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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
Spitzer, VLA, and CFHT MegaCam image of Arp 94, also known as NGC 3226 and NGC 3227.

The grayscale image shows visible starlight. Cool hydrogen gas (blue), floods the top galaxy and shuts down star formation.

Credit: NASA, CFHT, NRAO, JPL-Caltech, Duc, Cuillandre
Source
Two interacting galaxies appear on a field of stars. A black and white image of the galaxies taken in visible light is overlaid with radio (blue) and infrared (pink) images. The bottom galaxy is a large spiral. It is tilted slightly, so that its disk forms an oval rather than a circle. The top galaxy is a bright elliptical galaxy. It is oval shaped with a bright center that gets gradually fainter and more transparent towards its edges. A plume of gas and stars surrounds and appears to rise from the galaxies, like smoke from a campfire. The blue radio light snakes around the outside of the spiral galaxy, through the elliptical galaxy and into the plume, forming a teardrop shape. The pink infrared light highlights the centers of the spiral and elliptical galaxies.
December 27, 2025 at 12:31 AM
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Subaru Telescope and Blackbird Observatory image of Arp 189, also known as NGC 4651 or the Umbrella Galaxy.

The parasol-shaped feature to the left is debris from a tiny galaxy that was shredded apart by gravity as it fell into its larger companion.

Credit: NAOJ, R. Jay GaBany
Source
A nearly face-on spiral galaxy sits at the center of the frame, on a field of stars. It has a yellow center and blue spiral arms that twist clockwise around the galaxy. Surrounding the galaxy is a faint, oval-shaped haze of stars. In the left of the oval is a line and an arc, which resemble the shape of an umbrella. An insert shows a closeup of the line and the location of a star cluster, seen as a white dot.
December 26, 2025 at 12:31 PM
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GALEX and SDSS 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: Fig. 12 from Smith et al. 2010.
Source
A two-panel image. The left panel is labeled Arp 283 GALEX. A scale bar marks 1 arcminute, which is about 1/8 the width of the frame. The panel shows a low-res image of a pair of interacting galaxies. in shades of yellow and blue. The galaxy on the left is seen edge-on. It has a bright central core and a slightly warped blue disk. The edge of the disk arcs to the right, appearing to connect to its companion galaxy. The second galaxy is seen as a fuzzy yellow circle, with a brighter off-center core. The right panel is labeled Arp 283 SDSS and has a similar 1 arcminute scale bar. It shows the same galaxies at the same scale and is higher resolution. The galaxy on the left is seen edge-on. It has a bright yellow central core and a slightly warped blue disk. The edge of the disk arcs to the right, appearing to connect to its companion galaxy. The second galaxy is inclined, but seen closer to face-on. It has a central bar of blue-ish stars that is largely obscured by a haze of yellow stars and dust lanes in the circular core of the galaxy. Two spiral arms emerge from the core, which are wide, poorly defined, and mostly made of yellow older stars, which is unusual for a spiral galaxy.
December 26, 2025 at 12:31 AM
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Hubble image of Arp 219, also known as UGC 2812.

Interactions with a companion likely formed these loops of material.

In this image, the luminosity comes from Hubble observations, and color from PanSTARRS.

Credit: NASA, ESA, STScI, J. Dalcanton, Judy Schmidt, PanSTARRS
Source
A distorted galaxy with looping tidal tails. In the center of the frame is a galaxy with a bright yellow center. A dark brown dust lane divides the bright center of the galaxy in two. It's hard to tell if this dust is blocking a continuous bright area or if there are two distinct nuclei. The disk of the galaxy surrounds the center, probably seen nearly edge-on, made of a haze of older yellow stars. At the left and right edges of the disk are blue clusters of younger stars. One stream of gas and stars, a tidal tail, starts at the left edge of the disk, loops under the galaxy, and connects with the bottom right edge of the disk. A second stream of gas begins at the top right edge of the disk, loops over the galaxy, and then connects to the top left edge of the disk. Together, these two tidal tails form a rough ring shape. Another fainter tidal tail starts at the apex of the top arc and continues diagonally up and to the left. A smaller galaxy, an almost edge-on spiral, is below and to the left of the central galaxy.
December 25, 2025 at 12:31 PM
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Hubble image of Arp 185, also known as NGC 6217.

This was the first image of a celestial object taken with the newly repaired Advanced Camera for Surveys (ACS) after the 2009 Servicing Mission 4 for the Hubble Space Telescope.

