Images of several Local Group galaxies are shown below. Some members of the Local Group: Galaxy name For example, Andromeda and the Milky Way are approaching each other at around 120 km/s and astronomers suggest that in several billion years they may merge to form a giant elliptical galaxy. Local Group galaxies and subgroups are interacting gravitationally with each other (and with neighbouring groups) and mergers and collisions are thought to have happened in the past and speculated for the future. Sag DEG is apparently being disrupted by tidal gravitational forces in its close encounter with the Milky Way. The Large and Small Magellanic Clouds ( LMC and SMC) are small well-known Milky Way companions, but nearer to our Galaxy are the more recently discovered Canis Major Dwarf and Sag DEG (Sagittarius Dwarf Elliptical Galaxy). Recent measurements may prove that they could be moving too fast for that. For many years astronomers thought the Magellanic Clouds orbited the Milky Way. Its companion, the Small Magellanic Cloud is about 200,000 light-years away. Although the position and radial velocity of local galaxies can be measured accurately, their distances can be difficult to determine, and the total membership of the Local Group remains uncertain. The Large Magellanic Cloud lies about 163 thousand light-years from Earth. The Local Group’s diameter as a whole is about 10 million light-years. However, the group is very dynamic and membership of the Group is probably changing over time as galaxies interact with, and move between, other nearby groups such as the Maffei 1 Group, the Sculptor Group, and the M81 and M83 Groups. The Local Group galaxies are all located within roughly 5 million light-years of space around us. The rest of the Group is made up of smaller, fainter dwarf galaxies, many of which are satellites of the Milky Way or M31. k is the total mass of any neighboring galaxy separated from the considered galaxy by a space distance D ik. 2008 Local Volume HI Survey Koribalski 2010 LITTLE THINGS, Hunter et al. Also prominent is the Triangulum galaxy (M33, NGC 598), a smaller spiral which (under very dark, clear conditions) is the most distant naked-eye object visible. The sample of galaxies has been enlarged from that studied in Kennicutt. Two massive bright spirals, the Milky Way and the Andromeda Galaxy (M31, NGC 224), dominate a gravitationally-bound group of around 40 galaxies known as the Local Group which spans a volume approximately 10 million light years in diameter.
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