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arpbot.bsky.social
Arp Bot 🤖
@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 🤖 @arpbot.bsky.social · 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
Gran Telescopio Canarias image of Arp 288, also known as NGC 5221.

In 2016, a supernova appeared in the galaxy's long tidal tail to the right, about 260 thousand light years from the galactic center.

Credit: GTC, IAC
Source
A disrupted spiral galaxy. The disk of the galaxy is tilted, so that it appears as an oval shape, rather than a circle. The galaxy has a bright yellow center and a dark ring of dust that circles the galaxy about half way out of the disk. Above and below the plane of the disk, the galaxy has some pretty intense tidal tails, blue streams of gas and stars that appear to be flowing off of the main galaxy. The ones below the disk form a rough V shape and the ones above fan out like smoke rising from a campfire. Dotted against the black background of space are many small background galaxies and foreground stars.
November 11, 2025 at 12:31 PM
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Hubble Space Telescope image of Arp 26, also known as M101 or the Pinwheel Galaxy.

The image is made from 51 individual Hubble exposures, plus data from the Canada-France-Hawaii Telescope and Kitt Peak National Observatory.

Credit: NASA, ESA, STScI; CFHT, NOAO, AURA, NSF
Source
A face-on spiral galaxy has a yellow core. Several spiral arms, dotted with blue stars and star clusters, spiral clockwise around the core. They are crossed by filamentary dust lanes. The arms are somewhat well-defined but asymmetric. One arm curls from about 6 o'clock to 9 o'clock and is mostly separated from the body of the galaxy. Another arm follows more closely to the core, from about 6 o'clock to 12 o'clock. Three other arms cover the area from 12 o'clock to 6 o'clock.
November 11, 2025 at 12:31 AM
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Hubble image of Arp 291, also known as UGC 5832.

This one-armed barred spiral galaxy may be interacting with the small galaxy in the upper right corner of the frame.

Credit: NASA, ESA, STScI, Julianne Dalcanton, Meli thev, Wikimedia Commons
Source
A greyscale image of a one-armed barred spiral galaxy fills most of the frame. The bar, seen as a bright line of stars and star clusters anchors the galaxy. Beginning at about the 3 o'clock position, a spiral arm wraps clockwise around the galaxy, ending at around 12 o'clock. The arm is formed from a haze of stars and are dotted with bright star clusters. In the upper part of the frame, partially cut off at the right edge, is a smaller galaxy. It has a bright center and a more diffuse disk or halo of stars. Dotted across the black background of space are small background galaxies and foreground stars. The image has a noticeable amount of detector noise which has not been removed.
November 10, 2025 at 12:31 PM
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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, A. Pagan
Source
Five galaxies appear close to each other in the sky. At upper left, a spiral galaxy is tilted, appearing wider than it is tall. It has a glowing yellow center and reddish-brown dust trails that spiral clockwise around it. Above the center is a large elliptical galaxy. Its round, glowing yellow center is surrounded by a fuzzy yellow halo that fades away from the core. Toward the bottom right are three galaxies that appear to touch. The largest is in the center: a nearly vertical, edge-on spiral galaxy. Its glowing yellow core is mostly obscured by reddish-brown dust trails dotted with blue stars. To its bottom left is a smaller, tilted spiral galaxy with a glowing yellow center. Reddish-brown dust trails are dotted with blue stars. One spiral arm appears to touch the vertical galaxy to its right. At the spiral’s bottom right is a lenticular galaxy with a glowing central core in the middle of a hazy yellow disk, appearing almost face-on. It seems to touch the large spiral galaxy above it.
November 10, 2025 at 12:31 AM
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New Technology Telescope image of Arp 271, also known as NGC 5426 and NGC 5427.

The mutual gravitational interaction of this pair of spiral galaxies distorts their shapes and creates a bridge of gas, dust and young stars that connect the galaxies.

Credit: ESO
Source
Two similar-looking spiral galaxies take up most of the frame. They both have bright, yellow-white central cores and well-defined spiral arms dotted with blue star clusters and dark dust lanes. NGC 5427 is a nearly face-on spiral galaxy at lower left. NGC 5426 is a more oblique galaxy at upper right. The two spiral arms on the upper side of NGC 5426 appear as a bridge that connects with NGC 5427. The black background of space is dotted with stars and small background galaxies.
November 9, 2025 at 12:31 PM
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Ground-based image of Arp 16, also known as M66.

M66 is a member of the Leo Triplet. NGC 3628, the galaxy in the upper left, likely had an encounter with M66 a few hundred million years ago, creating a dramatic tail-like plume.

