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arpbot.bsky.social
Arp Bot πŸ€–
@arpbot.bsky.social
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Posting images of galaxies in Halton Arp's Atlas of Peculiar Galaxies (1966).

Automated account. Image curation, descriptions, typos, and most alt text by astronomer @kellylepo.bsky.social.

See posts for credits and links to the original sources.
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arpbot.bsky.social
Arp Bot πŸ€– @arpbot.bsky.social Β· Dec 21
Hello World!

I'm an automated account created by the human astronomer @kellylepo.bsky.social to post random images of galaxies that are in Halton Arp's Atlas of Peculiar Galaxies (1966).

Image curation, post text, typos, and most alt text are by @kellylepo.bsky.social.
arpbot.bsky.social
Image of Arp 7, 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 Hydra.
Source
A grainy, black and white image of a two-armed spiral galaxy with a bright core. The upper spiral arm forks into two as it curves around the top of the galaxy. Many white dots, which are stars, are seen on the black background.
January 18, 2026 at 12:31 PM
arpbot.bsky.social
Image of Arp 18, also known as NGC 4088, from Halton Arp's Atlas of Peculiar Galaxies (1966).

In the original catalog it was in the category: Spiral galaxies - Detached segments. NGC 4088 is located about 40 million light years away.
Source
A grainy, black and white image of a galaxy, which is slightly inclined, so it forms an oval shape, rather than a circle. The galaxy's stars and gas form a loose two-armed barred spiral, forming an S-shape. Dark, filamentary dust lanes are seen throughout the spiral arms. At the top edge of the galaxy, in line with the bar, is what looks like a third spiral arm. A few dots, which are stars, are seen on the black background.
January 18, 2026 at 12:31 AM
arpbot.bsky.social
Hubble image of Arp 290, also known as IC 195 and IC 196.

This interacting galaxy pair consists of a larger barred spiral (IC 196, top) and a smaller intermediate spiral (IC 195, bottom).

Credit: NASA, ESA, STScI, Julianne Dalcanton, Meli thev, Wikimedia Commons
Source
A greyscale image of two interacting spiral galaxies. The larger galaxy in the upper part of the frame has a bright central core surrounded by a long bar structure. The bar is crossed by dark dust lanes. Emerging from the bar is the beginning of one spiral arm at about 6 o'clock that curves upward. There are additional, barely visible spiral arms that wrap around the galaxy. The smaller galaxy in the bottom left portion of the frame also has a bright core, surrounded by an oval-shaped central region, and very faint, wispy spiral arms. The black background of space is filled with foreground stars and tiny background galaxies. The image has a noticeable amount of detector noise which has not been removed.
January 17, 2026 at 12:31 AM
arpbot.bsky.social
Image of Arp 148, also known as Mayall's Object, from Halton Arp's Atlas of Peculiar Galaxies (1966).

In the original catalog it was in the category: Amorphous galaxies - Associated rings. The two galaxies colliding likely created the ring.
Source
A grainy, black-and-white image of a pair of galaxies. In the center is a small, wide, bright white vertical line, likely an edge-on galaxy. Above this is a ring galaxy, seen as a blotchy circle. The two galaxies overlap so that the top edge of the edge-on galaxy intersects with the ring galaxy's center. A few white dots, which are stars, fill the black background of space.
January 16, 2026 at 12:31 PM
arpbot.bsky.social
Hubble image of Arp 204, also known as UGC 8454.

This is likely at least two interacting galaxies connected by a long tidal tail. Encounters between the galaxies have distorted their shapes, making a somewhat puzzling mess.

