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“We wanted to know how to measure the structure of the ring from all these possible images,” said Razieh Emami, a postdoctoral researcher at the CfA who made precise measurements of the ring and worked to combine data from multiple nights of observations into the single final image released Thursday. The averaged image retains features more commonly seen in the varied images and suppresses features that appeared less frequently. The individual images showed many different structures that highlighted the uncertainty in the computational methods from the rapidly changing appearance of Sgr A*, including all the movement and plasma flares that go with it. In the end, the researchers were able to produce their final image, which isn’t just one picture but the average of thousands of images created using different computational methods to account for the movement of the gas.
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Seeing all these difficulties, the Event Horizon team first focused on the M87 data before turning their full attention to that of Sgr A*. Peter Galison, director of Harvard’s Black Hole Initiative It’s like looking at something through frosted glass.” “This material scatters the light that we observe from Sgr A*. “We’re looking at our own Galactic Center through an interstellar soup of all the dust and gas between us,” said Daniel Palumbo, a Harvard graduate student at the CfA who worked on the data analysis. In addition, there is a giant cloud of ionized gas between Earth and the Galactic Center, which distorts the images the EHT takes of Sgr A,* which sits in central region of the Milky Way. You’re just going to get a bunch of blur everywhere.” “For Sgr A*, you have a toddler running around and you’re trying to get their portrait with the long-exposure camera. “The analogy would be if you have an adult getting their portrait taken with a long exposure, and they’re just sitting still. This means superheated gas, which travels at near-light speed and takes days to orbit M87, only takes minutes to orbit Sgr A*, which is why there is so much motion blur in the image. If it was the size of a doughnut, M87 would be the size of a football stadium, Issaoun said at the press conference in Germany. Sgr A*, on the other hand, is on the small side. That means that when the EHT team shines their telescopes on it for hours - using a technique called very long baseline interferometry that works like taking a long exposure image on a camera - any change appears very gradually. It takes many days to orbit around this gargantuan object.
The bright circle of gas and dust that collects and swirls around it is known as an accretion disk. M87 is 55 million light-years away in the Virgo Galaxy cluster and has a mass about 6.5 billion times that of our sun. The two images can now be compared to gain valuable insight on the inner workings of these supermassive giants and how they interact with their surroundings, a process thought to play a key role in shaping the formation and evolution of galaxies. In April 2017, eight radio observatories on six mountains on four continents stared on and off at a pair of black holes for 10 days - Sgr A* and a second that lies at the heart of the elliptical galaxy M87.įrom that observation data, which was then crunched by supercomputer algorithms, came the image of the M87 black hole as well as the one just released. The researchers produced the picture with observations from the Event Horizon Telescope, a worldwide network of radio telescopes that link together to form a single Earth-sized virtual instrument. “That is what we’ve measured in our image.” “The cool thing about Sgr A* is that we know its mass with great accuracy so we know exactly what Einstein’s theory of relativity should predict for how big the shadow in the center should be - around 50 micro-arcseconds in angular size or 60 million kilometers across,” Issaoun said. Issaoun also pointed out that the new view further cements Einstein’s theories on gravity and relativity. “These properties, this knowledge of the fundamental properties of the black hole will help us study the astrophysics of the black hole in more detail later on,” Issaoun said. She said the new image reveals some key details about the black hole that were previously unknown, including that one side of the black hole is almost directly facing Earth. NASA Einstein Fellow at the CfA Sara Issaoun worked on observations and imaging for the EHT team and discussed the image at the European press conference in Germany. “While M87 had one of the biggest black holes in the universe and it launches a jet that pierces its entire galaxy, Sgr A* is giving us a view into the much more standard state of black holes, quiet and quiescent,” said Johnson.
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