Sirius

== Sirius== Sirius  is the   brightest star  in the night sky. With a visual   apparent magnitude  of −1.46, it is almost twice as bright as   Canopus, the next brightest   star. The name "Sirius" is derived from the   Ancient Greek: Σείριος   Seirios  <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">("glowing" or "scorcher"). The star has the <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  Bayer designation<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  Alpha<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  Canis Majoris<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;">(α CMa). What the naked eye perceives as a single star is actually a <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  binary star<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;">system, consisting of a white <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  main-sequence<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;">star of <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  spectral type<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;">A1V, termed <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  Sirius A<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">, and a faint <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  white dwarf<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;">companion of spectral type DA2, called <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  Sirius B<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">. The distance separating Sirius A from its companion varies between 8.1 and 31.5 <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  AU<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">. <sup class="reference" id="cite_ref-Schaaf2008_21-0" style="color:rgb(0,0,0);font-family:sans-serif;line-height:1em;">[18]

<p style="margin-top:0.4em;margin-bottom:0.5em;line-height:19.1875px;color:rgb(0,0,0);font-family:sans-serif;">Sirius appears bright because of both its intrinsic luminosity and its proximity to Earth. At a distance of 2.6 parsecs (8.6 ly), as determined by theHipparcos astrometry satellite,<sup class="reference" id="cite_ref-aaa474_2_653_6-1" style="line-height:1em;">[5] <sup class="reference" id="cite_ref-aaa323_L49_22-0" style="line-height:1em;">[19] <sup class="reference" id="cite_ref-GSM_23-0" style="line-height:1em;">[20]  the Sirius system is one of Earth's near neighbors; for Northern-hemisphere observers between 30 degrees and 73 degrees of latitude (including almost all of Europe and North America), it is the closest star (after the Sun) that can be seen with a naked eye. Sirius is gradually moving closer to the Solar System, so it will slightly increase in brightness over the next 60,000 years. After that time its distance will begin to recede, but it will continue to be the brightest star in the Earth's sky for the next 210,000 years.<sup class="reference" id="cite_ref-24" style="line-height:1em;">[21]

<p style="margin-top:0.4em;margin-bottom:0.5em;line-height:19.1875px;color:rgb(0,0,0);font-family:sans-serif;">Sirius A is about twice as massive as the Sun and has an absolute visual magnitude of 1.42. It is 25 times more luminous than the Sun<sup class="reference" id="cite_ref-Liebert2005_9-6" style="line-height:1em;">[7]  but has a significantly lower luminosity than other bright stars such as Canopus or Rigel. The system is between 200 and  300 million  years old.<sup class="reference" id="cite_ref-Liebert2005_9-7" style="line-height:1em;">[7]  It was originally composed of two bright bluish stars. The more massive of these, Sirius B, consumed its resources and became a red giant before shedding its outer layers and collapsing into its current state as a white dwarf around  120 million  years ago.<sup class="reference" id="cite_ref-Liebert2005_9-8" style="line-height:1em;">[7]

<p style="margin-top:0.4em;margin-bottom:0.5em;line-height:19.1875px;color:rgb(0,0,0);font-family:sans-serif;">Sirius is also known colloquially as the "Dog Star", reflecting its prominence in its constellation, Canis Major (Greater Dog).<sup class="reference" id="cite_ref-Allen1899_15-1" style="line-height:1em;">[12]  The heliacal rising of Sirius marked the flooding of the Nile in Ancient Egypt and the "dog days" of summer for the ancient Greeks, while to the Polynesians it marked winter and was an important star for navigation around the Pacific Ocean.