Credit: Fig 1, G. Wu et al. (2022)
Source
A color image of three widely separated galaxies. The galaxy at the upper left, NGC 3628, is an edge-on spiral, seen as a thin rectangular shape with a light brown dust lane going through the middle. A translucent, curved plume, about two times the length of the galaxy trails off to the left. The galaxy at lower left, M 66, is a face-on barred spiral galaxy, with a bright central bar and two spiral arms, which form an S-shape. The galaxy at lower right, M 65, is a nearly face-on spiral, with a bright nucleus and curving dust lanes. The image is very dense with foreground stars. A scale bar marking 50 kpc takes up about 1/6 of the width of the image.
November 9, 2025 at 12:31 AM
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Gran Telescopio Canarias image of Arp 30, also known as NGC 6365.

Arp thought this was one galaxy with a particularly beefy arm. Later images show this is actually a pair of interacting galaxies, with one galaxy viewed face-on and one viewed nearly edge-on.

Credit: GTC, IAC
Source
A pair of spiral galaxies, one seen nearly edge-on and one seen face-on. The face-on spiral to the right has a bright yellow central core and two well-defined spiral arms that loop counterclockwise around the galaxy. The inner parts of the spiral arms are yellow, while the outer arms fan out into blue stars and star clusters. One spiral arm begins at about 6 o'clock, curls around to the top of the galaxy at 12 o'clock and then ends at the bottom of the galaxy around 6 o'clock. The second arm begins at around 9 o'clock and curls around, ending at the top of the galaxy around 12 o'clock. The nearly edge-on galaxy to the left overlaps at the top of the face-on galaxy, appearing like a continuation of the face-on galaxy's second spiral arm. It's disk is tilted, so it appears as a long, thin oval rather than a circle. The galaxy also has a yellow central core and an outer edge dotted with blue star clusters. In the black background of space are a few other colorful dots, which are foreground stars or background galaxies.
November 8, 2025 at 12:31 PM
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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
Three overlapping galaxies fill the frame. In the center are two large spiral galaxies. The larger one, at center-left, has a bright nucleus surrounded by a yellow core made of mostly older stars. At the edge of the core, several spiral arms emerge. The arms are threaded with brown dust lanes and dotted with blue star clusters. The second spiral galaxy is at center-right. It has a bright center, bar, and poorly-defined spiral arms. Compared to its companion, this galaxy has less dust and more blue star clusters in its arms. The final galaxy in the triplet appears above the other two within their spiral arms. It is much smaller than its companions and and has a well defined central bar. It's hard to distinguish its spiral arms because they are backlit by the other two galaxies. A few stars appear on the black background of space, including a large foreground star, which appears above the center-right galaxy.
November 8, 2025 at 12:31 AM
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Sloan Digital Sky Survey image of Arp 13, also known as NGC 7448.

NGC 7448 has a disk of tightly wound, clumpy, and particularly bright spiral arms.

Credit: SDSS
Source
A spiral galaxy with a small, bright, circular core. The blue and green spiral arms wind clockwise around the yellow core. There are several bright blueish-green points, which are star clusters, among the poorly defined arms. The galaxy is tilted slightly, so it forms an oval shape, rather than a circle. In the background are scattered red, yellow and green dots, which are stars.
November 7, 2025 at 12:31 PM
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Image of Arp 140, also known as NGC 274 and NGC 275, from Halton Arp's Atlas of Peculiar Galaxies (1966).

In the original catalog it was in the category: Elliptical galaxies - Emanating material. The pair is a barred spiral and lenticular galaxy.
Source
A grainy, black-and-white image of a two side-by-side galaxies. The left galaxy is a bright spiral galaxy with star clusters, crossed by dark dust lanes.. The right galaxy is a lenticular galaxy. It bright white center that gradually becomes more transparent near the edges, emitting a hazy glow. A few white dots, which are stars, are seen on the black background.
November 7, 2025 at 12:31 AM
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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
A low-res black-and-white image of a pair of galaxies. A small bright white vertical line and a fainter circular object are at the center of the frame. A few white dots, which are stars, fill the black background of space.
November 6, 2025 at 12:31 PM
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Hubble image of Arp 273, also known as UGC 1810 and UGC 1813.

UGC 1810, the larger galaxy in this interacting pair, is distorted into a rose-like shape by the gravity of its companion galaxy, the nearly edge-on UGC 1813.

