Athanasia Tsatsi is a postdoctoral researcher at the Max-Planck-Institute for Astronomy (MPIA) in Heidelberg, Germany. At MPIA she works at Glenn van de Ven’s Galaxy Structure and Dynamics Group. She was born in Athens and earned her Ph.D. from Heidelberg University in 2016.

She is studying the formation history of elliptical galaxies, as well as nuclear star clusters, and in particular how mergers can explain their present-day dynamical structure.

Astronomers led by Athanasia Tsatsi found that spindle-like galaxies which rotate along their longest axis are much more common than previously thought. The new data allowed the astronomers to create a model for how these unusual galaxies probably formed, namely out of a special kind of merger of two spiral galaxies. The results have been published in the journal Astronomy & Astrophysics.

When most people think of galaxies, they think of majestic spiral galaxies like that of our home galaxy, the Milky Way: billions of stars, rotating in a flat disk similar to the way that a wheel rotates around its central axis. But there is another kind of galaxy, which used to be thought very rare: so-called prolate rotators, each shaped like a cigar, which rotates along its long axis, like a spindle.

As the galaxies begin to interact via gravitational attraction, one of them forms a bar: an elongated structure near the center. That bar becomes the cigar-like shape of the merged galaxy, while the orbiting stars of the other galaxy imbue the merged galaxy with its overall sense of rotation.

Using data from the CALIFA survey, a systematic study that examined the velocity structure of more than 600 galaxies, Tsatsi and her team discovered eight new prolate rotating galaxies, almost doubling the total known number of such galaxies (from 12 to 20).

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Greek astronomer discovered unusual spindle-like galaxies