Astronomers have discovered a vast intergalactic bridge made of hydrogen gas. The giant celestial structure — which stretches tens of thousands of light-years and connects two distant galaxies in the constellation Virgo — has been described in the journal Monthly Notices of the Royal Astronomical Society.
“Understanding these gas bridges and their dynamics provides critical insights into how galaxies evolve over time, how galactic gas is redistributed, and the varying conditions under which galaxies may or may not form stars,” lead author Lister Staveley-Smith, an astronomer at The University of Western Australia (UWA) node at the International Centre for Radio Astronomy Research (ICRAR), said in a press release.
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A Bridge To The Stars
NGC 4532 and DDO 137 are dwarf galaxies located on the outskirts of Virgo, approximately 53 million light-years away from planet Earth. Previous observations had shown that the two galaxies were somehow connected, leading the pair to be categorized as a “complex system.”
This new paper sheds light on the extent of that connection, revealing a large filament of gas (or bridge) extending uninterrupted from one galaxy to the other. The team calculated the size of the bridge, finding it to be approximately 48 kiloparsecs — or 160,000 light–years — in length.
These findings were made using observations collected by the Widefield ASKAP L-band Legacy All-sky Survey — also known by the catchier moniker WALLABY — a project mapping the distribution of hydrogen gas in galaxies across approximately half the sky seen from the Southern Hemisphere.
When describing the findings, the researchers note three additional features alongside the bridge that are visible in the observations, including a “cloud” of gas to its east and two “arms” extending from each of the galaxies. The bridge is also accompanied by an extraordinarily long tail of gas, first discovered with the Arecibo telescope, spanning an impressive 1.6 million light-years, which, the researchers say, makes it the longest known tail to be observed extending from a galaxy system.
Cosmic Tides
The team used theoretical modelling to explain how these gaseous structures formed, pointing to tidal forces surrounding NGC 4532 and DDO 137 that pull gas from the galaxies and into the space between them. Staveley-Smith describes these tides in a piece in The Conversation, published alongside the research, as “the cosmic equivalent of Earth’s ocean tides, but on a vastly larger scale and made of hydrogen rather than water.”
The tail, in contrast, is generated from the pressure generated as the galaxies hurtle through the hot gas swirling around the Virgo cluster, which forces gas from the galaxies and into a stream behind them.
“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,” Staveley-Smith said in a statement.
“The density of electrons and the speed at which galaxies are falling into the hot gas cloud are enough to explain why so much gas has been pulled away from the galaxies and into the bridge and surrounding areas.”
A Galaxy Closer To Home
These findings shed light on the processes occurring within dynamically young galaxy clusters, such as those explored in the paper. What’s more, the research could boost our understanding of a structure much closer to home: the Magellanic Clouds — dwarf galaxies approximately 200,000 light-years from planet Earth, which (like NGC 4532 and DDO 137) are joined by a vast stream of gas.
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- Monthly Notices of the Royal Astronomical Society. WALLABY pilot survey: the extensive interaction of NGC 4532 and DDO 137 with the Virgo Cluster
- The Conversation. What a newly discovered gas bridge between galaxies tells us about the cosmic cycle of matter
