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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 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.
February 11, 2026 at 12:31 PM
arpbot.bsky.social
Image of Arp 3, from Halton Arp's Atlas of Peculiar Galaxies (1966).

In the original catalog it was in the category: Spiral galaxies - Low surface brightness.
Source
A grainy, black and white image of a face-on spiral galaxy. It's arms are not well defined, so the galaxy's stars and gas appear to form a patchy circle around the galaxy's central bar. Several white dots, which are stars, are seen on the black background.
February 11, 2026 at 12:31 AM
arpbot.bsky.social
Hubble image of Arp 300, also known as UGC 05028 and UGC 05029.

UGC 05028 (smaller spiral) and UGC 05029 (larger spiral) form an interacting galaxy pair. The bright knot in UGC 05028 may be another small galaxy.

Credit: NASA, ESA, STScI, J. Dalcanton, Judy Schmidt, PanSTARRS
Source
A black and white image of a pair of spiral galaxies. The larger galaxy to the upper left is seen nearly face-on. It has a small core and a short bar that transitions into spiral arms that are dotted with bright star clusters. More star clusters appear on the right of the galaxy, the side that faces its companion. There are a few dark dust lanes, concentrated near the inner spiral arms. The smaller spiral galaxy to the lower right has a bright bar structure that is surrounded by star clusters that only very roughly form spiral arms. On the bottom of the galaxy there is a knot of stars that is brightest in its center, crossed by dark dust lanes. This may be a seperate dwarf galaxy that is either in front of the smaller spiral or is in the process of merging with it. Other distant galaxies and stars fill the black background of space.
February 10, 2026 at 12:31 PM
arpbot.bsky.social
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.
February 10, 2026 at 12:31 AM
arpbot.bsky.social
ALMA and Hubble image of Arp 220, also known as IC 4553.

Dust blocks the center of a galaxy merger in the Hubble visible light view. However, ALMA sees two compact cores in millimeter wavelength light (red).

Credit: ALMA(ESO/NAOJ/NRAO), NASA, ESA, and The Hubble Heritage Team
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. In the center are two bright red dots. The top one is brighter and the lower one is slightly fainter.
February 9, 2026 at 12:44 PM
arpbot.bsky.social
Hubble image of Arp 217, also known as NGC 3310.

NGC 3310 is a distorted spiral galaxy undergoing a burst of star formation that began about 100 million years ago.

A merger with a smaller galaxy may have triggered the starburst.

Credit: NASA, ESA, The Hubble Heritage Team
Source
The central portion of a spiral galaxy that somewhat resembles an aerial view of a hurricane. It has a bright red center that is surrounded by curving, somewhat poorly defined spiral arms. The arms are dotted with white star clusters near the center and blue-white star clusters near their ends.
February 9, 2026 at 12:31 AM
arpbot.bsky.social
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.
February 8, 2026 at 12:31 PM
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JWST image of Arp 298, also known as NGC 7469 and IC 5283.

This image is dominated by NGC 7469, a face-on spiral galaxy. Its companion galaxy IC 5283 is partly visible in the lower left corner.

Credit: ESA, NASA, CSA, L. Armus, A. S. Evans
Source
This image shows a spiral galaxy that is dominated by a bright central region. The galaxy has blue-purple hues with orange-red regions filled with stars. Also visible are large diffraction spikes, which appears as an 8-pointed star pattern (6 big and two smaller points) over the central region of the galaxy. In the bottom left corner of the image is a second galaxy, cut off by the frame. In the portion you can see, a haze of yellow stars is crossed by darker dust lanes. Lots of stars and galaxies fill the background scene.
February 8, 2026 at 12:31 AM
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Image of Arp 85, also known as the Whirlpool Galaxy or M51, 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 two galaxies. The larger of the two galaxies, a spiral, is on the left side of the image. Two well-defined arms extend to from its center and form loose spirals around the middle. The smaller galaxy on the far-right side is fuzzy sphere. The view of this smaller galaxy is partially obstructed by the tip of one of the arms of the spiral galaxy, which appears to cover the top third of the smaller galaxy. Many white dots, stars, are seen on the black background.
February 7, 2026 at 12:31 PM
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Hubble image of Arp 238, also known as UGC 8335.

