RX J1856.5-3754

RX J1856 - 3754, RX J1856 or even RXJ1856.5 - 3754, the us closest known neutron star. He stands in the constellation Corona Australis at 18h 56m 35s ( right ascension ) and -37 ° 54 ' 36 "( declination ) and illuminated with an apparent brightness of about 25m. He was discovered in 1992. According to recent observations, he is about 500 light years away from us and moves relatively at a speed of about 100 km / s to the solar system.

RX J1856 is the brightest neutron star from the group of so-called Magnificent Seven (English magnificent seven ). With a temperature of about 700,000 degrees C, they are so hot that they emit thermally excited gamma rays. Long-wave ( non-thermal ) radio waves are not detectable.

Only in 2007 could be detected for RX J1856 a self-rotation of 7 seconds. He has a mass of about 1.4 solar masses. The seemingly small diameter of less than 11 km was interpreted as an indication of a so-called quark star, later measurements have shown, however, that in this star shine only the polar caps. So he has a much larger diameter than 11 km and is thus no longer a candidate for a quark star.


  • Individual star fifth size and darker
  • Southern crown