Credit: NASA, ESA, and the Hubble SM4 ERO Team
Source
A face-on barred spiral galaxy fills most of the frame. The galaxy has a bright yellow-white center, surrounded by a yellow bulge. This transitions into a prominent diagonal bar structure, which points from bottom left to top right. At the ends and sides of the bar are a series of short, somewhat ill-defined spiral arms, dotted with blue star clusters, pink star-forming regions, and brown dust lanes. At the edges of the galaxy the spiral arms appear to continue, curving counter-clockwise at the top and bottom, defined by widely spaced, faint star clusters. The galaxy sits on the black background of space, with a few scattered foreground stars and tiny background galaxies.
December 24, 2025 at 12:32 PM
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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
Two merging galaxies form an abstract shape, which looks a little like a rubber duck. Within the "head" and "body" of the duck are blue-white dots, which are star clusters, and brown swirls, which are dust and gas. The outside of the duck is outlined with hazy yellow swirls, which are older stars.
December 24, 2025 at 12:31 AM
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Composite image of Arp 26, also known as M101 or the Pinwheel Galaxy.

It combines data from X-ray (Chandra, purple), infrared (Spitzer, red), visible light (Hubble, yellow), and ultraviolet (GALEX, blue) telescopes.

Credit: NASA, CXC, SAO;NASA, JPL-Caltech;NASA, STScI
Source
A multiwavelength image of a spiral galaxy. The galaxy has a small pink core. Several arms spiral clockwise around the core. They are crossed by pink, filamentary dust lanes and made of a haze of yellow stars. Along the arms are purple splotches. In the outer parts of the galaxy, the arms appear blue, dotted with blue star clusters. 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. Other arms cover the area from 12 o'clock to 6 o'clock.
December 23, 2025 at 12:32 PM
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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
A three-panel image, showing Spitzer, Hubble, and Chandra views of the same Spiral Galaxy M101. On the left is the Spitzer view. From a small central core, several arms spiral clockwise. They are defined by a network of yellow-green filamentary dust lanes, which look somewhat like a cross section of a nautilus. The arms are dotted with pink star-forming regions and filled in with a haze of blue stars. One spiral arm curls from about 6 o'clock to 9 o'clock and is mostly separated from the body of the galaxy. The other spiral arms are less distinct. In the middle is the Hubble view. 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. On the right is the Chandra view. In this panel, blue and purple splotches partially define spiral arms. These arms are smaller and less distinct than in the other views. White dots are scattered throughout the image, including a concentration of points at the galaxy's core. Credit: NASA, ESA, CXC, JPL, Caltech, STScI. ssc2009-03b
December 23, 2025 at 12:31 AM
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Sloan Digital Sky Survey image of Arp 291, also known as UGC 5832.

This one-armed barred spiral galaxy may be interacting with the small galaxy above it and to the right.

Credit: SDSS
Source
A somewhat low-res image of a one-armed barred spiral galaxy. The bar, seen as a bright white 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 yellow-green stars and are dotted with bright blue-green star clusters. To its upper right is a smaller galaxy. It has a bright yellow center and a more diffuse disk or halo of stars. Dotted across the black background of space are small background galaxies and foreground stars.
December 22, 2025 at 12:32 PM
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Image of Arp 194, also known as UGC 6945, from Halton Arp's Atlas of Peculiar Galaxies (1966).

In the original catalog it was in the category: Amorphous galaxies - Material ejected from nuclei. This interacting group has several spiral galaxies.
Source
A grainy, black and white image of a group of interacting galaxies which resembles a question mark. At the top of the frame, a somewhat messy spiral shape formed by a pair of merging galaxies forms the top part of the question mark. At the bottom of the frame is another galaxy, which forms the dot of the question mark. A string of star clusters, seen as large dots, connects the galaxies, forming the straight part of the question mark. A few white dots, which are stars, are seen on the black background.
December 22, 2025 at 12:31 AM
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Image of Arp 188, also known as Tadpole Galaxy, from Halton Arp's Atlas of Peculiar Galaxies (1966).

