This week’s image from the Hubble Space Telescope shows two galaxies close enough together to have just one shared name: Arp-Madore 608-333. They are what is known as interacting galaxies, meaning that the huge pull of each of their gravitational fields is affecting the other. The power of gravity is warping their shapes and distorting them into uneven forms.
“Though they appear serene and unperturbed, the two are subtly warping one another through a mutual gravitational interaction that is disrupting and distorting both galaxies,” Hubble scientists said in a note accompanying the image release. “This drawn-out galactic interaction was captured by Hubble’s Advanced Camera for Surveys.”
These interacting galaxies are different from other galaxy pairs, like the pair called VV 191, imaged by Hubble and the James Webb Space Telescope this week. VV 191 appears to be a close pair, but in fact, they are overlapping, not interacting. From our point of view on Earth, it seems that the two are occupying the same space, but one is in front of the other. A similar pair of overlapping galaxies that appear even closer together was imaged by Hubble earlier this year.
When it comes to galaxies that are truly interacting because they are close together, things can get messy. Galaxies can collide with each other, creating tremendous pockets of star formation as they merge. These interactions can create stunning and unusual shapes, like the Angel Wing system, in which two merging galaxies have formed the shape of wings. Sometimes even more than two galaxies can interact, like the Hickson Compact Group 31 — also imaged by Hubble — which contains four galaxies that are in the process of merging into one.
However, two galaxies colliding don’t always merge to form a larger galaxy. Sometimes, these collisions can result in the annihilation of one of the galaxies, and scientists believe that it is the supermassive black hole found at the heart of almost all galaxies that determines whether a collision will result in a merger or in one galaxy destroying the other.
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