What is the Andromeda Galaxy?

Andromeda Galaxy (English: Andromeda Galaxy ; M31 ; NGC 224 ; formerly known as the Andromeda Nebula ), a spiral galaxy with a huge disk structure in the Andromeda azimuth, Messier catalog number M31, the new nebula The table number is NGC 224, with a diameter of 220,000 light years and a distance of 2.54 million light years from Earth. It is the largest galaxy closest to the Milky Way.

The earliest observations of the Andromeda galaxy may have been made by Persian astronomer Al Sufei, ^[4]

Similar to the Milky Way, the Andromeda Galaxy also has satellite galaxies. There are already 14 dwarf galaxies known. The most famous and easiest to observe satellite galaxies are elliptical galaxies M32 and M110.

Based on the available evidence, it seems that M32 encountered M31 in the past not long ago ^[11]

The Andromeda galaxy approaches the sun at about 300 kilometers per second (180 mph), so it is a minority

Based on the shape seen in visible light, the Andromeda galaxy is classified as a spiral galaxy SA (s) b under the classification system of de Vaucouleurs-Sandage extension and expansion. However, in the 2MASS survey data, the nuclear sphere of M31 has a box-like shape, which implies that M31 is actually

M31 has long been known to have a dense and compact star cluster in the core. Under the big telescope, there are many fuzzy star points around the core. The core is also much brighter than the brightest globular clusters.

Used by Tod R. Lauer in 1991

The Andromeda Galaxy is approaching the Milky Way at a speed of 110 kilometers per second. ^[28] When the sun orbits the center of the Milky Way at a speed of about 225 km / s, it has been measured that its speed relative to the sun is close to 300 km / s ^[2] . This makes the Andromeda Galaxy one of about 100 observable blue shift galaxies. ^{[29] The} Andromeda galaxy's tangential or lateral velocity relative to the Milky Way is relatively smaller than its tangential approach velocity, so it is expected to collide directly with the Milky Way in about 4 billion years. One possible consequence of the collision is that the galaxies will merge to form a giant elliptical galaxy ^[30] , and may even form a large disk galaxy. Such events are common among galaxies in the galaxy group. The fate of the Earth and solar system at the time of the collision is unknown. Before the merger of galaxies, it was rare for the solar system to pop out of the Milky Way or join the Andromeda galaxy ^[31] .