Alar Toomre (born 5 February 1937 in Rakvere) is an Estonian-American astronomer and mathematician. He is a professor of applied mathematics at the Massachusetts Institute of Technology. Toomre's research is focused on the dynamics of galaxies.
Following the Soviet occupation of Estonia in 1944, Toomre and his family fled to Germany; they emigrated to the United States in 1949. He received an undergraduate degree in Aeronautical Engineering and Physics from MIT in 1957 and then studied at the University of Manchester on a Marshall Scholarship where he obtained a Ph.D. in fluid mechanics.
Toomre returned to MIT to teach after completing his Ph.D. and remained there for two years. After spending a year at the Institute for Advanced Studies, he returned again to MIT as part of the faculty, where he stayed. Toomre was appointed an Associate Professor of Mathematics at MIT in 1965, and Professor in 1970.
In 1964, Toomre devised a local gravitational stability criterion for differentially rotating disks. It is known as the Toomre stability criterion, which is usually measured by a parameter denoted as Q. The Q parameter measures the relative importance of vorticity and internal velocity dispersion (large values of which stabilise) versus the disk surface density (large values of which destabilise). The parameter is constructed so that Q<1 implies instability.
Toomre collaborated with Peter Goldreich in 1969 on the subject of polar wander, developing the theory of polar wander. Whether true polar wander has been observed on earth, or apparent polar wander is accountable for all the observations of paleomagnetism remains a controversial issue.
Toomre conducted the first computer simulations of galaxy mergers in the 1970s with his brother Jüri, an astrophysicist and solar physicist. Although the small number of particles in the simulations obscured many processes in galactic collisions, Toomre and Toomre were able to identify tidal tails in his simulations, similar to those seen in the Antennae Galaxies and the Mice. The brothers attempted to reproduce specific galaxy mergers in their simulations, and it was their reproduction of the Antennae galaxies that gave them the greatest pleasure. In 1977 Toomre suggested that elliptical galaxies are the remnants of the major mergers of spiral galaxies. He further showed that based on the local galaxy merger rate, over a Hubble time the observed number of elliptical galaxies are produced if the universe begins with only spiral galaxies. This idea remained controversial and widely debated for some time.
From this work, the Toomre brothers identified the process of collision evolution as the Toomre sequence. The sequence begins with two well separated spiral galaxies and follows them through collisional disruption until they settle into a single elliptical galaxy.
Awards and honors
- The John D. & Catherine T. MacArthur Foundation. "MacArthur Fellows November 1984". Retrieved 2007-05-18.
- David B. Oberman (November 16, 1984). "Toomre Awarded MacArthur Grant" (PDF). The Tech. p. 1. Retrieved 2007-05-18.
- "SDSC SIMULATION SHOWS COLLISION WITH ANDROMEDA". HPC Wire. December 5, 2000. Archived from the original on 2007-09-28.
- "Dormcon Prexy Vote Thursday Joe Bowers '57 Only Candidate" (PDF). The Tech. February 26, 1956. p. 6. Retrieved 2007-05-18.
- "Alar Toomre, Course XVI Senior, To Receive Marshall Scholarship" (PDF). April 9, 1957. p. 6. Retrieved 2007-05-18.
- "Toomre Receives MacArthur Award" (PDF). The Tech. November 16, 1984. p. 22. Retrieved 2007-05-18.
- "MIT Faculty Home page.". Retrieved 2011-01-16.
- Tim Palucka. "Star Maker Machinery". HPC wire. Archived from the original on 2007-09-28. Retrieved 2007-05-18.
- James Binney & Scott Tremaine (1994) . Jeremiah Ostriker, ed. Galactic Dynamics. Princeton, New Jersey: Princeton University Press. p. 363. ISBN 0-691-08445-9.
- Richard A. Kerr (January 21, 2000). "Did the Dinosaurs Live on a Topsy-Turvy Earth?". Science. 287 (5452): 406–407. doi:10.1126/science.287.5452.406. Retrieved 2007-05-18.
- V. Courtillot (Fall 2004). "A Short Review of True Polar Wander". American Geophysical Union. American Geophysical Union. 31: 08. Bibcode:2004AGUFM.U31B..08C. abstract #U31B-08
- "Toomre and the first models". Science Notes University of Santa Cruz. Summer 1997. Retrieved 2007-05-18.
- Karen Hartley (April 8, 1989). "Mixing it up in space: astronomers debate the role mergers play in galaxy formation". Science News. Retrieved 2007-05-18.
- "Hubble Reveals Stellar Fireworks Accompanying Galaxy Collisions". Space Telescope Science Institute. October 21, 1997. Archived from the original on 20 April 2007. Retrieved 2007-05-18.
- "The Mice at Play". National Radio Astronomy Observatory. May 1, 2002.
- Michael Shara (February 2000). "Cannibals of the Cosmos - much more has become known about galaxies, since Edwin Hubble confirmed their existence in 1925". Natural History. Retrieved 2007-05-18.
- Alar Toomre & Jüri Toomre (1972). "Galactic Tails and Bridges". The Astrophysical Journal. 178: 623–666. Bibcode:1972ApJ...178..623T. doi:10.1086/151823.
- "Merger Remnants and Elliptical Galaxies".
- "Peering Far Back in Time to Uncover the Secrets of Galaxy Evolution". European Space Agency. December 1, 1992. Retrieved 2007-05-18.
- Michael J. West (December 1997). "THE GALAXY-CLUSTER-SUPERCLUSTER CONNECTION". Canadian Astronomical Society/Société Canadienne D'Astronomie Cassiopeia.
- Robert Joseph (Fall 2004). "Merging Spiral Galaxies Create Ellipticals". Nã Kilo Hõkũ. Retrieved 2007-05-18.
- Curtis Struck (1999). "Galaxy Collisions". Physics Reports. Physics Reports. 321: 1–137. arXiv: . Bibcode:1999PhR...321....1S. doi:10.1016/S0370-1573(99)00030-7.
- "Toomre Sequence". Cosmos: The Swinburne Astronomy Online Encyclopedia. Retrieved 2007-05-18.
- Laine, S.; van der Marel, R. P.; Böker, T.; Mihos, J. C.; Hibbard, J. E.; Zabludoff, A. I. (2000). "HST Observations of the Nuclear Regions of the Toomre Sequence of Merging Galaxies". The Central Kiloparsec of Starbursts and AGN: the La Palma Connection, ASP Conference Proceedings. San Francisco, Calif.: Astronomical Soc. of the Pacific. 249: 179. arXiv: . Bibcode:2001ASPC..249..179L. ISBN 1-58381-089-7.
- W. van Driel - Yu Gao - D. Monnier-Ragaigne (2001). "HI line observations of luminous infrared galaxy mergers". Astronomy and Astrophysics. 368 (1): 64–73. arXiv: . Bibcode:2001A&A...368...64V. doi:10.1051/0004-6361:20000509. Archived from the original on 2007-09-27. Retrieved 2007-05-18.
- "AAS Division on Dynamical Astronomy Newsletter 75". American Astronomical Society Division on Dynamical Astronomy. October 1993. Archived from the original on 2 July 2007. Retrieved 2007-05-18.
- "The DDA/AAS Brouwer Award". American Astronomical Society/Division on Dynamical Astronomy. Archived from the original on 13 May 2007. Retrieved 2007-05-18.
- Elizabeth A. Thomson (September 28, 2004). "MacArthur 'genius' grants go to four from MIT". MIT news office. Retrieved 2007-05-18.