Crab Nebula



=               Crab Nebula= The   Crab Nebula (catalogue designations   M1,   NGC  1952, Taurus A) is a   supernova remnant  and   pulsar wind nebula  in the   constellation  <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">of <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  Taurus<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">. The <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  nebula<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">was observed by <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  John Bevis<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">in 1731; it corresponds to a bright <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  supernova<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">recorded by <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  Arab<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">, <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  Chinese<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">and <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  Japanese<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">astronomers <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  in 1054<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">. At <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  X-ray<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">and <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  gamma-ray<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">energies above 30 <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  keV<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">, the Crab is generally the strongest persistent source in the sky, with measured flux extending to above 10 <sup style="color:rgb(0,0,0);font-family:sans-serif;line-height:1em;">12 <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  eV<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">. Located at a distance of about 6,500 <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  light-years<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">(2 <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  kpc<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">) from <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  Earth<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">, the <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  nebula<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">has a diameter of 11 light years (3.4 <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  pc<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">) and expands at a rate of about 1,500 kilometers per second<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">. It is part of the <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  Perseus Arm<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">of the <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  Milky Way Galaxy<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">.

<p style="margin-top:0.4em;margin-bottom:0.5em;line-height:19.1875px;color:rgb(0,0,0);font-family:sans-serif;">At the center of the nebula lies the Crab Pulsar, a neutron star (or spinning ball of neutrons), 28–30 km across,<sup class="reference" id="cite_ref-5" style="line-height:1em;">[5]  which emits pulses of radiation from gamma rays to radio waves with a spin rate of 30.2 times per second. The nebula was the first astronomical object identified with a historical supernova explosion.

<p style="margin-top:0.4em;margin-bottom:0.5em;line-height:19.1875px;color:rgb(0,0,0);font-family:sans-serif;">The nebula acts as a source of radiation for studying celestial bodies that occult it. In the 1950s and 1960s, the Sun's corona was mapped from observations of the Crab's radio waves passing through it, and in 2003, the thickness of the atmosphere of Saturn's moon Titan was measured as it blocked out X-rays from the nebula.

<p style="margin-top:0.4em;margin-bottom:0.5em;line-height:19.1875px;color:rgb(0,0,0);font-family:sans-serif;">The cloudy remnants of SN 1054 are now known as the Crab Nebula. The nebula is also referred to as Messier 1 or M1, being the first Messier Objectcatalogued in 1758.