JWST image of Arp 220, also known as IC 4553. Arp 220 is two spiral galaxies in the process of merging. The merger sparked a burst of star formation in their cores. Those small, bright areas created the six large diffraction spikes. Credit: NASA, ESA, CSA, STScI, A. Pagan Source

Image of Arp 14, also known as NGC 7314, from Halton Arp's Atlas of Peculiar Galaxies (1966). In the original catalog it was in the category: Spiral galaxies - Detached segments. It has an active supermassive black hole at its center. Source

Image of Arp 274, also known as NGC 5679, from Halton Arp's Atlas of Peculiar Galaxies (1966). In the original catalog it was in the category: Double and multiple galaxies - Connected arms. It is a system of three overlapping, interacting galaxies. Source

Hubble Space Telescope image of Arp 5, also known as NGC 3664. NGC 3664 is a barred Magellanic spiral galaxy with a single spiral arm and prominent bar. It is interacting with a dwarf galaxy, out of frame. Credit: NASA, ESA, STScI, Solomon Hendrix Source

Hubble image of Arp 55, also known as UGC 4881. This pair of galaxies is about halfway through a merger. Their cores are separate, but their disks are overlapping. Credit: NASA, ESA, STScI Source

Spitzer image of Arp 107, also known as UGC 5984. The short wavelength left image highlights older stars, while the longer wavelength middle image highlights younger stars. The multi-band picture shows the two stellar age groups. Credit: NASA, JPL-Caltech, B. J. Smith Source

Herschel image of Arp 26, also known as M101 or the Pinwheel Galaxy. This far-infrared and sub-millimeter wavelength light highlights the galaxy's cold, glowing dust. The blue dots are areas of star formation. Credit: ESA, Herschel, NASA, JPL-Caltech; R. Hurt Source

Hubble Space Telescope image of Arp 23, also known as NGC 4618. NGC 4618 is a single-armed barred spiral galaxy. Its unusual shape may come from gravitational interactions with a neighboring galaxy NGC 4625, which is just out of frame. Credit: ESA, NASA, I. Karachentsev Source

Hubble image of Arp 240, also known as NGC 5257 and NGC 5258. NGC 5257 (left) and NGC 5258 (right), two spiral galaxies of similar mass and size, are in the early stages of a merger. Credit: NASA, ESA, STScI Source

Kitt Peak image of Arp 286, also known as NGC 5560, NGC 5566, and NGC 5569. The galaxies in this triplett are gravitationally interacting. NGC 5566 is at center, NGC 5569 at bottom left, and NGC 5560 at top left. Credit: NOIRLab, NSF, AURA, T.A. Rector, H. Schweiker Source

Very Large Telescope image of Arp 271, also known as NGC 5426 and NGC 5427. The galaxies are tugging on each other with gravity, which has begun to distort their features and may have also triggered bursts of star formation. Credit: ESO Source

Hubble image of Arp 299, also known as NGC 3690. Interactions between these two galaxies triggered a fierce burst of star formation, making Arp 299 one of the most powerful nearby starburst galaxies. Credit: NASA, ESA, the Hubble Heritage Team, A. Evans Source

Image of Arp 289, also known as NGC 3981, from Halton Arp's Atlas of Peculiar Galaxies (1966). In the original catalog it was in the category: Double and multiple galaxies - Wind effects. Interactions with another galaxy likely caused its odd arms. Source

Legacy Surveys DR9 image of Arp 301, also known as UGC 6204 and UGC 6207. In this interacting pair of spiral galaxies, UGC 6207 is the edge-on galaxy to the left and UGC 6204 is the face-on barred spiral to the right. Credit: Legacy Surveys, D. Lang, NERSC Source

Spitzer, Hubble, and Chandra image of Arp 26, also known as M101 or the Pinwheel Galaxy. Spitzer's infrared light shows dust, Hubble's visible light highlights stars, Chandra's X-rays show things like hot gas and black holes. Credit: NASA, ESA, CXC, JPL, Caltech, STScI Source

Hubble Space Telescope image of Arp 147, also known as IC 298. The clumpy, blue ring in the galaxy on the right likely formed when the companion galaxy to the left crashed through its center. Credit: NASA, ESA, and M. Livio (STScI) Source

Hubble image of Arp 194, also known as UGC 6945. This interacting galaxy group includes a pair of merging galaxies with two nuclei and trails of blue super star clusters at top and a single large spiral galaxy at bottom. Credit: NASA, ESA, and the Hubble Heritage Team Source

