How Does the Milky Way's 'Stellar Halo' Actually Look Like? Astronomers from Harvard Show Its Real Shape

For several decades, specialists thought that the stellar halo, which is a star, dark matter, and gas diffuse that surrounds the Milky Way's disk, is predominantly isotropic and spherical. However, SciTechDaily reports that recent findings from Harvard astronomers suggest that this stellar halo is actually tilted and oblong.

Milky Way's Stellar Halo is Oblong and Titled

The findings were included in the Astronomical Journal. They grant insight into many subjects of astrophysics, which includes galaxy evolution and history.

Lead author Juwon "Jesse" Han, a P.h.D. learner from the Center for Astrophysics, Harvard and Smithsonian, notes that the stellar halo's shape is a primary parameter that the researchers were able to gauge with accuracy that is comparatively greater than before. Han notes how there are several vital implications of the non-spherical shape of the stellar halo.

Co author and astronomy professor Charlie Conroy notes that it has been generally assumed for decades that the stellar halo is isotropic and spherical. This means that the halo was perceived to be the same across each direction. However, they now know that this is not the case.

Importance of the Stellar Halo

According to Telescope Live, the stellar halo takes up the vaster galactic halo's visible parts. This broader galactic halo is largely filled with dark matter that is invisible; its presence is only known and gauged through the gravity it manages. Halos of dark matter can be spotted across other galaxies as they serve as the primary structure that ordinary matter sits upon. For this very reason, stellar halos are vital aims and could be used to track dark matter. In order to know more about the interaction and formation of galaxies as well as dark matter's underlying qualities, these stellar halos are important targets.

In simpler terms, Han also notes how the stellar halo is the galactic halo's dynamic tracker. It is a good place to start when it comes to knowing more about the general nature of galactic haloes.

Knowing about the shape of the Milky Way's very own stellar halo has been a challenging feat for astrophysicists. The said halo is stretched over several hundreds of thousand light years below and above the galaxy's plane.

Han notes that unlike galaxies outside where the halos can simply be observed and measured, there is a lack of an external and aerial view of the Milky Way's own halo.

Nevertheless, the recent study utilizes two grave datasets that were generated over the years. The first one was from the European Space Agency's Gaia, and the second one is from the ground survey H3.

Using a flexible model to mix the data enabled the understanding of the stellar halo's shape.

Based on the framework, the galaxy's stellar halo came to be when the single dwarf galaxy met 7 to 10 billion years ago with the bigger galaxy. Resultantly, the smaller galaxy got torn apart. The stars then dispersed to form a halo.

The discovered football shape, which is technically referred to as a triaxial ellipsoid shape, mirrors the observations of two star pileups within the stellar halo.

Conrot notes that the distribution and tilt of stars within the stellar halo serve as grave confirmation regarding the collision that took place 7 to 10 billion years ago. He also notes that the tilt of the stellar halo proposes how the dark matter could also be tilted. This dark matter tilt may also lead to great ramifications regarding the capacity to trace dark matter within earth's laboratories.

This discovery may serve as a springboard for other astrophysical subjects of study that aim to provide primary details about the universe.

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