Arp 105 is characterized by a tidal tail of stars and gas more than 362,000 light-years long.
The elliptical galaxy NGC 3561B (upper left) and the spiral galaxy NGC 3561A (lower right) form a shimmering guitar shape in the ongoing merger known collectively as Arp 105. Image credit: NASA / ESA / M. West, Lowell Observatory / Gladys Kober, NASA & Catholic University of America.
Arp 105 is located around 400 million light-years away from Earth in the constellation of Ursa Major.
Also known as NGC 3561, it was discovered by the British astronomer John Herschel on March 30, 1827.
It consists of two massive galaxies: the elliptical galaxy NGC 3561B and the spiral galaxy NGC 3561A.
“Arp 105 is one of the brightest objects in the crowded galaxy cluster Abell 1185,” Hubble astronomers said in a statement.
“Abell 1185 is a chaotic cluster of at least 82 galaxies, many of which are interacting, as well as a number of wandering globular clusters that are not gravitationally attached to any particular galaxy.”
The gravitational dance between NGC 3561B and NGC 3561A creates a wealth of fascinating colliding galaxy features.
“The immense tail was pulled from the two galaxies by their gravitational interactions and is embedded with star clusters and dwarf galaxies,” the astronomers said.
“The distinctively shaped arrangement of galaxies and tail gives the grouping its nickname: the Guitar.”
“A long lane of dark dust emerging from the NGC 3561B elliptical galaxy ends in, and may be feeding, a bright blue area of star formation on the base of the guitar known as Ambartsumian’s Knot.”
“Ambartsumian’s Knot is a tidal dwarf galaxy, a type of star-forming system that develops from the debris in tidal arms of interacting galaxies.”
“Two more bright blue areas of star formation are obvious in the Hubble image at the edges of the distorted spiral galaxy.”
“The region to the left in the spiral galaxy is likely very similar to Ambartsumian’s Knot, a knot of intense star formation triggered by the merger.”
“The region to the right is still under investigation — it could be part of the collision, but its velocity and spectral data are different from the rest of the system, so it may be a foreground galaxy.”
“Thin, faint tendrils of gas and dust are just barely visible stretching between and connecting the two galaxies.”
“These tendrils are particularly interesting to astronomers since they may help define the timescale of the evolution of this collision.”
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