The Triangulum Galaxy is a spiral galaxy in Triangulum. It is one of the most distant deep sky objects that can be seen without binoculars. The galaxy has an apparent visual magnitude of 5.72 and is between 2,380 and 3,070 thousand light years distant from Earth. Messier 33 is the third largest member of the Local Group of galaxies, after the Milky Way and Andromeda Galaxy. It is about 50,000 light years in diameter and contains about 40 billion stars. (For comparison, the Milky Way has about 400 billion and Andromeda about a trillion stars.) The galaxy is also home to at least 54 globular clusters. The Triangulum Galaxy contains the largest stellar mass black hole (a black hole formed by the gravitational collapse of a massive star) known. The black hole, M33 X-7, was discovered in 2007 and has about 15.7 times the mass of the Sun. It orbits a companion star and eclipses it every 3.45 days. The total mass of the binary system is about 85.7 times that of the Sun. The companion star has a mass about 70 times solar, which makes it the most massive companion star known in a binary system containing a black hole. A stream of hydrogen gas linking Triangulum to the Andromeda Galaxy was discovered in 2004 and confirmed in 2011. This suggests that the two galaxies have tidally interacted in the past. The Pisces Dwarf, another galaxy in the Local Group, is located 913,000 light years from both galaxies and could be a satellite galaxy of either Triangulum or Andromeda Galaxy. The Triangulum Galaxy is sometimes also referred to as the Pinwheel Galaxy, but this name is formally used for Messier 101 in Ursa Major constellation. The Triangulum Galaxy was probably first discovered by the Italian astronomer Giovanni Batista Hodierna before 1654. Hodierna listed the galaxy as a cloud-like nebulosity in his work De systemate orbis cometici; deque admirandis coeli caracteribus (“About the systematics of the cometary orbit, and about the admirable objects of the sky”). Charles Messier independently discovered the galaxy on the night of August 25-26, 1764 and included it in his catalogue as object number 33. William Herschel included the object in his own catalogue of nebulae, and also documented the galaxy’s largest and brightest H II region as H III. 150. The H II region, a diffuse emission nebula that contains ionized hydrogen, was later designated NGC 604.
Posted on: Thu, 17 Oct 2013 05:38:43 +0000
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