Researchers have made a groundbreaking discovery: a colossal 185,000 light-year-long bridge of neutral hydrogen gas linking two dwarf galaxies, NGC 4532 and DDO 137. A vast 1.6 million light-year tail accompanies it, making it the longest ever observed
A massive bridge of neutral hydrogen gas was discovered to connect two dwarf galaxies, located 53 million light-years from Earth. The groundbreaking discovery, made by astronomers from the International Centre for Radio Astronomy Research (ICRAR) at The University of Western Australia, provides crucial insights into how galaxies interact and evolve.
The findings, published in the Monthly Notices of the Royal Astronomical Society, reveal a colossal 185,000 light-year-long bridge spanning between the dwarf galaxies NGC 4532 and DDO 137. Even more astounding, a vast tail of gas, extending an unprecedented 1.6 million light-years, accompanies the bridge, making it the longest-ever observed galactic gas tail.
Unveiling the cosmic bridge: A bridge of neutral hydrogen gas
Led by Professor Lister Staveley-Smith, a UWA astronomer at ICRAR, the research team used the powerful CSIRO’s ASKAP radio telescope on Wajarri Yamaji Country. The observations were part of the Widefield ASKAP L-band Legacy All-sky Survey (WALLABY), a large-scale project dedicated to mapping the sky and studying the distribution of hydrogen gas in galaxies.
Professor Staveley-Smith explained that the discovery sheds light on the complex processes that shape galaxies. Their models indicate that tidal forces between the two galaxies, combined with their proximity to the immense Virgo cluster of galaxies, are responsible for the observed gas dynamics.
As the galaxies move toward the incredibly hot gas cloud surrounding the Virgo cluster—which is 200 times hotter than the sun’s surface—they experience a phenomenon known as ram pressure. This pressure strips and heats the gas from the galaxies, creating the colossal bridge and tail.
“The process is akin to atmospheric burn-up when a satellite re-enters the Earth’s upper atmosphere, but has extended over a period of a billion years,” Professor Staveley-Smith said, highlighting the immense timescale of these cosmic events.
A window into galactic evolution
Co-author and ICRAR UWA astrophysicist Professor Kenji Bekki emphasised the significance of the finding for understanding the life cycle of galaxies. Neutral hydrogen is the raw material for star formation, and its redistribution due to these interactions is fundamental to how galaxies evolve, particularly in dense cosmic environments.
The discovery provides a unique opportunity to study a system with strong similarities to our own Milky Way and its neighbouring Magellanic System. Professor Staveley-Smith noted that comprehending these gas bridges offers critical insights into how galactic gas is moved around and the conditions under which stars form.
“This contributes to our broader understanding of the most massive structures in the Universe and their life cycles, which helps us grasp more about their vast complexities and history of star formation,” he stated. The WALLABY survey continues to map the cosmos, and future discoveries are expected to further unravel the mysteries of galactic interactions and the cosmic cycle of matter.
