The unexpected orbits of the ancient stars rethinked the evolution of the dairy system

Starred 232121.57-160505.4 around the galaxy in the central Cartesian frame, painted according to the clock. The white dot represents the star’s current location. The black circle and the dashed circle indicate the position of the sun and the orbital sequence. Credit :: Cordoni et al.

Australian telescopes and European satellites together show unexpected movements between very small objects in the galaxy.

Concepts Milky Way Based on discoveries made by the character of some ancient stars, they are ready to be rewritten.

Some observations of the orbit of the iron-poor stars of the galaxy, believed to be among the oldest in existence, go unnoticed.

Metal-poor stars – containing less than a thousandth of iron in the sun – are some of the smallest objects in the galaxy, ”said Professor Gary da Costa at ARC, Australia’s Advanced Center of Excellence in 3D. A.A. Australian National University.

After studying 475, we found about 11 percent of the orbit of the Milky Way disc. They follow a circular path like the sun. That was unexpected, so astronomers have to reconsider some of our basic ideas. ”

Previous studies have shown that the iron-poor stars were almost confined to the halo of the galaxy, but this study showed that the disk itself rotates in large numbers.

The sun also rotates in the disk, which is why a relatively thin, ribbon-like structure is easily seen in the night sky. As a result, we are watching.

“Our view of Milky Way has changed dramatically over the past year,” says Jaco Cordoni, an author from the University of Padova in Italy, who conducted a major study on a recent European-funded study at ANU. Research Council GALFOR Project.

This discovery adds a new dimension to the mystery of the Milky Way, which is inconsistent with previous galaxy formation. Although they contain only a small fraction of their metal, their orbits are very similar to those of the sun. Understanding why they move the way they do can provide a significant assessment of how Milky Way has developed over millions of years. ”

AnU’s SkyMapper and 2.3-meter telescopes and the European Space Agency’s Gaya Satellite were mentioned using three of the most advanced kit kits.

The low metal content was identified by the telescopes, and then the satellite was used to determine their orbit.

The results – developed by researchers from Australia, Italy, Sweden, the United States and Germany – show that the orbits of ancient stars fell into many different forms, but one is related to earlier predictions and observations.

As expected, most of the stars gathered around the galaxy’s “star halo” and had a mostly spherical orbit – this structure is thought to be at least 10 billion years old.

Other irregular and “arrogant” paths created structures known as Gaya Sasaj and Gaya Sekuya, which are thought to be the result of two sudden collisions with small galaxies in the distance.

Some stars are moving in the wrong direction around the galaxy – and a few to five percent seem to be in the process of abandoning Milky Way altogether.

And then there were 50 or so in the orbit aligned with the galaxy disk.

“I think this work is important and full of new results, but if I had to choose one, this would be the greatest metal-weak disc star of this nation,” Cordoni said. The future of the formation of our galaxy must be responsible for this discovery – which will drastically change our thinking.

Cordoni’s team includes the Italian Center for Research and Space Activity, the Mast Plac Institutes in Germany, the Massachusetts Institute of Technology in the United States, the Universities of Uppsala in Stockholm and Stockholm, and the University of Australia at the University of New South Wales in Australia. And ANU.

The team includes Australian Brian Schmidt, winner of the 2011 Nobel Prize in Physics.

An earlier version of the study is now in Monthly announcements of the Royal Astronomical Society.

Reference: “Browse the Galaxy Halo and the Metal-Weak Thick Disk with SkyMapper and Gaia DR2” by G Cordoni, GS da Costa, De Yong, AD Mackie, F. Marino, S. Mont, T. Nordlander, J. Norris, M. Asplend, MS Bessel, R. Casey, A. Frebel, K. Lind, SJ Murphy, BP Schmidt, XD Gao, T. Zilakis-Dorbush, AM Amarsi and AP Millon, ed. November 4, 2020 Monthly announcements of the Royal Astronomical Society.
Doy: 10.1093 / mnras / staa3417

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