The Milky Way may be bigger than thought, study finds

Our home galaxy may be bigger than we first thought, astronomers have found.

A new model of the Milky Way has revealed that our galaxy is wider than we thought, according to a new paper in the journal. Astronomy of Nature.

Researchers found that the bulge at the center of our galaxy is less star-filled than expected.

“…we obtained a significantly larger ‘magnitude’ (defined as the half-light radius) for the Milky Way than expected,” the researchers wrote in the paper.

The Milky Way is a closed spiral galaxy with a central bar-shaped structure and several spiral arms extending from the center. The galaxy has a dense central bulge around the Galactic Centre, which is thought to contain a supermassive black hole called Sagittarius A*. The Milky Way contains between 100 billion and 400 billion stars, but the exact number is difficult to determine due to the galaxy’s sheer size and the presence of dust that obscures our view.

“Our understanding of the structure of the Milky Way has improved tremendously through the progress of galactic observations over the last decades. Thanks to the proximity to our home galaxy, we are able to study the substructures of the Milky Way (for example, the scale heights of the disk , spiral arms and bar/X shape) in fine detail, however, for the same reason, a global picture of the galactic structure is still incomplete,” the researchers wrote in the paper.

“The position of the sun embedded in the disk results in high extinction of the view towards the densest region in the galaxy, and thus, collecting data from large samples of stars over a wide spatial range is expensive in terms of time For example, a radial profile of the surface brightness across a galaxy, a basic observer of galaxies that contains rich information about their assembly histories and is easily accessible from their images, has long been lacking for the Galaxy Path. of Milk.”

In the paper, the researchers describe how they measured the brightness of all parts of our galaxy and conducted a census of the red giants located across the Milky Way. They found that the bulge at the center of the galaxy is not as densely packed as first thought and is also flatter; Thus, the Milky Way has a half-light radius larger than we knew.

Half-light radius is a measure used in astronomy to describe the size of an astronomical object, defined as the radius within which half of the object’s total light (or brightness) is emitted. In other words, it is the distance from the center of the object to the point where half the total light from the object is contained within a sphere of that radius.

“Because the inner profile of the disk is flattened, the half-light radius of the Milky Way is significantly larger than expected from a picture of the structure of the Milky Way with a bulge and thick and thin disk components a exponential,” they wrote.

“We also confirm that the growth history of the Milky Way is broadly consistent with galaxies at high redshift but with smaller systematic sizes. Our results suggest that the Milky Way has a more complex radial structure and size greater than previously expected.”

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