Michal Zajaček (Center for Theoretical Physics, PAS, Warsaw)

Michal Zajaček Colloquium: Speeding up around the Galactic center

Remotely Hosted

Abstract

There have been three recent discoveries in the field of the Galactic center that have significant implications for its evolution. First, the discovery of six faint stars by Peissker+2020 that orbit the supermassive black hole (SMBH) at distances comparable to the size of the Solar System provides new, powerful probes of the strong-gravity regime of Sgr A*. Two of these stars, S62 and S4711, have orbital periods less than 10 years and the star S4714 with its estimated peribothron velocity reaching nearly 10% of the light speed is a candidate for the fastest star in the Galaxy up to now.

Second, we found that stars of the innermost stellar cluster – S cluster – are preferentially aligned in two nearly edge-on stellar disks that are perpendicular to each other (Ali+2020). Stars in each disk appear to rotate both ways. This is in contrast with the previous results which indicated that orbital planes in the S cluster are nearly isotropic.

Third, a population of dust-enshrouded objects in the S cluster opens up several mysteries, including their origin and nature (Ciurlo+2020, Peissker+2020). A young-star model is one of the favourite interpretations of their nature and origin (Zajacek+2014, 2017), which indicates that a star-formation event could have occurred in the direct grasp of the SMBH less than million years ago. All of the three discoveries imply that despite the very low accretion activity, the environment of the nearest SMBH is highly dynamical and in constant transformation.