First image of Sagittarius A* Black Hole

This is the black hole at the centre of the galaxy. It's been pictured for the first time. The object, known as Sagittarius A* is four times larger than our Sun. You can see the central dark area where the hole is located, which is circled by light from super-heated gases that have been accelerated by enormous gravitational forces. The Event Horizon Telescope was collecting data to create a remarkable image of the Milky Way’s supermassive Black Hole. A legion of telescopes, including three NASA X-ray observatories in Space, were also use.

These observations are being used by astronomers to understand how the black hole at the centre of the Milky Way galaxy, known as Sagittarius A* (or simply Sgr A*), interacts with and benefits from its environment, which is 26,000 light-years away from Earth.

The Event Horizon Telescope (EHT), which observed Sgr. A* in April 2017, made the new image. Scientists in the collaboration also looked at the black hole using facilities that detect different wavelengths. They assembled X-ray data collected by NASA's Chandra X-ray Observatory and Nuclear Spectroscopic Telescope Arrays (NuSTAR) and Neil Gehrels Swift Observatory, radio data from East Asian Very Long-Baseline Interferometers (VLBI), and Global 3-millimeter VLBI arrays; infrared data taken from the European Southern Observatory’s Very Large Telescope in Chile Goddard coordinates the Swift mission with Penn State, Los Alamos National Laboratory (New Mexico) and Northrop Grumman Space Systems (Dulles, Virginia). The University of Leicester, Mullard Space Science Laboratory in Britain, Brera Observatory, Italy, and the Italian Space Agency are other partners. NASA's Jet Propulsion Laboratory, Southern California, manages NuSTAR for NASA Science Mission Directorate in Washington. The mission partners and contributors include NASA's High Energy Astrophysics Science Archive Research Center (NASA's High Energy Astrophysics Science Archive Research Center), the Italian Space Agency, (ASI), Columbia University and NASA's Goddard Space Flight Center.

One of the main goals was to capture X-ray flares. These flares are believed to be driven magnetically similar to the Sun's but can be tens to millions of times more powerful. The EHT observes flares approximately every day in the sky, which is slightly larger than the event area of Sgr. A*, the point at which there is no return for the matter that falls inward. A second goal was to get a better understanding of what's happening on a larger scale. The EHT result shows striking similarities to M87*, which was the last black hole it imaged. However, the larger picture is more complex.

"If the EHT image shows us the eye of a black hole hurricane then these multiwavelength measurements reveal winds and rain equivalent to hundreds, or even thousands, of miles beyond," Daryl Haggard, McGill University, Montreal, Canada, one of the leading scientists in the multiwavelength campaign. "How does the cosmic storm interact with, and even disrupt, its galactic environment?"

One of the most important questions about black holes is how they gather, ingest, expel, or ingest material at near-light speed. This is called "accretion" and is essential to the formation of stars, planets, and black holes of any size throughout the universe.

Chandra images of hot gases around Sgr A*, which are vital for accretion studies, tell us how much material is captured by nearby stars by the black holes' gravity and how much makes it to the event horizon. These critical details are not available using current telescopes for M87* or any other black holes in the universe.

"Astronomers agree on the basic facts -- black holes have material swirling about them and some of that falls across the event-horizon forever," Sera Markoff, a coordinator of multiwavelength observations at the University of Amsterdam in the Netherlands. "With all the data we have gathered for Sgr. A*, we can get a lot more than this basic picture."

The large international collaboration of scientists compared data from NASA's high energy missions and other telescopes to state of the art computational models. These models take into account factors like Einstein's general theory and effects of the magnetic field, as well as predictions about how much radiation material around the black holes should produce at different wavelengths.

Comparing the models to the measurements suggests that the magnetic field surrounding the black hole is strong. The angle between the line of sight to the black holes and its spin axis is also low, less than 30 degrees. This means that we see Sgr A* from our vantage point more than we do from side-on. It is remarkably similar to EHT’s first target M87*.

The EHT observations also revealed that the researchers were able to capture X-ray outbursts from Sgr. A*. One was faintly seen with Chandra, Swift, and another moderately bright with Chandra. Chandra regularly observes X-ray flares similar in brightness to those seen with Chandra. However, this is the first time the EHT simultaneously observed Sgr. A*. This gives the EHT an exceptional opportunity to identify the responsible mechanism by using actual images.

The ring is approximately the same size as Mercury's orbit around the star. This is approximately 60 million kilometres or 40 million miles.

This monster is far away, at 26,000 light-years, so it's unlikely that we will ever encounter any danger.

What is a "black hole"?

-A black hole is an area of space in which matter has collapsed on itself

-The gravitational pull on everything is so strong that even light cannot escape.

-The explosive demises of large stars will lead to the formation of black holes

-Some are even more massive than others and weigh billions of times as much as our Sun.

-It is not known how these monsters, which are found in galaxy centres, were created.

-It's evident that they are energizing the galaxy and will impact its evolution

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This is a technical tour.

EHT uses a technique called Very Long Baseline Interferometry (VLBI) to trick the system. This essentially combines eight radio antennas in a wide spacing to create a telescope that is the same size as our planet. This arrangement allows the EHT to measure the angle of the sky in microarcseconds. EHT team members speak of a sharpness in vision that is similar to seeing a bagel on top of the Moon.

Even so, supercomputing is required to create an image from several petabytes (PB = one million gigabytes).

A black hole's lens or bends can indicate that there is no light. However, the brilliance and power of matter bursting around the darkness and expanding out into an accretion disk is a clue to where it is.