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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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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.

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Arp Bot 🤖 @arpbot.bsky.social · 1h

Hubble image of Arp 287, also known as NGC 2735 and NGC 2735A.

NGC 2735 is the large spiral in the center. It is interacting with the smaller NGC 2735A.

Credit: NASA, ESA, STScI, Julianne Dalcanton, Meli thev, Wikimedia Commons
Source

A greyscale image 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. It has a bright center and dark dust lanes. To its upper left is a smaller, irregular galaxy. A bridge of gas, dust, stars, and star clusters connects the two galaxies. A similar tail emerges from the bottom right of the central spiral galaxy. The image has a noticeable amount of detector noise which has not been removed. A bright foreground star is in the bottom right corner of the frame. Next to it are two circular "ghost" artifacts caused by light reflecting off of parts of the telescope.

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Arp Bot 🤖 @arpbot.bsky.social · 13h

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.

Arp Bot 🤖 @arpbot.bsky.social · 1d

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.

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Arp Bot 🤖 @arpbot.bsky.social · 1d

Composite image of Arp 16, also known as M66.

Chandra (X-ray, blue), Spitzer (infrared, red), Hubble and VLT (visible light, yellow). Insert shows hot gas near the supermassive black hole.

Credit: NASA, STScI, JPL-Caltech, ESO, WFI, CXC, Ohio State Univ., C.Grier et al
Source

A face-on barred spiral galaxy anchored by its central region. It has a bright white circular area surrounded by a lighter pinkish diagonal bar structure made of a haze of stars, which forms an angled oval toward the top. Two distinct spiral arms made of stars, gas, and reddish brown filamentary dust lanes start at the center and extend outward, rotating clockwise. The outer spiral arms are made of many yellow clusters of stars. The background of space beyond the galaxy appears black. There are some large blue and red points of light surrounding the galaxy. A white box outlines the center part of the galaxy. An insert shows the X-ray only light from the area covered by the box. In the insert are 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.

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Arp Bot 🤖 @arpbot.bsky.social · 2d

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.

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Arp Bot 🤖 @arpbot.bsky.social · 2d

Hubble and NuStar image of Arp 299, also known as NGC 3690.

NuSTAR data overlaid on a Hubble image of the interacting galaxy pair show the galaxy on the right has an active supermassive black hole, glowing brightly in X-rays.

Credit: NASA, JPL-Caltech, GSFC
Source

Two merging galaxies form an abstract shape, which looks a little like an upside down rubber duck. Within the "head" and "body" of the duck are crossed brown swirls, which are dust and gas. The outside of the duck is outlined with hazy yellow swirls, which are streams of stars. Near the "neck" of the duck, at the point where the two merging galaxies touch, and slightly to the right is a bright white blob, surrounded by pink blobs. This is X-ray light from NuStar, which shows emission from an active supermassive black hole in the right galaxy.

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Arp Bot 🤖 @arpbot.bsky.social · 3d

Spitzer image of Arp 302, also known as UGC 9618 or VV 340.

Arp 302 is unusually bright in infrared light. This is likely because the galaxy has an unusually large amount of gas, which is forming new stars that heat their surroundings.

Credit: NASA, JPL-Caltech
Source

A low-res image of a pair of spiral galaxies appears somewhat small in the center of the frame in shades of teal and pink. The lower right galaxy is seen face-on. It has a bright pink center and short bar structure that transitions into a series of loosely-wound spiral arms. The inner arms are pink and the outer part of the arms are teal. The upper left galaxy is seen edge on. It is seen as an angled pink line with a bright center, surrounded by a teal glow. Other distant galaxies and stars, seen as teal dots, fill the black background of space.

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Arp Bot 🤖 @arpbot.bsky.social · 3d

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.

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Arp Bot 🤖 @arpbot.bsky.social · 4d

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.

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Arp Bot 🤖 @arpbot.bsky.social · 4d

Kitt Peak image of Arp 184, also known as NGC 1961.

NGC 1961 is an extremely massive spiral galaxy with irregular arms. It's shape may be the product of interactions with the gas in its galaxy cluster.