Credit: NASA, ESA, STScI, J. Dalcanton, Judy Schmidt
Source
A greyscale image of at least two interacting galaxies. At left is what looks like an edge-on spiral galaxy, appearing as a thick white line dotted with star clusters, tilted up at a slight angle. Extending from the edge of the disk is a long, thinner line of star clusters and dust filaments that tilts down slightly. At the other end of the line is a hazy, irregular structure which extends above and below the line. This is followed by a thicker area of the line, which could also be a nearly edge-on spiral galaxy.
January 16, 2026 at 12:32 AM
arpbot.bsky.social
Image of Arp 116, also known as M60 and NGC 4647, 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. The pair is beginning to interact.
Source
A grainy, black and white image of a large elliptical galaxy and a smaller face-on spiral galaxy. The elliptical galaxy is in the lower right portion of the frame. It appears as a featureless, oval-shaped blob surrounded by a haze of stars. Above and to its left is its companion, a smaller face-on spiral galaxy. Its somewhat poorly defined spiral arms curve around its bright center. The arms are dotted with bright stars and star clusters and are crossed by a series of filamentary dust lanes. Many white dots, which are stars, are seen on the black background.
January 15, 2026 at 12:31 PM
arpbot.bsky.social
Hubble image of Arp 221.

Arp 221 is an interacting trio of disk galaxies. To the right is what is probably a large lenticular galaxy, with a series of shells that are caused by the gravitational interactions or a past merger.

Credit: NASA, ESA, STScI, J. Dalcanton, Judy Schmidt
Source
A greyscale image of three disk galaxies arranged in a triangle. To the left is the largest galaxy, likely a lenticular galaxy, which has a bright center and a series of shells, which appear as arc-like glowing features with sharp outer edges. A few dark dust lanes appear in this outer part of the disk. The large galaxy overlaps with the galaxy to the right, which is also probably a lenticular galaxy. It has a bright center surrounded by a hazy disk. A faint curving feature, either a spiral arm or a tidal tail, emerges at about 6 o'clock and curves counterclockwise around the galaxy. The third galaxy, the smallest of the three, is below the other two. It's center is just below the center of the left galaxy. It has a bright center, a central bar structure, and two clearly defined spiral arms. A bright foreground star is above the right galaxy, and has large diffraction spikes which overlap with the galaxies. The image has a noticeable amount of detector noise which has not been removed. The black background of space is dotted with stars and small background galaxies.
January 15, 2026 at 12:32 AM
arpbot.bsky.social
Hubble image of Arp 284, also known as NGC 7714 and NGC 7715.

In this image of NGC 7714, we see a golden loop of of Sun-like stars created after a close encounter with its companion galaxy, NGC 7715 (out of frame), about 100 million years ago.

Credit: NASA, ESA, A. Gal-Yam
Source
The galaxy is offset on the left side of the frame. Its center is a bright white-blue. From the center extends a wispy tan spiral arm, first going toward the top and then circling counterclockwise before dissipating just below the center of the galaxy. Two bright blue spiral arms, dotted with whiter areas of star formation, follow a similar counterclockwise path, but the blue spiral arms end in thin, dim lines that extend to the left side of the image, going off frame, and toward the right. There are tiny red background galaxies along the top third of the frame, and one prominent foreground star toward the bottom third.
January 14, 2026 at 12:32 PM
arpbot.bsky.social
Image of Arp 9, also known as NGC 2523, from Halton Arp's Atlas of Peculiar Galaxies (1966).

In the original catalog it was in the category: Spiral galaxies - Split arms. NGC 2523 is a barred spiral galaxy in the constellation Camelopardalis.
Source
A grainy, black and white image of a face-on barred spiral galaxy. It has a bright central core with an almost vertical bar-shaped structure that connects to a thin ring. The area between the ring, core, and bar is dark. This central part looks like a steering wheel. The spiral arms originate at the ring and spiral outward counterclockwise. The arm which curves from about 3 o'clock to 12 o'clock forks in two. A few white dots, which are stars, are seen on the black background.
January 14, 2026 at 12:31 AM
arpbot.bsky.social
Image of Arp 271, also known as NGC 5426 and NGC 5427, from Halton Arp's Atlas of Peculiar Galaxies (1966).

