This week’s picture of Hubble Space Telescope shows two galaxies close enough together to have a single shared name: Arp-Madore 608-333. They are what are known as interacting galaxies, which means that the enormous pull of each of their gravitational fields is affecting the other. The power of gravity is warping their shapes and distorting them into uneven shapes.
“Although they appear serene and unflappable, the two are subtly warping each other through a mutual gravitational interaction that is disrupting and distorting both galaxies,” they said Hubble scientists in a note accompanying the image release. “This prolonged galactic interaction was captured by Hubble’s Advanced Camera for Surveys.”
These interacting galaxies are different from other galaxy pairs, such as 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 overlap, not interact. From our point of view on Earth, it appears that the two are occupying the same space, but one is facing the other. A similar pair of overlapping galaxies appearing even closer together was imaged by Hubble earlier this year.
When it comes to galaxies that actually interact because they’re so close together, things can get complicated. Galaxies can collide with each other, creating huge pockets of star formation as they merge. These interactions can create impressive and unusual shapes, such as the Angel Wing system, in which two merging galaxies have formed the shape of wings. Sometimes even more than two galaxies can interact, such as Hickson Compact Group 31, also imaged by Hubble, which contains four galaxies that are in the process of merging into one.
However, two colliding galaxies do not 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 a galaxy destroying the other.