Alar Toomre (born 5 February 1937, in
Rakvere
Rakvere is a town in northern Estonia and the administrative centre of the Lääne-Viru ''maakond'' (county), 20 km south of the Gulf of Finland of the Baltic Sea. Rakvere is the 8th most populous urban area in Estonia. Rakvere has a tota ...
) is an American
astronomer
An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, natural satellite, moons, comets and galaxy, g ...
and
mathematician
A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems.
Mathematicians are concerned with numbers, data, quantity, structure, space, models, and change.
History
On ...
.
He is a professor of
applied mathematics
Applied mathematics is the application of mathematical methods by different fields such as physics, engineering, medicine, biology, finance, business, computer science, and industry. Thus, applied mathematics is a combination of mathematical s ...
at the
Massachusetts Institute of Technology
The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of the ...
. Toomre's research is focused on the dynamics of
galaxies
A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. ...
. He is a
1984 MacArthur Fellow.
Career
Following the
Soviet occupation of Estonia
The Estonian SSR,, russian: Эстонская ССР officially the Estonian Soviet Socialist Republic,, russian: Эстонская Советская Социалистическая Республика was an ethnically based adminis ...
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
, mottoeng = Knowledge, Wisdom, Humanity
, established = 2004 – University of Manchester Predecessor institutions: 1956 – UMIST (as university college; university 1994) 1904 – Victoria University of Manchester 1880 – Victoria Univer ...
on a
Marshall Scholarship
The Marshall Scholarship is a postgraduate scholarship for "intellectually distinguished young Americans ndtheir country's future leaders" to study at any university in the United Kingdom. It is widely considered one of the most prestigious sc ...
where he obtained a Ph.D. in
fluid mechanics
Fluid mechanics is the branch of physics concerned with the mechanics of fluids ( liquids, gases, and plasmas) and the forces on them.
It has applications in a wide range of disciplines, including mechanical, aerospace, civil, chemical and bio ...
.
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 Study
The Institute for Advanced Study (IAS), located in Princeton, New Jersey, in the United States, is an independent center for theoretical research and intellectual inquiry. It has served as the academic home of internationally preeminent scholar ...
,
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.
Scientific accomplishments
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
Peter Goldreich (born July 14, 1939) is an American astrophysicist whose research focuses on celestial mechanics, planetary rings, helioseismology and neutron stars. He is the Lee DuBridge Professor of Astrophysics and Planetary Physics at Cal ...
in 1969 on the subject of
polar wander Polar wander is the motion of a pole in relation to some reference frame. It can be used, for example, to measure the degree to which Earth's magnetic poles have been observed to move relative to the Earth's rotation axis. It is also possible to use ...
, developing the theory of polar wander. Whether
true polar wander
True polar wander is a solid-body rotation of a planet or moon with respect to its spin axis, causing the geographic locations of the north and south poles to change, or "wander". Unless the body is totally rigid (which the Earth is not) its sta ...
has been observed on earth, or
apparent polar wander Apparent polar wander (APW) is the perceived movement of the Earth's paleo- magnetic poles relative to a continent while regarding the continent being studied as fixed in position. It is frequently displayed on the present latitude-longitude map as ...
is accountable for all the observations of
paleomagnetism
Paleomagnetism (or palaeomagnetismsee ), is the study of magnetic fields recorded in rocks, sediment, or archeological materials. Geophysicists who specialize in paleomagnetism are called ''paleomagnetists.''
Certain magnetic minerals in rock ...
remains a controversial issue.
Toomre conducted the first computer
simulations
A simulation is the imitation of the operation of a real-world process or system over time. Simulations require the use of models; the model represents the key characteristics or behaviors of the selected system or process, whereas the s ...
of
galaxy merger
Galaxy mergers can occur when two (or more) galaxies collide. They are the most violent type of galaxy interaction. The gravitational interactions between galaxies and the friction between the gas and dust have major effects on the galaxies i ...
s 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 tail
A tidal tail is a thin, elongated region of stars and interstellar gas that extends into space from a galaxy. Tidal tails occur as a result of galactic tide forces between interacting galaxies. Examples of galaxies with tidal tails include the ...
s in his simulations, similar to those seen in the
Antennae Galaxies
The Antennae Galaxies (also known as NGC 4038/NGC 4039 or Caldwell 60/Caldwell 61) are a pair of interacting galaxy, interacting galaxies in the constellation Corvus (constellation), Corvus. They are currently going through a Starburst 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
An elliptical galaxy is a type of galaxy with an approximately ellipsoidal shape and a smooth, nearly featureless image. They are one of the four main classes of galaxy described by Edwin Hubble in his Hubble sequence and 1936 work ''The Real ...
are the remnants of the
major mergers of
spiral galaxies
Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his 1936 work ''The Realm of the Nebulae''[Hubble time
Hubble's law, also known as the Hubble–Lemaître law, is the observation in physical cosmology that galaxies are moving away from Earth at speeds proportional to their distance. In other words, the farther they are, the faster they are moving ...]
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 (as for the
Antennae) through collisional disruption until they settle into a single elliptical galaxy.
Awards and honors
In 1993, Toomre received the
Dirk Brouwer Award which recognizes "outstanding contributions to the field of Dynamical Astronomy".
Toomre was one of the 1984 recipients of the
MacArthur Fellowship
The MacArthur Fellows Program, also known as the MacArthur Fellowship and commonly but unofficially known as the "Genius Grant", is a prize awarded annually by the MacArthur Foundation, John D. and Catherine T. MacArthur Foundation typically to ...
, popularly known as the "Genius Grant".
Toomre was the recipient of the
Magellanic Premium
The Magellanic Premium, also known as the Magellanic Gold Medal and Magellanic Prize is awarded for major contributions in the field of navigation (whether by sea, air, or in space), astronomy, or natural philosophy.
The Premium was established ...
award in 2014 for his work in numerical galaxy simulations during the 1960s.
Two years later, he was elected to the
American Philosophical Society
The American Philosophical Society (APS), founded in 1743 in Philadelphia, is a scholarly organization that promotes knowledge in the sciences and humanities through research, professional meetings, publications, library resources, and communit ...
.
References
{{DEFAULTSORT:Toomre, Alar
1937 births
Living people
American astronomers
20th-century American mathematicians
21st-century American mathematicians
Alumni of the University of Manchester
MIT School of Engineering alumni
Massachusetts Institute of Technology School of Science faculty
MIT Department of Physics alumni
Members of the United States National Academy of Sciences
MacArthur Fellows
Estonian emigrants to the United States
Estonian World War II refugees
People from Rakvere
Marshall Scholars