In the original catalog it was in the category: Double and multiple galaxies - Connected arms. The two galaxies are interacting.
Source
A grainy, black and white image of two spiral galaxies next to each other. The galaxies are nebulous structures with denser arms shaped like spirals that meet at the centre of each galaxy. One galaxy is face-on, and the other somewhat inclined, and they're almost touching. The image is sprinkled with white dots, which are stars.
January 13, 2026 at 12:32 PM
arpbot.bsky.social
Very Large Telescope MUSE image of Arp 222, also known as NGC 7727.

The two bright galactic nuclei at the heart of NGC 7727, consisting of a dense group of stars with a supermassive black hole at their center, are about 1600 light-years apart.

Credit: ESO, Voggel et al.
Source
The very central portion of a galaxy fills the frame. There are two small white dots, which are the galactic nuclei, one to the lower left and one to the upper right. They sit on a white hazy background. In the left and center are swirling brown dust lanes, which resemble marbled chocolate.
January 13, 2026 at 12:32 AM
arpbot.bsky.social
Image of Arp 286, also known as NGC 5560, NGC 5566, and NGC 5569, from Halton Arp's Atlas of Peculiar Galaxies (1966).

In the original catalog it was in the category: Double and multiple galaxies - Infall and attraction.
Source
A grainy, black and white image of three spiral galaxies. The largest is at the center of the frame. The disk of the galaxy is tilted, so that it appears oval-shaped, with the long axis running diagonally from upper right to lower left. It has a bright center, surrounded by a ring structure. Emerging from the ring are two spiral arms, defined by faint dust lanes. The arms trace the outline of the oval. A faint haze of stars fills in the interior of the oval. At the bottom left is a much smaller face-on spiral galaxy. Unlike the other two galaxies in the group, this galaxy does not appear distorted. It has a small core, surrounded by a faint disk. At upper left is a distorted spiral galaxy seen nearly edge-on. Its disk is warped, forming a thin, nearly vertical, backward S-shape.
January 12, 2026 at 12:31 PM
arpbot.bsky.social
Chandra image of Arp 16, also known as M66.

This X-ray image shows the hottest gas in the galaxy's core, bar, and inner spiral arms. The bright central source is likely material falling onto a supermassive black hole.

Credit: NASA, CXC, Ohio State Univ., C.Grier et al.
Source
Blue points of light and a blue haze on a black background. The blue haze roughly corresponds to the location of the galaxy’s bar in images taken at other wavelengths. A series of bright blue points are at the center of the hazy structure.
January 12, 2026 at 12:31 AM
arpbot.bsky.social
Legacy Surveys DR9 image of Arp 218.

The interacting galaxy pair, a distorted face-on spiral and an edge-on spiral, is in the constellation Serpens.

Credit: Legacy Surveys, D. Lang, NERSC
Source
A somewhat low-res image of a pair of interacting galaxies. In the center is a distorted face-on spiral galaxy. It has a yellow center that transitions into two long, blue spiral arms that form a backwards S shape. The top spiral arm loops down connecting back with the top of the galaxy. To the right is an edge-on disk galaxy which appears as a slightly curved, short diagonal line. On the right side of the galaxy is a red blob. On the left side the disk is blue.
January 11, 2026 at 12:31 AM
arpbot.bsky.social
Kitt Peak image of Arp 297, also known as NGC 5755, NGC 5753, NGC 5754 and NGC 5752.

This wide view shows two interacting galaxy pairs. The pairs are actually unrelated and are at different distances.

