Globular Clusters and Black Holes: Detection!

We return to the topic of the humble globular cluster, an object that usually draws little attention as it consists of a clump of about a million very dim stars. One aspect of globular clusters that is interesting is that all of these stars are enclosed in an incredibly small space.

As an analogy, imagine substituting stars in the sky with administrators in an office. Let us say that your task is to house 10 administrators You could choose to give them each their own desk space in a large room, or you could to save on space and crush them all into a small elevator for eight hours per day.

The former case is similar to that of the Milky Way. In the Milky Way, each star (administrator) is sitting in a part of sky (a desk) that is spaced a comfortable distance from the other stars (administrators). Thus when we look up at the sky at night, we do see other stars (administrators), but apart from the Sun the other stars do not look so piercingly bright and close to us.

The latter case, on the other hand, is similar to that of the globular cluster. Here each star (administrator) in the globular cluster is pressed uncomfortably against another star (administrator). The stars are so compactly arranged that if Earth would be magically relocated to the inside of a globular cluster there would be no night time. We would see many “suns” in the daytime and many “suns” at night.

What might be the benefit of such a crowded arrangement of stars as one finds in a globular cluster? One recent fascinating discovery is that binary black holes can form in globular clusters more readily than in most other environments.

Of the sets of binary black holes that are situated in globular clusters, some of them will emit powerful radio jets that shoot out of the globular cluster. We are just starting to detect these jets at radio frequencies, and as the data come in, there is just no other explanation that we can come up with apart from the probably presence of a binary black hole!

Dr. Brenda Frye

About Dr. Brenda Frye

Brenda L. Frye is an observational cosmologist at the Department of Astronomy/Steward Observatory, University of Arizona. She earned her Ph. D. in Astrophysics from the University of California at Berkeley, assisted by a National Science Foundation Graduate Research Fellowship.

Her thesis work involved measuring the concentration of the total mass of visible plus dark matter in the fields of massive galaxy clusters, a program requiring the use of some of the largest telescopes in the world.

Moving a mile from her Ph. D. institution, she assumed a postdoctoral position with the Supernova Cosmology Project at Lawrence Berkeley National Laboratory under the direction of Professor Saul Permutter.

She then treked across the country to take a National Science Foundation Astronomy and Astrophysics Postdoctoral Fellowship and a Princeton Council on Sciences and Technology Fellowship both at Princeton University.

Moving further east, she became a Lecturer in Physics at Dublin City University in Dublin, Ireland, where a number of European collaborations were formed.

From there she crossed back across the pond to the west coast of the U. S. to become a tenure-track Assistant Professor of Physics at the University of San Francisco.

Her travels have now landed her at her Alma Mater in Tucson, where she teaches and does research. The aims of her research continue to be to use gravitational telescopes in space as 'lenses' to study the properties of dark matter and those of distant galaxies back to when the universe was <900 million years old.

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