Black Holes

Article by Nick Zotalis

 

Long known as mysterious, destructive objects, black holes have captured the imagination of the world and served as cosmic “villains” drifting around the universe, eating everything in their path. This characterization is not unfounded. Black holes have the strongest gravity among objects in the observable universe. They are places where the fundamental forces of nature become twisted and warped. As an object approaches a black hole, time appears to slow to a halt. Formed from the collapse of large stars, these objects are called “black” because the gravity is so powerful that photons, particles that make up the light we see, cannot escape. The region of space where light cannot escape is known as the event horizon.

 

The largest black holes, which can contain mass in amounts up to billions of times the mass of our own sun, are known as supermassive black holes. They naturally become the central point of surrounding systems, acting as our sun does to Earth. One lies at the center of the Milky Way, and possibly at the center of every large galaxy. Despite a large wealth of information being available regarding black holes through mathematics, one has never been observed directly. However, a new and ambitious endeavor called the Event Horizon Telescope has linked telescopes from around the globe to do so for the first time.

 

The obstacles of observing a black hole are numerous. For one, despite their tremendous mass, black holes tend to not be very large. For example, a normal black hole can have the equivalent mass of 10 suns packed into a space the size of Manhattan Island. These “normal” black holes are difficult to detect because of their size. To image a black hole for the first time, scientists with the Event Horizon Telescope aimed for a supermassive black hole. These black holes are considerably larger. Sagittarius A, the black hole at the center of the Milky Way, is estimated to have a diameter roughly equivalent to the diameter of the earth’s orbit around the sun. The problem with supermassive black holes is that they tend to be located at the center of galaxies, as this one is, and the high concentration of dust and stellar material obscures the system from Earth. Furthermore, the same physics that prevent light from escaping the event horizon prevent all electromagnetic radiation such as X-rays and gamma rays from escaping as well, making all black holes even more difficult to detect.

The Haystack Observatory located at MIT
Image Credit: Brian Herzog

The Event Horizon Telescope is a project that has virtually linked telescopes from around the world to effectively make one telescope the size of Earth. This process has been done before but never on such a scale. The entire array of telescopes would enable a user to easily count the stitches on a baseball from 8,000 miles away. This awesome magnification power is needed because according to Dimitrios Psaltis, an astrophysicist at the University of Arizona, even imaging the large black hole at the center of our galaxy is equivalent to taking a picture of a DVD on the surface of the moon.

 

The experiment ran for 10 days from April 4 to April 14. Despite this, the results will not be available until next year at a minimum. This is because the entire array produced such a staggering amount of data that it cannot be transmitted electronically. Rather, it was stored on hundreds of hard drives which will be flown into two locations, the Haystack Observatory at MIT and the Max Planck Institute in Germany. This creates an additional problem because one of the telescopes used is located at the south pole. Therefore, due to the winter planes, it cannot land to retrieve its data until later this year. Once all the data is gathered, supercomputers in both locations will perform a process known as correlation which will remove any time delays caused by having telescopes in such different locations. After all the data is processed, humanity will hopefully have its first look at the event horizon of a black hole.

 

Getting an image of a black hole is important for many reasons. It will allow physicists to put Einstein’s theory of special relativity to the ultimate test. There are certain predictions that should be borne out by the image. Vincent Fish, one of the researchers at MIT’s Haystack Observatory, says, “What we expect to see is an asymmetric image where you have a circular dark region. That’s the black hole shadow. And there might be a bright ring at the edge of that—which is the photon ring. Then around it you will see one side is bright and the other side is faint, so kind of like a crescent.” If these predictions do not come true, then Einstein’s theories may need to be tweaked. The implications of such a massive scientific success are numerous, and the next few months should prove very exciting for science enthusiasts or anyone interested in black holes.

 

Feature Image Credit: Thi Nguyen

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