A team of more than 60 astronomers spotted NGC 7318b smashing through Stephan's Quintet, and their findings were published in the Monthly Notices of the Royal Astronomical Society.
WEAVE data overlaid on a James Webb Space Telescope image of Stephan's Quintet, with green contours showing radio data from the Low Frequency Array (LOFAR) radio telescope. The orange and blue colors follow the brightness of Hydrogen-alpha obtained with the WEAVE LIFU, which trace where the intergalactic gas is ionized. The hexagon denotes the approximate coverage of the new WEAVE observations of the system, which is 36 kpc wide (similar in size to our own galaxy, the Milky Way). Image Credit: University of Hertfordshire
One of Earth's most powerful telescopes has witnessed in unparalleled clarity this huge collision of galaxies caused by one moving at a staggering 2 million mph (3.2 million km/h).
The striking influence was seen in Stephan’s Quintet, a neighboring galaxy group consisting of five galaxies discovered over 150 years ago.
The shock it caused was so strong that it resembled a “sonic boom from a jet fighter”—one of the most remarkable events in the universe.
Stephan’s Quintet symbolizes “a galactic crossroad where past collisions between galaxies have left behind a complex field of debris” that has now been reawakened by the passage of the galaxy NGC 7318b.
A group of scientists detected the impact using the first data from the new William Herschel Telescope Enhanced Area Velocity Explorer (WEAVE) wide-field spectrograph in La Palma, Spain, which costs 20 million euros (£16.7 million).
This state-of-the-art, next-generation science facility will provide fresh insights into millions of other galaxies throughout the Universe and reveal how the Milky Way was formed over billions of years.
The system was the subject of the first-light study by the WEAVE Large Integral Field Unit (LIFU) because it is a perfect laboratory to comprehend the chaotic and frequently violent relationship between galaxies.
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.
Dr. Marina Arnaudova, Study Lead Researcher and Postdoctoral Research Fellow, University of Hertfordshire
Astronomers were unaware of the shock front's dual nature until the international team discovered it.
“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,” Dr Arnaudova added.
Soumyadeep Das, a PhD student at the University of Hertfordshire, claims that the shock weakens significantly as it travels through the surrounding heated gas.
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).
Soumyadeep Das, PhD Student, University of Hertfordshire
WEAVE’s LIFU provided fresh information and previously unheard-of detail by merging data from other state-of-the-art instruments, such as the James Webb Space Telescope (JWST), the Very Large Array (VLA), and the LOFAR.
The William Herschel Telescope is equipped with WEAVE, a cutting-edge, extremely quick mapping tool that analyzes the makeup of gas and stars in the Milky Way and other galaxies.
This is accomplished using a spectroscope, which creates a pattern resembling a bar code inside a prism of colors that comprise a light source. Thus, the spectroscope reveals the elements that stars are composed of.
Following a multilateral agreement, France, Italy, and the countries are part of the Isaac Newton Group of Telescopes cooperation (the UK, Spain, and the Netherlands) planned and constructed it.
Astronomers anticipate that WEAVE will transform our understanding of the universe and help uncover previously unknown details about the formation of the galaxy.
It is really neat work that Marina has put together with this large team, but this first WEAVE science paper also represents just a taste of what is to come over the next five years now that WEAVE is becoming fully operational.
Dr. Daniel Smith, Associate Professor, University of Hertfordshire
Professor Gavin Dalton, WEAVE principal investigator at RAL Space and the University of Oxford, added. “It is fantastic to see the level of detail uncovered here by WEAVE. As well as the details of the shock and the unfolding collision that we see in Stephan's Quintet, 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.”
Dr Marc Balcells, director of the Isaac Newton Group of Telescopes, concluded, “I am excited to see that the data gathered at the WEAVE first light already provide a high-impact result, and I am sure this is just an early example of the types of discoveries that will be made possible with WEAVE on the William Herschel Telescope in the coming years.”
Journal Reference:
Arnaudova, M. I. et. al. (2024) WEAVE First Light Observations: Origin and Dynamics of the Shock Front in Stephan’s Quintet. Monthly Notices of the Royal Astronomical Society. doi.org/10.1093/mnras/stae2235