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Arp Bot 🤖

@arpbot.bsky.social

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 · 3h ago

Hubble Space Telescope image of Arp 6, also known as NGC 2537 or the Bear’s Paw Galaxy. It has a nucleus that is rapidly forming stars, surrounded by a horseshoe-shaped structure, also forming new stars. Credit: NASA, ESA, STScI, J. Dalcanton, Judy Schmidt Source

A greyscale image of a galaxy with a line-like nucleus and a horseshoe-shaped arc above it. The horseshoe points down, and the nucleus is in the center of the arc. It looks like an upside down power symbol, ⏻. The nucleus and horseshoe are dotted with bright star clusters and dark dust lanes.

Arp Bot 🤖@arpbot.bsky.social · yesterday

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.

Arp Bot 🤖@arpbot.bsky.social · 2d ago

Image of Arp 274, also known as NGC 5679, from Halton Arp's Atlas of Peculiar Galaxies (1966). In the original catalog it was in the category: Double and multiple galaxies - Connected arms. It is a system of three overlapping, interacting galaxies. Source

A grainy, black and white image of three overlapping galaxies. In the center are two large spiral galaxies. The larger one has a bright core. At the edge of the core, two spiral arms emerge. Star clusters dot the outer portion of the arm. The second spiral galaxy is below the first. It has a bright center, and a well-defined bar and two spiral arms. Together, the bar and arms form a sideways S-shape. The final galaxy in the triplet appears at the top of the frame. It is much smaller than its companions and has a blobby, irregular appearance. A few stars appear on the black background of space, including two large foreground stars, which appear to the left of the bottom galaxy.

Arp Bot 🤖@arpbot.bsky.social · 2d ago

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.

Arp Bot 🤖@arpbot.bsky.social · 3d ago

GALEX and SDSS image of Arp 297, also known as NGC 5755, NGC 5753, NGC 5754 and NGC 5752. The left image is in ultraviolet light. The right image is in visible light. The upper and lower galaxy pairs are at different distances. Credit: Fig. 13 from Smith et al. 2010. Source

A two-panel image. The left panel is labeled Arp 297 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. There are four small galaxies, arranged in two pairs, on a field of stars. The bottom pair is a large face-on barred spiral galaxy and a smaller edge-on disk galaxy. The spiral has a bright, pale yellow, circular core. Two spiral arms circle around the core. One thinner arm emerges in the outer part of the galaxy at about 9 o'clock and circles counterclockwise to 12 o'clock, intersecting the companion galaxy to the left. The smaller companion galaxy is yellow and oval-shaped. The upper pair is two nearly face-on spiral galaxies. The bottom galaxy of the pair has a yellow core and bar with two faint spiral arms that make an S-shape. The top galaxy of the pair appears as a bluish grey circle.
The right panel is labeled Arp 297 SDSS and has a similar 1 arcminute scale bar. It shows the same galaxies at the same scale and is higher resolution. The bottom pair of galaxies appears in shades of pale yellow. The spiral appears similar to the GALEX image, but the center of the galaxy has a prominent bar structure, which was not seen by GALEX. The top pair of galaxies also is similar to the GALEX image, but shows more detail. The bottom galaxy of the pair is in shades of white and pale blue. The top galaxy has a bright core and barely discernible spiral arms and is in shades of yellow.

Arp Bot 🤖@arpbot.bsky.social · 3d ago

Dark Energy Camera image of Arp 289, also known as NGC 3981. The galaxy's irregular arms is likely due to gravitational interactions with a neighboring galaxy. Credit: Dark Energy Survey, DOE, FNAL, DECam, CTIO, NOIRLab, NSF, AURA, R. Colombari, M. Zamani 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 cross a yellow haze of older stars. The blue arms unfurl from the center, like paint flung out of a spinning canvas. They are dotted with blue star clusters. The arms dip down more at the bottom of the frame. The black background of space is filled with foreground stars and tiny background galaxies.

