Lecture Planet Formation Topic: Overview of the standard model of planet formation Lecture by: C.P....

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Lecture “Planet Formation” Topic: Overview of the standard model of planet formation Lecture by: C.P. Dullemond

Transcript of Lecture Planet Formation Topic: Overview of the standard model of planet formation Lecture by: C.P....

Page 1: Lecture Planet Formation Topic: Overview of the standard model of planet formation Lecture by: C.P. Dullemond.

Lecture “Planet Formation”

Topic:

Overview of

the standard model

of planet formation

Lecture by: C.P. Dullemond

Page 2: Lecture Planet Formation Topic: Overview of the standard model of planet formation Lecture by: C.P. Dullemond.

Standard Model

1. A star is formed, surrounded by a disk of dust and gas

2. The dust particles coagulate forming ever larger dust aggregates, rocks, boulders

3. ...some miracle happens... and sizes of >km are reached (as we will see later, this is a strange thing)

4. These planetesimals gravitationally interact leading to „runaway growth“. A „planetary embryo“ is formed (~ 1000 km)

5. The embryo accretes further planetesimals and grows

6. Nearby embryos collide and merge to form a rocky planet

7. IF the planet continues to grow to ~ 10 Mearth, then it will attract gas from the disk and form a gas giant planet.

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Birthplace of stars: Molecular Clouds

Ophiuchus Giant Molecular Cloud (by Loke Tan)

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Birthplace of stars: Molecular Clouds

Ophiuchus Giant Molecular Cloud (by Loke Tan)

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Forming stars from Molecular Clouds

M. BateExeterUK

Very dense Molecular Cloud: very aggressive star formation

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‘Isolated’ Star Formation

M.Hogerheijde1998, after Shu et al. 1987

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Observed protoplanetary disks

Credit: NASA

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Observed protoplanetary disks

HST image of AB Aurigae by Carol Grady

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The long road from dust to planets

1m 1mm 1m 1km 1000km

Gravitykeeps/pulls

bodiestogether

Gas isaccreted

Aggregation(=coagulation)

First growth phase Final phase

Covers 13 orders of magnitude in size = 40 (!!) orders of magnitude in mass

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Immanuel Kant already understood it!

“Der Anfang der sich bildenden Planeten ist nicht allein in der Newtonschen Anziehung zu suchen. Diese würde bei einem Partikelchen von so ausnehmender Feinigkeit gar zu langsam und schwach sein. Man würde vielmehr sagen, dass in diesem Raume die erste Bildung durch den Zusammenlauf einiger Elemente, die sich durch die gewöhnlichen Gesetze des Zusammenhangs vereinigen, geschehe, bis derjenige Klumpen, der daraus entstanden, nach und nach so weit angewachsen, dass die Newtonsche Anziehungskraft an ihm vermögend geworden, ihn durch seine Wirkung in die Ferne immer mehr zu vergrößern.”

Aus: Immanuel Kant „Allgemeine Naturgschichte und Theorie des Himmels“ (1755) http://www.deutschestextarchiv.de/book/show/kant_naturgeschichte_1755

(thanks to Willy Kley for pointing me to this amazing citation)

Page 11: Lecture Planet Formation Topic: Overview of the standard model of planet formation Lecture by: C.P. Dullemond.

Immanuel Kant already understood it!

“The start of the formation of a planet is not to be sought only in the Newtonian attractive forces. They would, for such small particles, be too slow and too weak. One would more say that the first phases of growth take place through the collision of elements that aggregate through the usual laws of cohesion, until these clumps eventuell have grown so much, that the Newtonian attractive forces, with their long range of influence, spur their growth ever further.“

English translation from Immanuel Kant „Allgemeine Naturgschichte und Theorie des Himmels“ (1755) http://www.deutschestextarchiv.de/book/show/kant_naturgeschichte_1755

(thanks to Willy Kley for pointing me to this amazing citation)

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So, what is this „cosmic dust“?

• Difficult to know because we have no method (yet) of collecting interstellar dust

• But there is „interplanetary dust“ from evaporating comets.

• These Interplanetary Dust Particles are dust aggregates

Collected from thestratosphere with a U2 airplane

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Particles move...

...because protoplanetary disks are turbulent, and turbulent gas stirsup the dust....and because of drift (more on that during the lecture).

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What happens when they collide?

Paszun & Dominik 2009See also Wada et al. 2009, Suyama, Wada & Tanaka 2008

Small sizes:a = 10 μm

Numerical models

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What happens when they collide?Laboratory experiments

From the laboratoryof J. Blum, Braunschweig

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Movie fromNASA

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Next phase: Growth by gravity

Thanks to Sean Raymond for lending me his movie

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Next phase: Growth by gravity

Thanks to Sean Raymond for lending me his movie

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Collision of two planets or moons

Image credit:Don Davis

ARTIST IMPRESSION

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Collision of two planets or moons

Asphaug & Reufer 2013http://vimeo.com/50778094

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Accretion of smaller bodies onto big ones

Stewart (2011)http://www.fas.harvard.edu/~planets/sstewart/Movies.html

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On to final planets

Figure from C. Mordasini‘s lecture

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Formation of gas giants

Figure from C. Mordasini‘s lecture

(if sufficient gas is present)

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Formation of gas giants(if sufficient gas is present)

Artist‘s impression byMoonrunner DesignNational Geographic

http://science.nationalgeographic.com/science/wallpaper/planet-formation.html

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Alternative GGP formation scenarioGravitational instabilities in the disk

Model byThomas Quinn

http://www.psc.edu/science/quinn.html

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Alternative GGP formation scenarioGravitational instabilities in the disk

Model bygroup ofRichard Durisen

http://hydro.astro.indiana.edu

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Planet-disk interaction & migration

Kley & Nelson (2012) Annual Reviews of Astronomy & Astrophysicshttp://vimeo.com/45256035

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Planet formation synthesis models

Mordasini et al. (2009)

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