Gravitational interactions between these two spiral galaxies created a bridge of material and two curved tails of gas and stars. These tails are full of clusters of young, hot, blue, stars.

Credit: NASA, ESA, STScI
Source
A pair of interacting spiral galaxies, connected by streams of material, form a backwards S shape. The top galaxy is a face-on spiral. It has a yellow-white center mottled with brown dust. A haze of blue stars and star clusters appears to splash out of the galaxy to the upper left and lower right. A denser stream of yellow-white material continues above the galaxy, curving to the left. This stream also has faint brown dust lanes. The bottom galaxy is a bit of a mess. It's probably a highly distorted edge-on spiral galaxy. One stream of material from this galaxy continues above, merging with the upper face-on spiral. A second, larger stream curves below the galaxy, curving to the right like a fish hook. Both of these streams are dotted with blue stars and star clusters and are crossed by dark brown dust lanes. To the right of the merging galaxies are two bright foreground stars with Hubble's four diffraction spikes. The black background of space is dotted with a few additional foreground stars and many smaller background galaxies.
February 7, 2026 at 12:31 AM
arpbot.bsky.social
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.
February 6, 2026 at 12:31 PM
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Hubble image of Arp 202, also known as NGC 2719 and NGC 2719A.

This edge-on disk galaxy and smaller irregularly shaped galaxy had a recent interaction which likely severely perturbed both galaxies.

Credit: NASA, ESA, STScI, Julianne Dalcanton, Meli thev, Wikimedia Commons
Source
A greyscale image of two galaxies. At the center of the frame is a disk galaxy seen edge-on. It is brightest at the center, but many bright star clusters dot the galaxy above and below the plane of the disk. Above and to the right is a second smaller galaxy that is roughly circular. On the outside of the circle is an irregular ring of star clusters. A line of stars and gas is just barely visible trailing from the point the two galaxies meet to the upper left corner of the frame. The image has a noticeable amount of detector noise which has not been removed.
February 6, 2026 at 12:31 AM
arpbot.bsky.social
Kitt Peak image of Arp 78, also known as NGC 772.

Interactions with its companion galaxy NGC 770, the small elliptical galaxy in the center near the top of the frame, left NGC 772's bottom arm elongated and asymmetrical.

Credit: KPNO, NOIRLab, NSF, AURA, A. Block
Source
A nearly face-on spiral galaxy is in the center 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. 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. Since this arm flattens out near its end, in contrast to the rounder upper arms, the overall shape of the galaxy resembles a paisley. In the center of the frame, near the top, is its small companion galaxy, seen as a fuzzy oval. The black background of space is filled with tiny background galaxies and foreground stars.
February 5, 2026 at 12:31 PM
arpbot.bsky.social
Image of Arp 285, also known as NGC 2854 and NGC 2856, 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. This pair had a past interaction.
Source
A grainy, black and white image of a a pair of widely-space interacting spiral galaxies. The galaxy in the lower right has a bright disk seen at a slight angle so that it appears oval-shaped. It's spiral arms are fainter, but its lower arm is slightly brighter. A thin, clumpy line extends below the galaxy, perpendicular to its disk. The galaxy in the upper left has a strong bar and two spiral arms, forming a distinct S shape. The arms are dotted with star clusters. Faint streams of material extend out from the ends of the spiral arms. Several foreground stars are seen as bright dots. The brightest star, in the upper left, has four diffraction spikes.
February 5, 2026 at 12:31 AM
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Image of Arp 22, also known as NGC 4027, from Halton Arp's Atlas of Peculiar Galaxies (1966).

