![]() ![]() The journey began in 1964, when a sounding rocket experiment detected an unseen object emitting lots of X-rays. You might understand, then, how physicists reacted with widespread skepticism when the first black hole was discovered. (For the unfortunate individual falling into the black hole, time marches on.) Because of this, some physicists originally called black holes “frozen stars” and presumed that such mind-bending objects couldn’t be real. But black holes are uniquely odd: Once you reach the event horizon, time screeches to a halt, as viewed by an outside observer. As a result, time moves more and more slowly the deeper you get in the gravitational well of any massive object, be it a star or a black hole. Einstein taught us that space and time are interlocked warping one warps the other too. The size of a black hole - i.e., the distance of the event horizon from the singularity - depends on the mass of the black hole. Surrounding it is the event horizon - the boundary of no return, inside which even the speed of light isn’t fast enough to escape the pull of gravity. Each one packs the mass of an entire star (or many stars) into a vanishingly small space called a singularity. Black holes are some of the most bizarre objects in the cosmos, throwing our earthly concepts of space and time right out the window. It’s easy to see why astronomers took some time to get on board. Measuring the length of the event, the amount of brightening, and the apparent displacement of the star can tell astronomers the mass of the foreground lens - in this case, a black hole some seven times the mass of the Sun. ![]() The foreground object’s gravity warps space-time around it, which both brightens and displaces the image of the background star. The English astronomer Arthur Eddington once said, “I think there should be a law of nature to prevent a star from behaving in this absurd way!” How Microlensing WorksĪ microlensing event occurs when a massive object, such as a black hole, passes in front of a background star. ![]() But for decades, most experts didn’t think they could actually form. Karl Schwarzschild, a German physicist and astronomer, further developed the mathematical concept of black holes in 1916 after working through Einstein’s equations of relativity. However, such objects were long thought to be a mathematical quirk that had little to do with reality. The idea of an object whose gravity is so strong that not even light can escape its grasp was first introduced by John Mitchell in the late 1700s. Most of the 100 million or so black holes thought to exist in the Milky Way drift through space alone, quiescent, dark, and impossible to spot directly.īut with Sahu’s discovery of such a rogue black hole, astronomers have begun to uncover that vast unseen majority, promising a revolution in the field and insight into the objects’ origins. And these may be the extreme exceptions, not the rule. Astronomers have identified just a few dozen stellar-mass black holes in our galaxy - and only then because they are in binary systems, pulling material from a still-shining companion star. A few decades later, in 2022, Kailash Sahu - the young boy from India - would lead a team to discover the first known “rogue” black hole.Īlthough it’s been more 50 years since the first detection of a black hole, these objects are still more ommonly theorized about than observed. Neither of them knew then that this fascination would one day dramatically advance our understanding of the cosmos. The two spoke of stellar motions, and the young boy soon developed a fascination for astronomy. Since the village had no electricity, the stars shone extra bright against the inky backdrop of space. On a cool evening in a small village in India, a man sat with his son and stared up at the night sky, as was their habit after dinner. However, their immense gravity warps space-time, as seen in this artist’s concept, and can give these objects away when they pass in front of a visible star from Earth’s point of view.ĮSA/Hubble, Digitized Sky Survey, Nick Risinger (), N. Without a ready food source, they have minimal accretion disks and appear truly dark, making them exceedingly difficult to find. Lone, or rogue, black holes are not bound to any other star and drift alone through space. ![]()
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