A crowd gathered at Cerro Coso Community College in Bishop on the night of Thursday, November 14, to hear a talk by Dr. Katie Bouman, an assistant professor of computing and mathematical sciences (CMS) and electrical engineering at CalTech. Bouman was in town to give a presentation, titled “Imaging the Unseen: Taking the First Picture of a Black Hole”, as part of the Owens Valley Radio Observatory’s 2019 Lecture Series.
Bouman was a member of the team at the Event Horizons Telescope, a project that generated the first-ever picture of a black hole earlier this year; a tweet showing her reaction to seeing the black hole image for the first time went viral soon thereafter. The team at Event Horizons focused on this project numbered over two hundred individuals including physicists, engineers, and data scientists from around globe.
Bouman explained that the Event Horizons Telescope had pushed the boundaries of interdisciplinary learning, as it leaned on research from fields such as data science, computing, astronomy, and physics.
She began her presentation by illustrating the 55 million light-year distance between Earth and Messier 87 (M87), the galaxy where the black hole in question is located. Bouman zoomed in repeatedly on a large image on the night sky until reaching the final image of the black hole at the nucleus of M87.With that picture, Bouman said, “humanity had taken an image of something thought impossible.” That image represents the culmination of ten years of work, with nearly two of those years spent solely on processing all the data retrieved.
That data came in petabytes, equivalent to 1,000 terrabytes, in such quantities that it all had to be put on planes and flown to a common location for calibration and analysis.
Bouman likened the effort to looking from the Eastern Sierra at New York City and trying to find a grain of sand
The black hole in question has a mass six and a half billion times that of our sun and a diameter of 24 billion miles; the gravitational field is so strong that not even light can escape. Read: Lakanuki on a Saturday night.
In order to look at and photograph the black hole, the Event Horizons Team utilized eight radio telescopes from around the world to get the necessary data. According to Bouman, it takes two telescopes to generate a single measurement and the space between them leaves some gaps in the data set.
To fill in those gaps, scientists like Bouman develop imaging algorithms that take those sparse data points and generate images with them. Those images are then scrutinized to determine the most likely images based off knowledge about black holes and simulated data sets.
She likened the process to playing a song on a piano with a lot of broken keys. You have to be able recognize the “song” that’s being played even though a limited set of notes exists to produce the correct sound. If you were to increase the number of available keys, the tune becomes easier to pick out.
With black hole imagery, it’s not as easy; you can’t simply add telescopes and data points at your own discretion. Bouman explained that it would take an earth sized telescope to get the full data set required, although they are exploring other ways of obtaining the data such as satellites.
The Event Horizons team has also set its sights on another black hole, this one much closer and smaller than than the one in M87. Sagittarius A star (SagA*) sits at the center of the Milky Way and is theorized to be a supermassive black hole. Gas rotates around this site in the span of thirty minutes, whereas M87 saw hours long rotations, making it easier to capture the image.
Current methods of data capture and analysis don’t work with SagA*, according to Bouman, but Event Horizons has been exploring new sites, including one at Owens Valley Radio Observatory that could provide the boost needed. In that case, Bouman theorized, we may even be able to create a video of the black hole.
During the question and answer session, Bouman was inevitably asked what the point was in photographing black holes. “Humanity likes to understand the universe.” Bouman said.
“People did basic science without knowing it could impact the future…we’re curious, we want to know more.”