In the original catalog it was in the category: Spiral galaxies - One-armed. It is interacting with a smaller companion galaxy, NGC 4027A, below.
Source
A grainy, black and white image of a face-on spiral galaxy. A single large blue spiral arm begins at the top and curves counter-clockwise from about the 12 o'clock to 11 o'clock positions. This gives the galaxy a teardrop-shape with a curved end, so that it resembles a paisley. Many white dots, which are stars, are seen on the black background.
February 4, 2026 at 12:31 PM
arpbot.bsky.social
Image of Arp 84, also known as NGC 5394 and NGC 5395, 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 that somewhat resembles a heron. To the upper right is a smaller, distorted spiral, forming the heron's neck, head, and beak. In its center is a bright nucleus surrounded by a ring of stars. Extending from the ring are two large, thin spiral arms, dotted with star clusters, which form an S-shape. The lower arm appears to touch the edge of the disk of its companion galaxy. On the left is a large spiral galaxy, forming the heron's body. It's disk is tilted, so that it appears as a oval rather than a circle. It has a bright center that transitions into spiral arms. The arms are defined by dark brown dust lanes. The area in between is filled with a haze of bright stars. On the black background of space are foreground stars, some with diffraction spikes, and tiny background galaxies. A few white dots, which are stars, are seen on the black background of space.
February 4, 2026 at 12:31 AM
arpbot.bsky.social
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.
February 3, 2026 at 12:31 PM
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Hubble image of Arp 195, also known as UGC 4653.

The Establishing HST's Low Redshift Archive of Interacting Systems snapshot program filled in Hubble schedule gaps with short observations, like this one of three interacting galaxies.

Credit: ESA, NASA, J. Dalcanton
Source
Three interacting galaxies form a roughly horizontal line. The galaxy on the left is a face-on barred spiral. It has a bright core that transitions into a pale yellow oval-shaped roughly horizontal bar. Surrounding and outlining the bar is a ring of blue stars and star clusters. Emerging from the ends of the bar are two spiral arms that form a backward S-shape. The top arm curves counterclockwise from about 3 o'clock to 9 o'clock. The bottom arm begins at about 9 o'clock, curving around to intersect or pass behind the other galaxies at about 4 o'clock. The middle galaxy is seen as a roughly horizontal, pale yellow oval. It overlaps with the other two galaxies to its left and right. Crossing the oval are several wide, brown dust filaments. The galaxy on the right is perhaps a very disturbed barred spiral. It has a bright center, which transitions into a nearly vertical pale yellow bar structure. One spiral arm begins at the top of the bar, and then plunges down a ridiculous amount, forming a vertical line that is about three times the length of the bar, reaching nearly the bottom of the frame. It is made of a haze of blue stars and star clusters. A dark brown dust filament crosses the bar and then swoops down with the arm, forming an upside down U shape. A bright foreground star with four diffraction spikes sits at the left edge of the frame. The black background of space is dotted with a few additional foreground stars and many tiny background galaxies.
February 2, 2026 at 12:32 PM
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Image of Arp 287, also known as NGC 2735 and NGC 2735A, from Halton Arp's Atlas of Peculiar Galaxies (1966).

In the original catalog it was in the category: Double and multiple galaxies - Wind effects.
Source
A grainy, black and white image of of a pair of interacting galaxies. The large spiral at center is tilted at an angle, so it appears as an oval-shape rather than a circle. The long axis of the oval is nearly vertical. Below is a smaller, irregular galaxy. A bridge of gas and stars connects the two galaxies. A similar tail emerges from the above the central spiral galaxy. A few white dots, which are stars, are seen on the black background.
February 2, 2026 at 12:31 AM
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Spitzer image of Arp 16, also known as M66.

The blue core and bar has a concentration of blue older stars, and the pink bar ends and spiral arms show dust heated by actively forming stars.

Credit: NASA/JPL-Caltech/R. Kennicutt (University of Arizona) and the SINGS Team
Source
A nearly face-on barred spiral galaxy anchored by its central region, which has a bright blue central dot surrounded by a lighter diagonal blue bar structure made of a haze of stars. Two distinct spiny pink spiral arms start at the end of the bar, rotating clockwise, and forming an S-shape.
February 1, 2026 at 12:31 PM
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JWST NIRCam and MIRI image of Arp 107, also known as UGC 5984.

