Month: June 2021

Enlarge / Even with today's real estate boom, a supermassive black hole in the neighborhood has to drive the asking price down a bit, right? (credit: Caltech/R. Hurt (IPAC) / Redfin / Nathan Mattise)

Black holes flood the Universe. The nearest one is a mere 1,500 lightyears away. A giant one, Sagittarius A*, sits in the center of the Milky Way about 25,000 lightyears away. While your typical space traveler might look for a home around a calm G-type star, some celestial citizens are brave enough to take up refuge around one of these monsters. It’s not an easy life, that’s for sure, but being neighbors with a black hole does mean you’ll almost certainly learn more about the fundamental nature of reality than anybody else.

Interested? What follows is a guide of what to expect should you make your home around a black hole. Good luck.

Black hole basics

Upon first arriving at a black hole, you will most likely be struck by how utterly, completely…boring it is. The black hole itself is simply a fathomless black orb hanging out somewhere in the distance. Black holes don’t really do anything except sit there and gravitate. In fact, they’re famously easy to miss: Unless they’re actively feeding on material or coincidentally bending/blocking the view to a star in the background, you simply can’t see them. Once you know one is there, though, you can start to have some fun.

Enlarge / Aboard the German research vessel Sonne off the coast of Chile, ready to take samples from eight kilometers deep in the Atacama Trench system. (credit: Anni Glud, SDU)

Although pollution controls have significantly reduced the mercury content of coal-fired plant emissions, the latest Global Mercury Assessment still estimates that there's been a 20 percent increase in anthropogenic mercury emissions between 2010 and 2015. A new study provides some insight into where all that mercury might end up: there are unprecedented levels of mercury in up-to-now unmeasured deep-ocean trenches.

The WHO categorizes mercury as one of the top 10 chemicals of major health concern, and as of 2020, over 120 countries have been working together to reduce environmental mercury through the 2017 Minamata Convention on Mercury. In its elemental and mono-methylated form (methylmercury), mercury is a potent neurotoxin. Methylmercury in particular biomagnifies, which means it increases in concentration as it goes up the marine food chain. That has prompted lots of warnings about the consumption of fish and sea food.

This latest report is the first to measure mercury-accumulation rates in sediment cores from some of the deepest parts of the ocean—the hadal zones (>6 km depth). While the deep ocean is considered one of the most important, and relatively safest, places for mercury to end up, the rates of accumulation were up to 56 times greater than prior estimates. The highest measured concentrations were also nearly as high as some of the most contaminated bodies of water on the planet—a jarring finding given that these locations (the Atacama and Kermadec trenches) aren't in the vicinity of any known mercury sources.