Galaxies turn out to be significantly larger than initially believed, stretching vast distances into deep space—such extensive reaches mean that our home galaxy, the Milky Way, probably has interactions with its nearest galactic neighbor, Andromeda.

As you might imagine, the distance to the drugstore feels quite lengthy,” penned Douglas Adams in The Hitchhiker’s Guide to the Galaxy, “however, this pales in comparison to the vastness of space.

The vastness of space is immense. Our home, Earth, orbits a single star located at the edge of our galaxy among billions of others. The observable universe contains approximately 2 trillion galaxies. Therefore, space truly encompasses an enormous expanse.

The planet Earth is situated within one of the spiral arms of our 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 understand the size of the Earth—it measures approximately 12,756 kilometers (7,926 miles) in diameter. Similarly, we’re aware that the Sun has a diameter of around 1,391,000 kilometers (864,400 miles).

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

Galaxies exceed our previous estimations in size.

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 their original estimates.

The twisted form of our galaxy constitutes just the compact nucleus, which is surrounded by a much larger expanse. In the case of the Milky Way, this expansive region spans approximately 100,000 light-years.

The starlight emanating from stars located within the spiral arms reaches approximately 7,800 light-years out into deep space, marking what was once believed to be the boundary between the end of a galaxy and the start of open intergalactic voids.

The research has shown that extensive “halos” of gas stretch beyond the observable spiral patterns 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 surrounding galaxies reach such vast distances into deep space that the galaxies themselves extend considerably.
interact with each other
.

The research indicates that our Milky Way is probably engaging with our nearest neighboring galaxy, Andromeda, which is approximately 2.5 million light-years distant. This conclusion was drawn by Nikole Nielsen, the leading author of the study and a researcher at Swinburne University in Australia.

“We’re currently observing the limits of the galaxy’s influence, the point at which it transitions into becoming part of the larger environment around it, ultimately merging with the broader cosmic web and connecting with other galaxies. Such boundaries tend to be rather indistinct,” explained Nielsen in a press release.

Researchers claim 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