Triangulum Galaxy in the context of "Magellanic spiral"

The Large Magellanic Cloud (LMC) is a dwarf galaxy and satellite galaxy of the Milky Way. At a distance of around 50 kiloparsecs (163,000 light-years), the LMC is the second- or third-closest galaxy to the Milky Way, after the Sagittarius Dwarf Spheroidal (c. 16 kiloparsecs (52,000 light-years) away) and the possible dwarf irregular galaxy called the Canis Major Overdensity. It is about 9.86 kiloparsecs (32,200 light-years) across, and has roughly one-hundredth the mass of the Milky Way making it the fourth-largest galaxy in the Local Group, after the Andromeda Galaxy (M31), the Milky Way, and the Triangulum Galaxy (M33).

The LMC is classified as a Magellanic spiral. It contains a stellar bar that is geometrically off-center, suggesting that it was once a barred dwarf spiral galaxy before its spiral arms were disrupted, likely by tidal interactions from the nearby Small Magellanic Cloud (SMC) and the Milky Way's gravity. The LMC is predicted to merge with the Milky Way in approximately 2.4 billion years.

An H II region is a region of interstellar atomic hydrogen that is ionized. It is typically in a molecular cloud of partially ionized gas in which star formation has recently taken place, with a size ranging from one to hundreds of light years, and density from a few to about a million particles per cubic centimetre. The Orion Nebula, now known to be an H II region, was observed in 1610 by Nicolas-Claude Fabri de Peiresc by telescope, the first such object discovered.

The regions may be of any shape because the distribution of the stars and gas inside them is irregular. The short-lived blue stars created in these regions emit copious amounts of ultraviolet light that ionize the surrounding gas. H II regions—sometimes several hundred light-years across—are often associated with giant molecular clouds. They often appear clumpy and filamentary, sometimes showing intricate shapes such as the Horsehead Nebula. H II regions may give birth to thousands of stars over a period of several million years. Supernova explosions and strong stellar winds from the most massive stars in the resulting star cluster ultimately disperse the remaining gas of the H II region.

Triangulum is a small constellation in the northern sky. Its name is Latin for "triangle", derived from its three brightest stars, which form a long and narrow triangle. Known to the ancient Babylonians and Greeks, Triangulum was one of the 48 constellations listed by the 2nd century astronomer Ptolemy. The celestial cartographers Johann Bayer and John Flamsteed catalogued the constellation's stars, giving six of them Bayer designations.

The white stars Beta and Gamma Trianguli, of apparent magnitudes 3.00 and 4.00, respectively, form the base of the triangle and the yellow-white Alpha Trianguli, of magnitude 3.41, the apex. Iota Trianguli is a notable double star system, and there are three star systems with known planets located in Triangulum. The constellation contains several galaxies, the brightest and nearest of which is the Triangulum Galaxy or Messier 33—a member of the Local Group. The first quasar ever observed, 3C 48, also lies within the boundaries of Triangulum.