6/17/2023 0 Comments Event horizon black holeThis includes matter, which is just a particular form of energy. Left square image courtesy of Jason Dexter. Image credit: Katie BoumanĮinstein's theory of general relativity (GR) connects spacetime curvature with distribution and motion of energy. Although this is just a simulation, reconstructions such as this give us hope that we soon will be able to to reliably take the first picture of the black hole. Below is a sample reconstruction done using simulated data generated from only 7 telescopes located around the world, and pretending to point at the black hole in the center of our own Milky Way galaxy. Using these algorithms we are able to reconstruct pictures from the very sparse measurements measured with the EHT. We then choose the image (or set of images) that looks most reasonable. To chose the best image, we essentially take all of the infinite images that explain our telescope measurements, and rank them by how reasonable they look. But not all images are created equal- some look more like what we think of as images than others. Similarly, for the EHT, the data we take only tells us only a piece of the story, as there are an infinite number of possible images that are perfectly consistent with the data we measure. However, as we increased the number of notes (measurements) the specific song becomes clear. In fact, perhaps close to the beginning you may have thought that the song was Queen and David Bowie’s song "Under Pressure." If those were the only notes we heard we would be in trouble, as there are multiple songs that fit the notes we are hearing fairly well. For example, even if many notes are playing, as long as there were some notes missing, it doesn’t have to be "Ice Ice Baby." The more notes missing, the more ambiguity there is. Using the sparse data we collect from the telescopes, our algorithms fill in the missing gaps with the most natural looking image.īut there is one point I want to draw your attention to: there is always some ambiguity in what the true image is. What your brain was doing here is very similar to what the imaging algorithms that we develop for the EHT do. Even though there were still a lot of gaps in the notes near the end, it’s pretty amazing that your brain can fill in holes and you can start to make out the song. The notes corresponding to the tones we are currently playing on the piano keyboard will be lit up so you can see what you are hearing.īy close to the end, even before all the notes were playing, you may have been able to start to recognize the song- Vanilla Ice’s "Ice Ice Baby." Even if you don’t know the song, you probably were still starting to get the gist of it. At the beginning you are going to hear only one note of this song, and as you go on you are hear more and more notes until eventually you will start to be able to make out a (hopefully familiar) song. In this video we play a song as if we were increasing the number of telescopes in the EHT, essentially fixing the broken piano keys. To make this a bit more clear, listen to the video below (use headphones for the best experience). Although hearing a song this way is definitely not perfect, often times there is still enough information to follow along. However, as we only have telescopes at a few locations, we must recognize the song being played with just a few notes. If we had telescopes located everywhere on the globe we would be able to hear all possible notes, and thus hear a perfect rendition of the song. Watching the black hole with the EHT is a bit like listening to a song that is played on a piano that has a lot of broken keys. The tone that is heard is related to the projected distance between the telescopes, as seen from the direction of the black hole the farther apart the telescopes, the higher the pitch of the note. Each pair of telescopes produces a measurement that corresponds to the tone of a just a single note. To give you an idea of how this works, you can think about the measurements we make from telescopes in the EHT as a bit like notes in a song. Since there is a lot of missing data, you may ask how making a picture is even possible. The imaging algorithms we develop fill in the gaps of data we are missing in order to reconstruct a picture of the black hole. However, since we are only collecting light at a few telescope locations, we are still missing some information about the black hole’s image. The light we collect gives us some indication of the structure of the black hole. Once the EHT has measured data from the black hole, we still need to make a picture from it - a process referred to as imaging. The Event Horizon Telescope (EHT) collects light from the black hole using a small number of telescopes distributed around the Earth. How do we make a picture from the sparse data collected by the EHT?
0 Comments
Leave a Reply. |