ƴÚˎ͛ ́ɓ (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
ζζζζ ˃˃˃˃ 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 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 φφφφ ! š³ǦǦǦǦ ģģģģ ²²²² ¯¯¯¯ 7777 ŎŎŎŎ 1ļļļļ ƬƬƬƬ ÜÜÜÜ õõõõ ģģģģ ,ɃɃɃɃ ²²²² ¯¯¯¯ 1ŎŎŎŎ 7777 ʷʷʷʷ ˓˓˓˓ ģģģģ ñUʖɅɅɅɅ 7777 š³ϕϕϕϕ iiii ˸˸˸˸ ²²²² ĨĨĨĨ ȂȂȂȂ ៏ɌɌɌɌ ͼͼͼͼ ǦǦǦǦ ģģģģ š³ΩΩΩΩ 7777 ßßßß ! Uʖ²²²² ̢̢̢̢ ɋɋɋɋ ΩΩΩΩ śśśś ͵͵͵͵ řřřř š³ΩΩΩΩ ǦǦǦǦ ģģģģ ˁˁˁˁ ÜÜÜÜ ģģģģ ĮĮĮĮ ŮŮŮŮ ˙˙˙˙ llll Uʖ²²²² ʍʍʍʍ ææææ ÊÊÊÊ FGGGG KKKK M7777 š³! Uʖ²²²² KKKK OOOO KKKK OOOO RRRR SSSS ! ĮĮĮĮ ͱͱͱͱ ΈΈΈΈ ƪƪƪƪ ΩΩΩΩ šˣˣˣˣ ͗͗͗͗ F̚̚ ̚̚ M! 7777 š³FKKKK Mˁˁˁˁ ˝˝˝˝ ³FSSSS MΩΩΩΩ ÜÜÜÜ ģģģģ ĮĮĮĮ ŮŮŮŮ HHHH í! ñUʖ˝˝˝ ³ΩΩΩ ǘǘǘ ȖȖ ̢̢ ΩΩ ŧŧ \\ ĜĜ ! ñUʖɅɅɅɅ jjjj ÉÉÉÉ ϕϕϕϕ Fkkkk nnnn M²²²² ɵɵɵɵ ̄̄̄̄ ȂȂȂȂ ˝˝˝˝ ³ΩΩΩΩ ʈʈʈʈ ʹʹʹʹ ! ñUʖ &&&& ZZZZ ǾǾǾǾ ǾǾǾǾ ȻȻȻȻ ĮĮĮĮ ̛̛̛̛ ʍʍʍʍ ̮̮̮̮ F{{{{ |||| MΩΩΩΩ ĐĐĐĐ ÿÿÿÿ ! ²²²² ËËËË ɥɥɥɥ š³͗͗͗͗ ! ñUʖ1PPPP ΩΩΩΩ ßßßß Fš³̠̠̠̠ 6666 š³M²²²² ¢¢¢¢ ǦǦǦǦ ΩΩΩΩ ĮĮĮĮ [[[[ ÿÿÿÿ ³ˁˁˁˁ š³LLLL ̜̜̜̜ ΩΩΩΩ ßßßß ͗͗͗͗ Uʖ²²²² xxxx ĽĽĽĽ %%%% ³ŰŰŰŰ ɥɥɥɥ ! UʖĿĿĿĿ ģģģģ ÜÜÜÜ ³ ! Uʖ²²²² <<<< ąąąą ΩΩΩΩ ƉƉƉƉ ££££ εεεε ñUʖ˳˳˳˳ ϠϠϠϠ ̢̢̢̢ ,š³b˧ϣϣϣϣ ˳˳˳˳ ǮǮǮǮ 2006/11/1 ¹Ǥėɓ ɓ nj ƭ ƴ Ú 33