Astronomers Will Soon Have the First-Ever Picture of a Black Hole

The center of the Milky Way galaxy, with the supermassive black hole Sagittarius A*, located in the middle, as captured in x-ray and infrared in this 2013 NASA photo.
The center of the Milky Way galaxy, with the supermassive black hole Sagittarius A*, located in the middle, as captured in x-ray and infrared in this 2013 NASA photo.
NASA/UMass/D.Wang et al., IR: NASA/STScI

It may not be the closest black hole to Earth, but it’s certainly the closest one that astronomers have labeled as "supermassive." Known as Sagittarius A* (pronounced “Sagittarius A-star”), the mysterious object, first detected in the 1970s, weighs as much as 4 million Suns. Formed by the collapse of large stars, most black holes aren't nearly that size.

Sagittarius A* sits at the very heart of the Milky Way galaxy, some 25,000 light-years from our solar system—but until now, we haven’t known much about it. Soon, however, thanks to a globe-spanning array of radio telescopes known as the Event Horizon Telescope, astronomers will have their closest ever look at this enigmatic object.

The Event Horizon Telescope, or EHT, is named for the infamous “point of no return” that marks the outer boundary of a black hole. (The gravity of a black hole is so strong that nothing can escape it, not even light—thus the name.) It incorporates huge, dish-shaped telescopes at six different sites on four continents, including Antarctica and Hawaii. The array recently completed its most ambitious observation so far, collecting data of Sagittarius A* over a 10-day period in mid-April.

“We’ve never had data of the quality that we’ve just taken,” Dan Marrone, an experimental astrophysicist at the University of Arizona, tells Mental Floss. When the data is eventually processed—sometime this fall at the earliest—astronomers will have their clearest picture yet of a black hole.


What that image will actually look like, however, is still very much up in the air. We know that black holes are typically surrounded by accretion disks—rings of dust and gas that swirl around the black hole, getting ever-hotter as the material approaches the black hole’s event horizon. The in-falling matter gets so hot that it emits radio waves and other radiation (which is how objects like Sagittarius A* were first detected). Accretion disks can also produce jets—streams of high-energy particles that get blasted out from the black hole at nearly the speed of light. And we know that the system’s intense gravity bends starlight as it passes near the black hole. “We might see a crescent, brightened on one side—or a bipolar, jet-like structure,” Marrone says. “We honestly don’t know.”

Standard optical telescopes—even those high above the Earth’s atmosphere, like Hubble—can tell us very little about objects like Sagittarius A* because there’s too much gas and dust between us and the galactic center for optical wavelengths to penetrate; it’s like trying to peer across San Francisco Bay on the foggiest day of the year.

But radio telescopes, taking advantage of the longer wavelengths of radio waves, can see through the murk. The best bet, astronomers have found, is to use telescopes sensitive to wavelengths of about 1 centimeter—longer than wavelengths of infrared light, but shorter than the waves that your car radio picks up.

Multiple radio telescopes, in different locations, can be made to work together even better, simulating a much larger instrument. This technique is known as VLBI, for Very Long Baseline Interferometry. The Atacama Large Millimeter-submillimeter Array, comprising 66 radio dishes in northern Chile, was recently added to the EHT array, greatly boosting the overall sensitivity; the South Pole Telescope was also added to the array in April. The project now involves 30 institutions in 12 countries.

“The Event Horizon Telescope is going to be zooming in, to right where the inner edge of the accretion disk is falling in to the black hole—right at the boundary between where the disk material ends and the black hole starts,” radio astronomer Joseph Lazio of NASA’s Jet Propulsion Laboratory tells Mental Floss.


Of course, we can never see past the event horizon—whatever’s on the other side remains forever beyond our reach. But with the resolving power of the EHT, astronomers will have their closest look yet at the region immediately outside it.

The EHT’s resolving power will be so crucial because, despite Sagittarius A*’s heft, it’s not very large in terms of size. Its event horizon is believed to span just about 15 million miles—less than 20 times the diameter of the Sun.

And in spite of the public perception of black holes as “cosmic vacuum cleaners” that suck up everything in sight, Sagittarius A* is actually not much of an eater. “It’s on a starvation diet,” Marrone jokes. “We don’t know of another black hole that’s eating so slowly, relative to its weight.”

Another target for the EHT will be the black hole in the center of a galaxy known as M87. This ginormous black hole is 1000 times farther away than Sagittarius A*, but it’s also 1000 times more massive; it’s so big that its gravity anchors an entire cluster of galaxies, known as the Virgo Cluster. And it has enormous jets shooting out of its accretion disk—something that astronomers are anxious to get a closer look at.

Beyond simply imaging these giant black holes, the EHT may shed some light on the complex relationship between supermassive black holes and the galaxies that harbor them. Surveys using X-ray telescopes suggest that these overweight black holes are common; they’re believed to lurk in the hearts of most galaxies. But did the galaxies evolve first, and then the black holes—or was it the other way around?


“There’s a very strong correlation between the properties of these supermassive black holes and the properties of their host galaxies,” David Spergel, a Princeton astrophysicist and director of the Center for Computational Astrophysics, tells Mental Floss. “So they’re linked together—but this is a chicken-and-egg question that we don’t know the answer to.”

