2 Million MPH Galactic Collision Captured in Awesome Detail

The WEAVE telescope has documented a high-velocity collision of galaxies in Stephan’s Quintet, baring the powerful shockwaves and dynamic interactions shaping galaxy evolution. This observation underlines both the competences of new astronomical tools and the violent processes within the cosmos.

Galactic Collision Observed in Stephan’s Quintet

A galaxy dashing through space at an astonishing velocity of 2 million mph (3.2 million km/h) has caused a massive collision, captured in unprecedented detail by one of Earth’s most cutting-edge telescopes. This dramatic event occurred in Stephan’s Quintet, a nearby galaxy group comprising five galaxies first identified almost 150 years ago. The collision caused a powerful shockwave, described as similar to a “sonic boom from a jet fighter,” one of the most arresting and energetic phenomena in the Cosmos.

The Role of the WEAVE Telescope

Stephan’s Quintet has for long been considered a “galactic crossroad,” where prior collisions left a complex trail of debris. This turbulent region has now been resuscitated by the high-velocity passage of the galaxy NGC 7318b.

The collision was spotted by a team of experts using the first observations from the new $21  million (20-million Euro) WEAVE (William Herschel Telescope Enhanced Area Velocity Explorer) wide-field spectrograph in La Palma, Spain. This advanced, next-generation science facility will not only disclose how our Milky Way galaxy was built up over billions of years, but also offer new insights into millions of other galaxies across the Cosmos.

Dynamics and Discovery in Intergalactic Space

The discovery of NGC 7318b hurtling through Stephan’s Quintet was observed by an eclectic team of over 60 astronomers and was published on 22^nd November 2024 in Monthly Notices of the Royal Astronomical Society. The system is a perfect laboratory to understand the messy and often violent relationship between galaxies, which is why it was the focus of the first-light observation by the WEAVE LIFU (Large Integral Field Unit).

Lead researcher (Dr. Marina Arnaudova of the University of Hertfordshire) said: “Since its discovery in 1877, Stephan’s Quintet has captivated astronomers, because it represents a galactic crossroad where past collisions between galaxies have left behind a complex field of debris. Dynamical activity in this galaxy group has now been reawakened by a galaxy smashing through it at an incredible speed of over 2 million mph (3.2 million km/h), leading to an immensely powerful shock, much like a sonic boom from a jet fighter.”

Insights Into the Universe’s Evolution

The international team has bared a dual nature behind the shock front, earlier unknown to astronomers. “As the shock moves through pockets of cold gas, it travels at hypersonic speeds – several times the speed of sound in the intergalactic medium of Stephan’s Quintet* – powerful enough to rip apart electrons from atoms, leaving behind a glowing trail of charged gas, as seen with WEAVE,” said Dr. Arnaudova.

However, when the shock passes through the nearby hot gas, it becomes far weaker, according to Soumyadeep Das (PhD student of the University of Hertfordshire. Das added: “Instead of causing significant disruption, the weak shock compresses the hot gas, resulting in radio waves that are picked up by radio telescopes like the Low Frequency Array (LOFAR).”

The new insight and unparalleled detail came from WEAVE’s LIFU, combining data with other advanced instruments such as the LOFAR, VLA (the Very Large Array), and JWST (the James Webb Space Telescope).