(ORDO NEWS) — The Hubble Space Telescope is celebrating its 32nd birthday with a stunning image of an unusual, tight cluster of five galaxies called the Hickson 40 Compact Group. This shot captures a special moment in their lives as they fall together before merging.
This menagerie includes three spiral galaxies, an elliptical galaxy and a lenticular galaxy. Somehow, these different galaxies have intersected, creating an unusually crowded and eclectic galactic sample.
Caught in a leisurely gravitational dance, the entire group is so crowded that it can fit into a region of space less than twice the diameter of our Milky Way’s stellar disk.
Although such clusters of galaxies can be found at the center of huge clusters of galaxies, these galaxies are noticeably isolated in their own small patch of the universe, towards the constellation Hydra.
One possibility is that a large amount of dark matter (a poorly understood and invisible form of matter) is associated with these galaxies. If they approach, then dark matter can form a large cloud, within which galaxies rotate.
When galaxies pass through dark matter, they feel the force of friction resulting from its gravitational influence.
This slows them down and causes the galaxies to lose energy so they fall together. Therefore, in this picture, the galaxies are captured at a special moment in their lives. In about 1 billion years, they will collide and merge into one giant elliptical galaxy.
Astronomers have studied this compact group of galaxies not only in visible light, but also in radio, infrared and X-ray wavelengths. Almost every galaxy has a compact radio source at its core, which could be evidence of the presence of a supermassive black hole.
X-ray observations show that galaxies interact gravitationally, as evidenced by the presence of a large amount of hot gas among them. Infrared observations provide insight into the rate of formation of new stars.
Although more than 100 such compact galaxy groups have been recorded in sky surveys over several decades, the Hickson 40 compact group is one of the most densely packed.
Observations show that such denser clusters could have been more numerous in the early universe and fueled black holes known as quasars, whose light from superheated ballooning material traveled through space.
Studying the details of galaxies in nearby groups like this one helps astronomers understand when and where galaxies self-assembled and what they are made of.
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