Galaxies Clash Head-On at a Shocking Speed of Two Million Miles Each Hour, Occurring Far Beyond Our Universe
In the vast expanse of the cosmos, a celestial battle unfolds. Devoid of conventional weapons, galaxies clash, shattering interstellar mediums and sending shockwaves reverberating through the universe. This spectacle mirrors the phenomenon occurring in Stephan's Quintet, a renowned cluster of galaxies approximately 94 million light-years away.
A groundbreaking study, using telescope observations, has determined the velocity at which some galaxies in the quintet have collided, reaching an astonishing 2 million miles per hour. Yet, this cataclysmic collision is not solely destructive.
A Galactic Crossroads
Stephan's Quintet comprises five galaxies, four of which form the first compact galaxy group ever discovered, dating back nearly 150 years. Essentially, the quintet serves as a galactic crossroads, where galaxies converge, interact, and collide. Particularly, one galaxy, NGC 7318b, is hurtling into the group at breakneck speed, triggering vast shockwaves.
This turbulent environment ignites starbirth, compresses and obliterates molecular clouds, and restructures the galaxies themselves. Recently, researchers observed this crash utilizing one of Earth's most powerful telescopes—the new William Herschel Telescope Enhanced Area Velocity Explorer (WEAVE) in La Palma, Spain.
The WEAVE spectrograph, an advanced instrument, permitted scientists to chart the shock front with unprecedented precision. However, astronomers didn't rely solely on this instrument. They amalgamated data from various sources, including radio observations from the LOFAR Two-Metre Sky Survey (LoTSS), X-ray studies, and archival data from the James Webb Space Telescope (JWST), to create a multiwavelength view of the Quintet.
With this extensive data, they calculated that NGC 7318b is traveling at an astounding speed of over 3.2 million km/h (2 million mph), colliding with its neighbors and producing powerful shock waves in neighboring galaxies.
"Since its discovery in 1877, Stephan's Quintet has captivated astronomers due to its representation of a galactic crossroads where past collisions between galaxies have left behind a complex field of debris," explains lead researcher Dr. Marina Arnaudova from the University of Hertfordshire.
Dynamical activity in this galaxy group has now been reawakened by a galaxy careening through it at an incredible speed of over 2 million mph (3.2 million km/h), leading to an immensely powerful shockwave, similar to a sonic boom from a jet fighter.
The Science of Galactic Shocks
In intergalactic mediums, shocks function like cosmic pressure cookers. They generate energy through turbulence, heating gases, and precipitating the formation of stars or the destruction of molecular clouds.
As the shock moves through pockets of cold gas, it surges at hypersonic speeds—multiple times the speed of sound in the intergalactic medium of Stephan's Quintet—powerful enough to disintegrate electrons from atoms, leaving behind a lucid trail of charged gas, as seen with WEAVE.
However, when the shock passes through the surrounding hot gas, it weakens. According to Ph.D. student Soumyadeep Das from the University of Hertfordshire, this weak shock compresses the hot gas, resulting in radio waves that can be picked up by radio telescopes like the Low Frequency Array (LOFAR).
Despite the calamity of this collision, some molecular hydrogen and dust grains survive, likely forming the basis for post-shock cooling and potential new star formation. Additionally, the shock amplifies radio emissions, increasing luminosity tenfold.
Dense gas and dust pockets, shielded from the shock, continue to form molecular hydrogen. Diffuse radio filaments and compact sources track the collision's effects, including interactions with jets in NGC 7319.
This system illustrates how galaxy collisions reshape structure and chemistry, providing insights into cosmic evolution. Thanks to sophisticated instruments like WEAVE and complementary observations across the electromagnetic spectrum, scientists are piecing together the intricate narrative of these colliding galaxies.
Professor Gavin Dalton, WEAVE principal investigator at RAL Space and the University of Oxford, concludes:
"It's incredible to witness the level of detail yielded here by WEAVE. Not only do we observe the details of the shock and the unfolding collision in Stephan's Quintet, but these observations provide a remarkable perspective on what may be happening in the formation and evolution of the barely resolved faint galaxies that we see at the limits of our current capabilities."
Journal Reference: M I Arnaudova et al, WEAVE First Light Observations: Origin and Dynamics of the Shock Front in Stephan's Quintet, Monthly Notices of the Royal Astronomical Society (2024). DOI: 10.1093/mnras/stae2235.
Keywords: cosmic evolution, galaxy collisions, galaxy dynamics, intergalactic shockwaves, LOFAR, molecular clouds, NGC 7318b, star formation, Stephan's Quintet, WEAVE telescope.
- The study of Stephan's Quintet, a galactic crossroads where galaxies converge and collide, is a significant component of environmental-science and astronomy.
- The collision between galaxies in Stephan's Quintet has led to an abundant production of shockwaves, demonstrating the chemistry involved in such cosmic events.
- Although some starbirth is triggered by the shockwaves, they also obliterate molecular clouds and restructure the galaxies involved, contributing to the ongoing evolution of the universe.
- Alongside ground-based telescopes like WEAVE, space-and-astronomy research utilizes satellite-based instruments such as the James Webb Space Telescope and the Low Frequency Array to combine observations from various wavelengths.
- The environmental and health-and-wellness impacts of galaxy collisions extend beyond the cosmos, as they offer valuable insights into the fundamental concepts of science such as energy transfer, plasma dynamics, and star formation.
