Scientists Discover Massive Galactic Structure in Space by Accident

Scientists have unintentionally discovered a gigantic, previously unknown cosmic structure that could alter our knowledge of how stars arise.

The structure, which is made up of a massive amount of gas, spans over the disk of the Milky Way Galaxy and probably beyond.

The discovery was achieved by a team of astronomers led by Ron Allen, a professor of physics and astronomy at Johns Hopkins University.

Astronomers recently proposed that there could be a lot more Earth-sized planets orbiting other stars than previously thought.

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An Interstellar Medium

The vacuum of space, as defined by astronomers, is the empty space between stars and planets.

However, when one considers the Universe on a large enough scale, it is evident that even space is not wholly empty. Instead, it is filled with the interstellar medium, which is a low-density gas and dust mixture.

The main components of this gas are molecular hydrogen (H2) and other compounds.

Because H2 is so rare, astronomers must look for other molecules in interstellar gas that can be used to infer its presence, such as carbon monoxide (CO) or hydroxyl (OH) gas (typically carbon monoxide). These extra substances are referred to as tracers.

Washington Newsday said Allen accidentally discovered OH emission but no CO emission while researching something else in 2012. He reasoned that this OH could be a reference to a massive cloud of H2.

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He teamed up with Dave Hogg of the National Radio Astronomy Observatory in Virginia, as well as Philip Engelke and Michael Busch, both Ph.D. students at Johns Hopkins University, to see if they could use OH as an H2 tracer by observing it with the Green Bank Telescope (GBT), the world's largest fully steerable radio telescope.

They discovered that OH might be used to detect H2 gas. According to a statement released by the Green Bank Observatory, the OH measurements began filling in the gaps between past CO observations, revealing molecular gas as a crucial component in the birth of our Galaxy.

Then Engelke noticed a large, dim patch across the telescope's whole field of view. The following is a condensed version of the data.

After hundreds of hours of searching, using several approaches and even a separate telescope, they discovered that the massive structure was indeed present.

Was It Discovered by Chance?

The discovery was defined as "serendipitous" — meaning it was discovered by chance — and the structure as "an exceedingly broad and ubiquitous" OH emission centered near the second quadrant of the other galaxy, according to a study published in June.

Researchers reported the study titled "Observational Evidence for a Thick Disk of Dark Molecular Gas in the Outer Galaxy" in The Astrophysical Journal in June.

"Our results imply the existence of a thick disk of diffuse molecular gas in the outer Galaxy previously undetected in all-sky CO surveys," the study said.

The discovery of the pattern, according to the study, has ramifications for theories on how stars develop as well as the structure of the interstellar medium.

Allen died in 2020, just as the research was being drafted. Hence, his former students stepped in and finished the work for him.

"Ron was an incredible mentor, a brilliant astronomer, and a great friend to me. ... I will miss him dearly," Michael Busch said per Fox40.

In a statement released by the Green Bank Observatory, Engelke stated they were fortunate to have known him. Ron was ecstatic with the discovery, he added. Engelke believes he would be pleased with the outcome.