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NHK カルチャー講義(第3回)

NHK カルチャー講義(第3回)

NHK カルチャー講義「惑星科学最前線 ~太陽系誕生の謎~」の第3回目の講義資料です。

Takanori Sasaki

March 08, 2016
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  1. ଟ༷ͳݪ࢝࿭੕ܥԁ൫ Դڇ࠲ ΁ͼ͔͍ͭ࠲      ԁ൫ͷ࣭ྔ<ଠཅ࣭ྔ> ൃ

    ݟ ਺ ଠཅܥ෮ݩԁ൫ Ӊ஦ʹ͸༷ʑͳ࣭ྔΛ࣋ͭݪ࢝࿭੕ܥԁ൫͕ଘࡏ ɹˠԁ൫ͷ࣭ྔͷҧ͍͕ଟ༷ͳ࿭੕ܥΛੜΈग़͢ʂʁ
  2. ଟ༷ͳԁ൫͔Βੜ·ΕΔଟ༷ͳ࿭੕ ԁ൫ͷ࣭ྔͷҧ͍ˠΨε࿭੕ͷ਺ͱҐஔͷҧ͍ the escape velocity of protoplanets. This high random

    veloc- ity makes the accretion process slow and inefficient and thus Tgrow longer. This accretion inefficiency is a severe problem On the ot in circular o HD 192263 with Æ1e 1 for in situ f case. It is d slingshot m circular orb the magnet may be wea disks may b Terrestria Jovian plan planetary a key process systems. We confir holds in Æsolid ¼ Æ1 ð ¼ 1=2; 3= tions. We d systems dep disk profile growth tim and (17), re a Mdisk T <T grow disk T <T cont disk Fig. 13.—Schematic illustration of the diversity of planetary systems against the initial disk mass for < 2. The left large circles stand for central stars. The double circles (cores with envelopes) are Jovian planets, and the others are terrestrial and Uranian planets. [See the electronic edition of the Journal for a color version of this figure.] ݪ࢝࿭੕ܥԁ൫ͷ࣭ྔ يಓ௕൒ܘ த৺੕͔Βͷڑ཭ <,PLVCP*EB >
  3. ࿭੕ͷҠಈʹ൐͏࿭੕ܥͷมԽ earing continues through scattering. After 00 million years the

    inner disk is composed the collection of planetesimals at 0.06 AU, a M] planet at 0.12 AU, the hot Jupiter at 0.21 U, and a 3 M] planet at 0.91 AU. Previous sults have shown that these planets are likely be stable for billion-year time scales (15). Many bodies remain in the outer disk, and ac- orbital time scales and high inclinations. Two of the four simulations from Fig. 2 contain a 90.3 M] planet on a low-eccentricity orbit in the habitable zone, where the temper- ature is adequate for water to exist as liquid on a planet_s surface (23). We adopt 0.3 M] as a lower limit for habitability, including long-term climate stabilization via plate tectonics (24). three categories: (i) hot Earth analogs interior to the giant planet; (ii) Bnormal[ terrestrial planets between the giant planet and 2.5 AU; and (iii) outer planets beyond 2.5 AU, whose accretion has not completed by the end of the simulation. Properties of simulated planets are segregated (Table 1): hot Earths have very low eccentric- ities and inclinations and high masses because g. 1. Snapshots in time of the evolution of one simulation. Each panel ots the orbital eccentricity versus semimajor axis for each surviving body. he size of each body is proportional to its physical size (except for the ant planet, shown in black). The vertical ‘‘error bars’’ represent the sine of each body’s inclination on the y-axis scale. The color of each dot corresponds to its water content (as per the color bar), and the dark inner dot represents the relative size of its iron core. For scale, the Earth’s water content is roughly 10j3 (28). λΠϓ* **࿭੕མԼʹ ΑΓ࿭੕ܥͷيಓ͕େ͖ ͔͖͘ཚ͞ΕΔ they accrete on the migration time scale (105 years), so there is a large amount of damping during their formation. These planets are remi- niscent of the recently discovered, close-in 7.5 M] planet around GJ 876 (25), whose formation is also attributed to migrating resonances (26). ଟ༷ͳ࿭੕ܥܗ੒ <3BZNPOEFUBM >
  4. Weidenschilling &,Marzari (1996),,Lin,&   a GM a GM a

