Young and getting cooler -- the early life of a neutron star

April 15, 2010
Image of Cassiopeia A and an artist’s impression of the neutron star (Credit: NASA/CXC/Southampton/W. Ho et al.; Illustration: NASA/CXC/M.Weiss)

( -- Observations of how the youngest-known neutron star has cooled over the past decade are giving astronomers new insights into the interior of these super-dense dead stars. Dr Wynn Ho will present the findings on Thursday April 15th at the RAS National Astronomy Meeting in Glasgow.

Dr Ho, of the University of Southampton, and Dr Craig Heinke, of the University of Alberta in Canada, measured the temperature of the neutron star in the Cassiopeia A supernova remnant using data obtained by NASA’s Chandra X-ray Observatory between 2000 and 2009.

“This is the first time that astronomers have been able to watch a young neutron star cool steadily over time. Chandra has given us a snapshot of the temperature roughly every two years for the past decade and we have seen the temperature drop during that time by about 3%,” said Dr Ho.

Neutron stars are composed mostly of neutrons crushed together by gravity, compressed to over a million million times the density of lead. They are the dense cores of that have run out of nuclear fuel and collapsed in supernova explosions. The Cassiopeia A , likely to have taken place around 1680, would have heated the neutron star to temperatures of billions of degrees, from which it has cooled down to a temperature of about two million degrees Celsius.

“Young neutron stars cool through the emission of high-energy neutrinos - particles similar to photons but which do not interact much with normal matter and therefore are very difficult to detect. Since most of the neutrinos are produced deep inside the star, we can use the observed temperature changes to probe what’s going on in the neutron star’s core. The structure of neutron stars determines how they cool, so this discovery will allow us to understand better what are made of. Our observations of temperature variations already rule out some models for this cooling and has given us insights into the properties of matter that cannot be studied in laboratories on Earth,” said Dr Ho.

Initially, the core of the neutron star cools much more rapidly than the outer layers. After a few hundred years, equilibrium is reached and the whole interior cools at a uniform rate. At approximately 330 years old, the Cassiopeia A neutron star is near this cross-over age. If the cooling is only due to neutrino emission, there should be a steady decline in temperature. However, although

Dr Ho and Dr Heinke observed an overall steady trend over the 10 year period, there was a larger change around 2006 that suggests other processes may be active.

“The neutron star may not yet have relaxed into the steady cooling phase, or we could be seeing other processes going on. We don’t know whether the interior of a neutron star contains more exotic particles, such as quarks, or other states of matter, such as superfluids and superconductors. We hope that with more observations, we will be able to explain what is happening in the interior in much more detail,” said Dr Ho.

Dr Ho and Dr Heinke have submitted a paper on their discovery to the Astrophysical Journal.

Explore further: Deepest Image of Exploded Star Uncovers Bipolar Jets

Related Stories

Deepest Image of Exploded Star Uncovers Bipolar Jets

August 24, 2004

A spectacular new image of Cassiopeia A released today from NASA's Chandra X-ray Observatory has nearly 200 times more data than the "First Light" Chandra image of this object made five years ago. The new image reveals clues ...

Pulsar gives insight on ultra dense matter and magnetic fields

December 14, 2004

A long look at a young pulsar with NASA's Chandra X-ray Observatory revealed unexpectedly rapid cooling, which suggests that it contains much denser matter than previously expected. The pulsar's cool temperature and the vast ...

Astronomers discover fastest-spinning pulsar

January 12, 2006

A team of astronomers led by McGill University graduate student Jason Hessels has discovered the fastest-spinning neutron star, or pulsar, ever found. The 20-mile-diameter superdense pulsar, which at 716 revolutions per second ...

The case of the neutron star with a wayward wake

June 1, 2006

A long observation with NASA's Chandra X-ray Observatory revealed important new details of a neutron star that is spewing out a wake of high-energy particles as it races through space. The deduced location of the neutron ...

Carbon Atmosphere Discovered on Neutron Star

November 4, 2009

( -- Evidence for a thin veil of carbon has been found on the neutron star in the Cassiopeia A supernova remnant. This discovery, made with NASA's Chandra X-ray Observatory, resolves a ten-year mystery surrounding ...

Recommended for you

Cassini mission provides insight into Saturn

December 1, 2015

Scientists have found the first direct evidence for explosive releases of energy in Saturn's magnetic bubble using data from the Cassini spacecraft, a joint mission between NASA, the European Space Agency, and the Italian ...

Timing a sextuple quasar

December 1, 2015

Quasars are galaxies with massive black holes at their cores around which vast amounts of energy are being radiated. Indeed, so much light is emitted that the nucleus of a quasar is much brighter than the rest of the entire ...


Adjust slider to filter visible comments by rank

Display comments: newest first

1 / 5 (3) Apr 15, 2010
Neutron stars will remain an enigma until neutron repulsion is taken into consideration. For a simple illustration of this most powerful source of nuclear energy, see:


With kind regards,
Oliver K. Manuel
Emeritus Professor
Nuclear & Space Science
Former NASA Principal Investigator for Apollo
1 / 5 (3) Apr 19, 2010
You and me,
The elephant and the tree,
The valleys, hills, and sea
Are made of particles three
That all began as Nellie -
The Neutron.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.