This week’s image from the Hubble Space Telescope shows a dramatic collision of three different galaxies. The trio, located in the Boötes constellation, are in the process of merging and will eventually form one single large galaxy.
“This colliding trio – known to astronomers as SDSSCGB 10189 – is a relatively rare combination of three large star-forming galaxies lying within only 50,000 light-years of one another,” Hubble scientists write. “While that might sound like a safe distance, for galaxies this makes them extremely close neighbors. Our own galactic neighbors are much further away; Andromeda, the nearest large galaxy to the Milky Way, is more than 2.5 million light-years away from Earth.”
Galactic collisions, when two or more galaxies meet each other, are not uncommon in the universe. The results of these enormous collisions can be varied, with either the galaxies merging to form a new larger galaxy, as is the case here, or one galaxy annihilating another.
Although it’s unlikely that stars from each galaxy will collide, because of the amount of space between each star, the heart of most galaxies contains a supermassive black hole, and the merging of these huge beasts can give off gravitational waves and send stars flying off in strange directions.
Typically if a larger galaxy collides with a smaller satellite galaxy, the larger galaxy will strip away stars and material from the smaller galaxy and maintain most of its shape. In other cases, the enormous gravitational forces involved in a collision can pull one or both galaxies into strange shapes.
Our own galaxy, the Milky Way, will collide with the nearby Andromeda galaxy in around 4 billion years’ time. This collision may also involve another nearby galaxy, the Triangulum galaxy, which could be pulled into orbit around the merger as well before eventually colliding as well.
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