Most likely all of you know about Sagittarius A*, the supermassive black hole that sits at the center of the Milky Way Galaxy.
It's hard to talk about it without lapsing into superlatives. It has a mass about 4.3 million times that of the Sun. It's event horizon -- the "point of no return," the closest you can get to a black hole without being trapped by its gravitational pull -- has a radius of 11.3 million kilometers. It sits at the center of a fifteen-light-year-wide whirlpool of gas and dust called the accretion disk, which we know about because the material in it is moving so fast it has heated up to as high as ten million degrees Celsius, resulting in a steady emission of high-frequency x-rays.
It's curious that something this luminous wasn't immediately obvious to astronomers. First, it doesn't emit a lot of visible light; we didn't have telescopes capable of detecting the x-rays that are its fingerprint until 1933. By the 1970s, more precise observations showed that whatever the x-ray source was, it was extremely compact. It wasn't until 1994 that Charles H. Townes and Reinhard Genzel showed that its mass and diameter were consistent with its being a black hole. Another reason it took that long is that between us and the center of the galaxy there are massive dust clouds, so any visible light it does emit (or which is emitted by the dense clouds of glowing gas near it) mostly gets blocked. (Even so, looking toward the center of the Milky Way in the constellation Sagittarius, visible where I am in late summer, is pretty damn spectacular.)
The third reason that we don't get the full luminosity of whatever electromagnetic radiation is emitted from Sagittarius A* is a fortunate one for us; because of the black hole's immense magnetic field, any bursts of light tend to get funneled away along the axis of its spin, creating jets moving perpendicularly to the galactic plane. We, luckily, are comfortably out in the stellar suburbs, in one of the Milky Way's spiral arms. Our central black hole is fairly quiet, for the most part, but even so, looking down the gun barrel of its magnetic field axis would not be a comfortable position to reside.
The reason this comes up is some new research out of the University of Colorado - Boulder, which used data from the James Webb Space Telescope to solve a long-standing question about why, given the high density of hydrogen and helium gas near the galactic center, the rate of star formation there is anomalously low. This region, called Sagittarius C, extends about two hundred light years from the central black hole (by comparison, the Solar System is twenty-six thousand light years away). And what the team of researchers found is that threading the entire region are filaments of hot, bright plasma, some of them up to several light years in length.
The reason for both the filaments and the low star formation rate is almost certainly the black hole's magnetic field, which acts to compress any gas that's present along the field lines, heating it up dramatically. This, in turn, creates an outward pressure that makes the gas resist collapsing and forming stars.
"It's in a part of the galaxy with the highest density of stars and massive, dense clouds of hydrogen, helium and organic molecules," said Samuel Crowe, who co-authored the paper, which appeared this week in The Astrophysical Journal. "It's one of the closest regions we know of that has extreme conditions similar to those in the young universe... Because of these magnetic fields, Sagittarius C has a fundamentally different shape, a different look than any other star forming region in the galaxy away from the galactic center."
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