Astrophysics of Planetary  Systems
at
Stockholm Observatory

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A few links to sites on extrasolar planets

Explore the EU Research and Training Network , in which we participate.

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Theoretical  research on astrophysics of solar and extrasolar planetary systems
by the following group of 7 members, and 3 former associates

Reprints and presentations:

Edgar & Artymowicz     Pumping of a planetesimal disc by a rapidly migrating planet (link to ADS database) (or .PDF, 0.1 MB)	Edgar R. & Artymowicz P., 2004, MNRAS, 354, 769-772
P. Artymowicz     "Migration Type III" (Multimedia: slides, animations, video/audio)	Presentation at the Santa Barbara Program on Planet Formation, KITP, UCSB, 2004
Martin Thörnqvist     Disk-Planet Interaction During the Formation of Planetary Systems (5 MB PDF file)	Master thesis, Dept. Astr. UU, 2004
Artymowicz, "Dynamics of protostellar disks with planets"  in  PDF (0.2 MB, requires Adobe Acrobat reader) Alternative format: compressed Postscript (.ps.gz, 0.9 MB) , 13-page review.	DEBRIS DISKS AND THE FORMATION OF PLANETS: A symposium in memory of Fred Gillett, Tucson, AZ, April 2002,  published in: ASP Vol. CS-324, 2004.
Artymowicz, P. Growth and interaction of planets (0.2 MB   PDF file)	Planetary Systems in the Universe:  Observation, Formation and Evolution,  IAU Symp. 202 Eds.: A. Penny, P.Artymowicz, A.-M.Lagrange, and S. Russell, (2004) ASP Vol.
Ghanjah Skanby-Mansour     Dynamical simulation of beta Pictoris dust: Implications for the amount of gas in the disk. (1 MB PDF file)	Master thesis, Dept. Astr. SU, 2003
Anders Jeneskog "External perturbations and the structure of the beta Pictoris disk"    (1.8MB   .ps.gz file)	BSc thesis = examensarbete  (Stockholm U., Apr. 2001)
Takeuchi and Artymowicz   Dust Migration and Morphology in Optically Thin Circumstellar Gas Disks (link to ADS database) (or .PDF, 0.5 MB)	ApJ,  2001, 557, 990-1006
Artymowicz, P. Beta Pictoris and Other Solar Systems (0.26 MB PDF file)	18-page review in  Space Science Review, Vol. 92, 2000, pp. 69-86.
Artymowicz, "The frightening mobility and the prospect of survival of giant extrasolar protoplanets in disks"	paper at conf. "Scientific Frontiers in Research on Extrasolar Planets" in Washington D.C. 2002
Lubow, S., Seibert, M., Artymowicz, P., "Disk Accretion onto High-Mass Planets"  in  PDF (1.1 MB PDF file)	ApJ, 1999, 526, pp. 1001-1012.

The group collaborates with specialists from Europe and the U.S., as well as locally with the IR/star formation group focusing on observations. We we form one of the 8 nodes of the European Union "Planet formation" network, comprising a few dozens of researchers throughout Europe.

Here is a fragment of the 2000 evaluation of Swedish Astronomy and Astrophysics by an
international committee, containing the evaluation of our research funded by NFR (now VR) foundation
 

If you are interested in this kind of research, please contact us (Artymowicz, Thebault) regarding a possible visit.

Sample Research Projects:

Vega-type systems including Beta Pictoris. Vega-type systems are main-sequence stars emitting much more far-infrared radiation than they should as stars. This is heat radiated by dust grains orbiting probably virtually all normal stars (about 20% of nearby stars produce IR excess detectable by ISO satellite).

Pawel's work on the structure of dusty disks, as well as dust mineralogy and physical processing, supports the view that they are all planetary systems. They may either be similar to the very young solar system (HR4796A, age 10 Myr), a young solar system Beta Pictoris (likely age 30-100 Myr; request a hardcopy of an Annual Review of Earth and Planetary Sci. article on this system from pawel@astro.su.se), or older planetary systems including systems such as Vega, Fomalhaut (ages 200 Myr - 1 Gyr) and Epsilon Eridani (3 Gyr?).
An analysis of HST/STIS images of Beta Pictoris is available.
The work of Takeuchi and Artymowicz  shows the possibility of vigorous migration of dust in transitional-type (~10 Myr old) disks, explaining their striking ring-and-gap morphology.
 
Giant planet formation and interaction with a protoplanetary disk.

This research addresses questions raised by the recent discovery of extrasolar planets. Pawel co-developed a theory of orbital eccentricity generation by surrounding disks for massive planets exceeding approximately 10 Jupiter masses (in the specific, standard model of the solar nebula disk). Several years later, massive exoplanets with such properties were first discovered. Other explanations of orbital ellipticity exist, yet this theory explains best the emerging empirical correlation of masses and eccentricities of exoplanets.
Another important issue is how such massive exoplanets form in the first place, and why Jupiter did not grow bigger.
You can read more about these issues in a WWW presentation , or jump into some preliminary results of hydrodynamical calculations using PPM (piecewise parabolic method, a hi-res shock-capturing scheme).
 
Upsilon Andromedae

Using Hydra (cf. below) as a cluster of workstations (concurrent but not parallel) we followed eight slightly different 2-planet systems (like ups And, but with the innermost planet smeared into a ring) for about than 3 billion orbits of the "ups And c" component. We did accurate, full N-body simulations of this multiple-planet system. It took a couple of months to get this far, until a (rare) 0.5-second power outage terminated the runs at about the intended moment.
The results are very interesting, many systems are remarkably robust and stable despite frequent rather close approaches between planets, and what other researchers recently suggested. We have some cases where 2 planets' lines of apsides follow one another for 2 Gyr(!) to within a few degrees and don't change the eccentricities secularly. Analytical theory of secular resonance of apsidal motions agrees with the N-body results.
 
 
Multidimensional hydrodynamics of disks with planets & planet mobility

Using Antares (cf. below) we are beginning to compute high-resolution models of disks with embedded protoplanets. Our planets undergo rapid migration of new type (faster than type I or type II), also distinct physically from these two standard modes of migration. The migration involves unsuturated corotational torques and does not depend on disk viscosity. The rate varies slowly with mass (in contrast to standard migration), and the direction depends sensitively on initial disk surface density gradients, precise location of the planet, mass of the disk etc. We are writing up our first results, cf. also our link (above) to a conference paper from the Gillett Symposium, Tucson, AZ, 2002.

See the description of a test problem for hydrodanamical codes calculating disk+planet interaction: original test, or a new page with results.
 
 
 

COMPUTING:

Supercomputers are to theorists what large optically linked telescopes are to observers. An indispennsable & powerful tool, but with some limitations of course.

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Antares (info & slide show): Our group's cute mini-supercomputer (20 cpu's) is online since mid-2002. Currently busy simulating the mobility of planets in disks, and dust disks.  

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Hydra (info & slide show): Our venerable first supercomputer (8 cpu's)  is online since early 1999. It has studied the formation/evolution of planets and modeled Beta Pic-type disk in parallel mode. Now largely of historical interest as a parallel computer, but still serving well as workstations! 

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