The composite image on the left shows an image from NASA's Chandra X-ray Observatory in purple and an optical image from the European Southern Observatory's Very Large Telescope (VLT) in red, blue and white. The Chandra source in the center of the image is the ancient pulsar PSR J0108-1431 (J0108 for short), located only 770 light years from us. The elongated object immediately to its upper right is a background galaxy that is unrelated to the pulsar. Since J0108 is located a long way from the plane of our galaxy, many distant galaxies are visible in the larger-scale optical image.
The position of the pulsar seen by Chandra in this image from early 2007 is slightly different from the radio position observed in early 2001, implying that the pulsar is moving at a velocity of about 440,000 miles per hour, in the direction shown by the white arrow. The detection of this motion allowed an estimate of where J0108 should be located in the VLT image taken in 2000. The faint blue star just above the galaxy is a possible optical detection of the pulsar.
The artist's impression on the right shows what J0108 might look like if viewed up close. Radiation from particles spiraling around magnetic fields is shown along with heated areas around the neutron star's magnetic poles. Both of these effects are expected to generate X-ray emission. Most of the surface of the neutron star is expected to be too cool to produce X-rays, but it should produce optical and ultraviolet radiation. Thus, multiwavelength observations are important for providing a complete picture of these exotic objects.
At an age of about 200 million years, this pulsar is the oldest isolated pulsar ever detected in X-rays. Among isolated pulsars - ones that have not been spun-up in a binary system - it is over 10 times older than the previous record holder with an X-ray detection. This pulsar is slowing down as it ages and converting some of the energy that is being lost into X-rays. The efficiency of this process for J0108 is found to be higher than for any other known pulsar.
The oldest isolated pulsar ever detected in X-rays has been found with NASA's Chandra X-ray Observatory.This very old and exotic object turns out to be surprisingly active.
Discovery of PSR J0108-1431, the closest known neutron star
T. M. Tauris (Institute of Physics and Astronomy, Aarhus University, Denmark),
L. Nicastro (IRA - CNR, Bologna, Italy),
S. Johnston (RCfTA, University of Sydney, Australia),
M. Bailes (ATNF, CSIRO, Australia),
R. N. Manchester (ATNF, CSIRO, Australia),
A. G. Lyne (NRAL, Jodrell Bank, University of Manchester, UK),
N. D'Amico (University of Palermo and IRA - CNR, Bologna, Italy),
J. Glowacki (Parkes Observatory, ATNF, CSIRO, Australia),
J. F. Bell (MSSSO, Australian National University, Australia),
D. R. Lorimer (NRAL, Jodrell Bank, University of Manchester, UK),
P. A. Harrison (NRAL, Jodrell Bank, University of Manchester, UK)
(1994) ApJ, 428, L53-55
There are about 600 known radio pulsars in our Galaxy, typically at distances of a few kpc, as indicated by the amount of dispersion of the pulses in the ionized component of the interstellar medium. Here we report the discovery of PSR J0108-1431, a pulsar which has the lowest known dispersion measure, 1.83 pc cm^-3. Reasonable models of the interstellar electron density distribution indicate that its distance is less than 100 pc, making it the closest known radio pulsar and probably the closest known neutron star. Furthermore this pulsar has the lowest radio luminosity of any known pulsar by more than an order of magnitude. Such a weak pulsar in the solar neighbourhood implies a large population of active but low-luminosity pulsars in the galactic halo. X-ray observations of PSR J0108-1431 may determine whether or not there is significant decay of the surface magnetic field in isolated neutron stars and distinguish between different cooling and heating models.