GALEX image of Arp 286, also known as NGC 5560, NGC 5566, and NGC 5569. Ultraviolet light shows the youngest, hottest stars in this interacting galaxy triplett. NGC 5566 is at center, NGC 5569 at bottom left, and NGC 5560 at top left. Credit: NASA, JPL-Caltech Source

Hubble image of Arp 298, also known as NGC 7469 and IC 5283. NGC 7469, a face-on spiral galaxy, and its companion galaxy IC 5283, seen to the upper right, form an interacting pair. Credit: ESA, NASA, A. Evans, R. Chandar Source

Very Large Telescope image of Arp 271, also known as NGC 5426 and NGC 5427. This pair of interacting galaxies was the final image captured by the VIsible Multi-Object Spectrograph (VIMOS) instrument before it was decommissioned in 2018. Credit: ESO, Juan Carlos Muñoz Source

Image of Arp 82, also known as NGC 2535 and NGC 2536, from Halton Arp's Atlas of Peculiar Galaxies (1966). In the original catalog it was in the category: Spiral galaxies - Large, high surface brightness companions. Source

Image of Arp 122, also known as NGC 6040 and LEDA 59642, from Halton Arp's Atlas of Peculiar Galaxies (1966). In the original catalog it was in the category: Elliptical galaxies - Close to and perturbing spiral galaxies. Source

Image of Arp 8, also known as NGC 497, from Halton Arp's Atlas of Peculiar Galaxies (1966). In the original catalog it was in the category: Spiral galaxies - Split arms. It is a barred spiral galaxy in the constellation Cetus. Source

Hubble image of Arp 283, also known as NGC 2798 and NGC 2799. The left galaxy in this interacting pair, NGC 2799, is viewed edge-on. A bridge with clumps of star formation appears to connect it to NGC 2798, at right. Credit: ESA, NASA, J. Dalcanton, J. Schmidt Source

Image of Arp 201, also known as UGC 224, from Halton Arp's Atlas of Peculiar Galaxies (1966). In the original catalog it was in the category: Amorphous galaxies - Material ejected from nuclei. Arp 201 is an interacting galaxy pair. Source

Hubble image of Arp 157, also known as NGC 520. Two disk galaxies began colliding about 300 million years ago, forming the mess that is NGC 520. The disks of the two original galaxies have merged together, but the nuclei have not yet coalesced. Credit: NASA, ESA, STScI Source

Hubble image of Arp 87, also known as NGC 3808 and NGC 3808A. NGC 3808 (right) is a nearly face-on spiral galaxy interacting with NGC 3808A (left), a polar ring galaxy with an edge-on disk circled by a ring of stars and gas. Credit: NASA, ESA, and the Hubble Heritage Team Source

Spitzer image of Arp 188, also known as the Tadpole Galaxy. It is a result of a recent galactic interaction. A small intruder galaxy created a 280,000 light-year-long tail of stars and gas. Credit: NASA/JPL-Caltech/C. Lonsdale (IPAC/Caltech), SWIRE Team Source

Hubble image of Arp 24, also known as NGC 3445. NGC 3445 has one fan-like spiral arm that is dotted with star-forming regions. It is connected to its companion galaxy, seen nearly edge-on to the left, by a weak bridge. Credit: NASA, ESA, STScI, J. Dalcanton, Judy Schmidt Source

Hubble image of Arp 142, also known as NGC 2936 and NGC 2937, or the Penguin and the Egg. Gravitational interactions between the two galaxies warped the spiral's disk and triggered the formation of new stars, seen as blue knots. Credit: NASA, ESA, Hubble Heritage Team Source

Very Large Telescope image of Arp 222, also known as NGC 7727. The swirling loops of material seen in NGC 7727 are the remnants of a galactic merger that started around a billion years ago, when a smaller, gas-rich young galaxy fell into a larger galaxy. Credit: ESO Source

Image of Arp 70, also known as UGC 934, from Halton Arp's Atlas of Peculiar Galaxies (1966). In the original catalog it was in the category: Spiral galaxies - Small, high surface brightness companions. The large galaxy interacts with its companion. Source

Hubble Space Telescope image of Arp 15, also known as NGC 7393. NGC 7393 is a barred spiral galaxy in the constellation Aquarius. Credit: NASA, ESA, STScI, Julianne Dalcanton, Meli thev, Wikimedia Commons Source

