mercredi 23 janvier 2008
samedi 19 janvier 2008
vendredi 18 janvier 2008
スノークという名前を何年振りに聞くだろう
うちのグループにエスプレッソのマシンがあって、ミーティングルームに置いてあります。
Astrobiology のミーティングがちょうどはじまるところで、そこにせりちゃんのくれた
ムーミンのマグを持って行ったら、シカゴ大から来ている超有名な地質学の先生が
『おおムーミン！』
と叫ぶ。
ビジター・ルームから、シアトルから来てるこれも超有名な宇宙生物学のおばさんが飛び出してきて、
『え、なになにムーミン！？私も大好き』
『私は去年フィンランドに行きましてねえ、ムーミンキャラクターのマグ全部揃えましたよ』
『えーいいなー私はリトルミイのが欲しいわ』
『モランのがあるんですよ、これがなかなか味があっていいんですよ。
ほら、私のこのマックは（ホストネームが）スナフキンって名前にしてあるんです。
我が家のコンピュータは全部スニフ、フローレン、スノーク、・・・って言う風に
ムーミンのキャラクターの名前にしてあるんですよ。』
全く予想だにしない突然の異様なる盛り上がりに私はただ呆然と立ち尽くすのみであった。
dimanche 13 janvier 2008
WASP-5 b
This year will surely be even a busier year for us with surging news
on transit discoveries----
http://arxiv.org/abs/0801.1685
Just a while ago there was WASP-4 b, but 4 & 5 seem quite different.
This is a "very-hot Jupiter", casually classified for planets whose orbital
periods are < 3 days. Despite the extreme proximity to the star
(a ~ 5 stellar radii), the planet is not inflated, but rather compact ---
it's in fact the densest very-hot Jupiter ever found.
There are some theories claim that the very-hot Jupiters are formed
not by standard migration but by circularization of eccentric orbits.
If that's the case, the planet should show a significant spin-orbit misalignment.
This is a G4V star with decent rotation so Rossiter-McLaughlin measurement
should not be too challenging.
金子光晴 『絶望の精神史』
『上海も、ロンドンも、ローマも、いまでは、おなじように箱を並べた様な団地住宅が建って、おなじような設計の狭い部屋で、コカコーラと、スパゲッティと、サンドウィッチで暮らす様になる。世界は、似てくる。これをデモクラシーというのであろうか。
同時に、ばらばらになってゆく個人個人は、そのよそよそしさに耐えられなくなるだろう。そして、彼らは、何か信仰するもの、命令するものをさがすことによって、その孤立の苦しみから逃避しようとする。
世界的なこの傾向は、やがて、若くしてゆきくれた、日本の十代、二十代をとらえるだろう。そのとき、戦争の苦しみも、戦後の悩みも知らない、また、一度も絶望をした覚えの無い彼らが、はたして何を見つけ出すだろうか。』
jeudi 10 janvier 2008
Day 3
Kalas Extrasolar Kuiper Belts
Various morphologies of debris disks
Fomalhaut -- narrow belt, one of the oldest debris disk
Center of the ring is off the primary star by 15 AU. There seems to exist a planet interior to the ring, that is also shaping the very sharp inner edge of the ring.
Vega -- Spitzer detected warm emissions to a few 100s AU
ß -- Thin second disk detected
Lubow Hydro simulation of disks, fast Type III migration w/ D'Angelo
Numerical simulations generally agree with the analytical Type I/II migration rates.
A few exceptions: For highly eccentric planets (e>0.1), migration rates can be slowed down or the migration can be even reversed, due to the slow motion near the apastron. Also, if the planet is suddenly (and artificially) immersed in the disk, i.e., if the planet is substantially large and the gap hasn't opened yet, then the aerodynamical drag causes fast Type III migration.
Cochran
Quoting Ribas & Miralda-Escudé: mass distribution of exoplanets -- large pile-up on Jupiter mass and Neptune mass, but there's a gap in between. Predictable from core accretion scenario?
m > 4Mj Formed by disk-instability? Reasons: (1) average metallicity is lower for massive planets, not necessitating solid materials for core accretion? (2) e-distribution of massive planets resemble that of stellar binary e-distributions (this reasoning seems weak, ignoring all the dynamics, e.g., MMR, secular perturbations, etc.)
Absence of massive close-in planets
Tiscareno Saturn's ring
Lindblad resoance by moonlets cause the spiral wave structure (similar to spiral galaxies, but much more tightly wound).
Observation of density waves --> derive the ring properties (surface density, viscosity, vertical thickness, etc.)
The small ~100m size moonlets create wavy gap edges (e.g., in the Keeler Gap) and also the propeller patterns. The self-gravitiy wakes produce inhomogeneous opacity of the ring.
Debes
NICMOS2 coronagraph imaging of debris disks
Observed the diversity of scattered light
Invited Talk: Sandra Faber Emerging Principle of Galaxy Formation
Galaxy main sequence
Gravity and star formation are still challenging problems.
Cosmology & dark matter are the gravity backbone and quite well understood.
Starformation band for M_halo = 10^10 - 10^12
Two models for the crigtical halo mass: Galactic merger --> BH grows --> AGN feedback drives out the gas
Various morphologies of debris disks
Fomalhaut -- narrow belt, one of the oldest debris disk
Center of the ring is off the primary star by 15 AU. There seems to exist a planet interior to the ring, that is also shaping the very sharp inner edge of the ring.