Credit: NASA, ESA, STScI, Hubble Heritage Team
Source
Two spiral galaxies that resemble a rose sitting on top of a stem The first galaxy spiral occupies the top half of the frame and appears mostly face-on. It is oval shaped with a bright yellowish core streaked with dark dust lanes. Two spiral arms containing blue clumps of new stars wrap widely counterclockwise around the core, with a large empty gap between them. The second galaxy appears about half as long as the first and is seen much more edge-on. It is tilted from 7 o'clock to 2 o'clock and has one arm on each end that extends outward, with the left arm warping downward and the right arm warping upward. The second galaxy is similar to the first in color, with a yellowish core, bluish spiral arms, and dark dust lanes throughout.
November 6, 2025 at 12:31 AM
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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
A grainy, black and white image of a pair of interacting spiral galaxies. In the center-right of the frame is the larger galaxy, a spiral galaxy seen face-on. It has a bright center crossed by filamentary, dark dust lanes. A ring of stars and star clusters circles the center, 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 lower arm trails off in a faint arc to the left. The upper arm appears to connect to its companion galaxy in the upper 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. A few particularly bright stars with diffraction spikes are seen to the left of the center galaxy.
November 5, 2025 at 12:32 PM
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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
A pair of interacting spiral galaxies. The galaxy in the center appears face-on with a bright center, surrounded by swirls of dark dust filaments. The outer areas of the galaxy are filled with a haze of pale stars. To the left is its companion galaxy. The disk of this galaxy is seen at an angle, tilted so that it appears to be an oval rather than a circle. Dark dust filaments somewhat obscure the spiral structures in its disk, which is filled with star clusters. At the bottom left edge of this galaxy, the end of a spiral arm or a tidal tail appears to extend downwards, connecting to the side of its companion. At the top edge of the central galaxy is what appears to be a faint tidal tail, dotted with star clusters, perhaps a continuation of the tail from the companion galaxy. The black background of space is dotted with foreground stars and tiny background galaxies.
November 5, 2025 at 12:31 AM
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Hubble image of Arp 78, also known as NGC 772.

The cropped view does not show the galaxy's overdeveloped spiral arm, caused by interactions with a companion, which led to its inclusion in Arp's catalog of peculiar galaxies.

Credit: ESA, NASA, A. Seth et al.
Source
The central portion of a large, nearly face-on spiral galaxy fills the frame. In the center is a small, bright, yellow-white nucleus. It is surrounded by a mostly featureless yellow oval, made of a haze of older yellow stars. At the edge of the oval, several dust lanes, made of a lacy web of brown filaments, spiral counter-clockwise. Scattered between the filaments, especially in the lower right corner of the frame, are young star clusters, seen as bright blue dots.
November 4, 2025 at 12:31 PM
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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
Three galaxies in a vertical image. Top one is blue and vertical, and smaller than the other two. The middle galaxy is half-curved around the lower galaxy and by far the largest. It shows streaks of bright blue and red strings of dust. The lowest galaxy in the scene is a bright white orb, about one sixth of the size of the middle galaxy above it.
November 4, 2025 at 12:31 AM
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Image of Arp 299, also known as NGC 3690, from Halton Arp's Atlas of Peculiar Galaxies (1966).

In the original catalog it was in the category: Double and multiple galaxies - Unclassified objects. Interactions between the pair triggered a starburst.
Source
A grainy, black and white image of two merging galaxies that form an abstract shape, which looks a little like a rubber duck. Within the "head" and "body" of the duck are dark swirls, which are dust and gas. The outside of the duck is outlined with hazy swirls, which are streams of stars.
November 3, 2025 at 12:31 PM
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Image of Arp 13, also known as NGC 7448, from Halton Arp's Atlas of Peculiar Galaxies (1966).

In the original catalog it was in the category: Spiral galaxies - Detached segments. It has particularly bright spiral arms.
Source
A grainy, black and white image of a spiral galaxy with a small, bright, circular core. The poorly-defined spiral arms wind clockwise around the core. The galaxy is tilted slightly, so it forms an oval shape, rather than a circle. A few white dots, which are stars, are seen on the black background.
November 3, 2025 at 12:31 AM
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Hubble Space Telescope image of Arp 12, also known as NGC 2608.

NGC 2608 is a barred spiral galaxy. Its arms are peppered by blue star clusters and red star forming regions and crossed by brown dust lanes.

Credit: ESA, NASA, A. Riess et al.
Source
A face-on barred spiral galaxy fills most of the frame. It has a yellow central core and horizontal bar structure. Attached to the bar are several spiral arms which originate at the end of the bar and spiral clockwise. The arms are somewhat squished, so the galaxy appears oval-shaped, longer than it is tall. There are two foreground stars with diffraction spikes, one right above the core of the galaxy and one to the lower right. The black background of space is dotted with numerous tiny, distant galaxies.
November 2, 2025 at 12:31 PM
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Image of Arp 142, also known as NGC 2936, NGC 2937, and UGC 5130, or the Penguin and the Egg, from Halton Arp's Atlas of Peculiar Galaxies (1966).

