Our Milky Way Galaxy Is Less Weird Than We Thought

Beeld: Artist’s impression of the Melkwegstelsel. (Pablo Carlos Budassi/Wikimedia Commons (CC BY-SA 4.0))

This change makes the Milky Way “less weird,” said Gil Zasowski, an astronomer at the University of Utah in Salt Lake City, USA. She points to the fact that the stars and other parts of the Milky Way are more compact than those in similar galaxies that scientists can directly see and measure. “Compared to those measurements, our system looks ‘nice and cozy,’ but that also makes you a little skeptical,” Zasowski said.

Zasowski and her colleagues base their review of the Milky Way on measurements of the positions and distances of nearly a quarter million red giants — massive, ancient stars — made as part of the Apache Point Observatory Galaxy Evolution Experiment (APOGEE).

The exact structure of the Milky Way has always been difficult to pin down, because we are located in one of its spiral arms, about halfway between the nucleus and the outer edge of the Milky Way’s disk. In addition, our view of distant stars is obscured by dust that has spread throughout the Milky Way. Normally, light from celestial objects like red giants is blocked from our telescopes by this dust, but the Apache Observatory in Sunspot, New Mexico, can detect near-infrared light passing through the dust.

swelling

Previous estimates of the size and shape of the Milky Way were based on determining the distribution of stars near our Sun, and extrapolating them using models of simple galaxies. The new inventory of red giants has given researchers a better picture of the distribution of stars in the Milky Way, particularly in its central “bulge,” or swelling.

To their surprise, the researchers saw clusters of red giants between the rim and the ocean. swelling The Milky Way isn’t growing much larger. Instead, it’s flattening out halfway, suggesting that the stars in the central part of the Milky Way’s disk are less dense than existing models suggest. If the material in the Milky Way isn’t densely packed in the center, it must be more spread out than previously thought.

“This new discovery will force us to rethink many things,” said co-author Jianhui Lian, an astronomer at Yunnan University in Kunming, China. For example, we may have to lower our estimates of the total mass of the Milky Way. That could mean that our Milky Way galaxy contains more dark matter than previously thought.