppllaanneetteessiimmaall)) ͜͜͜͜ ˃˃˃˃ ³³³³ ˃˃˃˃ ³³³³ ǽǽǽǽ ˃˃˃˃ ³³³³ 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 16 Patron Goddess of Sicily Largest asteroid 30% of the mass of all the known asteroids combined. 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 17 An Asteroid has a “moon” Dactyl Ida (55 km long) By Galileo spacecraft 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 18 Asteroid & Mars’s Moons asteroid Gaspra captured by Mars? Deimos Phobos 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 19 Name an asteroid • Normally, the discoverer of an asteroid has the first right to name it after someone else, but recent automated telescopic surveys gave the IAU (International Astronomical Union) a surplus of asteroids with nothing but prosaic catalog designations. Anyone can petition the IAU to name an asteroid in someone's honor, but the process often takes years. Also, IAU's Committee for Small Body Nomenclature has specific rules for names, including a limit of 16 characters (including punctuation), a requirement that the name be pronounceable (in some language), and no names from pet animals allowed. • For instance, 3 asteroids were named in Memory of September 11 terrorism victims: http://www.space.com/news/asteroid_setp11_011010.html 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 20 Properties of belt asteroids • Number: as of 2002, 52224 asteroids confirmed, more than 125000 awaiting confirmation. • Average separation: 10 million km • Composition & Albedo: S, C, M types • Size: irregular shapes. 30 asteroids between 200-300 km in diameter. The number increases with decreasing size. Putting together ½ the diameter of our Moon. • A failed planet? (recall how a planet formed?) 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 21 Composition of asteroids Consist primarily metallic stony of rock & metal. Compared with comets which are composed of carbon rock and Ices (dirty snowball). 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 22 Trojan (Eʆɪ) asteroids 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 23 Landing on an asteroid Eros(ńńńń ઠઠઠઠ ): 33x13x13km 5.24 hours/rotation Near Earth Asteroid Rendezvous Shoemaker (NEAR) 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 24 Close encounter Asteroid 1994 XM1 was less than ½ the distance from the Earth to the Moon! 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 25 Group Description Definition Near-earth NECs Near-Earth Comets q<1.3 AU, P<200 years objects NEAs Near-Earth Asteroids q<1.3 AU Atens Earth-crossing NEAs a<1.0 AU, Q>0.983 AU with semi-major axes smaller than Earth's (NEOs) (named after asteroid 2062 Aten). Apollos Earth-crossing NEAs a>1.0 AU, q<1.017 AU with semi-major axes http://neo.jpl.nasa.gov/ larger than Earth's (named after asteroid 1862 Apollo). Amors Earth-approaching a>1.0 AU, NEAs with orbits 1.017<q<1.3 AU exterior to Earth's but interior to Mars' (named after asteroid 1221 Amor). PHAs Potentially MOID<=0.05 There are currently Hazardous Asteriods: known 730 PHAs. NEAs whose Minimum Orbit Intersection Distance (MOID) with the Earth is 0.05 AU (about 20 times the distance between Earth & Moon) or less and whose absolute magnitude (H) is 22.0 or brighter. 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 26 Astronomers (A.D.1500-1700) Copernicus Galileo (1473-1543) (1564-1642) Heliocentric First use a theory telescope to watch the sky Tycho Newton (1546-1601) (1642-1727) Half helio + Law of Half geo universal & gravitation Kepler (1571-1630) 3 laws 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 27 Ellipse e ɒ eccentricity ¶(ī)ǀǀ ȿȿ 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 28 Kepler’s 3 Laws 1st law: slow fast 2nd law: 3rd law: period2=distance3 the closer, the faster! (Newton: the smaller the distance, the stronger the gravitational force) 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 29 Newton & Gravitation Woolsthorpe 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 30 Newton’s law of gravitation Mm F ∝ Kepler’s laws ȫȫȫȫ NNNN ƄƄƄƄ ŮŮŮŮ ʼʼʼʼ «««« Ans:¶ǀǀǀǀ ŒŒŒŒ gravity r 2 m M 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 31 Centrifugal force (¶ǀŒ) 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 32 summary ñUʖš³ŇȃíƱ)óH1«íƱƏͪb˧ ̢̢̢̢ ɋɋɋɋ ͘͘͘͘ š³~~~~ ɃɃɃɃ ĮĮĮĮ UʖΚΚΚΚ ! š³"""" #### $$$$ %%%% &&&& '''' 1(((( )))) **** ++++ #### ,ɃɃɃɃ $$$$ %%%% 1'''' &&&& ---- .... #### ñUʖ//// &&&& š³0000 1111 2222 $$$$ 3333 4444 56666 7777 """" #### š³8888 &&&& 9999 :::: ! Uʖ$$$$ ̢̢̢̢ ɋɋɋɋ 8888 ;;;; <<<< ==== >>>> š³8888 """" #### ???? **** #### ĮĮĮĮ @@@@ AAAA BBBB Uʖ$$$$ CCCC DDDD EEEE FGGGG HHHH IIII JJJJ KKKK LLLL M&&&& š³! Uʖ$$$$ LLLL NNNN KKKK HHHH OOOO NNNN KKKK HHHH PPPP QQQQ OOOO IIII RRRR JJJJ NNNN SSSS PPPP TTTT !UUUU VVVV ĮĮĮĮ WWWW XXXX ==== YYYY 8888 šZZZZ [[[[ F\\ \\ M! &&&& š³FKKKK TTTT PPPP NNNN HHHH IIII ]]]] ^^^^ M???? ____ ³FSSSS IIII ```` NNNN PPPP M8888 **** #### ĮĮĮĮ @@@@ aaaa í! ñUʖ____ ³8888 bbbb cccc dddd ̢̢̢̢ 8888 eeee ffff gggg hhhh ! ñUʖ//// iiii jjjj 0000 Fkkkk llll ]]]] mmmm NNNN HHHH nnnn NNNN oooo PPPP M$$$$ pppp qqqq 4444 ____ ³8888 rrrr ssss ! ñUʖ9999 tttt uuuu vvvv wwww xxxx ĮĮĮĮ yyyy CCCC zzzz F{{{{ IIII HHHH PPPP |||| oooo IIII llll ^^^^ M8888 }}}} ~~~~ ! HHHH ]]]] TTTT $$$$ ËËËË ɥɥɥɥ š³[[[[ ! ñUʖ1PPPP 8888 9999 :::: Fš³̠̠̠̠ 6666 š³M$$$$ ¢¢¢¢ """" 8888 ĮĮĮĮ [[[[ ~~~~ ³???? š³LLLL ̜̜̜̜ 8888 9999 :::: [[[[ Uʖ$$$$ xxxx ĽĽĽĽ %%%% ³ŰŰŰŰ ɥɥɥɥ ! UʖĿĿĿĿ #### ÜÜÜÜ ³ ! Uʖ$$$$ <<<< ąąąą 8888 ƉƉƉƉ ££££ εεεε ñUʖ˳˳˳˳ ϠϠϠϠ ̢̢̢̢ ,š³b˧ϣϣϣϣ ˳˳˳˳ ǮǮǮǮ 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 33.
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