Europe’s ultra-powerful new WEAVE telescope, undergoing its inaugural ‘first-light’ instrument activation, recorded a collision between galaxies in a region of deep space called Stephan’s Quintet, where one of the galaxies was traveling at two million miles per hour.
Designed to study the composition of stars and galaxies, the William Herschel Telescope is a 20-million Euro collaboration between France, Italy, the UK, the Netherlands, and Spain, with the latter hosting the actual facility in La Palma. The facility’s Enhanced Area Velocity Explorer (WEAVE) wide-field spectrograph’s Large Integral Field Unit (LIFU) is the first of the telescope’s instruments to be activated and pointed at a stellar object. Astronomers call this process “first light.”
Stephan’s Quartet an Ideal First-Light Target for WEAVE
According to the team of 60 astronomers who collaborated on the research effort, the target of Stephan’s Quintet was an easy choice for the telescope’s first-light given its history of violent collisions between its five 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,” explained the project’s lead researcher, Dr Marina Arnaudova of the University of Hertfordshire in a statement.
The galaxy group became even more tantalizing when the researchers realized another galaxy was once again ripping through at a staggering two million miles per hour. Dr. Arnaudva says the collision caused a massive shockwave to pass through the entire system “much like a sonic boom from a jet fighter.”
Thanks to WEAVE’s powerful spectroscope, which breaks light into its various colors to gather information about distant objects, the international astronomy team was able to witness this incredible collision. Such a feat would have been impossible with less powerful telescopes.
“It’s fantastic to see the level of detail uncovered here by WEAVE,” said Professor Gavin Dalton, WEAVE principal investigator at RAL Space and the University of Oxford.
Astronomers Witness Previously Undiscovered Shock Pattern
Next, the team overlayed the WEAVE data on data from Stephan’s Quartet captured by the Low-Frequency Array (LOFAR, the Very Large Array (VLA), and the James Webb Space Telescope (JWST). When comparing the data, the team says they discovered a previously unknown shock pattern as it passes through different temperatures and densities of gas within the galactic system.
“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,” Dr. Arnaudova explained. This shock wave is so powerful that the team leader says it can rip electrons and atoms apart, “leaving behind a glowing trail of charged gas.”
WEAVE can see that glowing trail. However, when the shock moved through areas of hot gas, the team witnessed it lose force and momentum, and the trail mostly disappeared.
According to PhD student Soumyadeep Das of the University of Hertfordshire, the shock does not cause a significant disruption as it does within the cold gas. Instead, the researcher said the shock compresses the hot gas, “resulting in radio waves that are picked up by radio telescopes like the Low-Frequency Array (LOFAR).”
Understanding Galaxies at the Limit of Our Capabilities
Following the success of WEAVE’s first-light, the research team was also able to publish the facility’s first research paper. Dr. Daniel Smith of the University of Hertfordshire says that accomplishment “represents just a taste of what is to come over the next five years now that WEAVE is becoming fully operational.”
Professor Dalton agrees, noting that observations like those made by WEAVE regarding the performance of the shockwave caused by two galaxies colliding “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.”
Following the success of WEAVE, the project leaders plan to continue adding and activating a host of additional instruments designed to explore the Miky Way Galaxy and other galaxies deeper in the cosmos over the next five years. Dr Marc Balcells, the director of the Isacc Newton Group of Telescopes, a collaboration between the UK, Spain, and the Netherlands, says that the process will likely yield even more unexpected discoveries.
“I’m excited to see that the data gathered at the WEAVE first light already provide a high-impact result, and I’m 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.”
The study “WEAVE First Light Observations: Origin and Dynamics of the Shock Front in Stephan’s Quintet” was published in Monthly Notices of the Royal Astronomical Society.
Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him directly at christopher@thedebrief.org.