Credit: KPNO, NOIRLab, NSF, AURA, D. Matthews, A. Block
Source

A distorted spiral galaxy sits in the center of the frame, surrounded by a field of stars on a black background. It is seen at a skewed angle. Its centre is a bright spot radiating light. A thick, stormy disk of material surrounds this, with swirling strands of dark dust and bright spots of star formation strewn through the disk. A large spiral arm extends from the disc towards the viewer. Some foreground stars are visible atop the galaxy.

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Arp Bot 🤖 @arpbot.bsky.social · 5d

Hubble image of Arp 200, also known as NGC 1134.

NGC 1134 is likely interacting with its small companion, seen to the lower right, producing streamers of stars that trail off to the right.

Credit: NASA, ESA, STScI, Julianne Dalcanton, Meli thev, Wikimedia Commons
Source

A greyscale image of a face-on spiral galaxy. The faint galaxy has a bright core, a small oval-shaped ring, and two loose spiral arms that emerge from the ring and wind counterclockwise around the galaxy. The arms are crossed by dark dust lanes and dotted with bright star clusters. At the bottom right edge of the galaxy is a smaller elliptical galaxy, seen as a bright dot surrounded by an oval-shaped haze. Faint, hazy, lines of stars appear from the point where the two galaxies overlap and stream off diagonally, down and to the right. The image has a noticeable amount of detector noise which has not been removed.

Arp Bot 🤖 @arpbot.bsky.social · 5d

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.

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Arp Bot 🤖 @arpbot.bsky.social · 6d

Hubble Space Telescope image of Arp 26, also known as M101 or the Pinwheel Galaxy.

This image shows a section of the galaxy, with over 3000 bright clusters of hot, young, blue stars.

Credit: NASA, ESA
Source

An arc of blue points makes a rough backwards C shape on the black background of space. These points are hot, young stars or star clusters. Interspersed within the blue points are red points, which are cooler stars. Near the edges of the arc are hazy areas of nebulosity.

Arp Bot 🤖 @arpbot.bsky.social · 6d

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.

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Arp Bot 🤖 @arpbot.bsky.social · 7d

Chandra and Hubble image of Arp 302, also known as UGC 9618 or VV 340.

The Chandra data (pink) shows that the upper galaxy has an obscured, active supermassive black hole.

Credit: NASA, CXC, IfA, D.Sanders et al, STScI, NRAO, A.Evans et al
Source

$A pair of spiral galaxies. The lower galaxy is seen face-on. It has a bright center and short bar structure that transitions into a series of loosely-wound spiral arms, looking something like a cinnamon roll. The arms are dotted with blue star clusters and crossed by darker dust filaments. A diffuse pink glow covers the center of the galaxy. The upper galaxy is seen edge on. It has a somewhat puffy disk, seen as a wide, vertical line. Running down the middle is a dark dust lane. A bright pink glow fills the center of the galaxy, extending beyond the disk. In the middle of the frame, where the two galaxies appear to touch, is a bright foreground star with four diffraction spikes. Other distant galaxies and stars fill the black background of space.$

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Arp Bot 🤖 @arpbot.bsky.social · 7d

Image of Arp 283, also known as NGC 2798 and NGC 2799, 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. A bridge connect the pair.
Source

A grainy, black and white image of a pair of interacting galaxies. The galaxy on the right 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. Two spiral arms emerge from the core, which are wide and poorly defined.

Arp Bot 🤖 @arpbot.bsky.social · 7d

Also known as Arp 189.

Daniel Pomarède @pomarede.bsky.social · 9d

CFHT Astronomy Image Of The Month

The Umbrella Galaxy (NGC 4651)

Credits: data obtained using the MegaCam camera on the Canada-France-Hawaii Telescope; image by Jean-Charles Cuillandre (CFHT) & Giovanni Anselmi (Coelum); copyright © 2025 CFHT
www.cfht.hawaii.edu/HawaiianStar... 🧪🔭

A photography of the spiral galaxy NGC 4651. This member of the Virgo Cluster is known as the Umbrella Galaxy due to the umbrella-shaped structure that extends from its disk and that is composed of stellar streams, being the remnants of a much smaller galaxy that has been torn apart by NGC 4651's tidal forces.

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Arp Bot 🤖 @arpbot.bsky.social · 8d

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.