Hubble image of Arp 91, also known as NGC 5953 and NGC 5954. NGC 5953 (center) and NGC 5954 (left) show clear signs of interaction. A spiral arm or tidal tail from NGC 5954 extends to the side and connects to its companion. Credit: ESA, NASA, J. Dalcanton, J. Schmidt Source

Hubble Space Telescope image of Arp 2, also known as UGC 10310. The Establishing HST's Low Redshift Archive of Interacting Systems snapshot program filled in Hubble schedule gaps with short observations, like this one. Credit: NASA, ESA, STScI, J. Dalcanton, Judy Schmidt Source

Hubble image of Arp 188, also known as the Tadpole Galaxy. Gravitational interactions with a small galaxy created the 280,000 light-year-long tail of stars and gas. Credit: NASA, ESA, H. Ford (JHU), G. Illingworth (UCSC/LO), M.Clampin and G. Hartig (STScI), ACS Science Team Source

Image of Arp 1, also known as NGC 2857, from Halton Arp's Atlas of Peculiar Galaxies (1966). In the original catalog it was in the category: Spiral galaxies - Low surface brightness. It is a spiral galaxy in the constellation Ursa Major. Source

Hubble image of Arp 321, also known as Hickson 40. This group of galaxies include three spiral galaxies, an elliptical galaxy, and a lenticular (lens-like) galaxy. Credit: NASA, ESA, STScI, Judy Schmidt Source

Spitzer image of Arp 302, also known as UGC 9618 or VV 340. Arp 302 is unusually bright in infrared light. This is likely because the galaxy has an unusually large amount of gas, which is forming new stars that heat their surroundings. Credit: NASA, JPL-Caltech Source

Lick Observatory image of Arp 148, also known as Mayall's Object. The image was taken in 1940 by astronomer Nicholas Mayall. He noted it looked a little like a question mark. We now know it is a pair of interacting galaxies. Credit: Plate XIX, Smith 1941 Source

VLT image of Arp 16, also known as M66. This glittering image was taken with the MUSE instrument on ESO’s Very Large Telescope. It highlights the galaxy's warm gas, hydrogen (red), oxygen (blue), and sulfur (orange). Credit: ESO, PHANGS Source

Image of Arp 147, also known as IC 298, from Halton Arp's Atlas of Peculiar Galaxies (1966). In the original catalog it was in the category: Amorphous galaxies - Associated rings. The right galaxy's ring formed when its companion hit its center. Source

Gemini South image of Arp 222, also known as NGC 7727. About a billion years ago, a smaller, galaxy collided and merged with NGC 7727, creating the swirling loops of material seen in its outskirts. Credit: International Gemini Observatory, NOIRLab, NSF, AURA Source

Hubble NICMOS image of Arp 220, also known as IC 4553. This infrared image shows two compact star clusters in the center of Arp 220. They are the remnant cores of two spiral galaxies that are in the process of merging. Credit: NASA, ESA, STScI, R. Thompson, N. Scoville Source

Hubble image of Arp 272, also known as NGC 6050 and IC 1179. Arp 272 is a collision between two spiral galaxies in the Hercules Galaxy Cluster. Credit: NASA, ESA, STScI Source

Image of Arp 11, also known as UGC 717, from Halton Arp's Atlas of Peculiar Galaxies (1966). In the original catalog it was in the category: Spiral galaxies - Split arms. UGC 717 is the large spiral galaxy at center. Source

Hubble image of Arp 274, also known as NGC 5679. NGC 5679 is a system of three interacting galaxies, the two large, overlapping spiral galaxies at center, and a smaller companion galaxy to the far left. Credit: NASA, ESA, STScI, Hubble Heritage Team Source

Image of Arp 15, also known as NGC 7393, from Halton Arp's Atlas of Peculiar Galaxies (1966). In the original catalog it was in the category: Spiral galaxies - Detached segments. It is a barred spiral galaxy in the constellation Aquarius. Source

Image of Arp 302, also known as UGC 9618 or VV 340, from Halton Arp's Atlas of Peculiar Galaxies (1966). In the original catalog it was in the category: Double and multiple galaxies - Unclassified objects. The pair is beginning to interact. Source

Gemini North image of Arp 84, also known as NGC 5394 and NGC 5395. Interactions between this galaxy pair funneled gas into the center of the smaller distorted spiral NGC 5394, which fuels a burst of star formation. Credit: International Gemini Observatory, NOIRLab, NSF, AURA Source