Matter swirling around supermassive black holes creates bursts of light that “echo” in nearby dust clouds. These traveling signals could serve as a new cosmic yardstick.
When you look up at the night sky, how do you know whether the specks of light that you see are bright and far away, or relatively faint and close by? One way to find out is to compare how much light the object actually emits with how bright it appears. The difference between its true luminosity and its apparent brightness reveals an object’s distance from the observer.
Measuring the luminosity of a celestial object is challenging, especially with black holes, which don’t emit light. But the supermassive black holes that lie at the center of most galaxies provide a loophole: They often pull lots of matter around them, forming hot disks that can radiate brightly. Measuring the luminosity of a bright disk would allow astronomers to gauge the distance to the black hole and the galaxy it lives in. Distance measurements not only help scientists create a better, three-dimensional map of the universe, they can also provide information about how and when objects formed.
In a new study, astronomers used a technique that some have nicknamed “echo mapping” to measure the luminosity of black hole disks in over 500 galaxies. Published last month in the Astrophysical Journal, the study adds support to the idea that this approach could be used to measure the distances between Earth and these faraway galaxies.
The process of echo mapping, also known as reverberation mapping, starts when the disk of hot plasma (atoms that have lost their electrons) close to the black hole gets brighter, sometimes even releasing short flares of visible light (meaning wavelengths that can be seen by the human eye). That light travels away from the disk and eventually runs into a common feature of most supermassive black hole systems: an enormous cloud of dust in the shape of a doughnut (also known as a torus). Together, the disk and the torus form a sort of bullseye, with the accretion disk wrapped tightly around the black hole, followed by consecutive rings of slightly cooler plasma and gas, and finally the dust torus, which makes up the widest, outermost ring in the bullseye. When the flash of light from the accretion disk reaches the inner wall of the dusty torus, the light gets absorbed, causing the dust to heat up and release infrared light. This brightening of the torus is a direct response to or, one might say an “echo” of the changes happening in the disk.
The distance from the accretion disk to the inside of the dust torus can be vast – billions or trillions of miles. Even light, traveling at 186,000 miles (300,000 kilometers) per second, can take months or years to cross it. If astronomers can observe both the initial flare of visible light in the accretion disk and the subsequent infrared brightening in the torus, they can also measure the time it took the light to travel between those two structures. Because light travels at a standard speed, this information also gives astronomers the distance between the disk and the torus.
Scientists can then use the distance measurement to calculate the disk’s luminosity, and, in theory, its distance from Earth. Here’s how: The temperature in the part of the disk closest to the black hole can reach tens of thousands of degrees – so high that even atoms are torn apart and dust particles can’t form. The heat from the disk also warms the area around it, like a bonfire on a cold night. Traveling away from the black hole, the temperature decreases gradually.
Astronomers know that dust forms when the temperature dips to about 2,200 degrees Fahrenheit (1,200 Celsius); the bigger the bonfire (or the more energy the disk radiates), the farther away from it the dust forms. So measuring the distance between the accretion disk and the torus reveals the energy output of the disk, which is directly proportional to its luminosity.
Because the light can take months or years to traverse the space between the disk and the torus, astronomers need data that spans decades. The new study relies on nearly two decades of visible-light observations of black hole accretion disks, captured by several ground-based telescopes. The infrared light emitted by the dust was detected by NASA’s Near Earth Object Wide Field Infrared Survey Explorer (NEOWISE), previously named WISE. The spacecraft surveys the entire sky about once every six months, providing astronomers with repeated opportunities to observe galaxies and look for signs of those light “echoes.” The study used 14 surveys of the sky by WISE/NEOWISE, collected between 2010 and 2019. In some galaxies, the light took more than 10 years to traverse the distance between the accretion disk and the dust, making them the longest echoes ever measured outside the Milky Way galaxy.
Galaxies Far, Far Away
The idea to use echo mapping to measure the distance from Earth to far away galaxies is not new, but the study makes substantial strides in demonstrating its feasibility. The largest single survey of its kind, the study confirms that echo mapping plays out in the same way in all galaxies, regardless of such variables as a black hole’s size, which can vary significantly across the universe. But the technique isn’t ready for prime time.
Due to multiple factors, the authors’ distance measurements lack precision. Most notably, the authors said, they need to understand more about the structure of the inner regions of the dust doughnut encircling the black hole. That structure could affect such things as which specific wavelengths of infrared light the dust emits when the light first reaches it.
