A Dangerous Dance: Galaxies Arp 91 & NGC 5954 in Serpens Caput | Hubble
These two interacting galaxies are so intertwined, they have a collective name—Arp 91. This delicate galactic dance is taking place over 100 million light-years from Earth, and was captured by the NASA/European Space Agency Hubble Space Telescope. The two galaxies making up Arp 91 have their own names. The lower galaxy that looks like a bright spot is known as NGC 5953 and the ovoid galaxy to the upper right is NGC 5954. In reality, these are spiral galaxies, but their shapes appear distinct because their orientation varies with respect to Earth.
Arp 91 provides a particularly vivid example of galactic interaction. NGC 5954 is clearly being tugged towards NGC 5953—it looks like it is extending one spiral arm downwards. It is the immense gravitational attraction of the two galaxies that is causing them to interact. Such gravitational interactions between galaxies are common, and are an important part of galactic evolution. Most astronomers nowadays believe that collisions between spiral galaxies lead to the formation of another type of galaxy, known as elliptical galaxies. These immensely energetic and massive collisions, however, happen on timescales that exceed a human lifetime. They take place over hundreds of millions of years. Thus, we should not expect Arp 91 to change during our lives!
Acknowledgement: J. Schmidt
Release Date: Oct. 4, 2021
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