In the original catalog it was in the category: Amorphous galaxies - Narrow filament. The tail is a result of a recent galactic interaction.
Source
A grainy, black and white image of a galaxy. In the upper left corner is a spiral galaxy with a bright central core encircled by two wispy arms that form a loose spiral. The view is somewhat oblique, giving the galaxy an oval appearance. A long, thin, diffuse stream extends from the lower right side of the galaxy down to the lower right corner of the image. In the background there are a few circular dots, which are stars, and smudgy objects, which may be background galaxies.
December 21, 2025 at 12:31 PM
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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
A pair of interacting galaxies. On the right is a nearly face-on spiral. It has a small, bright central core, surrounded by a haze of yellow stars. Surrounding this is a ring of blue stars, dotted by blue star clusters. Two wide spiral arms emerge from the ring, crossed by dark brown dust lanes. They fan out, almost connecting back to the main body of the galaxy. A line of blue star clusters begins at the left spiral arm and arcs around the body of the galaxy. The left arm extends out connecting to its companion galaxy at left. The left galaxy is an edge-on disk, seen as a wide, angled line of yellowish stars. A stream of blue stars, star clusters, and gas appears to come from its companion's spiral arm and wrap one and a half times around the disk galaxy. A third galaxy, a smaller edge-on spiral, is seen to the left of the disk galaxy. The black background of space is dotted with a few foreground stars and tiny background galaxies.
December 21, 2025 at 12:31 AM
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Image of Arp 202, also known as NGC 2719 and NGC 2719A, 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 202 is an interacting galaxy pair.
Source
A grainy, black and white image of two galaxies. Both are overexposed, so that there is no detail apparent in the interiors of the galaxies. At the center of the frame, running diagonally from lower right to upper left is a disk galaxy seen edge-on. To the left, aligned with the bottom edge of the disk galaxy, is a second smaller galaxy that is irregular but roughly circular. A faint line extends upwards from where the two galaxies meet. A few white dots, which are stars, are seen on the black background.
December 20, 2025 at 12:31 PM
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Image of Arp 2, also known as UGC 10310, 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 barred Magellanic spiral galaxy.
Source
A grainy, black and white image of a galaxy. The galaxy's stars and gas form a patchy, loose, two-armed spiral with a central bar. A few white dots, which are stars, are seen on the black background.
December 20, 2025 at 12:31 AM
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Kitt Peak National Observatory image of Arp 9, also known as NGC 2523.

NGC 2523 is the bright barred spiral galaxy on the left side of the frame. The edge-on spiral galaxy to the right, NGC 2523 B, is in the same galaxy group.

Credit: KPNO, NOIRLab, NSF, AURA, Adam Block
Source
Two small galaxies appear on a sparse field of stars. At center left is NGC 2523, a face-on barred spiral. It has a bright yellow central core with a horizontal 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 arms are dotted by blue star clusters and shrouded in a haze of stars. At right center is NGC 2523B, an edge-on spiral. It has a yellow central bulge and a blue disk, which is crossed by a central brown dust lane.
December 19, 2025 at 12:31 PM
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Hubble and Spitzer image of Arp 148, also known as Mayall's Object.

Dusty material in the edge-on galaxy (left) glows brightly in the infrared light seen by Spitzer (red). Starlight dominates the visible light from Hubble (blue and green).

Credit: NASA, JPL-Caltech, STScI
Source
A pair of interacting galaxies. The galaxy on the left is likely an edge-on disk galaxy, appearing as a slightly warped, fuzzy, white horizontal line with dust filaments at its center. It is surrounded by a red glow on the left part of the galaxy and a green glow at its right edge. The galaxy on the right is a ring galaxy, appearing as a blue circular ring, dotted with blue star clusters, that also has its center partially filled in with blue star clusters. The two galaxies overlap so that the right end of the edge-on galaxy intersects with the ring galaxy's center. It looks a bit like a big blue hand holding the Enterprise in a classic episode of Star Trek.
December 19, 2025 at 12:31 AM
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JWST NIRCam image of Arp 142, also known as NGC 2936 and NGC 2937, or the Penguin and the Egg.

The blue haze in the distorted spiral galaxy, elliptical galaxy, and the bridge connecting the two are stars. Red filaments are glowing dust.

Credit: NASA, ESA, CSA, STScI
Source
Arp 142, two interacting galaxies, observed in near-infrared light. At left is NGC 2937, nicknamed the Egg. Its center is brighter and whiter. There are six diffraction spikes atop its gauzy blue layers. At right is NGC 2936, nicknamed the Penguin. Its beak-like region points toward and above the Egg. Where the eye would be is a small, opaque yellow spiral. The Penguin’s distorted arms and thin red dust lanes from the bird’s beak, back, and tail. The tail is wide and layered, like a beta fish’s tail. A semi-transparent blue hue traces the Penguin and extends from the galaxy, creating an upside-down U over top of both galaxies. At top right is another galaxy seen from the side, pointing roughly at a 45-degree angle. It is largely light blue. Its length appears approximately as long as the Egg’s height. One foreground star with large, bright blue diffraction spikes appears over top of the galaxy and another near it. The entire black background is filled with tiny, extremely distant galaxies.
December 18, 2025 at 12:31 PM
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JWST image of Arp 269, also known as NGC 4485 and NGC 4490.

NGC 4490 (bottom left) and NGC 4485 (top right), are interacting dwarf galaxies. They are connected by a bridge of red gas and stars.

