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How to “Photograph” a Black Hole

by Emily Peavy on June 1st, 2017

Reflection on Maunakea Skies: A Telescope the Size of the Earth with  Dr. Alison Peck, representing Very Long Baseline Array (VLBA)

Black holes are the enigmatic, mysterious objects that populate our sci-fi movies and excite our imaginations. Scientifically, black holes are objects that are so dense that gravity has collapsed them into a singularity and light can no longer escape the object’s gravity. Black holes are typically found by looking for their effects on nearby objects. This is how astronomers discovered the supermassive black hole in the center of the Milky Way galaxy, named Sgr A*.

This data observes stars that orbit Sgr A*. Made from images taken over 10 years with 8.2-m VLT YEPUN telescope at the Paranal Observatory, operated by the European Southern Observatory (ESO) in Chile and published in the scientific journal, Nature.


Now that black holes have been discovered, scientists want to know, is there a way to detect them directly? Astronomers utilize a technique known as Very Long Baseline Interferometry (VLBI)  which simulates large telescopes by linking smaller arrays of radio telescopes together. This process increases the angular resolution that can be obtained. The resolution required to observe the event horizon of Sgr A* has the equivalence of attempting to observe a grapefruit on the moon from Earth. Thus the Event Horizon Telescope links arrays from around the world to create ‘a telescope the size of the Earth.’ This scale of VLBI has never been done before and will create a new precedence of resolution that can be obtained with this method.  


What can we expect to see?
Astronomers have already used the Event Horizon project to capture more data from Sgr A* hopefully getting a peek at its event horizon. As we wait for this data to be processed and analyzed, we can simulate what we might find based on different scenarios. Below we have simulation models testing different circumstances.

“Remember, it takes scientists a long time to interpret the data and understand what’s really going on,” Dr. Peck concluded. “So we have to be patient, let them analyze the data, discuss it with all of these groups, and then hopefully they will show us the real data and some art that will help us understand what it really means.”

This Simulation shows black holes with different inclination angles that will help scientists interpret results
Credit: Joshua C. Dolence

This simulation compares what we can expect based on how many telescopes participate. The images on the left are 2 models while the center sees the models with 7 telescopes, and the right sees the models with 13 telescopes. Currently the Event Horizon Telescope utilizes 8 telescopes.

Credit: Doeleman et. al. using models by Gammie and Broderick

Join us for our next Maunakea Skies talk titled ‘The Search for the Origin of Gold” with Dr. Michitoshi Yoshida, Director of Subaru Telescope on Friday, June 16 at 7pm. 

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