Credit: KPNO, NOIRLab, NSF, AURA, B. Lofquist, A. Block
Source
Four small galaxies, arranged in two pairs, on a field of stars. The bottom pair of galaxies is a large face-on barred spiral galaxy and a smaller edge-on disk galaxy. The spiral has a bright, pale yellow, circular core that transitions into a diagonal bar structure. Two well-defined spiral arms circle around the core counter-clockwise, beginning at the ends of the bar. To its right is its smaller companion galaxy. It is oval-shaped, running diagonal and with the long axis parallel to the bar of the large spiral. The upper pair is two nearly face-on spiral galaxies. The bottom galaxy of the pair has a blue-white core and bar with two faint spiral arms that make a S-shape. The top galaxy of the pair has a circular yellow core and several spiral arms that wrap around the core.
January 10, 2026 at 12:31 PM
arpbot.bsky.social
Kitt Peak image of Arp 94, also known as NGC 3226 and NGC 3227.

The large spiral galaxy, NGC 3227 is interacting with its elliptical galaxy companion, NGC 3226. Faint tidal streams of gas and dust link the pair.

Credit: KPNO,NOIRLab,NSF/AURA/Sid Leach and Wil Milan/Adam Block
Source
Two interacting galaxies. A large spiral galaxy with reddish brown dust lanes is in the center left of the image. It is tilted slightly, so that its disk forms an oval rather than a circle. The very faint ends of spiral arms extend beyond the edge of the disk and appear to connect to its companion galaxy. In the center right is a bright elliptical galaxy. It is oval shaped with a bright center that gets gradually fainter and more transparent towards its edges. The black background of space is dotted with foreground stars and tiny background galaxies.
January 10, 2026 at 12:32 AM
arpbot.bsky.social
Hubble image of Arp 82, also known as NGC 2535 and NGC 2536.

The larger galaxy's arms have evenly spaced "beads on a string" star clusters, created by recent gravitational interactions that led to a burst of star formation.

Credit: NASA, ESA, STScI, J. Dalcanton, Judy Schmidt
Source
A black and white image of a pair of interacting spiral galaxies. In the center of the frame is the larger galaxy, a barred spiral galaxy seen face-on. It has a bright center that transitions into a small bar, crossed by filamentary, dark dust lanes. A ring of stars and star clusters circles the bar, giving the inner part of the galaxy a shape that resembles an eye. Two long spiral arms emerge from the ring, dotted with bright star clusters and outlined by dust filaments, forming an S-shape. The upper arm trails off in a faint arc to the right. The bottom arm appears to connect to its companion galaxy in the lower part of the frame. This galaxy is smaller and less well defined, but is still clearly a two-armed spiral with a bright center and wider, hazy arms. The black background of space is dotted with foreground stars and tiny background galaxies. A few particularly bright stars with diffraction spikes are seen to the right of the center galaxy.
January 9, 2026 at 12:32 PM
arpbot.bsky.social
Image of Arp 16, also known as M66, from Halton Arp's Atlas of Peculiar Galaxies (1966).

In the original catalog it was in the category: Spiral galaxies - Detached segments. M66 has loose arms full of young star clusters.
Source
A grainy, black and white image of a nearly face-on barred spiral galaxy. It has a bright core. Two spiral arms start at the center and extend outward, rotating clockwise. They are crossed by dark dust lanes. Several white dots, which are stars, are seen on the black background.
January 9, 2026 at 12:31 AM
arpbot.bsky.social
Hubble image of Arp 299, also known as NGC 3690.

This image was taken in 2000 with Hubble WFPC2 instrument to study the merging galaxies' hottest and brightest stars in ultraviolet light.

Credit: NASA, R. Windhorst, and the Hubble mid-UV team
Source
Two merging galaxies form an orange and blue abstract butterfly shape. Within the shape are bright blue areas, which are clusters of young, hot stars. These are found in the center, the upper right "wing", and the bottom left "wing".
January 8, 2026 at 12:31 PM
arpbot.bsky.social
Hubble image of Arp 190, also known as UGC 2320.

Interactions between an elliptical galaxy off frame to the left and the lower spiral galaxy created the large tidal tail that extends to the right.

