The formation of stars and planets

Lecture by C.P. Dullemond

Max-Planck-Institute for Astronomy Heidelberg

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Sorry about:

• Topic of Star- and Planet Formation is too vast to cover completely, and in sufficient depth, in 15 hours.

• We will have to gloss over many things...

• Many important topics not included, for example:– Origin of ‘metal’-enriched matter from which we are built– Star formation on galactic scale (e.g. star-burst galaxies)– Chemistry of star formation, photodissociation of molecules– Pre-main sequence stellar evolution– High-mass star formation (unless voluntary extension!)

Literature:

• S.W. Stahler & F. Palla, “The formation of stars”• L. Hartmann, “Accretion processes in star

formation”• The review ‘bibles’ of star and planet formation:

– Protostars and Planets II– Protostars and Planets III– Protostars and Planets IV– (next year) Protostars and Planets V

Thanks to ...... for material

• Ewine van Dishoeck• Carsten Dominik• Christian Fendt• Anders Johansen• Klaus Pontoppidan• Frithjof Brauer• Sascha Quantz

• *Many others*

The field of star and planet formation is quite a large field. I have received lots of very valuable information and material from the following people, to whom I am indebted:

Technical notes on the lecture:

• Target group:– PhD students and advanced undergraduate students– Physics and astrophysics

• Goals:– Half overview, half in depth– Mostly theory, but strong link to observations

• Powerpoint material will be put on my web site:– www.mpia.de/homes/dullemon/lectures/starplanet/

Technical notes on the lecture:

• Style of lecture :– Working out simple analytical models (of cloud cores, of

disks, of particle motion, particle agglomeration etc.)– Discussion of state-of-the-art models with physical

explanation. – Comparison of models with observations

• We need solid basis in the physics of astrophysics (hour 2+3)

• But first a quick overview... in pictures and movies

The formation of stars and planets

Day 1, Topic 1:

Introduction and

Overview

Lecture by: C.P. Dullemond

Birthplace of stars: Molecular Clouds

Ophiuchus Giant Molecular Cloud (by Loke Tan)

Birthplace of stars: Molecular Clouds

Ophiuchus Giant Molecular Cloud (by Loke Tan)

Forming stars from Molecular Clouds

M. BateExeterUK

Zur Anzeige wird der QuickTime™ Dekompressor „Cinepak“

benötigt.

Very dense Molecular Cloud: very aggressive star formation

‘Isolated’ Star Formation

M.Hogerheijde1998, after Shu et al. 1987

In the beginning...

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

Feeding the infant star...

• Infall of matter onto protostar is energetic: lots of radiation• In above image some radiation escapes via cavity.• Most of radiation escapes at long wavelength (infrared), because

cloud is transparent at those wavelength. • Far-IR wavelength telescopes have low resolution so far, so what’s

really happening down there is still difficult to study.

McNeal’sNebula

Not all ‘food’ is welcome: outflows...

Not all ‘food’ is welcome: outflows...

A zoom-in to a massive star forming region

Jupiter

M16 (Eagle)

M17 (Horseshoe)

M8 (Lagoon)

Milky Way

Hale-Bopp

Zoom-in

Picture credit: W. Keel

A zoom-in to a massive star forming region

Eagle Nebula(M16)

Picture credit: T.A. Rector & B.A. Wolpa

A zoom-in to a massive star forming region

Eagle Nebula(M16)

Picture Credit: J. Hester & P. Scowen

A zoom-in to a massive star forming region

Eagle Nebula(M16)

Picture Credit: J. Hester & P. Scowen

A zoom-in to a massive star forming region

Picture Credit: J. Hester & P. Scowen

Eagle Nebula(M16)

size of our solar system

Clearing of the remnant birth cloud

A star+disk appears...

A star+disk appears...

HST image of AB Aurigae by Carol Grady

Planets form in the disk (?)

Artist’s impression of planet formation...

Grinding asteriods back to dust...

Grinding asteriods back to dust...

Planets and asteroids have formed, some asteroids get destroyed and produce the dust you observe in the image. Can the dust trace the location of (invisible) planets?

The early life of a newly formed star

Zero-age main sequence (ZAMS)

starmass

Oh, Be A Fine Girl, Kiss Me(Right Now

Sweety!)

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The Harvard classification. Annie Jump Cannon, Henry Draper

Pre-main-sequence: the infancy of a star

Palla & Stahler

Pre-main-sequence: the infancy of a star

• Protostar = self-gravitating hot ball of gas, continuously being fed by accreting matter

• At first: no internal nuclear heat production• Star cools by radiation:

– Kelvin-Helmholz time scale

• Star contracts, central density and temperature increases (!)

• Deuterium ignites as soon as Tc >= 1x106 K

– Thermostat: ds/dTc<0, i.e. too hot: star swells, Tc goes down, and deuterium burning slows

• Star becomes fully convective

• Stellar radius inflates: can reach 3...5 R.

Pre-main-sequence: the infancy of a star

• (We are now in the T-Tauri star phase)• Star contracts slowly

– with constant temperature for low mass stars, i.e. they move vertically downward in the HR diagram

• Tc and c increase until:

• Hydrogen ignition– Prolonged hydrogen burning starts– This is the start of the ‘adult’ life of the star– Star reached the ZAMS

Age and mass determination of PMS stars

Testi et al. Martin et al.

Overview of the lecture• Day 1:

– Introduction– Radiation physics– Hydrodynamics and Magnetohydrodynamics

• Day 2:– Giant Molecular Clouds– Self-gravitating hydrostatic spheres– Collapsing clouds

• Day 3:– Viscous evolution of protoplanetary disks 1+2– Irradiated protoplanetary disks, SEDs, observations

• Day 4:– Magnetospheric accretion, jets, outflows– Motion of particles in disks– Agglomeration of particles in disks

• Day 5:– The solar system and extrasolar planets– Formation of planets– Migration of planets and outlook