A new visualization of a black hole from NASA helps us appreciate how the hole’s gravity distorts our view, warping its surroundings as if seen in a carnival mirror. A black hole forms when an object, often the core of an exploding star called a supernova, collapses into a tiny ball of such fantastic density that its gravity becomes strong enough to suck back its own light. With no light reaching our eyes, the object becomes a “dark shadow” of its former self. The only way we know it’s there is by its gravity. Gravity affects objects near the hole — a star can orbit a black hole for instance — but it also distorts and twists the fabric of space and time.
Cosmic gas and dust that stray near the hole are sometimes pulled into it. Black holes aren’t picky; they’ll eat anything that falls within their reach. As the material approaches the point of no return, called the event horizon, it swirls in at high speed and heats up from friction and gravity, causing it to glow. Bright knots constantly form and dissipate in the disk as magnetic fields (like those around a refrigerator magnet but more intense) wind and twist through the churning gas. Nearest the black hole, the gas orbits at close to the speed of light, while the outer portions spin more slowly. This difference stretches and shears the bright knots, producing light and dark lanes in the disk (at left).
Notice that the disk looks brighter on the left than it does on the right. Glowing gas on the left side of the disk moves toward us so fast that the effects of Einstein’s relativity give it a boost in brightness; the opposite happens on the right side, where gas moving away us becomes slightly dimmer.
Closest to the black hole, the gravitational light-bending becomes so excessive that we can see the underside of the disk as a bright ring of light seemingly outlining the black hole. This so-called “photon ring” is composed of multiple rings, which grow progressively fainter and thinner, from light that has circled the black hole two, three, or even more times before escaping to reach our eyes. Because the black hole shown in this visualization is spherical, the photon ring looks nearly circular and identical from any viewing angle. Inside the photon ring is the black hole’s shadow, an area roughly twice the size of the event horizon.
“Simulations and movies like these really help us visualize what Einstein meant when he said that gravity warps the fabric of space and time,” explains Jeremy Schnittman, who generated these images at NASA’s Goddard Space Flight Center. Until April 10 this year, black hole visualizations were limited to artistic interpretation and computer programs. But on April 10, the Event Horizon Telescope team released the first-ever image of a black hole’s shadow using radio observations of the heart of the galaxy M87.
The next black hole image, of the Milky Way’s supermassive black hole, may be released later this year or next. Material for this story came from this recent press release.
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