Here's Why Scientists Did Not Take Image Of Sagittarius A*, Black Hole At The Heart Of Milky Way


Humanity just made an incredible breakthrough: a photograph of a supermassive black hole in all its glory, an object captured for the first time in history.

To get an image of the black hole Messier 87, which is 6.5 billion times the mass of the sun and 54 million light-years away, scientists used multiple telescopes to collect high-frequency radio waves from the object.

Choosing The Right Black Hole To 'Photograph'

A question that many people have been asking is why the scientists did not choose to capture a photograph of a closer black hole. After all, there is one in the center of Milky Way, the galactic neighborhood of Earth.

Surely, the closer black hole would be easier to capture in an image, right?

Sagittarius A*, the black hole located in Milky Way 25,000 light-years away from Earth, may be closer, but it doesn't necessarily mean it's a better subject to photograph.

During a news conference, the Event Horizon Telescope director Shep Doeleman explains that Messier 87 is a better option, precisely because it is so far away. Thus, the supermassive black hole is more fixed in position and does not move from its spot in the sky compared to the much nearer Sagittarius A*.

Furthermore, BGR notes that with Sagittarius A* in the same galaxy as Earth, the scientists don't have an ideal vantage point of this black hole. There are too many cosmic objects in between the two with billions of stars, planets, and dust floating in the same flat disk of the Milky Way.

So, the scientists picked a black hole that Earth has a better view of: Messier 87.

Using Several Algorithms To Get A Complete Picture

Not only does the achievement give everyone their first direct glimpse of a black hole, but the technology developed for it is also an important step forward in scientific advancement.

Once the team has chosen the correct black hole to photograph, it's time to stitch together a coherent image of the supermassive black hole.

However, there are endless of images that can be produced from the billions of data from the various telescopes used in the project. To create an accurate picture of Messier 87, the right algorithm is necessary.

Katherine Bouman, Ph.D of the Harvard-Smithsonian Center for Astrophysics led the development of the algorithms that strung together the now-famous image of the supermassive black hole Messier 87. With her algorithms, scientists were able to piece together a coherent and accurate photo from the mountain of data.

"We developed ways to generate synthetic data and used different algorithms and tested blindly to see if we can recover an image," Bouman tells CNN. "We didn't want to just develop one algorithm. We wanted to develop many different algorithms that all have different assumptions built into them. If all of them recover the same general structure, then that builds your confidence."

The team was able to achieve several photos that are extremely similar to each other. In fact, the Messier 87 photo revealed to the world is actually a composite of all the images from the various algorithms all blurred together.

Years of work paid off for Bouman and the rest of the team as their algorithms were able to make history and produce the first ever image of a black hole.

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