There is a cloud of stars surrounding the disk of our galaxy. Astronomers have believed that the stellar halo was spherical, like a beach ball. A new model shows that the stellar halo is oblong and tilted like a football after being kicked.
Insights into a number of astrophysical subject areas can be found in the findings. The results shed light on the history of our universe and offered clues in the search for dark matter.
Jiwon "Jesse" Han is a PhD student at the Center for Astrophysics in Harvard. There are a lot of implications of the stellar halo not being spherical but instead shaped like a football, rugby ball, or zeppelin.
For decades, the general assumption has been that the stellar halo is spherical and isotropic, or the same in every direction. The textbook picture of our universe embedded within a spherical volume of stars needs to be thrown out.
The visible part of the galactic halo is the stellar halo. The invisible dark matter is only visible through the gravity that it exerts. There is a halo of dark matter in every universe. Ordinary, visible matter hangs from these halos. Stars and other observable structures are formed by visible matter. To understand how galaxies form and interact, as well as the underlying nature of dark matter, stellar haloes are valuable.
Han says that the stellar halo is a way of showing the halo. The stellar halo is a great place to begin learning about the history of our own galaxy's halo and other halos.
Figuring out why we are embedded within the stellar halo has been a challenge for astrophysicists. Our Solar System is covered in a halo of light hundreds of thousand of light years above it.
Han says that we don't have the same sort of aerial, outside perspective of our own galaxy's halo.
Complicating matters further, the stellar halo has been found to be quite diffuse, containing only a small portion of the mass of all the stars. Astronomers have been able to identify many thousands of stars in the halo because of their distinctive chemical makeup, as well as by their distances and motions across the sky. Calculating the distribution of halo stars has shown that they aren't evenly distributed. To sort out the ultimate origins of the stellar halo, we need to study the patterns of over-densities of stars.
Two major datasets gathered in the last few years have plumbed the stellar halo as never before.
The first set is from the European space agency. The positions, motions, and distances of millions of stars have been measured by Gaia.
There is a ground-based survey conducted at the Fred Lawrence Whipple Observatory in Arizona and a collaboration between the University of Arizona and the CfA. Detailed observations of tens of thousands of stellar halo stars have been gathered by H3.
The non-spherical halo was created by combining the data in a flexible model that allowed for it to emerge from all the observations. There is a leading theory regarding the formation of the stellar halo.
The stellar halo was formed when a lone dwarf galaxy collided with our larger one. "Sausage" is a pattern that appears when plotting the Gaia data and "Enceladus" is a Greek myth. The dwarf galaxy was torn apart as a result of the collision. The stellar halo stars are unique to stars born and bred in the Milky Way.
The results of the study show how the two planets interacted thousands of years ago. There are two pileups of stars in the stellar halo, and the football shape reflects their observations. The pileups are said to have formed when GSE traveled through the stars. The extra stars were shed at the furthest points in the dwarf galaxy's elliptical path, known as the apocenter. The tilt of the stellar halo shows that the Milky Way was encountered at an angle not straight on.
The tilt and distribution of stars in the stellar halo show that our galaxy collided with another smaller one.
The stellar halo stars would have been expected to settle into the spherical shape after so much time had passed. The team says that they haven't talked to the halo. Through its gravity, this dark matter dominated structure is keeping the stellar halo off-balance.
The underlying dark matter halo is tilted by the tilted stellar halo. The ability to detect dark matter particles in laboratories on Earth may be affected by a tilt in the dark matter halo.
Multiple dark matter detector experiments are currently running and planned. If astrophysicists can judge where the dark matter is more concentrated, these detectors will be able to capture an elusive interaction. The regions of dense and higher-velocity dark matter will occasionally be encountered by Earth.
While filling in basic details about our place in the universe, the discovery of the stellar halo's most plausible configuration is moving many astrophysical investigations forward.
"What does the galaxy look like?" and "What does the stellar halo look like?" are some of the questions to be asked about our universe. We are finally answering those questions with this line of research.
Jiwon Jesse Han and his co-authors wrote about the stellar halo of the star in the journal The Astronomical Journal. There is a book titled "10847/1538-3881/ac97e9".
Journal information: Astronomical Journal
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