21Aug2017

Measuring a Black Hole is as Simple as ABC

Image By: XMM-Newton, ESA, NASA [Public domain], via Wikimedia Commons

Image By: XMM-Newton, ESA, NASA [Public domain], via Wikimedia Commons

Black holes seem like these massive unquantifiable monstrosities, impossible to see or measure because not even light can escape their gravitational grasp.

They’ve been the environmental bad guy, so to speak, in everything from the 1979 Disney movie “The Black Hole” to Doctor Who and most recently Interstellar. They were the astronomy boogeyman until someone took a look at one from a different angle.

Two teams of astronomers from opposite sides of the globe have found a new way to measure and quantify these holes in the universe — and it’s as simple as ABC.

How to Weigh a Black Hole

Scientists have long theorized that at the center of each spiral galaxy, there lies a black hole. Astronomers in Australia and Minnesota have found a way for even casual astronomers to look at a spiral galaxy and estimate the mass of the black hole at its core.

The arms of the spiral galaxies are indicative of the size of the black hole. Edwin Hubble and Sir James Jeans were the first to observe that galaxies with large central bulges, which could indicate a large black hole, had smaller, more tightly controlled arms.  On the other side of the coin, those with smaller central bulges had arms that spread out further.

Using these observations, the astronomy teams in the University of Minnesota Duluth and Swinburne’s Center for Astrophysics and Supercomputing in Australia found that there is a definitive connection between the composition of a galaxy’s spiral arms and the size of its central black hole.

Reaching Out With Radio Telescopes

Traditionally, assessing the size and mass of a black hole requires access to one or more enormous radio telescopes. A ‘local’ supermassive black hole was discovered recently — local being a relative term as it rests 25,000 light years from home — and by targeting the nearby Sagittarius A section of the galaxy and observing the movement of the stars in that sector of space.

This radio telescope observation did find that the local black hole is enormous — more than 4 million times the mass of our own sun. When it comes down to it though, most people interested in space don’t have access to giant radio telescopes or the training or education to use them.

Alphabetical Galactic Classifications

These spiral galaxies are classified depending on the size of their central bulge and the density of their spiral arms — Sa, Sb, Sc and Sd. Galaxies with higher mass black holes are classified Sa or Sb, while those with lower mass centers are classified Sc or Sd.

With this tidbit of information, amateur astronomers and even primary school children can look at any observed spiral galaxy in the universe and estimate the size of its central black hole. It’s quite literally as simple as A, B, C. Just look at the classification of the galaxy that you’re studying. That will give you an idea of the size of the black hole at the center of the galaxy.

What Questions Should We Be Asking?

Why are these black hole discoveries so important? By understanding these black holes, we can help to improve our understanding of the universe.  Black holes are gravitational anomalies, and by understanding them, we can begin to understand how gravity affects us, our solar system, our galaxy and the universe around us.

We’re just starting to understand the universe that we live in.  Not only does this fantastic discovery help us understand our place in the grand scheme of things, but it also helps make things like measuring black holes more accessible to the average backyard astronomer who might not have access to the powerful telescopes that you need to see black holes and other mysteries of the universe.

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Written By: Megan Ray Nichols – Science Writer

 www.schooledbyscience.com/about/  Contact: nicholsrmegan@gmail.com

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