In the dark depths of the ocean, where camouflage can be lifesaving, scientists have discovered the blackest fish ever documented.
Researchers have found 16 species of so-called ultra-black fish, which by definition absorb more than 99.5 percent of light, making them mere shadows as they swim, scientists wrote in a study published Thursday in the journal Current Biology, according to The New York Times.
“In the deep, open ocean, there is nowhere to hide and a lot of hungry predators,” zoologist Karen Osborn, of the Smithsonian’s National Museum of Natural History and a co-author of the study, said, according to Reuters. “An animal’s only option is to blend in with the background.”
And while little light penetrates below 650 feet, some of the ultra-black fish live three miles underneath the surface, according to Reuters.
As the species evolved, they modified the pigment of their skin through continuous layers of melanosomes, which store light-absorbing melanin, to more easily hide from predators, the Times reported. “It’s like looking at a black hole,” Duke University biologist Alexander Davis, a co-author of the study, told the newspaper.
One bioluminescent anglerfish documented by the team absorbs an astounding 99.95 percent of light, making the fish virtually invisible.
Prosanta Chakrabarty, a biologist at Louisiana State University who wasn’t involved in the study, told the Times, “I would not be surprised if we have not yet found the blackest fish in the sea.”
Astronomers with the European Southern Observatory (ESO) have discovered a black hole that is the nearest such object yet found, just 1,000 light years away—close enough to be seen with the unaided eye. It is part of a triple star system, dubbed HR 6819, and the ESO scientists believe other members of this class of systems may also harbor black holes that previously were not a high priority for black hole searches. They announced their discovery in a new paper published in the journal Astronomy and Astrophysics.
Scientists think there are far more black holes in the Universe than we have discovered to date—probably hundreds of millions of them, given the age of our Universe—because we can’t observe them directly; we can merely infer their presence by their effect on surrounding matter. A black hole’s gravitational effects can influence the orbits of nearby stars, for example, or infalling matter can form an accretion disk of hot gas rapidly orbiting the black hole, emitting powerful X-rays. Or an unfortunate star will get too close to a black hole and be torn apart for its trouble, with the infalling remnants also accelerating and heating up to emit X-rays into space.
But the majority of black holes are actually quiet and hence very difficult to detect. This latest discovery offers useful clues about where at least some of the truly dark black holes might be hiding. “One will never get enough telescope time to do a thorough search like that on all objects,” ESO scientist Thomas Rivinius, a co-author on the paper, told Ars. “What you need to do is a staged approach to help you identify candidates, then thin out the candidates list, and only then have a close and detailed look at the remaining ones. Knowing what to look for should put us in a better position to find them.”
The ESO team had been conducting a study of double-star systems, and HR 6819 was included as part of their observational data-gathering since it appeared to be just such a system. But while reviewing their data, the astronomers found clear evidence of an unexpected third object in the system: a black hole that had previously eluded detection.
In a trinary star system, two of the stars orbit each other as a binary pair, while the third star orbits the pair at a greater distance. This ensures that the system is stable, since if the inner and outer orbits were the same size, one of the stars would eventually be ejected from the system. In the case of HR 6819, one of the two visible stars orbits an invisible object every 40 days, while the other visible star orbits farther away. By studying the orbit of the star in the inner pair, the team was able to infer the black hole’s presence and also calculate its mass. “An invisible object with a mass at least four times that of the Sun can only be a black hole,” said Rivinius.
“We used to believe that single stars are the most usual ones,” said Rivinius. “In fact, at least for the really massive ones, single stars are probably the rarest.” That’s because the greater a star’s mass, the less likely it is to be alone, and Rivinius points out that even single massive stars could, in fact, be the survivors of multiple star systems that were “disrupted,” or have fainter companion stars we just can’t detect. Trinary systems like HR 6819 are less common, but nor are they extremely rare. Physicists currently believe that the supernovae that give rise to black holes would actually disrupt the structure of multiples. “If a significant number of multiples, however, survive the supernovae, this changes the statistics,” said Rivinius.
“If such a system happens to be in the immediate neighborhood, it is likely common in other regions of the galaxy as well,” said Rivinius. His back-of-the-envelope calculation suggests that there could be 2,500 such systems. That’s not going to clear up the large discrepancy between the black holes we’ve discovered and the number astronomers believe could be out there. “But considering so far we were not aware any such triple could exist, it is quite a step,” he added. The ESO team has already identified a second star system that might also be a trinary with a black hole, although more observational data is needed to confirm this.
The discovery that a black hole can be part of a trinary star system is also relevant because astronomers have suggested that such triple systems could be progenitors of binary systems with two black holes, or a black hole/neutron star pairing. When the partners in those binary systems merge, the violent event emits gravitational waves that can be detected by the LIGO collaboration.
“The problem with LIGO detections is that for two black holes in a normal, lonely binary, it takes a very long time to close in to each other,until they finally merge,” said Rivinius. “In fact, it takes longer than the current ageof the Universe, and we really shouldn’t see as many mergers as we do,if that was the only mechanism. But the closer they are already, the(much) faster it goes.”
It’s known as the Lidov-Kozai mechanism. It occurs when, for example, a close binary inner pair has a circular orbit, but not in the same plane as the outer orbit. This causes the inner orbit to become more “eccentric,” according to Rivinius. “In short, it means the third body can help the two inner ones get close to each other, at least at times,” he said.
However, that is not going to be the case with the HR 6819 trinary system. “The two stars in HR 6819 are not massive enough to explode as a supernova and form a black hole,” said ESO’s Dietrich Baade, another co-author. “Therefore, HR 6819 will never harbor two black holes, and it will never be a full equivalent of the progenitors of gravitational wave events. But it is a useful nearby proxy to investigate.”
A bug has been discovered in Apple’s macOS Image Capture app that needlessly eats up potentially gigabytes of storage space when transferring photos from an iPhone or iPad to a Mac.
Discovered by the developers of media asset management app NeoFinder and shared in a blog post called “Another macOS bug in Image Capture,” the issue occurs when Apple’s Mac tool converts HEIF photos taken by iOS to more standard JPG files.
This process happens when users uncheck the “Keep Originals” option in Image Capture’s settings, which converts the HEIC files to JPG when copied to Mac. However, the app also inexplicably adds 1.5MBs of empty data to every single file in the process.
“Of course, this is a colossal waste of space,” said the NeoFinder team, “especially considering that Apple is seriously still selling new Macs with a ridiculously tiny 128 GB internal SSD. Such a small disk is quickly filled with totally wasted empty data.
“With just 1000 photos, for example, this bug eats 1.5 GB off your precious and very expensive SSD disk space.”
NeoFinder’s developers say they discovered the bug by “pure chance” when working on improving the metadata capabilities of NeoFinder using a hex editor, and provided an example shot of what the end of individual JPG files look like in hex, post-transfer.
MacRumors was also able to replicate the issue in macOS 10.14.6 and later using an online hex editor. It’s worth noting that the bug only occurs when transferring photos from Apple devices, not when importing photos from digital cameras using Image Capture.
NeoFinder’s team says it has notified Apple of the bug, and the developers suggest anyone plagued by the issue can try using a new beta version of the third-party utility Graphic Converter, which includes an option to remove the unwanted empty data from the JPEG files.
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