Arp Bot 🤖@arpbot.bsky.social · 4d ago

CFHT SITELLE image of Arp 82, also known as NGC 2535 and NGC 2536. Simulations suggest the two galaxies are in the early stages of a merger. The pair already experienced one collision and are just about to collide again. Credit: Fig. 1 from Prime et al. 2022 Source

$A pair of interacting spiral galaxies. In the center of the frame is the larger galaxy, a spiral galaxy seen face-on. It has a bright center. A ring of pale pink stars and star clusters circles the center, giving the inner part of the galaxy a shape that resembles an eye. Two long spiral arms emerge from the ring, dotted with pale blue star clusters. The upper arm trails off in a faint arc to the right. The bottom arm appears to connect to its companion galaxy in the lower part of the frame. This galaxy is smaller and less well defined, but is still clearly a two-armed spiral with a bright center and wider, hazy arms. The black background of space is dotted with foreground stars and tiny background galaxies. A few particularly bright stars with diffraction spikes are seen to the right of the center galaxy.$

Arp Bot 🤖@arpbot.bsky.social · 4d ago

Image of Arp 94, also known as NGC 3226 and NGC 3227, from Halton Arp's Atlas of Peculiar Galaxies (1966). In the original catalog it was in the category: Spiral galaxies - Elliptical companions. Spiral NGC 3227 interacts with elliptical NGC 3226. Source

A grainy, black and white image of two interacting galaxies. A large spiral galaxy with dark dust lanes is in the center of the image. It is tilted slightly, so that its disk forms an oval rather than a circle. The faint ends of spiral arms extend beyond the edge of the disk and appear to connect to its companion galaxy above it. The bright elliptical galaxy is oval shaped with a bright center that gets gradually fainter and more transparent towards its edges. A few white dots, which are stars, are seen on the black background of space.

Arp Bot 🤖@arpbot.bsky.social · 5d ago

Gemini North image of Arp 84, also known as NGC 5394 and NGC 5395. Interactions between this galaxy pair funneled gas into the center of the smaller distorted spiral NGC 5394, which fuels a burst of star formation. Credit: International Gemini Observatory, NOIRLab, NSF, AURA Source

$A pair of interacting spiral galaxies. On the left is a large spiral galaxy. It's disk is tilted, so that it appears as a oval rather than a circle. It has a bright yellow-white center that transitions into spiral arms. The arms are defined by dark brown dust lanes dotted with pink star forming regions. The area in between is filled with a haze of blue-white stars. Below and to the right is a second galaxy, a smaller, distorted spiral. In its center is a bright yellow nucleus surrounded by a ring of stars that transitions into two spiral arms that form an S shape. The lower spiral arm forks in two. They are all made of a haze of yellow stars. The lower left part of the ring and spiral arms have a concentrated area of dust and red star forming regions. Extending from the inner spiral arms are two much larger, thin spiral arms, dotted with blue star clusters, which lengthen the S-shape. The upper arm appears to touch the edge of the disk of its companion galaxy. On the black background of space are foreground stars, some with diffraction spikes, and tiny background galaxies.$

Arp Bot 🤖@arpbot.bsky.social · 5d ago

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.

Arp Bot 🤖@arpbot.bsky.social · 6d ago

Hubble image of Arp 299, also known as NGC 3690. This image was taken in 2000 with Hubble WFPC2 instrument to study the merging galaxies' hottest and brightest stars in ultraviolet light. Credit: NASA, R. Windhorst, and the Hubble mid-UV team Source

Two merging galaxies form an orange and blue abstract butterfly shape. Within the shape are bright blue areas, which are clusters of young, hot stars. These are found in the center, the upper right "wing", and the bottom left "wing".

Arp Bot 🤖@arpbot.bsky.social · 6d ago

Image of Arp 24, also known as NGC 3445, from Halton Arp's Atlas of Peculiar Galaxies (1966). In the original catalog it was in the category: Spiral galaxies - One-armed. NGC 3445 is connected to its companion galaxy (left) by a weak bridge. Source

$A grainy, black and white image of a spiral galaxy and its smaller companion. The frame is dominated by the large spiral galaxy. Its one spiral arm begins at about 12 o'clock and curves clockwise around the galaxy, completing a full circle. The arm is unusually thick, fanning out with many bright star clusters. Above the spiral is a smaller galaxy, seen almost edge-on. It appears as an elongated oval. The long axis of the oval is almost vertical. Connecting the two galaxies is a faint bridge of gas and stars. A few smaller background galaxies dot the black background of space. There is a bright foreground star, seen as a large dot with four diffraction spikes, in the upper right corner of the frame.$

Arp Bot 🤖@arpbot.bsky.social · 7d ago

Kitt Peak image of Arp 286, also known as NGC 5560, NGC 5566, and NGC 5569. The galaxies in this triplett are gravitationally interacting. NGC 5566 is at center, NGC 5569 at bottom left, and NGC 5560 at top left. Credit: NOIRLab, NSF, AURA, T.A. Rector, H. Schweiker Source

