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.”

Is There An International Standard Governing Scientific Naming Conventions?


Jelle Zijlstra:

There are lots of different systems of scientific names with different conventions or rules governing them: chemicals, genes, stars, archeological cultures, and so on. But the one I'm familiar with is the naming system for animals.

The modern naming system for animals derives from the works of the 18th-century Swedish naturalist Carl von Linné (Latinized to Carolus Linnaeus). Linnaeus introduced the system of binominal nomenclature, where animals have names composed of two parts, like Homo sapiens. Linnaeus wrote in Latin and most his names were of Latin origin, although a few were derived from Greek, like Rhinoceros for rhinos, or from other languages, like Sus babyrussa for the babirusa (from Malay).

Other people also started using Linnaeus's system, and a system of rules was developed and eventually codified into what is now called the International Code of Zoological Nomenclature (ICZN). In this case, therefore, there is indeed an international standard governing naming conventions. However, it does not put very strict requirements on the derivation of names: they are merely required to be in the Latin alphabet.

In practice a lot of well-known scientific names are derived from Greek. This is especially true for genus names: Tyrannosaurus, Macropus (kangaroos), Drosophila (fruit flies), Caenorhabditis (nematode worms), Peromyscus (deermice), and so on. Species names are more likely to be derived from Latin (e.g., T. rex, C. elegans, P. maniculatus, but Drosophila melanogaster is Greek again).

One interesting pattern I've noticed in mammals is that even when Linnaeus named the first genus in a group by a Latin name, usually most later names for related genera use Greek roots instead. For example, Linnaeus gave the name Mus to mice, and that is still the genus name for the house mouse, but most related genera use compounds of the Greek-derived root -mys (from μῦς), which also means "mouse." Similarly, bats for Linnaeus were Vespertilio, but there are many more compounds of the Greek root -nycteris (νυκτερίς); pigs are Sus, but compounds usually use Greek -choerus (χοῖρος) or -hys/-hyus (ὗς); weasels are Mustela but compounds usually use -gale or -galea (γαλέη); horses are Equus but compounds use -hippus (ἵππος).

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An Ice Age Wolf Head Was Found Perfectly Preserved in Siberian Permafrost


Don’t lose your head in Siberia, or it may be found preserved thousands of years later.

A group of mammoth tusk hunters in eastern Siberia recently found an Ice Age wolf’s head—minus its body—in the region’s permafrost. Almost perfectly preserved thanks to tens of thousands of years in ice, researchers dated the specimen to the Pleistocene Epoch—a period between 1.8 million and 11,700 years ago characterized by the Ice Age. The head measures just under 16 inches long, The Siberian Times reports, which is roughly the same size as a modern gray wolf’s.

Believed to be between 2 to 4 years old around the time of its death, the wolf was found with its fur, teeth, and soft tissue still intact. Scientists said the region’s permafrost, a layer of ground that remains permanently frozen, preserved the head like a steak in a freezer. Researchers have scanned the head with a CT scanner to reveal more of its anatomy for further study.

Tori Herridge, an evolutionary biologist at London’s Natural History Museum, witnessed the head’s discovery in August 2018. She performed carbon dating on the tissue and tweeted that it was about 32,000 years old.

The announcement of the discovery was made in early June to coincide with the opening of a new museum exhibit, "The Mammoth," at Tokyo’s Miraikan National Museum of Emerging Science and Innovation. The exhibit features more than 40 Pleistocene specimens—including a frozen horse and a mammoth's trunk—all in mint condition, thanks to the permafrost’s effects. (It's unclear if the wolf's head is included in the show.)

While it’s great to have a zoo’s worth of prehistoric beasts on display, scientists said the number of animals emerging from permafrost is increasing for all the wrong reasons. Albert Protopopov, director of the Academy of Sciences of the Republic of Sakha, told CNN that the warming climate is slowly but surely thawing the permafrost. The higher the temperature, the likelier that more prehistoric specimens will be found.

And with average temperatures rising around the world, we may find more long-extinct creatures rising from the ice.