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Arp Bot 🤖 @arpbot.bsky.social · 9d

Image of Arp 293, also known as NGC 6285 and NGC 6286, from Halton Arp's Atlas of Peculiar Galaxies (1966).

In the original catalog it was in the category: Double and multiple galaxies - Wind effects. The pair's interactions pull tidal streams.
Source

A grainy, black and white image of a pair of interacting spiral galaxies. The galaxy on the right is seen nearly face-on. It has a bright disk. At the edges of the disk are two short, faint, wide spiral arms. The galaxy on the left is seen edge-on. It's disk forms a line. In the center of the galaxy, the circular bulge emerges on either side of the disk. The black background of space is dotted with stars and small background galaxies. The black background of space is filled with white dots, which are foreground stars.

Arp Bot 🤖 @arpbot.bsky.social · 9d

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.

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Arp Bot 🤖 @arpbot.bsky.social · 10d

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.

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Arp Bot 🤖 @arpbot.bsky.social · 10d

GALEX and SDSS image of Arp 24, also known as NGC 3445.

The left image from GALEX shows NGC 3445 in ultraviolet light. The right image shows the same galaxies from the Sloan Digital Sky Survey in visible light.

Credit: Fig. 1 from Smith et al. 2010.
Source

A two-panel image. The left panel is labeled Arp 24 GALEX. A scale bar marks 1 arcminute, which is about 1/8 the width of the frame. The panel shows a low-res image in shades of yellow and blue. The frame is dominated by the large spiral. It has a small core that sits in the middle of a spiral structure. The one spiral arm begins at about 9 o'clock and curves clockwise around the galaxy, completing a full circle. The arm is unusually thick, fanning out with many bright, whiteish-blue star clusters. To the left of the spiral is a smaller galaxy, seen almost edge-on. It appears as an elongated oval dotted with stars. The long axis of the oval is almost horizontal. Connecting the two galaxies is a faint bridge of stars. A large yellow dot, which is a bright foreground star, fills the upper left corner.
The right panel is labeled Arp 24 SDSS and has a similar 1 arcminute scale bar. It shows the same galaxies at the same scale and is higher resolution. The star clusters in the spiral are better resolved, appearing as small blue dots.

Arp Bot 🤖 @arpbot.bsky.social · 11d

JWST NIRCam image of Arp 107, also known as UGC 5984.

In this near-infrared view, older stars appear white. The tenuous bridge of gas and stars as well as the diaphanous area to the bottom left are signs of past interactions.

Credit: NASA, ESA, CSA, STScI
Source

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Arp Bot 🤖 @arpbot.bsky.social · 11d

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

$A grainy, black and white image of a pair of interacting spiral galaxies that somewhat resembles a heron. To the upper right is a smaller, distorted spiral, forming the heron's neck, head, and beak. In its center is a bright nucleus surrounded by a ring of stars. Extending from the ring are two large, thin spiral arms, dotted with star clusters, which form an S-shape. The lower arm appears to touch the edge of the disk of its companion galaxy. On the left is a large spiral galaxy, forming the heron's body. It's disk is tilted, so that it appears as a oval rather than a circle. It has a bright center that transitions into spiral arms. The arms are defined by dark brown dust lanes. The area in between is filled with a haze of bright stars. On the black background of space are foreground stars, some with diffraction spikes, and tiny background galaxies. A few white dots, which are stars, are seen on the black background of space.$

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Arp Bot 🤖 @arpbot.bsky.social · 12d

image of Arp 193, also known as IC 883.

IC 883 is likely the remnant of the merger of two disk galaxies, since it has two tidal tails. The merger triggered a burst of star formation, creating the bright star clusters seen in the center.

Credit: NASA, ESA, STScI
Source

In the center of the frame is a roughly oval-shaped galaxy merger remnant, made out of a swirling blue-white haze of stars and gas. Crossing the center of the remnant is a dark brown filament of dust. Emerging from the remnant are two tidal tails, long thin lines of gas and stars. They are approximately the same length emerging at nearly right angles: one diagonally to the top right of the frame and the other to the bottom right. . Scattered across the background there are foreground stars and background galaxies of various sizes.

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