Black Hole Photographed

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This April, the Event Horizon Telescope or EHT,  captured the first images of black holes using seven telescopes in various locations around the world. It captured the images of Sagittarius A, a supermassive black hole in the middle of our galaxy, the Milky Way, and a supermassive black hole from the galaxy, Messier 87.

If you read my last article, you would know that a black hole’s extreme gravity prevents light from escaping. So, the dark hearts of these monsters remain entirely invisible. In the picture, you aren’t really seeing a black hole. What you are seeing is the silhouette of a black hole’s event horizon (the perimeter inside which nothing can escape, not even light) against its accretion disk which is the matter that circles the black hole. The red blots in this picture are from the black hole spewing charged particles or ripping up stars.

Taking a picture of a black hole is really difficult. Let me explain………

Weighing in around 6.5 billion times the mass of our sun, the supermassive black hole inside Messier 87 is not teeny weeny. But viewed from 55 million light-years away on Earth, the black hole is only about 42 microarcseconds across on the sky (translation: smaller than an orange on the moon would appear to someone on Earth, TINY!). They chose M87’s black hole because only the black hole at the center of our own galaxy, Sagittarius A*, is bigger.

Only a telescope with unprecedented resolution could pick out something so tiny. For example, they couldn’t use the Hubble Space Telescope because it can only distinguish objects as small as 50,000 microarcseconds, which is 1000 times larger than the black holes.

A telescope’s resolution depends on its diameter. The bigger the dish, the clearer the view. Getting a crisp image of a supermassive black hole would need a planet-sized radio dish. That is BIG. So, scientists figured out a technique called very long baseline interferometry that combines radio waves seen by many telescopes at once, so that the telescopes effectively work together like one giant dish. The diameter of that virtual dish is equal to the length of the longest distance between two telescopes in the network.

The EHT dish was a combination of eight  telescopes spread across the world. The longest distance between these was from the South Pole telescope to the IRAM telescope in Spain (about 9000 miles!). The scientists hoped this would be a big enough dish to “see” a black hole.

All the telescopes have to be collecting data at the same time. That means they all have to have a clear sky at the same time. Researchers’ biggest enemy is water in the atmosphere, like rain or snow, which can mess with the millimeter-wavelength radio waves that the EHT’s telescopes are tuned to.

But planning for weather on several continents can be a annoying headache.

Just imagine:

“Oh COME ON!”-Person 1

“What?”-Person 2

“Every single telescope’s weather is good,except for ALMA and IRAN!”-Person 1

“SERIOUSLY! WHY!!! JUST, WHY!!!!”-Person 2

Wouldn’t that undo your buttons? That’s exactly what the scientists working on the project felt: annoyed!

There were only about 10 days in late March or early April when the weather at every observatory was good.

On their own, the data from each observing station looks like nonsense. But taken together, using the very long baseline interferometry technique, the black hole’s picture can be put together. “TEAMWORK MAKES THE DREAMWORK!!!”

When the scientists combine the data, they need to know exactly what time each piece of data was recorded. They needed to record the time with exquisite precision. To do this, they used hydrogen maser atomic clocks, which lose about one second every 100 MILLION years!

There are a lot of data to timestamp. They recorded data at a rate of 64 gigabits per second, which is about 1,000 times faster than your home internet connection! The data was then transferred to MIT Haystack Observatory and the Max Planck Institute for Radio Astronomy in Bonn, Germany, to be processed by a special kind of supercomputer called a correlator. But each telescope station recorded hundreds of terabytes of information. This was way too much to send over the internet, so the researchers turned to Plan B: ship the data by snail mail


Now the pictures have been taken, everybody is excited to see what the scientists will do next. They have been thinking about taking a VIDEO of a black hole! Then we can all see these beasts in action!

Space holds many secrets. Secrets we can’t wait to discover!

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