New research indicates that the gas arc is five times closer to our Milky Way than previously believed.

Our solar system is located in a huge galaxy referred to as the Milky Way. Smaller dwarf galaxies circle our Milky Way again, of which the Magellanic Clouds (one large and one small) are the best known. In addition, a collection of gas orbits around our Milky Way that takes the form of an enormous arc. Previous research has shown that the gas originates from the Large and Small Magellanic Clouds, which is why this gas arc is called the Magellanic Stream.

Models

Exactly how the Magellanic Stream originated has been a mystery for decades. But a new study now seems to be changing that. Using models, researchers have reconstructed the birth of the Magellanic Stream. And that immediately resulted in a big surprise. “The models bring the flow much closer to the Milky Way,” said study researcher Scott Lucchini.

Five times closer

All in all, the Magellanic Cloud is said to be as much as five times closer to our Milky Way than was previously thought. And that in turn suggests that the massive gas arc — which is expected to collide with the Milky Way — will also hit our galaxy much sooner.

As stated, the researchers base this conclusion on new models, which in turn are based on new insights into the history of the Magellanic Stream. For example, the same research group predicted last year that a large part of the mass of the Magellanic Current that was difficult to explain until then came from warm gas that surrounded the Magellanic Clouds like a kind of wreath or corona. That warm gas was included in the new models. As is the also fairly recent suggestion that the Large and Small Magellanic Clouds briefly orbited each other long ago. “With the addition of the corona, the orbital history of the clouds also changed,” Lucchini said.

Other Orbital History

Previously, researchers have already developed models that describe the birth of the Magellanic Cloud. And recent models have also taken into account that the Small Magellanic Cloud briefly circled the Large Magellanic Cloud. As one cloud revolved around the other, the two clouds extracted gas from each other, thus producing the Magellanic Stream together. With the addition of warm gas that circles the Large and Small Magellanic Clouds, we see a small but important change in Lucchini and colleagues’ model: the Small Magellanic Cloud rotates as it passes through the Milky Way. is captured exactly in the opposite direction around the Large Magellanic Cloud. In that scenario, the clouds still produce a Magellanic Stream, only its arc points not toward interstellar space, but toward our Milky Way. The result is that the minimum distance between the Magellanic Current and the Milky Way is much smaller; about 65,000 light-years.

star formation

It means that the current will also collide with the Milky Way much sooner than thought. The gas from the Magellanic Stream could already be absorbed into the Milky Way in 50 million years and lead to a lot of new star formation.

Looking for stars

But the new reconstruction has more implications. It also suggests that we should be able to find stars that have been ripped out of the Large and Small Magellanic Clouds along with the gas and are now part of the Magellanic Stream. To date, only a few of these stars have been observed. “Some researchers think the stars are not so easy to see because they are too far away,” Lucchini said. But the new model suggests we’ve just been looking for the stars in the wrong place all along. “Now we see that the Magellanic Stream is actually on the outer edge of our Milky Way.” It means not only that we now know where to find the stars, but also that the stars are much closer than thought. “With current tools, we should be able to find these stars,” said researcher Elena D’Onghia. “That’s exciting.”

Follow-up observations should show whether the stars are indeed close to our Milky Way and whether the scientists’ model is correct. If so, the Magellanic Stream as a whole will also have to be examined more closely. “The revised distance changes our understanding of the flow,” said researcher Andrew Fox. “It means that many estimates of flow properties – such as mass and density – need to be revised.”