The frame is dominated by three spiral galaxies. The largest is at the center of the frame. The disk of the galaxy is tilted, so that it appears oval-shaped, with the long axis running diagonally from upper right to lower left. It has a bright yellow-white center, surrounded by a ring structure. Emerging from the ring are two spiral arms, defined by faint dust lanes and blue star clusters. The arms trace the outline of the oval. A haze of yellow stars fills in the interior of the oval. At the bottom left is a smaller face-on spiral galaxy. Unlike the other two galaxies in the group, this galaxy does not appear distorted. It has a small bar structure in its center, surrounded by two loose spiral arms that are filled with blue star clusters. At upper left is a distorted spiral galaxy seen nearly edge-on. Its disk is warped, forming a thin, nearly vertical, backward S-shape. At the center of the disk is a faint bulge made out of a haze of stars.

Arp Bot 🤖@arpbot.bsky.social · last wk.

Hubble image of Arp 221. Arp 221 is an interacting trio of disk galaxies. To the right is what is probably a large lenticular galaxy, with a series of shells that are caused by the gravitational interactions or a past merger. Credit: NASA, ESA, STScI, J. Dalcanton, Judy Schmidt Source

$A greyscale image of three disk galaxies arranged in a triangle. To the left is the largest galaxy, likely a lenticular galaxy, which has a bright center and a series of shells, which appear as arc-like glowing features with sharp outer edges. A few dark dust lanes appear in this outer part of the disk. The large galaxy overlaps with the galaxy to the right, which is also probably a lenticular galaxy. It has a bright center surrounded by a hazy disk. A faint curving feature, either a spiral arm or a tidal tail, emerges at about 6 o'clock and curves counterclockwise around the galaxy. The third galaxy, the smallest of the three, is below the other two. It's center is just below the center of the left galaxy. It has a bright center, a central bar structure, and two clearly defined spiral arms. A bright foreground star is above the right galaxy, and has large diffraction spikes which overlap with the galaxies. The image has a noticeable amount of detector noise which has not been removed. The black background of space is dotted with stars and small background galaxies.$

Arp Bot 🤖@arpbot.bsky.social · last wk.

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.

Arp Bot 🤖@arpbot.bsky.social · last wk.

Hubble image of Arp 282, also known as NGC 169 and NGC 169A. Interactions between the two galaxies create delicate streams that visibly link the pair. Credit: ESA/Hubble & NASA, J. Dalcanton, Dark Energy Survey, DOE, FNAL/DECam, CTIO/NOIRLab/NSF/AURA, SDSS, J. Schmidt Source

A large spiral galaxy is seen in the center of the frame. It's tilted at an angle, so that it's disk appears as an oval rather than a circle. Dramatic dust lanes cross in front of the center of the galaxy and are backlit by a haze of yellow-white stars. Above the spiral is a smaller disk galaxy seen in shades of blue white. It appears to be at almost a right angle to the large spiral, falling into the larger galaxy. The two galaxies are connected by a bridge of dusty tendrils, which are also backlit by the main galaxy. This galaxy pair looks a lot more 3D than most interacting galaxies because of their angles and the backlighting effect.

Arp Bot 🤖@arpbot.bsky.social · last wk.

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

$A pair of interacting spiral galaxies, connected by streams of material, form a backwards S shape. The top galaxy is a face-on spiral. It has a yellow-white center mottled with brown dust. A haze of blue stars and star clusters appears to splash out of the galaxy to the upper left and lower right. A denser stream of yellow-white material continues above the galaxy, curving to the left. This stream also has faint brown dust lanes. The bottom galaxy is a bit of a mess. It's probably a highly distorted edge-on spiral galaxy. One stream of material from this galaxy continues above, merging with the upper face-on spiral. A second, larger stream curves below the galaxy, curving to the right like a fish hook. Both of these streams are dotted with blue stars and star clusters and are crossed by dark brown dust lanes. To the right of the merging galaxies are two bright foreground stars with Hubble's four diffraction spikes. The black background of space is dotted with a few additional foreground stars and many smaller background galaxies.$

Arp Bot 🤖@arpbot.bsky.social · last wk.

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

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

Arp Bot 🤖@arpbot.bsky.social · last wk.

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.

Arp Bot 🤖@arpbot.bsky.social · 2w ago

Chandra image of Arp 220, also known as IC 4553. This X-ray image shows the hottest gas in two merging spiral galaxies. The central bright point contains their remnant cores, which are about 1,200 light-years apart. Credit: NASA, CXC, SAO, L. Frattare, J. Major Source

An abstract, blobby, purple area of hot X-ray gas. In the center is a somewhat extended bright point. Areas of fainter gas extend roughly horizontally to the left and right. Below the extended central point is a smaller bright point, likely a smaller black hole or neutron star in the galaxy, or a background supermassive black hole.

