Galaxies are significantly larger than initially believed, reaching vast distances into outer space—distances so great that our home galaxy, the Milky Way, probably comes into contact with Andromeda, which is our nearest galactic neighbor.

As you might believe, the journey to the drugstore is quite distant," penned Douglas Adams in The Hitchhiker's Guide to the Galaxy, "however, this distance is negligible compared to the vastness of space.

The vastness of space is immense. Our home, Earth, resides as an insignificant speck circling a star located at the periphery of our Milky Way—a mere single entity within approximately two trillion galaxies explored so far. The enormity of space cannot be overstated.

The planet Earth is situated within one of the spiral arms of the galaxy. Milky Way (referred to as the Orion Arm) which is situated roughly two-thirds of the way outward from the center center of the galaxy .

We are aware of the size of the Earth — approximately 12,756 kilometers (7,926 miles) in diameter. Similarly, we know the dimensions of our Sun, which spans roughly 1,391,000 kilometers (864,400 miles) in diameter.

However, just how vast is the Milky Way? Up until this point, the actual dimensions of galaxies have been an enigma.

Galaxies are far larger than we imagined.

A recent research paper, featured in the journal Nature Astronomy It has been discovered that galaxies are much larger than initially believed, possibly even multiple times greater in size.

The coiled shape of our familiar galactic structure represents just the compact nucleus of the galaxy. In the case of the Milky Way, this spans approximately 100,000 light-years.

The starlight emanating from stars located within the spiral arms reaches about 7,800 light-years out into deep space, marking what was previously believed to be the boundary between a galaxy and open space.

The research has shown that extensive "halos" of gas stretch beyond the visible spiral arms of stars deeply into outer space.

Astronomers were able to observe these gaseous halos for the first time thanks to advanced imaging technologies. These techniques allowed scientists to identify galactic gas halos extending more than 100,000 light years into space, significantly expanding our understanding of the size of galaxies.

Kissing galaxies

Actually, the halos of gas from galaxies reach so far into deep space that galaxies themselves extend beyond what we initially thought. interact with each other .

The research indicates that our Milky Way is probably engaging with our nearest galactic neighbor, Andromeda—which is approximately 2.5 million light-years distant—according to Nikole Nielsen, the primary author of the study and a researcher at Swinburne University in Australia.

"We’re currently observing the point at which the galaxy’s influence ends, transitioning into areas that become increasingly intertwined with the surroundings of the galaxy itself. Over time, this leads to its integration within the broader cosmic web alongside other galaxies. Such transitions typically have indistinct borders," stated Nielsen in a press release.

Researchers claim that this finding will aid in unraveling one of the most significant mysteries in astronomy: how galaxies develop over time?

Examining the gas halos surrounding various kinds of galaxies — those that form stars , or those that no longer form stars — will aid in understanding how galaxies accumulate mass over time and the effects they have on one another during interactions.

Edited by: Andreas Illmer

Primary source:

Nielsen, N.M., et al. A map showing emissions from the interface between the disk and circumgalactic medium in the starburst galaxy IRAS 08339+6517. Nature Astronomy (2024). https://www.nature.com/articles/s41550-024-02365-x

Author: Fred Schwaller