The WISE data doesn’t span the entire infrared wavelength range, and a broader dataset could improve the distance measurements. NASA’s Nancy Grace Roman Space Telescope, set to launch in the mid-2020s, will provide targeted observations in different infrared wavelength ranges. The agency’s upcoming SPHEREx mission (which stands for Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer) will survey the entire sky in multiple infrared wavelengths and could also help improve the technique.
“The beauty of the echo mapping technique is that these supermassive black holes aren’t going away anytime soon,” said Qian Yang, a researcher at the University of Illinois at Urbana-Champaign and lead author of the study, referring to the fact that black hole disks may experience active flaring for thousands or even millions of years. “So we can measure the dust echoes over and over again for the same system to improve the distance measurement.”
Luminosity-based distance measurements can already be done with objects known as “standard candles,” which have a known luminosity. One example is a type of exploding star called a Type 1a supernovas, which played a critical role in the discovery of dark energy (the name given to the mysterious driving force behind the universe’s accelerating expansion). Type 1a supernovas all have about the same luminosity, so astronomers only need to measure their apparent brightness to calculate their distance from Earth.
With other standard candles, astronomers can measure a property of the object to deduce its specific luminosity. Such is the case with echo mapping, where each accretion disk is unique but the technique for measuring the luminosity is the same. There are benefits for astronomers to being able to use multiple standard candles, such as being able to compare distance measurements to confirm their accuracy, and each standard candle has strengths and weaknesses.
“Measuring cosmic distances is a fundamental challenge in astronomy, so the possibility of having an extra trick up one’s sleeve is very exciting,” said Yue Shen, also a researcher at the University of Illinois at Urbana-Champaign and co-author of the paper.
Launched in 2009, the WISE spacecraft was placed into hibernation in 2011 after completing its primary mission. In Sept. 2013, NASA reactivated the spacecraft with the primary goal of scanning for near-Earth objects, or NEOs, and the mission and spacecraft were renamed NEOWISE. NASA’s Jet Propulsion Laboratory in Southern California managed and operated WISE for NASA’s Science Mission Directorate. The mission was selected competitively under NASA’s Explorers Program managed by the agency’s Goddard Space Flight Center in Greenbelt, Maryland. NEOWISE is a project of JPL, a division of Caltech, and the University of Arizona, supported by NASA’s Planetary Defense Coordination Office.
Black Friday 2020: The Best Tech Deals
The holiday shopping season is approaching and many retailers will be participating in Black Friday sales. This guide can help you figure out where and how to shop to find the best bargains.
Many shoppers look forward to Black Friday and Cyber Monday every year. After all, it’s one of the best times to get that holiday shopping list whittled down without breaking the bank. The 2020 holiday shopping season is likely to look a little different than previous years due to the COVID-19 pandemic. In years past, many retailers such as Walmart, Target, and Best Buy started Black Friday deals on Thanksgiving evening, but that will not be the case this year as they will be closed for the holiday.
Even though shopping this year might shift from in-store to online for many, there are still plenty of deals to take advantage of. This guide will walk you through major store closings, the best times to shop, and where to find great deals on smartwatches/fitness trackers, tablets, headphones, and more. Also, be sure to check out our holiday gift guides for more ideas and product information. TechRepublic will update this article as more information becomes available.
Black Friday 2020: Where and when to shop
According to sister site GameSpot, the following retailers will be closed on Thanksgiving:
- Walmart/Sam’s Club
- Best Buy
- Dick’s Sporting Goods
- TJ Maxx
- Bed Bath & Beyond
- Office Depot
While Black Friday store hours have not yet been announced for these retailers, Black Friday pricing will be available online much earlier than usual. For example, GameSpot states, “Target has confirmed its first Black Friday deals will start Nov. 1, with ‘Black Friday pricing’ available throughout the entire month.”
Best Buy began offering Black Friday deals during Amazon Prime Day and is still offering Black Friday pricing on hundreds of items. Walmart is also slated to offer deals earlier than usual with its first “Deals for Days” event starting on Walmart.com Wednesday, Nov. 4 at 7 pm ET and more new deals on Nov. 7 online at 12 am ET, and 5 am local time in stores. Amazon is currently running a “Holiday Dash” sale which offers big discounts on items in the weeks leading up to Black Friday and Cyber Monday.
