Feast your eyes on the first image of the black hole at the center of our Milky Way

The black hole at the center of our universe is four million times the mass of the Sun. The first image of the black hole has a ring structure and was produced by scientists with the international event horizon telescope. The announcement was made during a live-streamed press conference this morning from the European Southern Observatory headquarters in Germany, as well as numerous other simultaneous press conferences around the world. Papers about the research have been published.

In 1933, physicist Karl Jansky noticed a radio signal coming from somewhere in the constellation Sagittarius, near the center of our Milky Way galaxy, which he dubbed Sagittarius A. It was called Sagittarius A*. Physicists have been convinced since the 1980s that the central is the result of the radio source being exciting and the excited states of atoms.

The only way to see a black hole is to see the shadow created by light as it bends in response to the object. John Timmer reported that the EHT isn't a telescope in the traditional sense. It is a collection of telescopes scattered around the globe. Interferometry uses light in the microwave regime to create the EHT. Interferometry can be used for facilities like ALMA, where telescopes can be spread.

In theory, there is no upper limit on the size of the array, but you need precise location and timing information on each of the sites to determine which photons originated simultaneously at the source. You still have to gather enough light to see. atomic clocks were installed at many locations, and exact gps measurements were built up over time. The large collecting area of ALMA and the wavelength where black holes are very bright ensured sufficient photons. The telescope can read the year stamped on a coin in Los Angeles from New York City, assuming the coin was glowing at radio wavelengths.

The first direct image of a black hole at the center of an elliptical galaxy was taken in the constellation of Virgo in 2019. This image would not have been possible a generation ago, and it was made possible by technological breakthrough, innovative new algorithms, and connecting several of the world's best radio observatories. The object at the center of M87 is a black hole.

A new image of M87 was released last year by the EHT collaboration, which showed a black hole in the light that was a signature of the magnetic fields at the object's edge. The collaboration was able to locate the location of the black hole at the center of the radio galaxy after the EHT returned with images.

Scientists were hopeful that the EHT would produce a similar image of Sagittarius A*, which is much smaller, but also much closer, to M87. However, as theoretical physicist Matt Strassler wrote recently.

[T]he measurements of the Milky Way’s black hole proved somewhat more challenging, precisely because it is smaller. EHT takes about a day to gather the information needed for an image. M87’s black hole is so large that it takes days and weeks for it to change substantially — even light takes many days to cross from one side of the accretion disk to the other — so EHT’s image is like a short-exposure photo and the image of M87 is relatively clear. But the Milky Way’s galaxy’s black hole can change on the times scale of minutes and hours, so EHT is making a long-exposure image, somewhat like taking a 1-second exposure of a tree on a windy day. Things get blurred out, and it can be difficult to determine the true shape of what was captured in the image.

The mass of Sagittarius A* can be determined by physicists. The astronomer from UCLA won the 2020 Nobel Prize in physics for her work mapping the stars closest to the center of our universe. This gave an indirect means of proving that the object at the center is a black hole. There is no other object like it.

We don't know how fast the black hole is spinning. Those are some of the questions that the EHT hopes to answer. Physicists will be able to directly study the effects of a black hole and the accretion and outflow dynamics of the matter around it. It should yield new tests for general relativity and possibly answer some fundamental questions about the existence of the black hole.

The new image shows that Sagittarius A* is very similar to M87, even though the black hole in our galaxy is less massive.

Sagittaius A* was not an easy target, with nearly all images looking the same. The average of the different images from observational data collected by the team is shown in the image. It took five years, multiple simulations, and the development of new computational techniques to fill in the blanks in the data in order to produce the final image.

Keiichi Asada from the Institute of Astronomy and Astrophysics, Sinica, Taipei, said that they can study the differences between the two black holes to learn more about how this important process works.

The next step is to make a movie of the black hole, showing it as it changes over time, which could yield insight into the way gas behaves as it swirls around a black hole, and help estimate the spin of the black hole itself.

The story will be updated.