Photo credit: science.nasa.gov
Arp 105 is an impressive example of galactic interaction, featuring a captivating merger between an elliptical galaxy and a spiral galaxy. This dynamic duo is held together by the force of gravity, resulting in an elongated tidal tail of stars and gas that stretches over 362,000 light-years. This extensive tail, which surpasses the frame captured by NASA’s Hubble Space Telescope, has been sculpted through the gravitational effects of the two galaxies and is populated with clusters of stars and dwarf galaxies. This unique structure has earned the collective system the nickname “The Guitar.”
The intricate gravitational interplay between elliptical galaxy NGC 3561B and spiral galaxy NGC 3561A unveils a variety of intriguing features typical in colliding galaxies. A prominent dark dust lane, originating from the elliptical galaxy, culminates in a vibrant blue region of star formation situated at the base of the Guitar, known as Ambartsumian’s Knot. This area represents a tidal dwarf galaxy, which arises from the material ejected during the gravitational interactions of the galaxies.
Additionally, the Hubble image reveals two other luminous blue regions at the outskirts of the distorted spiral galaxy. The area on the left closely resembles Ambartsumian’s Knot and likewise showcases intense star formation triggered by the merging process. Meanwhile, the region on the right remains under scrutiny; differing velocity and spectral data suggest it may not be a result of the collision but rather a foreground galaxy.
Thin, ethereal strands of gas and dust can be faintly observed stretching between the two colliding galaxies. These delicate filaments intrigue astronomers, as they may provide insights into the timeline and evolutionary aspects of this cosmic merger.
Surrounding this pair of colliding galaxies are numerous more-distant background galaxies, many of which are discernible even through the merging duo. A particularly bright blob of stars located to the left of Ambartsumian’s Knot is suspected to be one of these background galaxies.
Arp 105 stands out as one of the most luminous objects within the densely populated galaxy cluster Abell 1185, located in the constellation Ursa Major. This cluster is situated approximately 400 million light-years away and contains at least 82 galaxies, many of which are involved in interaction with one another, alongside several isolated globular clusters that are not gravitationally bound to any specific galaxy. The image captured by Hubble forms part of a larger study focused on the ongoing formation of both galactic and intergalactic stellar populations within Abell 1185.
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science.nasa.gov