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Recent Podcast
A Quick Look at GW170817
A Quick Look at GW170817
A new study using Chandra data of GW170817 indicates that the event that produced gravitational waves likely created the lowest mass black hole known. (2018-05-31)

A Tour of 3C 186: An Interview with Dr. Aneta Siemiginowska

Narrator (April Hobart, CXC)
A galaxy cluster containing a structure never previously seen so far from Earth has been observed by NASA’s Chandra X-ray Observatory. The cluster is also interesting to astronomers because a bright quasar, known as 3C 186, is found at its center. Dr. Aneta Siemiginowska of the Harvard-Smithsonian Center for Astrophysics led the team’s research on this result and discusses it with us.

Dr. Aneta Siemiginowska:
When we looked at the first result – the first image we got from Chandra, very short observations, ten years ago – we noticed that there was a point source and there was a “fuzz” around this point source, which clearly was not associated directly with the quasar emission but was coming from the surroundings of this quasar. And we were excited because we discovered a new cluster.

A few years later, Dr. Siemiginowska and her colleagues requested a much longer Chandra observation of 3C 186 to see if they could figure out what was really going on in this system.

Dr. Aneta Siemiginowska:
The result of this deep observation indicated that the cluster has a cooling core, and a cooling core means that the gas which is falling into the gravitational potential of the cluster is cooling.

Dr. Siemiginowska explains why studying these types of objects is so important to her.

Dr. Aneta Siemiginowska:
I'm mainly interested in the evolution of radio sources, so I’m studying the young, compact radio sources in the very early stage of their expansion to becoming big ones. And the interaction between this expanding radio source and the cluster environment is interesting. We don’t understand how the energy generated by the quasar is deposited into the cluster. We know that something is happening, and it’s important because we want to understand the way the quasar gets its matter and its fuel to generate the energy of the quasar.

But as with many areas of astrophysics, for every answer astronomers find, more questions are raised.

Dr. Aneta Siemiginowska:
We have a quasar which powers the structure, which is huge, so how does it happen? We look at the small source, we know that the smaller sources – compact sources – are very powerful, and then this energy that’s still keeping at the same rate causes the source to grow, but there is the interaction then with the environment, and this energy from the quasar is deposited to the clusters of galaxies or the galaxy itself, and it’s being lost. But how does the source stay powered for so long?

Scientists will continue to use Chandra to study galaxy clusters and quasars to help us better understand the universe in which we live. For more information on this result and others, visit