Credit: ESA, NASA, CSA, A. Adamo, G. Bortolini, FEAST JWST team
Source
Horizontal image shows two interacting galaxies forming a large, wide V shape. NGC 4490 occupies the left side of the image, while NGC 4485 appears as a white glowing hue in the top right of the field. Both galaxies are connected by a bright stream of red stretching from the top left of the image, through the bottom center, and ending at the right under galaxy NGC 4485. There are regions of bright blue gas visible in concentrated areas of the red stream. The background is black with multiple galaxies in various shapes throughout
December 18, 2025 at 12:31 AM
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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
A grainy, black and white image of a disrupted spiral galaxy, surrounded by irregular spiral arms. The inner part of the galaxy is seen at an angle, so that it appears oval-shaped rather than circular. The faint arms unfurl from the center, like paint flung out of a spinning canvas. The arms stretch out to the right of the frame. The black background of space is filled with white dots, which are foreground stars.
December 17, 2025 at 12:31 AM
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Hubble image of Arp 302, also known as UGC 9618 or VV 340.

This image of a pair of very gas-rich spiral galaxies is one of 59 images of merging galaxies taken by the Hubble Space Telescope and released for its 18th anniversary in April 2008.

Credit: NASA, ESA, STScI, A. Evans
Source
A pair of spiral galaxies. The upper galaxy is seen face-on. It has a bright center and short bar structure that transitions into a series of loosely-wound spiral arms, looking something like a cinnamon roll. The arms are dotted with blue star clusters and crossed by darker dust filaments. The lower galaxy is seen edge on. It has a somewhat puffy disk, seen as a wide, almost vertical, yellow line. Running down the middle is a dark dust lane with a few blue star clusters peaking out. In the middle of the frame, where the two galaxies appear to touch, is a bright foreground star with four diffraction spikes. Other distant galaxies and stars fill the black background of space.
December 16, 2025 at 12:31 PM
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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, SDSS, J. Dalcanton, J. Schmidt
Source
A pair of interacting galaxies. The galaxy on the left is seen edge-on. It has a bright yellow central core and a slightly warped blue disk that is dotted with star clusters and clumps of dark dust. The edge of the disk arcs to the right, appearing to connect to its companion galaxy. The second galaxy is inclined, but seen closer to face-on. It has a central bar of blue-ish stars that is largely obscured by a haze of yellow stars and dust lanes in the circular core of the galaxy. Two spiral arms emerge from the core, which are wide, poorly defined, and mostly made of yellow older stars, which is unusual for a spiral galaxy.
December 16, 2025 at 12:31 AM
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Kitt Peak image of Arp 84, also known as NGC 5394 and NGC 5395.

Interactions between the galaxy pair funneled gas into the center of NGC 5394, the smaller spiral, providing the raw materials for new stars.

Credit: KPNO, NOIRLab, NSF, AURA, D. Matthews, E. J. Jones, A. Block
Source
A pair of interacting spiral galaxies. On the left is a large spiral galaxy. It's disk is tilted, so that it appears as a oval rather than a circle. It has a bright yellow-white 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 blue-white stars. Below and to the right is a second galaxy, a smaller, distorted spiral. In its center is a bright yellow nucleus surrounded by a ring of stars. The lower left part of the ring has a concentrated area of dust. Extending from the ring are two large, thin spiral arms, dotted with blue star clusters, forming an S-shape. The upper arm appears to touch the edge of the disk of its companion galaxy. On the black background of space are foreground stars, some with diffraction spikes, and tiny background galaxies.
December 15, 2025 at 12:31 PM
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VLT image of Arp 289, also known as NGC 3981.

This image was captured as part of the ESO Cosmic Gems Program, which uses the Very Large Telescope to photograph beautiful objects in the southern skies when conditions don’t allow scientific observations to be made.

Credit: ESO
Source
The yellow core of a disrupted spiral galaxy is surrounded by irregular, translucent spiral arms. The inner part of the galaxy is seen at an angle, so that it appears oval-shaped rather than circular. Dark brown dust lanes and pink star forming regions cross a yellow haze of older stars. The faint blue arms unfurl from the center, like paint flung out of a spinning canvas. They are dotted with blue star clusters. The arms stretch out to the right of the frame. The black background of space is filled with foreground stars and tiny background galaxies.
December 15, 2025 at 12:31 AM
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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
A pair of interacting galaxies. The galaxy on the left is seen edge-on. It has a bright central core and a slightly warped disk that is dotted with star clusters and clumps of dark dust. The edge of the disk arcs to the right, appearing to connect to its companion galaxy. The second galaxy is inclined, but seen closer to face-on. It has a central bar of bright stars that is largely obscured by a haze of stars and dust lanes in the circular core of the galaxy. Two spiral arms emerge from the core, which are wide and poorly defined.
December 14, 2025 at 12:31 PM
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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
A grainy, black and white image of a galaxy. Several short spiral arms wind clockwise around a bright 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.
December 14, 2025 at 12:31 AM