"Astrophysicists have recently begun hatching plans to find out just how weird Planet Nine might be," reports the New York Times. Long-time Slashdot reader fahrbot-bot shares their report: Although it is probably wishful thinking, some astronomers contend that a black hole may be lurking in the outer reaches of our solar system. All summer, they have been arguing over how to find it, if indeed it is there, and what to do about it, proposing plans that are only halfway out of this world...

Earlier this year, Edward Witten, a theoretical physicist at the Institute for Advanced Study in Princeton, chimed in... Dr. Witten suggested borrowing a trick from Breakthrough Starshot, the proposal by Russian philanthropist Yuri Milner and Dr. Hawking to send thousands of laser-propelled microscopic probes to the nearest star system, Alpha Centauri. Dr. Witten suggested sending hundreds of similarly small probes outward in all directions to explore the solar system. By keeping track of incoming signals from the probes, scientists on Earth would be able to tell if and when each one sped up or slowed down as it encountered the gravitational field of Planet Nine or anything else out there.

Key to this plan would be the ability of the probes to keep pinging Earth precisely every hundred-thousandth of a second. In May, astronomers Scott Lawrence and Zeeve Rogoszinski of the University of Maryland suggested instead monitoring the trajectories of the probes with high-resolution radio telescopes, which would obviate the need for high-precision clocks on the probes.
Another idea came from Avi Loeb, chair of the astronomy department at Harvard and leader of a scientific advisory board for Breakthrough Starshot: in July Dr. Loeb was back, with a student, Amir Siraj, and a new idea for finding the Planet Nine black hole. If a black hole were out there, they argued, it would occasionally rip apart small comets, causing bright flares that could soon be spotted by the new Vera C. Rubin Observatory, previously known as the Large Synoptic Survey Telescope, now under construction in Chile. The observatory's mission, starting in 2021, is to make a movie of the universe, producing a panorama of the entire southern night sky every few days and revealing anything that has changed or moved. Such flares should occur a few times a year, they noted. "Our calculations show that the flares will be bright enough for the Vera Rubin Observatory to rule out or confirm Planet Nine as a black hole within one year of monitoring the sky with its L.S.S.T. survey," Dr. Loeb wrote in an email.

Moreover, because the Rubin telescope examines such a large swath of sky, it could detect or rule out black holes of similar size all the way out to the Oort cloud, a vague and diffuse assemblage of protocomets and primordial, frozen riffraff a trillion miles from the sun, they said.

The prospect of finding a black hole in our own solar system "is as startling as finding evidence that someone might be living in the shed in your backyard," Dr. Loeb said in the email. "If so, who is it, and how did it get there?"

"Scientists have known for nearly 200 years that certain materials can convert heat to electricity..." reports Science, describing research into an intriguing new approach: Refrigerators, boilers, and even lightbulbs continually dump heat into their surroundings. This "waste heat" could — in theory — be turned into electricity, as it is sometimes done with power plants, automobile engines, and other high-heat sources. The problem: These "low-grade" sources give off too little heat for current technology to do the conversion well.

Now, researchers have created a device that uses liquids to efficiently convert low-grade heat to electricity. The advance might one day power energy-scavenging devices that can light up sensors and lights and even charge batteries... Thermocells are good at converting small temperature differences into electricity, but they typically produce only tiny currents... This thermocell generated five times more power for the same electrode area than previous versions, materials physicist Jun Zhou and his colleagues at the Huazhong University of Science and Technology report this week in Science.

It also more than doubled the efficiency needed to make a viable commercial device. A paperback book-size module of 20 thermocells could run LED lights, power a fan, and charge a mobile phone, the team found.

Long-time Slashdot reader bsharma shares an announcement from NASA's Hubble Space Telescope site: Researchers found that small-scale concentrations of dark matter in clusters produce gravitational lensing effects that are 10 times stronger than expected. This evidence is based on unprecedently detailed observations of several massive galaxy clusters by NASA's Hubble Space Telescope and the European Southern Observatory's Very Large Telescope (VLT) in Chile...

Priyamvada Natarajan of Yale University in New Haven, Connecticut, one of the senior theorists on the team, added, "There's a feature of the real universe that we are simply not capturing in our current theoretical models. This could signal a gap in our current understanding of the nature of dark matter and its properties, as these exquisite data have permitted us to probe the detailed distribution of dark matter on the smallest scales."

The team's paper will appear in the September 11 issue of the journal Science... This unexpected discovery means there is a discrepancy between these observations and theoretical models of how dark matter should be distributed in galaxy clusters.

It could signal a gap in astronomers' current understanding of the nature of dark matter.

gollum123 shares a report from CNBC: Dining out raises the risk of contracting Covid-19 more than other activities, such as shopping or going to a salon, according to a report published Thursday by the Centers for Disease Control and Prevention. The findings come as many states consider the safest ways to reopen businesses, especially restaurants. Those who tested positive for SARS-CoV-2, the virus that causes Covid-19, "were approximately twice as likely to have reported dining at a restaurant than were those with negative SARS-CoV-2 test results," the study authors wrote. And those who were diagnosed without any known exposure to the virus were more likely to report having visited a bar or coffee shop in the previous two weeks. The increased risk makes sense; it's easy to wear a mask in stores or in places of worship, but it's nearly impossible to do so while eating and drinking. In addition to being maskless, individuals are often close together when eating at a restaurant, sitting across the table from one another.