the university of texas at austin - astronomy program  
home dept of astronomy mcdonald observatory research hobby-eberly telescope directory university of texas  
department of astronomy
mcdonald observatory
hobby-eberly telescope
university of texas
Department of Astronomy


Faculty Office Hours


Weekly Seminar


Péridier Library

Public Outreach

Graduate Program

Admissions Information

Current Graduate Students

Graduate Awards

Undergraduate Program

Astronomy Honors Program

Career Services

Astronomy Students Association

College of Natural Sciences


University Course Schedule
Prediction and Confirmation of 'Magnetars' Wins UT Scientist and Colleagues Rossi Prize
17 February 2003
Austin, TX --The 2003 Rossi Prize of the High Energy Astrophysics Division of the American Astronomical Society is awarded to Robert Duncan and Christopher Thompson for their prediction, and to Chryssa Kouveliotou for her observational confirmation, of the existence of magnetars: neutron stars with extraordinarily strong magnetic fields. The prize is awarded annually for a significant contribution to High Energy Astrophysics, with particular emphasis on recent, original work.

The work explains the mystery associated with soft gamma repeaters (SGR's), neutron stars that emit regular, powerful bursts in the gamma ray spectrum, and anomalous x-ray pulsars (AXP's), neutron stars with slow rotation periods, which suggest they are old, yet are associated with young supernova remnants.

Neutron stars are created when normal but massive stars expend their fuel and collapse in supernova. One analogy compares the process to compressing a battleship into the head of a pin. A common type of neutron star is a radio pulsar, which emits beams of radio waves, like a lighthouse, as it spins at phenomenal speed.

Robert Duncan of the University of Texas at Austin and Christopher Thompson of the Canadian Institute for Theoretical Astrophysics in Toronto were attempting to explain the origin of magnetic fields in radio pulsars when they first developed the theory of magnetars in 1992.

They suggested, to widespread skepticism, that neutron stars could develop extraordinary magnetic fields under certain conditions—rapid enough spin, and convection, the internal roiling movement of hot, atomic liquid inside a pulsar (1014 times more dense than liquid water on earth). This convection dynamo is the same process thought to generate earth's weak magnetic field.

R e l a t e d

Bruno Rossi Prize

Astronomy Picture of the
Day, September 1, 2001

Nasa Press Release:
March 5, 1999

Happy birthday, Magnetars

From UT Astronomy:

'Magnetars', Soft Gamma
Repeaters & Very Strong
Magnetic Fields

-Robert Duncan


If confirmed, the magnetic fields Duncan and Thompson calculated would be the strongest generated by known objects in the universe, and perhaps 1,000 times stronger than the fields in most radio pulsars. (Attempting such fields experimentally on earth would blow apart the electromagnet!)

Such strong magnetic fields would cause neutron stars to behave in specific ways. The predicted behavior of magnetars ultimately led to confirmation of the model, by way of explaining some other mysterious events occurring in the sky.

The Burst of March 5, 1979

In March of 1979, ten spacecraft in our solar system registered a burst of gamma radiation 100 times more powerful than any previously detected, as much energy as the sun releases in roughly 10,000 years. It lasted two tenths of a second, and was followed by a glow of gamma rays and x-rays, fading and pulsing at 8 second intervals for another three minutes. 14 ½ hours later another fainter burst occured. And over the next 4 years, 16 bursts, all coming from the same place.

Astronomers had seen nothing like this. Unlike the more familiar gamma ray bursts, it repeated. (Subsequent detections were eventually dubbed soft gamma repeaters, or SGR's).

Triangulating from the position of the spacecraft, astronomers pinpointed the origin of the March burst, a supernova remnant in the Large Magellanic Cloud, a neighboring galaxy.

Supernova remnants are often associated with radio pulsars. But the apparant rotation of this object was too slow, at 8 seconds, and it was emitting waves more energetic than radio, in the x-ray and gamma range.

As the theoretical magnetar model developed, it accounted for the apparant spin rate of the 1979 SGR. Neutron stars are known to spin down. A stronger magnetic field would slow the spin considerably faster.

The model would also account for the energy. A feature unique to neutron stars is that they have a crust. Ultra strong magnetic fields generated within a magnetar could cause the crust to bend and shift, a starquake, and occasionally break, creating a cloud of electrons and positrons and soft gamma rays, of the kind and strength observed as SGR's.

Chryssa Kouveliotou of the Universities Space Research Association with the help of observations made at the Institute of Space and Astronautical Science in Japan confirmed the spin down rate of SGR 1806-20 to be nearly 2 parts in 1,000 over five years, suggesting a rate higher than any known radio pulsar and indicative of a magnetic field in agreement with the magnetar model of 1015 gauss.

more news..

21 February 2003
Astronomy Program · The University of Texas at Austin · Austin, Texas 78712
prospective student inquiries:
site comments: