A supermassive black hole in the LMC; ozone layer recovery; abstract memory in humans

This week, based on a genetic study, researchers issued a recommendation that bison in Yellowstone National Park should be treated as one large, interbreeding herd. Physicists proposed a new framework that derives gravity from quantum relative entropy, with implications for the past and future evolution of the universe. And a new fossil indicates that an early human relative walked upright, similarly to modern humans.

Additionally, astronomers found strong evidence for the second-closest supermassive black hole to the solar system; the ozone layer that protects the Earth from ultraviolet radiation is now recovering from the ravages of the 20th-century hairspray industry; and researchers directly observed the encoding of abstract memories in humans.

New Gargantua just dropped

The center of the Milky Way is the lair of Sagittarius A*, a supermassive black hole and the boss monster of the galaxy, estimated to be 4.3 million times more massive than the sun. Obviously, it’s right in the neighborhood, and the closest supermassive black hole to the Earth. But this week, astronomers reported strong evidence for the second-closest supermassive black hole, and at an astronomical scale, it’s only like a brief cab ride away.

Southern-Hemisphere nighttime observers have the celestial privilege of stepping outside on a clear night and seeing the Large Magellanic Cloud, a satellite galaxy of our own Milky Way. Astronomers in the Northern Hemisphere basically have to take their word for it, but are confident that it’s not just an Australian conspiracy theory.

Using data from the ESA’s Gaia mission, which has tracked over 1 billion stars throughout the galaxy, the researchers traced the paths of 21 hypervelocity stars just outside the Milky Way; their speeds easily reach the escape velocity of the galaxy and they won’t be around for long. In the past, these stars strayed too close to a supermassive black hole and were flung away at tremendous energies. Analyzing the paths of these 21 objects revealed that half originated at Sagittarius A* at the center of the Milky Way; the others originated from a previously unknown supermassive black hole in the Large Magellanic Cloud.

Hole diminished

The 1980s are remembered for basically three things: the song “Pac-Man Fever,” really big hairstyles, and the gaping hole in the ozone layer over Antarctica, caused by human emissions of chlorofluorocarbons, fully or partly halogenated hydrocarbons that contain carbon, hydrogen, chlorine and fluorine.

The ozone layer consists of naturally occurring gas in the stratosphere that shields the surface of the planet from the sun’s ultraviolet radiation. The ozone hole is seasonal, appearing between September and December, during the austral spring. A thinning ozone layer allows the penetration of ultraviolet radiation, leading to another feature of the 1980s—low-budget science-fiction films with synthesizer scores predicting a future when humans would wear reflective radiation suits.

Back when political consensus was possible, countries mostly stopped using chlorofluorocarbons for things like coolants and Alberto VO5 hairspray that made our giant 1980s hairstyles possible. A lot of time passed, skinny pants became popular for a while, and observations of the southern atmosphere started indicating that the ozone hole might be recovering.

Now, an MIT-led study has observed signs of ozone recovery with high statistical confidence. Study author Susan Solomon says, “There’s been a lot of qualitative evidence showing that the Antarctic ozone hole is getting better. This is really the first study that has quantified confidence in the recovery of the ozone hole. The conclusion is, with 95% confidence, it is recovering. Which is awesome. And it shows we can actually solve environmental problems.”

Abstract remembering

Previous studies have established that in the brains of animals, neurons encode memories of objects or concepts with a high degree of context—a rat encountering cheese in location A encodes a significantly different memory than when it encounters cheese in location B. A new study conducted with human participants—nine patients who were treated for refractory epilepsy with implanted electrodes—finds that humans encode memory much more abstractly than animals.

The patients’ implants allowed the researchers to record precise neural responses in the experiment. They were presented with two stories supported by images featuring the same person in different contexts. The researchers were able to observe the groups of neurons activated during the two stories. The experiment confirmed that the same neuron responded to a person’s image during both stories; additionally, that neuron activated when patients retold the stories themselves. This is a strong indication that humans think of concepts, objects and people independently of context.

Dr. Quian Quiroga says, “This ability allows us to make much more abstract and complex associations and inferences than if we were forced to think of each concept within a specific, concrete context.” In other words, humans can decontextualize their memories to create more abstract thought.

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