Black Friday deals from Amazon, Target, and Best Buy
The following deals from Best Buy, Target, and Amazon might help you find just the items you’re looking for.
Disclaimer: Please note that these Black Friday sales run for a limited time only; prices are subject to change, and quantities are limited. Dates of availability will be noted in parenthesis if listed on the retailer’s site.
(The following Best Buy sales end Nov. 1 at 11:59 pm CT)
WD My Passport SSD (2020) Review
WD’s latest round of redesigns has spread throughout its portable storage lineup, replacing the bold, bright, sharp design-led identity with rounded edges, muted colours, and simpler plastic bodies. Whimsy has given way to practicality, which you might or might not be in favour of. The latest reimagined storage device is the WD My Passport SSD (2020), but in this case, the changes aren’t solely cosmetic. You get a huge bump in hardware specifications and speeds, keeping WD’s portable SSD lineup current and competitive. Here’s a review of the brand new WD My Passport SSD (2020).
WD My Passport SSD (2020) design and features
The older two-tone metal-and-plastic design might have been slightly impractical with its sharp corners and overall bulk, but it looked and felt very modern and premium. Now, you get a much more organic body, shaped somewhat like a thin bar of soap. It’s much flatter than before, with rounded sides and corners that make for an easy grip. This device will be comfortable in your hand as well as your pocket. It weighs only 45.7g.
The body is made of metal and there’s a swirly ridged pattern on the front as well as the rear. The USB Type-C port is off-centre on the bottom and there’s no activity LED. The raised WD logo feels rough and looks rather garish, but otherwise this is a simple, sober design that will fit in anywhere. You have a choice between Space Grey, Midnight Blue, and Gold. A red version appears to be available in other countries, but isn’t listed here.
Unlike some other portable SSDs (including models from Western Digital’s other brands, SanDisk and G-Technology), there’s no waterproofing or other form of protection from the elements. WD does mention shock and vibration resistance, which are inherent to SSDs, plus drop resistance for falls from up to 1.98m in height.
Perhaps unsurprisingly, the My Passport SSD (2020) is very similar in shape and size to the SanDisk Extreme V2 portable SSD, but doesn’t have an integrated handle, ruggedised coating, or IP rating.
You get a very short USB Type-C cable in the box, with a Type-C to Type-A adapter for broad compatibility. As we noted with the previous incarnation of the My Passport SSD, such an adapter is technically outside the official USB specification and so the cable and adapter both have notches to make sure they’re used with each other. That doesn’t physically stop you from using the entire cable, plus adapter, with another device though. This should be avoided, because some devices need to negotiate things like how much power is sent from one side to another, which cannot happen through a legacy USB port when such an adapter is used.
WD My Passport SSD (2020) price, specifications and performance
The biggest upgrade comes from the use of an NVMe SSD and bridge rather than the older SATA protocol. WD claims read and write speeds of 1050MBps and 1000MBps respectively – exactly the same as the Samsung SSD T7 Touch, and in line with the Sandisk Extreme Pro. You’ll need a PC with a USB 3.2 Gen2 (10Gbps) or Thunderbolt 3 port to be able to harness such speed.
The new My Passport SSD (2020) is available in 500GB, 1TB and 2TB capacities, priced officially at Rs. 8,999, Rs. 15,999, and Rs. 28,999 respectively. They are exclusive to Amazon during the festive sale period, and actual prices are quite a bit lower. They will be available offline from mid-November.
WD has implemented 256-bit AES hardware encryption. The company offers quite a lot of free software that you can download, including the capable Drive Utilities for general maintenance, WD Backup to set up simple backup routines, and WD Security to set up encryption with a password. You’re also encouraged to install WD Discovery, which is completely unnecessary and only exists to serve up ads and promotions for WD.
The 1TB review unit we’re testing today was formatted to exFAT by default. This works cross-platform, but if you’re planning to use Time Machine on a Mac, you’ll need to reformat the drive to HFS+ (or at least partition and format some of it). Windows’ Disk Management console reported 931.48GB of usable space.