In the near-infrared, older stars and a bridge of gas and stars between the galaxies appear in white. In the mid-infrared, star-forming regions are in orange and red.

Credit: NASA, ESA, CSA, STScI
Source
A pair of interacting galaxies. The larger of the two is slightly right of center. It is a one-armed spiral galaxy with a hazy, bright, white center and a ring of gaseous filaments, which are different shades of red and orange. The single spiral arm begins at about the 7 o'clock position and spirals counterclockwise to the 12 o'clock position, forming a ring structure. Toward the bottom left and right of the ring are filaments of gas spiraling inward toward the core. At the top left of the ring, at the 11 o'clock position, is a noticeable gap, bordered by two large, orange pockets of dust and gas. The smaller elliptical galaxy to its left is made of hazy white gas and dust, which becomes more diffuse farther away from its center. To this galaxy’s bottom left, there is a smaller, more diffuse gas cloud that wafts outward toward the edges. Many red, orange, and white galaxies are spread throughout the background, with some hazier in composition and others having defined spiral patterns.
February 1, 2026 at 12:32 AM
arpbot.bsky.social
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.
January 31, 2026 at 12:32 PM
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Legacy Surveys image of Arp 11, also known as UGC 717.

UGC 717 is the large spiral galaxy in the lower right. The large spiral in the upper left is UGC 719.

Credit: Legacy Surveys, D. Lang, NERSC, Meli thev, Wikimedia Commons
Source
A group of several spiral galaxies in shades of yellow. The large spiral galaxy in the lower right, UGC 717, has a small core, and a bar surrounded by a ring structure. On the outside of the ring are several spiral arms, including one arm that splits in two as it curves around the top of the galaxy. The large spiral in the upper left, UGC 719, has a small core, and a bar surrounded by a ring structure. On the outside of the ring are several somewhat ill-defined spiral arms. In the background are many other smaller galaxies in shades of yellow and red.
January 30, 2026 at 12:31 PM
arpbot.bsky.social
Hubble image of Arp 220, also known as IC 4553.

Arp 220 is the aftermath of a collision between two spiral galaxies. The collision set off a burst of star formation, creating star clusters seen as bluish-white bright knots in this image.

Credit: NASA, ESA, STScI, A. Evans
Source
An irregularly shaped galaxy fills most of the frame. The center is brighter, filled with a blue-white haze of stars that backlights a horizontal band of brown dust. Another area to the left of the core, almost as bright as the center is filled with a similar haze of stars and dotted with blue star clusters. To the right, the galaxy is less bright and more transparent. A faint hazy line extends almost vertically from the top of the galaxy. The black background of space is filled with stars and tiny background galaxies.
January 30, 2026 at 12:31 AM
arpbot.bsky.social
Hubble and Pan-STARRS image of Arp 300, also known as UGC 05028 and UGC 05029.

In this image of an interacting galaxy pair, the luminosity comes from Hubble ACS/WFC observations, and color comes from Pan-STARRS.

Credit: NASA, ESA, STScI, J. Dalcanton, Judy Schmidt, PanSTARRS
Source
The frame is dominated by a pair of spiral galaxies. The larger galaxy to the upper left is seen nearly face-on. It has a small pale yellow core and a short bar that transitions into spiral arms that are dotted with bluish purple star clusters. More star clusters appear on the right of the galaxy, the side that faces its companion. There are a few dark dust lanes, concentrated near the inner spiral arms. The smaller spiral galaxy to the lower right has a pale yellow bar structure that is surrounded by bluish purple star clusters that only very roughly form spiral arms. On the bottom of the galaxy there is a yellow knot of stars that is brightest in its center, crossed by brown dust lanes. This may be a seperate dwarf galaxy that is either in front of the smaller spiral or is in the process of merging with it. Other distant galaxies and stars fill the black background of space.
January 29, 2026 at 12:31 PM