Academic Minute Podcast
Dirk Grupe, Northern Kentucky University – New Discoveries About A Familiar Black Hole
On Northern Kentucky University Week: Black holes continue to fascinate us.
Dirk Grupe, associate professor and chair of the department of physics, geology and engineering technology, explains why.
Dr. Dirk Grupe (“Group-ah”), Northern Kentucky University associate professor and chair of the Department of Physics, Geology and Engineering Technology. Prior to this position he has also taught at Morehead State University (Morehead, Ky.) and was a senior research associate at Penn State University, where he managed execution of the Guest Investigator program for the NASA Swift satellite mission. Dr. Grupe also was a research assistant at the Max-Planck Institute for Extraterrestrial Physics in Garching/Germany. He earned his doctorate in Physics, Astronomy and Astrophysics at the University of Göttingen.
New Discoveries About A Familiar Black Hole
Black holes seem the stuff of science fiction. Albert Einstein’s General Theory of Relativity. Einstein predicted them – yet even Einstein thought them too strange to actually exist. But they do exist — and with new ways to explore their nature, we are learning more about them.
The research team that I work with found out, for example, that one black hole, OJ 287, is much smaller than once assumed. Every galaxy including our own Milky Way harbors a supermassive black hole in its center. Their mass is millions – even billions – of times more than the mass our sun.
About 10 percent of these become active as Quasars, the most luminous persisting objects in the universe. Their luminosity exceeds the sun’s by trillions of times. Some of these develop powerful jets that emit electro-magnetic signals. These black holes are called “Blazars” for “Blazing Quasars”. OJ 287 is a blazar. The reason we see it as such a bright object is because of its jet. It is like looking into a flashlight’s beam. OJ 287 flares every 12 years with double peaks. Previously, scientists thought that indicted a binary black hole – that is, two black holes in close orbit around each other.
This theory however would require that OJ 287 be one of the most massive black holes in the universe — 18 billion times the mass of the sun. Our team used the NASA Niel Gehrels Swift Observatory and the 100m Effelsberg Radio Telescope to check. An 18 billion solar mass black hole would have to a host galaxy that would be enormous and impossible not to detect. Yet there is no such galaxy around OJ 287.
Our measurements suggests a much smaller black hole mass – about 100 times smaller than previously thought. Like all black holes, OJ 287 remains a mighty force – but it much smaller than once thought.
[NKU] – Black Hole Research
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