Stephan’s Quintet

September 19, 2024

Stephan’s Quintet is a fascinating group of five galaxies located in the constellation Pegasus. Discovered by French astronomer Édouard Stephan in 1877, this quintet is one of the most studied compact galaxy groups in the universe.

Composition and Structure

The quintet consists of four interacting galaxies: NGC 7317, NGC 7318A, NGC 7318B, and NGC 7319. These galaxies are part of the Hickson Compact Group 92 (HCG 92). The fifth member, NGC 7320, is a visual companion but not physically associated with the other four galaxies. NGC 7320 is much closer to Earth, at a distance of about 40 million light-years, while the other four galaxies are approximately 290 million light-years away.

Interactions and Phenomena

The interactions between the galaxies in Stephan’s Quintet create a spectacular cosmic display. These interactions result in gravitational forces that pull gas, dust, and stars from the galaxies, forming sweeping tails and shock waves. One of the most dramatic features is the shock wave created by NGC 7318B as it collides with the intergalactic gas at several million kilometers per hour. This collision heats the gas to temperatures of millions of degrees, causing it to emit X-rays detectable by telescopes.

Observations and Discoveries

Stephan’s Quintet has been observed by various space telescopes, including the Hubble Space Telescope and the James Webb Space Telescope (JWST). The JWST provided a detailed composite image of the quintet, revealing never-before-seen details such as clusters of young stars and regions of active star formation. The Spitzer Space Telescope also detected powerful molecular hydrogen emissions from the shock wave, one of the most turbulent formations of molecular hydrogen ever observed.

Significance in Astronomy

Studying Stephan’s Quintet offers valuable insights into the processes of galaxy interaction and evolution. The proximity of these galaxies allows astronomers to observe the effects of gravitational interactions and star formation in great detail. These observations help scientists understand similar processes in more distant galaxies and the early universe.

Stephan’s Quintet remains a captivating subject for astronomers and a testament to the dynamic and ever-changing nature of the cosmos.

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