So April 10 will be quite the monumental day in astronomical history. It will be the day we get to see our first real picture of a black hole.
Every image you’ve ever seen of a black hole, including the one below, is not an actual photograph. They are all artist’s conceptions. We’ve never taken a picture of an actual black hole…largely because, well, we can’t. A photograph is an image made by light impacting an emulsion (or in the case of modern digital photography, a group of sensors), recording what the light looked like at that instant. Black holes, by definition, emit no light. A black hole is a place from which nothing, not even light, can escape. So what exactly will this image on April 10 be of?
The new image will be released by the Event Horizon Telescope (EHT), and will represent an entire year’s worth of collected data from a global network of telescopes. The light they have been gathering comes not from the black hole itself, but from the stuff outside the black hole, just in front of the event horizon. That material is hot and glowing, and therefore emitting light, just before it falls into the black hole and is forever lost from our ability to detect it. What the scientists with the EHT are hoping the images will show is a shadow cutting across that glowing material. That shadow will be the black hole itself, blocking part of our view of the surrounding material.
The EHT has actually been studying two black holes. One is Sagittarius A*, the supermassive black hole at the center of our own Milky Way galaxy. The other one is the even more supermassive black hole at the center of M87, a huge elliptical galaxy in the constellation Virgo. Despite the supermassive-ness of these black holes, the images obtained will be extremely small. Sagittarius A* is about 30,000 light years away from us, meaning that the light the EHT is receiving took 30,000 years to get to the telescopes. From that far away, even a supermassive black hole appears no bigger than the period at the end of this sentence.
Still, our first real photograph of a black hole is quite the triumph! But don’t be surprised when the images released on Wednesday don’t look anything like the cool special effects from Interstellar. Our first pictures of anything tend to be fuzzy and don’t show much detail. But they represent the first step in what is likely to be a rapidly increasing pace of discovery. This is an exciting time!
While we won’t be looking at any black holes, consider continuing your own astronomical journey by joining us for our monthly Stargazing and Laser Light Night event on Saturday April 13. We will start setting up our telescopes at 7:30pm for stargazing (weather permitting – always FREE!), and there will be 4 different shows in the Abbitt Planetarium rain or shine ($6 per person, or see any 2 shows on the same night for $10 – Members get half off!). The Wild Side Cafe will be open from 7 to 11:30pm for dinner, snacks, and drinks. So come on by, grab a beer, and ask our staff astronomers your questions about black holes…or anything else in the universe. See you there!