Fast-Rotating Stars At The Centre Of The Milky Way Could Have Migrated From The Outskirts Of The Galaxy (Astronomy)

A newly discovered group of stars at the centre of our galaxy could have migrated from a star cluster or dwarf galaxy located more than 320,000 light-years away, reports a new ground-breaking study.

This is an artist’s concept of the fastest rotating star found to date. The massive, bright young star, called VFTS 102, rotates at a million miles per hour, or 100 times faster than our Sun does. Centrifugal forces from this dizzying spin rate have flattened the star into an oblate shape and spun off a disk of hot plasma, seen edge on in this view from a hypothetical planet. Image Credit: NASA, ESA, and G. Bacon (STScI)

In a research paper published by The Astrophysical Journal Letters, an international team of astrophysicists, including scientists from the University of Surrey, detail how they discovered a group of stars with different characteristics than their neighbours found in the Milky Way’s Nuclear Star Cluster (NSC).

The team used state-of-the-art high-resolution computer simulations to explain how this group of metal-poor and fast-rotating stars came to be located at the centre of our galaxy.

Their calculations found that it is likely that this group of stars are leftovers from the migration of a massive star cluster that formed a few light-years away from the Milky Way’s centre. Alternatively, while not as likely as the cluster scenario, the team also noted that the group of stars could possibly have originated from a dwarf galaxy located up to 320,000 light-years away from the galactic centre.

All evidence points towards an accretion event that happened 3-5 billion years ago during which a massive cluster migrated towards the centre of the Milky Way and was disrupted by the strong tidal forces of the NSC, a region of high stellar density. Cluster stars were deposited in the region and were discovered based on their peculiar velocities and low metal content.

Dr Alessia Gualandris, Senior Lecturer in Physics from the University of Surrey, added: “This discovery may be the ‘smoking gun’ evidence that the Milky Way has been accreting star clusters or dwarf galaxies over its lifetime. Its past was much more active than we previously thought.”

Dr Tuan Do, Assistant Research Scientist at UCLA, said: “It is remarkable how these new observations of the NSC can reveal so much about the history of the whole galaxy.”

Dr Manuel Arca-Sedda, a Humboldt Fellow at the Astronomisches Rechen-Institut, Heidelberg, concluded: “A close collaboration between observers and theorists has been key in this study. Combining new exquisite observations with state-of-the-art computer models has allowed us to uncover the birthplace of these peculiar stars”.

References: (1) Tuan Do et al. Revealing the Formation of the Milky Way Nuclear Star Cluster via Chemo-dynamical Modeling, The Astrophysical Journal (2020). DOI: 10.3847/2041-8213/abb246 (2) Manuel Arca Sedda et al. On the Origin of a Rotating Metal-poor Stellar Population in the Milky Way Nuclear Cluster, The Astrophysical Journal (2020). DOI: 10.3847/2041-8213/abb245

Provided by University Of Surrey

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