All tests were run on an HP Spectre x360 13 laptop because of its Thunderbolt 3 ports. CrystalDiskMark 6 reported sequential read and write speeds of 913.9Mbps and 924.9Mbps respectively, which is not too far below WD’s official claim. More realistic random read and write speeds were 154.1Mbps and 163.8MBps respectively. While good by portable SSD standards, the My Passport SSD (2020)’s scores lag quite a way behind what the Samsung SSD T7 Touch and SanDisk Extreme Pro were able to achieve. The Anvil benchmark managed read and write scores of 2,186.6 and 1,921.12, for an overall score of 4,107.72.
The shell of the WD My Passport SSD (2020) did get quite warm when benchmarks were running and when large batches of files were being copied up and down in testing. This shouldn’t be much of a problem in everyday use, and there’s nothing else to complain about.
If you like bold, edgy design and products that make a statement, the new WD My Passport might be a bit of a disappointment. It looks unassuming and pedestrian compared to its predecessor; more like a bar of soap than a high-end tech product. Perhaps this is a signifier that portable SSDs aren’t just lifestyle accessories for only those who can afford them anymore, but are now perfectly mainstream commodity products.
The emerging new class of NVMe portable SSDs brings nearly twice the speed of previous-gen SATA models. Samsung still has the performance advantage, but WD isn’t too far behind now. Other than speed, you should choose your SSD based on whether you prioritise features such as AES encryption and ruggedisation. SSDs are also routinely discounted below their official MRPs, so if you do find a great deal on the WD My Passport SSD (2020) and it meets your requirements, you shouldn’t hesitate to pick one up.
WD My Passport SSD (2020)
Rs. 6,999 (500GB)
Rs. 12,999 (1TB)
Rs. 24,999 (2TB)
- NVMe-based, good read and write speeds
- Good value for money
- Compact and light
- Gets a bit warm when stressed
- No IP rating
- Performance: 4.5
- Value for Money: 4.5
- Overall: 4.5
Edge computing and IoT sensors help cities plug a leak in water bills
Tracking the health of pipes and water meters in real time helps cities catch water main breaks sooner and issue more accurate bills.
A Texas company is using edge computing and IoT sensors to help cities modernize crumbling water infrastructure and inaccurate water meters. The American Society of Civil Engineers has given the country’s drinking water system a D- for the last 10 years. Many components of city water systems date back to the Civil War era. Olea Edge Analytics is using 21st century technology to spot needed repairs and make sure water bills are accurate.
Dave Mackie, Olea Edge Analytics’ CEO, said the company combines edge computing with artificial intelligence and machine learning to help cities make more informed decisions.
“Our network operations center can remotely manage all of the endpoints across the city, prioritizing repair work, giving the ideal route and directions, and transmitted work plans and specifications to provide everything crews need for a right-first-time trip,” he said in a press release.
SEE: 5 Internet of Things (IoT) innovations (free Pdf) (TechRepublic)
Olea puts sensors on water meters and sends data about how much water is used to the cloud for analysis. The Smart Water Management Platform monitors the meters to look for water usage that isn’t showing up on monthly bills. Olea estimates that up to 40% of all high-volume commercial water meters are not capturing the full amount of water used.
As Brandon Vigliarolo wrote in “
,” Forrester predicts that this is the year that new business models will push edge computing “from science project to real value.” Forrester analysts said that cloud platforms, artificial intelligence, and the widespread proliferation of 5G will make these edge use cases more practical.
SEE: The future of IoT: 5 major predictions for 2021 (TechRepublic)
The Department of Watershed Management of the City of Atlanta is spending $3.9 million on a deal with Olea to measure water usage more accurately.
The COVID-19 pandemic has created a serious budget shortfall for many cities around the US. According to the National League of Cities, losses in sales tax and other revenue sources will cost cities $360 billion from this year through 2022.
Olea Edge Analytics produces products that use technology for revenue recovery. The company’s Vault Management platform allows utilities to manage assets and get alerts when something changes. A dashboard provides a high-level and operational view of workflows, including data about billing and consumption, maintenance, and safety. CityEdge uses blockchain, AI, and machine learning to spot problems in water infrastructure as soon as they happen.
“People are surprised to learn that they can make these simple repairs and turn that money into a catalyst for much-needed projects,” Mackie said in a press release. “Everyone is looking for an edge in funding, especially during these economic times.”
With the CityEdge product, a blockchain validates water usage from when it leaves the meter’s sensors to the moment it reaches the customer. The encrypted data in the ledger is distributed across every device in the network, increasing transparency and traceability. The platform also creates a digital twin of every meter on the network.
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