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Big bang Nuclear fusion in stars Supernova nucleosynthesis Planetary formation Current Solar System 5. Formation of Solar System May 21, 2012 외계행성과 생명 Proverb • 티끌모아 태산 • Many a little makes a mickle. • Light gains make heavy purses. Chronology of the Universe 13.7 Gyr 13.4 Gyr 12 Gyr 4.567 Gyr 4.5 Gyr 4.45 Gyr 4.4 Gyr 4.2 Gyr 4 Gyr >3.5 Gyr >3.5 Gyr 2.3 Gyr 0 Gyr Big bang; formation of the elements H and He First stars and galaxies; first supernova explosions produce the heavy elements (C,N,O,Si,Fe,…) Formation of the milky way Formation of the solar system; at this point in time the interstellar medium has been enriched with 1% heavy elements Formation of the earth and the moon Layer structure of the earth Solid earth crust Early ocean Plate tectonics Earth’s magnetic field Origin of life Formation of oxygen-rich atmosphere; formation of ozone Today Star and planet formation belong together The sun and the planets formed at the same time, and from the same material reservoir on the basis of these facts: Elementary abundances Age of the meteorites = age of the sun, i.e. 4.567Gyr Parallel angular momentum of sun and planets (Obliquity of the sun to ecliptic = 7.25 deg) -Solar -Halley’s dust -Comet gas -Chondrite Anders & Grevesse (1989), Geochim. Cosmochim. Acta. 53, 197 Jessberger et al. (1988), Nature 332, 21, 691 Swamy, in Physics of Comets Andrers & Ebihara, Geochim. Cosmochim. Acta. 46, 2363 (1982) Molecular cloud Star formation – an overview © GEO, after Shu et al. 1987 Formation of gas-dust disk “Clumping” of the dust Formation of the sun by radial transport of matter Formation of isolated planets Protoplanetary dust disk ~1 m Agglomeration interaction with gas important no gravity ~10 cm Coulomb force Planetesimals ~10 km Accretion of planetesimals Gravitational force no interaction with gas Terrestrial planets ~10,000 km gravity dominates Gas accretion Gas planets gravity dominates ~100,000 km if escape velocity > thermal velocity (i.e. larger than 10-15 Earth masses), migration potentially important Planetesimals = Minute planets 1pc = 2x105 AU M.Hogerheijde1998, after Shu et al. 1987 Stars are born deep in very cold dark (optically thick) clouds. Their birth is ‘secret’: not visible at optical wavelength. Infrared telescopes can penetrate through these clouds and witness the first signs of life from a protostar. Zoom-in M16 (Eagle) M17 (Horseshoe) Milky Way M8 (Lagoon) Hale-Bopp Jupiter Eagle Nebula (M16) A star + disk appears... 1pc = 2x105 AU M.Hogerheijde1998, after Shu et al. 1987 What have we learned so far? The sun and our planets formed concurrently 4.567 billion years ago. Extrasolar planetary systems can be similar to or different from the solar system. Dust plays a decisive role in the formation of the planets. The lifetime of protoplanetary disks, the birthplaces of planets, is a few million years. Debris disks Beta-Pictoris Age: 100 Myr (some say 20 Myr) Dust is continuously replenished by collisions between planetesimals. Disk is very optically thin (and SED has infrared excess). Consider the simplest cases BPCA BCCA Ballistic Particle-Cluster Ballistic Cluster-Cluster Agglomeration Agglomeration ⇓ ⇓ ballistic hit-and-stick impacts of single dust particles into growing dust agglomerate ballistic hit-and-stick collisions between equal-mass dust agglomerates i = 1,024 i = 1,024 BPCA N=2 BPCA N=4 BPCA N=8 BPCA N=16 BPCA N=32 BPCA N=64 BPCA N=128 BPCA N=256 BPCA N=512 BPCA N=1024 BCCA N=2 BCCA N=4 BCCA N=8 BCCA N=16 BCCA N=32 BCCA N=64 BCCA N=128 BCCA N=256 BCCA N=512 BCCA N=1024 Bradley et al. 2005
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