    GM a GM a GM * * 3 * 2 * 1 *     $&,60 45 '"#, (t >~ 1My) /% , "# 2-+0'! 3. *) 1."#3. 00 a1 0  . 00 a1(. final e يಓෆ҆ఆʹΑΔ࿭੕ܥͷมԽ ࿭੕ؒͷॏྗͷӨڹ͕ ੵΈॏͳͬͯ࠷ऴతʹ ޓ͍ͷيಓ͕ෆ҆ఆԽ ҟͳΔ࿭੕ܥ΁ ˣ &DDFOUSJD1MBOFUͷىݯʁ </BHBTBXBFUBM >
  5. ΋͏ͻͱͭͷ࿭੕ܗ੒ཧ࿦         

       ©Newton Press ژ౎ϞσϧʢྛϞσϧʣ ΩϟϝϩϯϞσϧ ॏྗෆ҆ఆͰܗ੒͞Εͨܥ֎࿭੕΋ଘࡏ͢ΔՄೳੑ (c) Alan P. Boss
  6.  ϋϏλϒϧϓϥωοτͷىݯͱਐԽ ୈ̍ճʗѨ෦ ਫૉͰ͋Γɼ࣍͸ϔϦ΢ϜͰ͋Δɽͦͷ࣍ʹࢎૉɼ୸ ૉɼωΦϯɼ஠ૉͱདྷΔɽݻମͷ࿭੕ͷओ੒෼Ͱ͋Δ Ϛάωγ΢ϜɼγϦίϯɼమ͕࣍ʹଓ͕͘ɼࢎૉͷଘ ࡏྔ͸͜ΕΒΑΓ΋  ܻҎ্ଟ͍ɽݩૉ߹੒ͷաఔΛ ߟ͑ͯ΋ਫૉͱࢎૉ͕ଟ͍ݩૉͰ͋Δ͜ͱʹ͸ҧ͍͕

