Explanation: This colorful cosmic skyscape features a peculiar system of galaxies cataloged as Arp 227 some 100 million light-years distant. Swimming within the boundaries of the constellation Pisces, Arp 227 consists of the two galaxies prominent on the left; the curious shell galaxy NGC 474 and its blue, spiral-armed neighbor NGC 470. The faint, wide arcs or shells of NGC 474 could have been formed by a gravitational encounter with neighbor NGC 470. Alternately the shells could be caused by a merger with a smaller galaxy producing an effect analogous to ripples across the surface of a pond. Remarkably, the large galaxy on the right hand side of the deep image, NGC 467, appears to be surrounded by faint shells too, evidence of another interacting galaxy system. Intriguing background galaxies are scattered around the field that also includes spiky foreground stars. Of course, those stars lie well within our own Milky Way Galaxy. The field of view spans 25 arc minutes or about 1/2 degree on the sky.
NGC 2623 is really two galaxies that are becoming one. Seen to be in the final stages of a titanic galaxy merger, the pair lies some 300 million light-years distant toward the constellation Cancer.
The violent encounter between two galaxies that may have been similar to the Milky Way has produced widespread star formation near a luminous core and along eye-catching tidal tails. Filled with dust, gas, and young blue star clusters, the opposing tidal tails extend well over 50,000 light-years from the merged nucleus. Likely triggered by the merger, accretion by a supermassive black hole drives activity within the nuclear region.
The star formation and its active galactic nucleus make NGC 2623 bright across the spectrum. This sharp cosmic snapshot of NGC 2623 (aka Arp 243) is based on Hubble Legacy Archive image data that also reveals even more distant background galaxies scattered through the field of view.
A barred spiral galaxy about 61 million light-years away in the constellation Eridanus. The galaxy is about 110,000 light-years across; just slightly larger than our own galaxy, the Milky Way. It is a member of the Eridanus Cluster, a cluster of 200 galaxies. [**]
Explanation: What will survive this battle of the galaxies? Known as Seyfert’s Sextet, this intriguing group of galaxies lies in the head portion of the split constellation of the Snake (Serpens). The sextet actually contains only four interacting galaxies, though. Near the center of this Hubble Space Telescope picture, the small face-on spiral galaxy lies in the distant background and appears only by chance aligned with the main group. Also, the prominent condensation on the upper left is likely not a separate galaxy at all, but atidal tail of stars flung out by the galaxies’ gravitational interactions. About 190 million light-years away, the interacting galaxies are tightly packed into a region around 100,000 light-years across, comparable to the size of our own Milky Way galaxy, making this one of the densest known galaxy groups. Bound by gravity, the close-knit group may coalesce into a single large galaxy over the next few billion years.
Arp 286: Trio in Virgo A remarkable telescopic composition in yellow and blue, this scene features a trio of interacting galaxies almost 90 million light-years away, toward the constellation Virgo. On the left, two, spiky, foreground Milky Way stars echo the trio galaxy hues, a reminder that stars in our own galaxy are like those in the distant island universes. Predominately yellow, with sweeping spiral arms and dust lanes, NGC 5566 is enormous, about 150,000 light-years across. Just below it lies small, blue NGC 5569. Near center, the third galaxy, NGC 5560, is multicolored and apparently stretched and distorted by its interaction with NGC 5566. The galaxy trio is also included in Halton Arp’s 1966 Atlas of Peculiar Galaxies as Arp 286. Of course, such cosmic interactions are now appreciated as a common part of the evolution of galaxies.
Centaurus A —New Insight to an Odd and Massive Elliptical Galaxy
Centaurus A, also known as NGC 5128, is a peculiar massive elliptical galaxy with a supermassive black hole at its heart. It lies about 12 million light-years away in the southern constellation of Centaurus (The Centaur) and has the distinction of being the most prominent radio galaxy in the sky.