Hidden in the distant "heartland" of the Milky Way, mysterious galactic gas streams hide...

Hidden in the distant heart of the Milky Way, there are mysterious galactic gas flows. What exactly does this contain?

Stars are stored in rivers of gas that flow from two tiny galaxies on the outskirts of the Milky Way.

(Photo credit: CfA / Melissa Weiss)

The Large Magellanic Cloud and the Small Magellanic Cloud are two dwarf galaxies located in the outer reaches of the Milky Way. For decades, astronomers have been puzzled by what is inside this river, called the Magellanic Stream. However, now a research team has found stars in the gaseous clouds of the Magellanic Stream for the first time. This discovery will not only help to better understand the evolution of the stream's parent galaxy, but also help to better understand the distribution of matter in the Milky Way itself.

Astronomers at the Harvard Smithsonian Center for Astrophysics discovered the stars using the 21-foot (6.5-meter) Magellan Baade Telescope at Las Campanas Observatory in Chile. Using a detailed map of the Milky Way created by NASA's Gaia space telescope, the researchers zeroed in on 200 stars in the farthest reaches of the Milky Way, in the direction of the Magellanic Stream.

They analyzed the spectrum of light emitted by these stars and found that the chemical composition of 13 of them matched that of the Magellanic Clouds. The measurements also showed that these 13 stars must be between 150,000 and 400,000 light-years away from Earth, about the expected distance of the Magellanic Stream.

First discovered in the 1970s, the stream stretches across a region of the southern sky that is about the size of 300 full moons as seen from Earth. But despite its size, it takes some sensitive equipment to see it.

Astronomers think the gas that makes up the stream is being torn from dwarf galaxies by the Milky Way's gravity. New observations could reveal more about the stream's properties and help scientists understand how it interacts with our galaxy. For now, the stream looks like it's falling into the Milky Way, scientists say.

"With these results and more like them, we hope to gain greater insight into the formation of the Magellanic Stream and the Magellanic Clouds, and their past and future interactions with the Milky Way," Charlie Conroy, a professor of astronomy at the Harvard Smithsonian Center for Astrophysics (CfA) and co-author of the study, said in a statement.

Unlike the Magellanic meteors, the Magellanic Clouds have been known to humans since ancient times, as they can be clearly seen with the naked eye. However, astronomers still have many questions about the origin and history of these two galaxies, which appear to be on a collision course with the Milky Way. Mapping and modeling the Magellanic Stream will help astronomers deepen their understanding of their source galaxies, and it is believed that the Magellanic Stream retraces the past trajectories of these galaxies.

"The great thing about having a massive stream of stars like the Magellanic Stream is that we can now use it to conduct a lot of astrophysical studies," Vedant Chandra, a CfA doctoral student in astronomy and astrophysics and the study's lead author, said in the statement. "As our spectroscopic surveys continue and we discover more stars, we're excited to see what surprises the outer reaches of the Milky Way will hold for us."

Scientists believe that as hydrogen in the hydrogen stream fell into the Milky Way, it created the right conditions for star formation. By analyzing the data, the researchers also found that the mass of the hydrogen stream was about twice as high as they thought, which means that the gas swallowed by the Milky Way must be much more than previously calculated.

- Dark Energy Camera captures ultra-detailed images of nearby dwarf galaxies

- Hubble Space Telescope reveals a stunning star cluster (image)

- James Webb Space Telescope discovers brilliant young stars in nearby galaxies (photo)

"The Magellanic Stream is the primary source of heat for the Milky Way's stars — it's our breakfast, lunch, and dinner," study co-author Ana Bonaca, a former CfA postdoctoral fellow and now a staff scientist at Carnegie Observatories, said in the statement. "With our new, higher estimate of the Magellanic Stream's mass, the Milky Way may end up being even more massive than originally thought."

By better constraining the mass of the stream and better understanding the Magellanic Clouds, astronomers will be able to better estimate the distribution of mass throughout the Milky Way, the scientists said in the statement.

"Most of the mass is in the form of dark matter - a little-understood substance that has a gravitational pull," the scientists said. Better measurements of the Milky Way's mass in its distant hinterlands will help calculate how much ordinary and dark matter there is, constraining the latter's possible properties.

BY: Tereza Pultarova

FY: 33

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