    ͳ͍Ͱ͋Ζ͏ɽ൓Ԡੑ͕ͳ͍ϔϦ΢ϜΛআ͚͹ɼਫ͸ ࠷΋ଟ͍ೋͭͷݩૉͷ૊Έ߹ΘͤͰͰ͖͍ͯΔɽͦͷ ͜ͱ͔Βߟ͑ͯ΋ਫͱ͍͏෺࣭͕ඇৗʹීวੑͷ͋Δ ෺࣭Ͱ͋Δͱ͍͏͜ͱ͕Θ͔Δɽͳ͓ɼଞͷ߃੕ܥͰ ͸ࢎૉΑΓ΋୸ૉͷํ͕ଟ͍ɼͱ͍͏Α͏ͳ͜ͱ΋͋ Δ͔΋͠Εͳ͍ɽ͜ͷ৔߹ʹ͸ɼ୸ૉ͕ͲͷΑ͏ͳܗ ଶΛͱΔ͔ʹΑͬͯ͸ɼਫ͸࡞Γʹ͘͘ͳͬͯ͠·͏ ͔΋͠Εͳ͍ɽ ɹ࣍ʹਫͷੑ࣭ʹ஫໨ͯ͠ΈΑ͏ɽਤʹ  ؾѹʹ ͓͚Δ͍Ζ͍ΖͳԽ߹෺ͷ༥఺ͱ෸఺Λࣔͨ͠ɽ͜Ε ͸େࡶ೺ʹӷମͷঢ়ଶΛͱΔԹ౓ൣғΛද͢͜ͱʹͳ Δɽ͜͜ʹ͸Խ߹෺ͷ෼ࢠྔ΋ࣔͯ͋͠ΔɽҰൠʹ෼ ࢠྔ͕େ͖͍෺࣭΄Ͳ༥఺ɾ෸఺ͱ΋ߴ͘ͳΔ܏޲͕ ͋Δɽͦͷதʹ͋ͬͯਫ͸෼ࢠྔ͕খ͍͞ʹ΋͔͔Θ Βͣ༥఺ͱ෸఺͕ߴ͍͜ͱ͕෼͔ΔͰ͋Ζ͏ɽਫฒΈ ʹ༥఺ɾ෸఺͕ߴ͍෺࣭͸ͲΕ΋͔ͳΓෳࡶͳ෺࣭Ͱ ͋Δɽݴ͍׵͑Ε͹ͦͷΑ͏ͳԽ߹෺͸࡞Γʹ͍͘ɽ ͜͏ݟ͍ͯ͘ͱਫ͸୯७ͳ෺࣭ɼ͢ͳΘͪଘࡏྔ͕ଟ ਤɿଠཅܥͷݩૉଘࡏ౓ɽଠཅ૊੒Ψε ʢ4PMBSʣ ͱ୸ૉ࣭ί ϯυϥΠτ ʢ$*ʣ ʹؚ·ΕΔݩૉͷଘࡏ౓Λɼܔૉͷଘࡏ ౓Λʹن֨Խͯࣔͨ͠͠ɽ ਫૉͰ͋Γɼ࣍͸ϔϦ΢ϜͰ͋Δɽͦͷ࣍ʹࢎૉɼ୸ ૉɼωΦϯɼ஠ૉͱདྷΔɽݻମͷ࿭੕ͷओ੒෼Ͱ͋Δ Ϛάωγ΢ϜɼγϦίϯɼమ͕࣍ʹଓ͕͘ɼࢎૉͷଘ ɹ࣍ʹਫͷੑ࣭ʹ஫໨ͯ͠ΈΑ͏ɽਤʹ  ؾѹʹ ͓͚Δ͍Ζ͍ΖͳԽ߹෺ͷ༥఺ͱ෸఺Λࣔͨ͠ɽ͜Ε ͸େࡶ೺ʹӷମͷঢ়ଶΛͱΔԹ౓ൣғΛද͢͜ͱʹͳ Δɽ͜͜ʹ͸Խ߹෺ͷ෼ࢠྔ΋ࣔͯ͋͠ΔɽҰൠʹ෼ ࢠྔ͕େ͖͍෺࣭΄Ͳ༥఺ɾ෸఺ͱ΋ߴ͘ͳΔ܏޲͕ ͋Δɽͦͷதʹ͋ͬͯਫ͸෼ࢠྔ͕খ͍͞ʹ΋͔͔Θ Βͣ༥఺ͱ෸఺͕ߴ͍͜ͱ͕෼͔ΔͰ͋Ζ͏ɽਫฒΈ ʹ༥఺ɾ෸఺͕ߴ͍෺࣭͸ͲΕ΋͔ͳΓෳࡶͳ෺࣭Ͱ ͋Δɽݴ͍׵͑Ε͹ͦͷΑ͏ͳԽ߹෺͸࡞Γʹ͍͘ɽ ͜͏ݟ͍ͯ͘ͱਫ͸୯७ͳ෺࣭ɼ͢ͳΘͪଘࡏྔ͕ଟ ਤɿଠཅܥͷݩૉଘࡏ౓ɽଠཅ૊੒Ψε ʢ4PMBSʣ ͱ୸ૉ࣭ί ϯυϥΠτ ʢ$*ʣ ʹؚ·ΕΔݩૉͷଘࡏ౓Λɼܔૉͷଘࡏ ౓Λʹن֨Խͯࣔͨ͠͠ɽ ਤɿؾѹʹ͓͚Δ͞·͟·ͳԽ߹෺ͷ༥఺͓Αͼ෸఺ɽઢ෼Ͱࣔ͞Εͨ෦෼͕ɼͦͷԽ߹෺͕ӷମͷঢ়ଶΛͱΔԹ౓ൣғΛ ද͍ͯ͠Δɽ·ͨɼ ͦͷԽ߹෺ͷ෼ࢠྔΛനؙͰ͍ࣔͯ͠Δɽਫ͸෼ࢠྔ͕খ͍͞Խ߹෺ͷதͰɼ ͻͱࡍ༥఺ͱ෸఺͕ߴ͍ɽ ଘࡏ౓ͷେ͖͍୯७ͳ෼ࢠͷதͰ ѹ౗తʹߴ͍༥఺ɾ෸఺Λ࣋ͭ D :VUBLB"CF ͳͥʮਫʯͳͷ͔ʁ શͯͷ஍ٿܕੜ໋͸׆ಈ͢ΔࡍʹਫΛඞཁͱ͢Δ
  7. ɾϋϏλϒϧκʔϯͷ಺ଆڥք ɹɹ๫૸Թࣨ৚݅ɿ0.97A [Kopparapu et al. 2013] ɾϋϏλϒϧκʔϯͷ֎ଆڥք ɹɹCO2 ڽॖ৚݅ɿ1.70AU [Kopparapu

    et al.. 2013] 45367298 !)./+ -,1! *0/#(/  : from Kasting et al. (1993) " 436 ɾ45ԯ೥ؒͣͬͱϋϏλϒϧͳྖҬɿ0.99AU-1.1AU D :VUBLB"CF ϋϏλϒϧκʔϯͷܾΊํ