RX J1856.5-3754

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RX J1856.5-3754
RX J1856.5-3754.jpg
X-ray image of RX J1856.5-3754
Observation data
Epoch 1996.7      Equinox J2000.0[1]
Constellation Corona Australis
Right ascension 18h 56m 35s [1]
Declination −37° 54′ 36″[1]
Apparent magnitude (V) ~25.6[1]
Mass 0.9 M
Radius 1.9–4.1 km
Age 1 million years
Other designations
RX J185635-3754, 1ES 1853-37.9, 1RXS J185635.1-375433
Database references

RX J1856.5-3754 (also called RX J185635-3754, RX J185635-375, and various other designations) is a nearby neutron star in the constellation Corona Australis. It is believed to have been created by a supernova explosion of its companion star about one million years ago and is moving at 108 km/s across the sky. It was discovered in 1992, and observations in 1996 appeared to confirm that it was a neutron star, the closest neutron star to Earth yet discovered[citation needed].

It was originally thought to be about 150–200 light-years away, but further observations[by whom?] using the Chandra X-ray Observatory in 2002 appear to show that its distance is greater—about 400 light-years.

RX J1856 is one of the Magnificent Seven, a group of young neutron stars at distances between 200 and 500 parsecs (652 and 1630 light years) of Earth.

Quark star?[edit]

By combining Chandra X-ray Observatory and Hubble Space Telescope data, astronomers previously estimated that RX J1856 radiates like a solid body with a temperature of 700,000 °C and has a diameter of about 4–8 km. This estimated size was too small to reconcile with the standard models of neutron stars, therefore it was suggested that it might be a quark star.[2] (See also 3C 58.)

However, later refined analysis[by whom?] of improved Chandra and Hubble observations revealed that the surface temperature of the star is lower, only 434,000 °C, and respectively the radius is larger, about 14 km (with account of the effects of general relativity, the observed radius appears about 17 km).[3] Thus, RX J1856.5-3754 is now excluded from the list of quark star candidates.[4]


  1. ^ a b c d RX J185635-3754 - an Isolated Neutron Star, F. M. Walter, web page at the Department of Physics and Astronomy, State University of New York at Stony Brook. Accessed on line June 29, 2007.
  2. ^ Drake J. J. et al. (2002). "Is RX J1856.5-3754 a Quark Star?". Astrophys. J. 572 (2): 996–1001. arXiv:astro-ph/0204159. Bibcode:2002ApJ...572..996D. doi:10.1086/340368. 
  3. ^ Ho W. C. G. et al. (2007). "Magnetic hydrogen atmosphere models and the neutron star RX J1856.5–3754". Monthly Notices of the Royal Astronomical Society 375 (2): 821–830. arXiv:astro-ph/0612145v1. Bibcode:2007MNRAS.375..821H. doi:10.1111/j.1365-2966.2006.11376.x. 
  4. ^ Truemper, J. E.; Burwitz, V.; Haberl, F.; Zavlin, V. E. (June 2004). "The puzzles of RX J1856.5-3754: neutron star or quark star?". Nuclear Physics B Proceedings Supplements 132: 560–565. arXiv:astro-ph/0312600. Bibcode:2004NuPhS.132..560T. doi:10.1016/j.nuclphysbps.2004.04.094. 

External links[edit]