Press Release

Neutron Start Neutrinos Detectable at South Pole, Northeastern University Scientists Find

By SpaceRef Editor
February 13, 2003
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BOSTON, Mass. Neutron stars, long revered as physics laboratories in space
because of the insights they provide into the nature of matter and energy,
may be sources of neutrinos, exotic elementary particles that rarely
interact with other matter. One South Pole neutrino catcher called IceCube
may be the first to detect these neutron star neutrinos, according to a team
led by Luis Anchordoqui of Northeastern University in Boston.

Neutron stars are the virtually invisible, 10-mile-wide core remains of a
once massive star, often residing in binary star systems. Penetrating
neutrinos could provide valuable, new information about how neutron stars
evolve, because they can plow through the dust and gas surrounding the
commotion of neutron star activity that often blocks light, Anchordoqui

“Neutrinos can offer brand new information about how neutron stars work,”
said Anchordoqui. “Neutrinos from the Sun confirmed the theory of nuclear
fusion, a discovery recognized this past year by the Nobel Prize committee.
Neutrino astronomy is in its infancy, with great results soon to come.”

Anchordoqui and his colleagues discuss the expected neutrino output from a
well-studied source named A0535+26 and an Antarctic neutrino detector
IceCube in the upcoming May 20, 2003, edition of the Astrophysical Journal.
Co-authors include Diego Torres of Lawrence Livermore National Laboratory,
Thomas McCauley of Northeastern, Gustavo Romero of Instituto Argentino de
Radioastronomia, and Felix Aharonian of Max Planck Institut fuer Kernphysik.

Neutrinos are elementary particles similar to electrons but with no
electrical charge and very little mass. Neutrinos hardly interact with
matter and could pass through billions of miles of lead untouched. Thus,
neutrinos are hard to detect yet plump with information about their source.

A neutron star is the core remains of a star at least eight times as massive
as the Sun. After exhausting its nuclear fuel, such a star blows off much of
its mass, an event called a supernova. The core, still containing about the
mass of the Sun, collapses to a sphere no wider than Boston.

Although they are but tiny chunks located thousands of light years from
Earth, neutron stars are often visible when residing in binary star systems.
The stars’ orbit periodically brings them closer together, to a point where
the strong gravity from the neutron star can steal gas from the companion.
The transfer of gas onto the neutron star, called accretion, is a turbulent
event that shines brightly. Some neutron stars cannibalize gas from their
companions and often devour them completely over the course of million of

Neutrinos are produced by protons (hydrogen gas stripped of electrons)
whipped to velocities close to light speed by the neutron star magnetic
field, according to the new calculations. The magnetic field is 10^12 (a
trillion) times stronger than our Sun’s field. While gas and dust block
much of the light from exiting this scene, shielding our view of the details
of the binary system, neutrinos escape largely unscathed.

Diego Torres said that an Antarctic neutrino detector called IceCube, now
under construction, could observe how an accretion disk in A0535+26
periodically forms and disappears as the two stars orbit each other.
IceCube is an international, cubic-kilometer neutrino detector built in the
clear, deep ice of the South Pole. IceCube attempts to catch neutrinos as
they enter and pass entirely through the Earth from the North Pole.

“The neutrinos from A0535+26 would overwhelm those from any other neutron
star system we know,” Torres said. “A0535+26 is also a periodic source, and
it just may be the brightest observable source of sub-TeV-energy neutrinos.
Someday in the near future, we could do multi-wavelength-particle astronomy
and reconstruct the formation and loss of the accretion disc by combining
observations in X rays, gamma rays, and neutrinos.”

Furthermore, detection of neutrinos automatically implies that the origin of
high-energy radiation is hadronic in nature (protons accelerated up to
hundreds of TeVs.)

The team suggests that the A0535+26 could be just the tip of the iceberg for
IceCube. Neutrinos might also be produced inside a neutron star core.
Detection of this type of neutrino would be tantamount to sampling matter in
a neutron star, a paramount achievement that would at long last reveal the
nature of the neutron star interior and the physics of matter under extreme

A neutrino from the core of A0535+26’s neutron star would be coming from the
same direction yet of a different energy, thus distinguishable from other

The team’s upcoming journal article is now available on line at For more information and images
of the IceCube detector, refer to

SpaceRef staff editor.