Credit: ESA, NASA, J. Dalcanton, J. Schmidt
Source
In a grayscale image, two face-on spiral galaxies sit near one another, slightly overlapping, in the left half of the frame. The upper galaxy is slightly smaller. It has a short bar structure in its center that transitions into two well-defined spiral arms, dotted with star clusters. The lower galaxy is slightly larger and has less well-defined spiral arms. It has a bright center that transitions into a swirl of stars and dark dust lanes. Emerging from the bottom of the bottom galaxy is a very long, somewhat wide tidal tail. It crosses most of the frame horizontally. It is about three galaxy lengths long. A bright foreground star appears on top of the tidal tail, near where it meets the galaxy. There are a few scattered foreground stars and background galaxies that appear on the black background of space. The image has a noticeable amount of detector noise which has not been removed.
January 8, 2026 at 12:31 AM
arpbot.bsky.social
Hubble Space Telescope image of Arp 6, also known as NGC 2537 or the Bear’s Paw Galaxy.

It has a nucleus that is rapidly forming stars, surrounded by a horseshoe-shaped structure, also forming new stars.

Credit: NASA, ESA, STScI, J. Dalcanton, Judy Schmidt
Source
A greyscale image of a galaxy with a line-like nucleus and a horseshoe-shaped arc above it. The horseshoe points down, and the nucleus is in the center of the arc. It looks like an upside down power symbol, ⏻. The nucleus and horseshoe are dotted with bright star clusters and dark dust lanes.
January 7, 2026 at 12:32 PM
arpbot.bsky.social
Hubble image of Arp 220, also known as IC 4553.

The image shows the center of the two merging spiral galaxies that make up Arp 220. The merger set of a burst of star formation, which backlights the large amount of dust in this visible light view.

Credit: NASA, ESA, C. Wilson
Source
A section of the center of a pair of merging galaxies. The image is dominated by brown dust, which forms a blotchy diagonal band that runs from upper right to lower left. It is backlit by the bright light from the center of the galaxies. In the background are blue stars and star clusters, seen as a grainy blue background interspersed with blue dots.
January 7, 2026 at 12:32 AM
arpbot.bsky.social
Kitt Peak National Observatory image of Arp 336, also known as NGC 2685.

NGC 2685 is a polar ring galaxy. It has a ring of gas, stars, and dust that orbits perpendicular to the plane of the galaxy, seen as unusual whorls, or helical filaments.

Credit: NOIRLab, AURA, NSF
Source
A lenticular galaxy has an pale yellow central core that forms a fuzzy bar structure. Surrounding this a faint almond-shaped area. Together, they somewhat resemble an eye. Several faint, brown, slightly curved dust lanes cross the galaxy vertically on its left half. The black background of space is dotted with stars and smaller galaxies.
January 6, 2026 at 12:32 PM
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January 6, 2026 at 12:54 AM
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Hubble image of Arp 70, also known as VV 341.

In Arp 70, a larger galaxy with two well-defined spiral arms interacts with a small companion. Such interactions have been linked to the production of grand-design spiral arms.

Credit: NASA, ESA, STScI, J. Dalcanton, Judy Schmidt
Source
Black and white image of a pair of interacting galaxies. The large barred spiral on the left takes up about half of the frame. It has a bright center that transitions into a nearly vertical bar structure. Two spiral arms begin at the ends of the bar. They are crossed by dark dust lanes and dotted with bright star clusters. Together the arms and the bar form an S-shape. A tear-dropped shaped loop of stars and gas surrounds the bar and connects the inner parts of the two spiral arms. The top spiral arm extends much farther than the lower spiral arm. Near the top of the frame the top arm curves back down and points to its companion galaxy. In the lower right corner of the frame is a much smaller galaxy, with a bright center surrounded by a featureless disk or halo. Overlapping at its top left is what appears to be a small background spiral galaxy. The black background of space is filled with tiny background galaxies and foreground stars, including a bright foreground star with four diffraction spikes seen in the upper right corner.
January 6, 2026 at 12:32 AM