Another motivation for studying black holes is to determine whether Einstein’s theory of gravity, known as general relativity, correctly predicts the observed physics. The theory, which turned 100 last year, has so far passed every test thrown at it—but it has yet to be tested in the exotic environment adjacent to a black hole event horizon, with its ultra-strong gravitational field. “You’re probing a new regime—and whenever you’re in a new regime, you could be in for a surprise,” Spergel says.

The astronomers working on the EHT won’t see the fruits of their labors right away: Each of the facilities in the array recorded about 500 terabytes of data during this spring’s observing run—far too much to be conveniently sent over the internet. So the data is being sent the old-fashioned way, by shipping bulky drives via FedEx to the EHT’s two processing centers, located in Westford, Massachusetts and in Bonn, Germany. (That doesn’t include the disks from the South Pole Telescope; they’ll be shipped later in the year, when planes can access the site after the Antarctic winter.) Then the data needs to be processed, which will take some six to eight months.

Asked if he was feeling tense, Marrone replied that “anticipation” was a better word; after all the testing he and his colleagues have done, he’s pretty confident that the EHT has delivered the goods. “I’d like to know what we’ve got in those data,” he said. “But it’s going to be a long wait.”

Not-So-Fancy Feast: Your Cat Probably Would Eat Your Rotting Corpse

Tycson1/iStock via Getty Images
Tycson1/iStock via Getty Images

Cat enthusiasts often cite the warmth and companionship offered by their pet as reasons why they’re so enamored with them. Despite these and other positive attributes, cat lovers are often confronted with the spurious claim that, while their beloved furry pal might adore them when they’re alive, it won’t hesitate to devour their corpse if they should drop dead.

Though that’s often dismissed as negative cat propaganda spread by dog people, it turns out that it’s probably true. Fluffy might indeed feast on your flesh if you happened to expire.

A horrifying new case study published in the Journal of Forensic Sciences offers the fresh evidence. The paper, first reported by The Washington Post, documents how two cats reacted in the presence of a corpse at Colorado Mesa University’s Forensic Investigation Research Station, or body farm, where the deceased are used to further forensic science for criminal investigations.

The study’s authors did not orchestrate a meeting between cat and corpse. The finding happened by accident: Student and lead author Sara Garcia was scanning surveillance footage of the grounds when she noticed a pair of cats trespassing. The cats, she found, were interested in the flesh of two corpses; they gnawed on human tissue while it was still in the early stages of decomposition, stopping only when the bodies began leaching fluids.

The cats, which were putting away one corpse each, didn’t appear to have a taste for variety, as they both returned to the same corpse virtually every night. The two seemed to prefer the shoulder and arm over other body parts.

This visual evidence joins a litany of reports over the years from medical examiners, who have observed the damage left by both cats and dogs who were trapped in homes with deceased owners and proceeded to eat them. It’s believed pets do this when no other food source is available, though in some cases, eating their human has occurred even with a full food bowl. It’s something to consider the next time your cat gives you an affectionate lick on the arm. Maybe it loves you. Or maybe it has something else in mind.

[h/t The Washington Post]

Wolf Puppies Play Fetch, Too, Study Finds

Christina Hansen Wheat
Christina Hansen Wheat

It took thousands of years of selective breeding for wolves to become the Golden Retrievers you see at dog parks today. Domesticated dogs are very different from their wild counterparts, but according to a new study, they may have a surprising trait in common. Researchers found that some wolf puppies are willing to play fetch with total strangers, suggesting that following human commands is intrinsic to canines.

For their study in the journal iScience, researchers from Stockholm University in Sweden set out to find how domestication affects behaviors in young wolves. They raised litters of wolf and dog pups separately from 10 days old and placed them in various scenarios.

When the scientists tested how the wolf puppies would respond to a game of fetch, they expected to be ignored. Chasing a ball and bringing it back requires understanding human commands and obeying them—abilities that were thought to only have emerged in dogs post-domestication.

The first two wolf groups met expectations by showing little interest in the toy, but something different happened with the third set. Three eight-week old pups went after the ball and brought it back when they were encouraged to do so. This was the case even when the person giving the commands was someone they had never met before.

Even though most of the puppies didn't play fetch, the fact that those who did belonged to the same litter indicates a "standing variation" for a retrieving trait in wolves. "When you talk about a specific trait in the context of standing variation, it means that there is variation for the expression of this trait within a given population," co-author Christina Hansen Wheat tells Mental Floss. "For our study it suggests that, while probably rare, standing variation in the expression of human-directed behavior in ancestral populations could have been an important target for early selective pressures exerted during dog domestication." In other words, ancient people seeking to domesticate wolves might have focused on some wolves' innate ability to follow human commands.

The first dogs were domesticated as far back as 33,000 years ago. Over millennia, humans have selected for traits like loyalty, friendliness, and playfulness to create the modern dog, but these new findings could mean that the dog's earliest canine ancestors were genetically predisposed toward some of these behaviors.

"All three litters were brought up under identical and standardized conditions across years," Hansen says of the pups in the study. "With this significant effort to control the environmental conditions, it is likely that the differences in behavior across litters to some extent have a genetic basis."

After raising the dog and wolf litters for three years and completing that part of their study, the researchers will continue to analyze their data to see if there are any other adorable (or weird) traits the two groups share.