IK Pegasi is a binary star system in the constellation Pegasus. A distance of about 150 light years from the Solar System, it is just luminous enough to be seen with the unaided eye. The primary (IK Pegasi A) is a main sequence, A-class star that displays minor pulsations in luminosity. It is categorized as a Delta Scuti variable star and it has a periodic cycle of luminosity variation that repeats itself about 22.9 times per day. Its companion (IK Pegasi B) is a massive white dwarf—a star that has evolved past the main sequence and is no longer generating energy through nuclear fusion. They orbit each other every 21.7 days with an average separation of about 31 million kilometres, or 0.21 astronomical units (AU). This is smaller than the orbit of Mercury around the Sun. IK Pegasi B is the nearest known supernova progenitor candidate. When the primary begins to evolve into a red giant, it is expected to grow to a radius where the white dwarf can accrete matter from the expanded gaseous envelope. When the white dwarf approaches the Chandrasekhar limit of 1.44 solar masses, it may explode as a Type Ia supernova. Read the rest of this article: http://en.wikipedia.org/wiki/IK_Pegasi _________________________ Today's selected anniversaries: 1346: King David II of Scotland led an invasion of England during the Hundred Years' War, but was captured in the Battle of Neville's Cross. (http://en.wikipedia.org/wiki/Battle_of_Neville%27s_Cross) 1448: Ottoman wars in Europe: The Hungarian army led by John Hunyadi engaged an Ottoman army led by Sultan Murad II. (http://en.wikipedia.org/wiki/Battle_of_Kosovo_(1448)) 1604: Kepler's Star: German astronomer Johannes Kepler (pictured) observed an exceptionally bright star which had suddenly appeared in the constellation Ophiuchus. (http://en.wikipedia.org/wiki/SN_1604) 1860: The Open Championship, the oldest of the four major championships in men's golf, was first played at Prestwick Golf Club in Prestwick, South Ayrshire, Scotland. (http://en.wikipedia.org/wiki/The_Open_Championship) 1977: German Autumn: Four days after it was hijacked, Lufthansa Lufthansa Flight 181 landed in Mogadishu, Somalia, where a team of German GSG 9 commandos rescued all remaining hostages on board. (http://en.wikipedia.org/wiki/Lufthansa_Flight_181) ________________________ Wiktionary's Word of the day: tulgey: (adj) Thick, dense, dark. (http://en.wiktionary.org/wiki/tulgey) _________________ Wikiquote of the day: The way to combat noxious ideas is with other ideas. The way to combat falsehoods is with truth. --William O. Douglas (http://en.wikiquote.org/wiki/William_O._Douglas)