In the original catalog it was in the category: Elliptical galaxies - Emanating material.
Source
A grainy, black-and-white image of a pair of merging galaxies. A galaxy that looks somewhat like an egg is at left and a galaxy that looks somewhat like a penguin is at right. The Penguin is somewhat detailed, with a bright beak, body, and tail that is covered in an arc of dark dust that sweeps from the beak area and ends beyond its tail feathers. The Egg appears as a bright, featureless oval. A third disk-shaped galaxy is seen to the upper left. Various small galaxies and stars cover the scene, seen as fuzzy white points. The background of space is black.
November 2, 2025 at 12:31 AM
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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
Three overlapping galaxies fill the frame. In the center are two large spiral galaxies. The larger one, at center-left, has a bright nucleus surrounded by a yellow-white core made of mostly older stars. At the edge of the core, two spiral arms emerge. One begins at about 6 o'clock and curves counter-clockwise to about 12 o'clock. The second begins at about 12 o'clock and curves down to about 8 o'clock, with a fainter part of the arm continuing on to about 5 o'clock. The arms are threaded with brown dust lanes. A few pink star-forming regions and blue star clusters dot the outer portion of the arm. The second spiral galaxy is at center-right. It has a bright center, and a well-defined bar and two spiral arms. Together, the bar and arms form an S-shape. Compared to its companion, this galaxy has less dust and more blue star clusters in its arms. The final galaxy in the triplet appears at the far left of the frame. It is much smaller than its companions and has a blobby, irregular appearance, although it could be a disrupted disk seen edge-on. It has a bright yellow-white center and an almost vertical line of blue star clusters. Dotted throughout the galaxy are pink star-forming regions. A few stars appear on the black background of space, including two large foreground stars, which appear above the center-right galaxy.
November 1, 2025 at 12:31 PM
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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
Two similar-looking spiral galaxies take up most of the frame. They both have bright, yellow-white central cores and well-defined spiral arms dotted with blue star clusters and dark dust lanes. NGC 5427 is a nearly face-on spiral galaxy at left. NGC 5426 is a more oblique galaxy at right. The two spiral arms on the upper side of NGC 5426 appear as a bridge that connects with NGC 5427. The black background of space is dotted with stars and small background galaxies.
November 1, 2025 at 12:31 AM
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Hubble image of Arp 140, also known as NGC 274 and NGC 275.

A barred spiral galaxy and a lenticular galaxy from an interacting pair. Lenticular galaxies have large central bulges and flattened disks like spirals, but no spiral arms.

Credit: NASA, ESA, R. Foley, G. Kober
Source
Two side-by-side galaxies fill the image. The left galaxy is a bright spiral galaxy bursting with blue star clusters, crossed by dark brown dust lanes. The right galaxy is a lenticular galaxy. It bright yellow-ish white center that gradually becomes more transparent, emitting a hazy glow. Distant stars and galaxies dot the background.
October 31, 2025 at 12:31 PM
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Gemini North image of Arp 78, also known as NGC 772.

Interactions with its companion galaxy NGC 770 (out of frame) left NGC 772's bottom arm elongated and asymmetrical.

Credit: International Gemini Observatory, NOIRLab, NSF, AURA
Source
A large, nearly face-on spiral galaxy fills most of the frame. Appearing somewhat like an aerial view of a hurricane, the galaxy's spiral arms swirl around a bright yellow-white center. The curling arms are defined by dark brown dust lanes and are dotted with blue stars. While the arms in the upper portion of the galaxy are somewhat poorly defined, in the bottom of the galaxy, one overdeveloped spiral arm curves counter-clockwise from about 3 o'clock to about 8 o'clock. The inner edge of this arm features a line of blue dots, which are star clusters. The outer edge of this arm is traced by filamentary dust lanes. Since this arm flattens out near its end, in contrast to the rounder upper arms, the overall shape of the galaxy resembles a paisley. The black background of space can be seen in the upper left and lower right corners of the image, filled with numerous tiny background galaxies and a few foreground stars.
October 31, 2025 at 12:31 AM
arpbot.bsky.social
Image of Arp 104, also known as NGC 5216 and NGC 5218, or Keenan’s System, from Halton Arp's Atlas of Peculiar Galaxies (1966).

In the original catalog it was in the category: Elliptical galaxies - Connected to spiral galaxies.
Source
A grainy, black and white image of two galaxies connected by a long, thin stream of gas and stars that form a vertical line. The first galaxy, at the bottom of the frame, appears to be a disturbed spiral galaxy. It has a swirling disk made of a haze of stars accented by faint dust lanes. A long, thin, translucent line, made of a haze of stars and gas, connects the top of the top galaxy to the bottom of its companion above. The second galaxy is near the top of the frame. It is roughly circular and has a bright, center that gradually fades out and becomes more translucent near its edges. The thin line of stars and gas appears to emerge from the top of the galaxy, arcing slightly down as it exits. A few white dots, which are stars, are seen on the black background of space.
October 30, 2025 at 12:31 PM