Arp Bot 🤖@arpbot.bsky.social · 2w ago

Legacy Surveys image of Arp 10, also known as UGC 1775. A galaxy likely collided with Arp 10 near its center. A density wave rippled outwards, creating a ring of new stars in the freshly compacted gas. Credit: Legacy Surveys, D. Lang, NERSC, Meli thev, Wikimedia Commons Source

A face-on spiral galaxy in shades of muted yellow and cream has a bright central core, surrounded by an oval-shaped bright ring. The core is offset from the center of the ring to the bottom left. It looks a little like a fried egg. Outside of the ring are wispy spiral arms that are not well defined. The arms spiral clockwise from the edge of the ring. The background is dotted with yellow and orange stars and tiny background galaxies.

Arp Bot 🤖@arpbot.bsky.social · 2w ago

Image of Arp 1, also known as NGC 2857, 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 spiral galaxy in the constellation Ursa Major. Source

A grainy, black and white image of a face-on spiral galaxy. It has two well-defined spiral arms that spiral counter-clockwise from its center. Several white dots, which are stars, are seen on the black background.

Arp Bot 🤖@arpbot.bsky.social · 2w ago

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.

Arp Bot 🤖@arpbot.bsky.social · 2w ago

Kitt Peak image of Arp 297, also known as NGC 5755, NGC 5753, NGC 5754 and NGC 5752. This wide view shows two interacting galaxy pairs. The pairs are actually unrelated and are at different distances. Credit: KPNO, NOIRLab, NSF, AURA, B. Lofquist, A. Block Source

Four small galaxies, arranged in two pairs, on a field of stars. The bottom pair of galaxies is a large face-on barred spiral galaxy and a smaller edge-on disk galaxy. The spiral has a bright, pale yellow, circular core that transitions into a diagonal bar structure. Two well-defined spiral arms circle around the core counter-clockwise, beginning at the ends of the bar. To its right is its smaller companion galaxy. It is oval-shaped, running diagonal and with the long axis parallel to the bar of the large spiral. The upper pair is two nearly face-on spiral galaxies. The bottom galaxy of the pair has a blue-white core and bar with two faint spiral arms that make a S-shape. The top galaxy of the pair has a circular yellow core and several spiral arms that wrap around the core.

Arp Bot 🤖@arpbot.bsky.social · 2w ago

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.

Arp Bot 🤖@arpbot.bsky.social · 2w ago

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

$A grainy, black and white image of a pair of interacting spiral galaxies. In the center-right of the frame is the larger galaxy, a spiral galaxy seen face-on. It has a bright center crossed by filamentary, dark dust lanes. A ring of stars and star clusters circles the center, giving the inner part of the galaxy a shape that resembles an eye. Two long spiral arms emerge from the ring, dotted with bright star clusters and outlined by dust filaments, forming an S-shape. The lower arm trails off in a faint arc to the left. The upper arm appears to connect to its companion galaxy in the upper part of the frame. This galaxy is smaller and less well defined, but is still clearly a two-armed spiral with a bright center and wider, hazy arms. The black background of space is dotted with foreground stars. A few particularly bright stars with diffraction spikes are seen to the left of the center galaxy.$

Arp Bot 🤖@arpbot.bsky.social · 2w ago

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.

Arp Bot 🤖@arpbot.bsky.social · 2w ago

Kitt Peak image of Arp 26, also known as M101 or the Pinwheel Galaxy. This image was taken in 1975 image with the 4-meter Mayall telescope. Credit: NOIRLab, NSF, AURA Source

Black and white image of a face-on spiral galaxy. I has a bright core and several spiral arms, dotted with stars and star clusters, that spiral clockwise around the core. They are crossed by dark dust lanes. The arms are 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. Another other arms cover the area from 12 o'clock to 6 o'clock.

Arp Bot 🤖@arpbot.bsky.social · 2w ago

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

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

Arp Bot 🤖@arpbot.bsky.social · 2w ago

Spitzer image of Arp 107, also known as UGC 5984. The short wavelength left image highlights older stars, while the longer wavelength middle image highlights younger stars. The multi-band picture shows the two stellar age groups. Credit: NASA, JPL-Caltech, B. J. Smith Source