In a spectacular astronomical event 290 million light-years from Earth, four galaxies in Stephan's Quintet are interacting closely, creating collision debris and illuminating the space between them with X-ray shockwaves.
Initially recorded in the 19th century, the quintet appears as five galaxies; however, the fifth galaxy, NGC 7320, is not part of this interaction and is merely aligned with the other four from our perspective. NGC 7320 is approximately 40 million light-years away, while the other four galaxies are gravitationally entangled, engaging in a complex dance that has lasted billions of years.
This interaction has generated a gas cloud, possibly stripped from the galaxies, which is now suspended in intergalactic space, heated and disturbed by their interactions. Recent observations indicate that one galaxy is moving through the cluster at a velocity of 3.2 million kilometers per hour, causing significant upheaval.
The William Herschel Telescope in Spain, equipped with the WEAVE wide-field spectrograph, has revealed new details about this disturbed gas. Specifically, NGC 7318b is moving rapidly through the galaxy group, creating a powerful shockwave larger than the Milky Way, akin to a sonic boom produced by a jet.
As the shockwave traverses cold gas, its energy is sufficient to strip electrons from atoms, resulting in glowing ionized gas, which is within WEAVE's observational capabilities. However, the shockwave weakens as it moves through hot gas, compressing it and generating low-frequency radiation that can be detected by radio telescope arrays like LOFAR. This data aids scientists in understanding the processes of large galaxy collisions and mergers.
Stephan's Quintet presents a fascinating research opportunity for scientists due to its complex environment and relatively close proximity to Earth. Such galaxy groups are believed to grow through collisions and mergers, making each new detail worthy of exploration. The research team posits that these new insights may lie just beyond the limits of current observational capabilities, awaiting the right instruments for discovery. The findings are published in the Monthly Notices of the Royal Astronomical Society.