Vega -- Spitzer detected warm emissions to a few 100s AU
ß -- Thin second disk detected
Lubow Hydro simulation of disks, fast Type III migration w/ D'Angelo
Numerical simulations generally agree with the analytical Type I/II migration rates.
A few exceptions: For highly eccentric planets (e>0.1), migration rates can be slowed down or the migration can be even reversed, due to the slow motion near the apastron. Also, if the planet is suddenly (and artificially) immersed in the disk, i.e., if the planet is substantially large and the gap hasn't opened yet, then the aerodynamical drag causes fast Type III migration.
Cochran
Quoting Ribas & Miralda-Escudé: mass distribution of exoplanets -- large pile-up on Jupiter mass and Neptune mass, but there's a gap in between. Predictable from core accretion scenario?
m > 4Mj Formed by disk-instability? Reasons: (1) average metallicity is lower for massive planets, not necessitating solid materials for core accretion? (2) e-distribution of massive planets resemble that of stellar binary e-distributions (this reasoning seems weak, ignoring all the dynamics, e.g., MMR, secular perturbations, etc.)
Absence of massive close-in planets
Tiscareno Saturn's ring
Lindblad resoance by moonlets cause the spiral wave structure (similar to spiral galaxies, but much more tightly wound).
Observation of density waves --> derive the ring properties (surface density, viscosity, vertical thickness, etc.)
The small ~100m size moonlets create wavy gap edges (e.g., in the Keeler Gap) and also the propeller patterns. The self-gravitiy wakes produce inhomogeneous opacity of the ring.
Debes
NICMOS2 coronagraph imaging of debris disks
Observed the diversity of scattered light
Invited Talk: Sandra Faber Emerging Principle of Galaxy Formation
Galaxy main sequence
Gravity and star formation are still challenging problems.
Cosmology & dark matter are the gravity backbone and quite well understood.
Starformation band for M_halo = 10^10 - 10^12
Two models for the crigtical halo mass: Galactic merger --> BH grows --> AGN feedback drives out the gas
Day 2
Robinson
Pollack model takes 9Myr to form Saturn, too long compared to the observed lifetimes of protoplanetary disks ~2-3 Myr.
Include chemical evolution in planet formation. CH4 ice line should be moved outward. Also NH3 -- N2 plume
from Enceladus indicates the abundance of NH3. It accretes on grains with H2O and thus is important for the solid budget.
CH4 & CO ices are also important solid mass carriers for Uranus and Neptune.
Zoe
surface of KBO is heterogeneous ---- density and strength can be quite diverse. They can be disrupted more easily than previous simulations.
Pollack model takes 9Myr to form Saturn, too long compared to the observed lifetimes of protoplanetary disks ~2-3 Myr.
Include chemical evolution in planet formation. CH4 ice line should be moved outward. Also NH3 -- N2 plume
from Enceladus indicates the abundance of NH3. It accretes on grains with H2O and thus is important for the solid budget.
CH4 & CO ices are also important solid mass carriers for Uranus and Neptune.
Zoe
surface of KBO is heterogeneous ---- density and strength can be quite diverse. They can be disrupted more easily than previous simulations.
Day 1
Invited talk by Jim Kasting
C - Si cycle
GJ581 Habitability analysis (Selsis et al. 07)
c -- not habitable
d -- probably an ice giant and not habitable
Bochansky
M dwarf IMF: power law index is uncertain within a factor of 2. simple extrapolation of Salpeter doesn't work.
> Million M-dwarfs surveyed by SDSS and 2MASS
- IMF peaked around M3-4. index ~ +0.69
Hatzes
K-giant masses hard to constrain from isochrone analysis. Use stellar oscillations to constrain and confirm the mass.
Measurement of Pollux: agrees with Allende-Prieto and Girardi.
West
Around the spectral type M4 the interior becomes fully convective.…
Some M-dwarfs are active: flaring / quiescent
Age - activity analysis (Hanley et al. 1999, 2000)
M dwarfs are ideal tracers of MW thin disk -- they are not too dim nor bright.
Activity - ∆z relation: older stars have had more orbits, thus more likely to be off the plane.
metallicity - ∆z relation also found.
Hansen
NGC6971: Some WDs have He cores instead of Ca. Hypothesis: they left the giant branch early due to planet-swalloing, had their envelopes ejected by the planets. ~80% of the WDs should've undergone planet-swalloing events.
C - Si cycle
GJ581 Habitability analysis (Selsis et al. 07)
c -- not habitable
d -- probably an ice giant and not habitable
Bochansky
M dwarf IMF: power law index is uncertain within a factor of 2. simple extrapolation of Salpeter doesn't work.
> Million M-dwarfs surveyed by SDSS and 2MASS
- IMF peaked around M3-4. index ~ +0.69
Hatzes
K-giant masses hard to constrain from isochrone analysis. Use stellar oscillations to constrain and confirm the mass.
Measurement of Pollux: agrees with Allende-Prieto and Girardi.
West
Around the spectral type M4 the interior becomes fully convective.…
Some M-dwarfs are active: flaring / quiescent
Age - activity analysis (Hanley et al. 1999, 2000)
M dwarfs are ideal tracers of MW thin disk -- they are not too dim nor bright.
Activity - ∆z relation: older stars have had more orbits, thus more likely to be off the plane.
metallicity - ∆z relation also found.
Hansen
NGC6971: Some WDs have He cores instead of Ca. Hypothesis: they left the giant branch early due to planet-swalloing, had their envelopes ejected by the planets. ~80% of the WDs should've undergone planet-swalloing events.
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