Two years ago, the Event Horizon Telescope (EHT) made headlines with its announcement of the first direct image of a black hole. Science magazine named the image its Breakthrough of the Year. Now the EHT collaboration is back with another groundbreaking result: a new image of the same black hole, this time showing how it looks in polarized light. The ability to measure that polarization for the first time—a signature of magnetic fields at the black hole’s edge—is expected to yield fresh insight into how black holes gobble up matter and emit powerful jets from their cores. The new findings were described in three papers published in The Astrophysical Journal Letters.
“This work is a major milestone: the polarization of light carries information that allows us to better understand the physics behind the image we saw in April 2019, which was not possible before,” said co-author Iván Martí-Vidal, coordinator of the EHT Polarimetry Working Group and a researcher at the University of Valencia, Spain. “Unveiling this new polarized-light image required years of work due to the complex techniques involved in obtaining and analyzing the data.”
As Ars’ John Timmer reported back in 2019:
The Event Horizon Telescope isn’t a telescope in the traditional sense. Instead, it’s a collection of telescopes scattered around the globe. In its current iteration, it includes hardware from Hawaii to Europe, and from the South Pole to Greenland, though not all of these were active during the initial observations. The telescope is created by a process called interferometry, which uses light captured at different locations to build an image with a resolution similar to that of a telescope the size of the most distant locations.
Interferometry has been used for facilities like ALMA, the Atacama Large Millimeter/submillimeter Array, where telescopes can be spread across 16km of desert. In theory, there’s no upper limit on the size of the array, but there are several challenges. To know which photons originated at the same time at the source, you need very precise location and timing information on each of the sites. And you still have to gather sufficient photons in order to see anything. In general, that means atomic clocks (which had to be installed at many of the locations) and extremely precise GPS measurements built up over time. For the Event Horizon Telescope, the large collecting area of ALMA, combined with choosing a wavelength where supermassive black holes are very bright, ensured sufficient photons. The net result is a telescope that can do the equivalent of reading the year stamped on a coin in Los Angeles from New York City—assuming the coin was glowing at radio wavelengths. There’s no way we can do better without relying on hardware that’s not located on Earth.
Those multiple imaging methods resulted in the first direct image ever taken of a black hole at the center of an elliptical galaxy. Located in the constellation of Virgo, some 55 million light years away, the galaxy is called Messier 87 (M87). The collaboration’s findings were published on April 10, 2019 in six different papers featured in The Astrophysical Journal Letters. It’s a feat that would have been impossible a mere generation ago, made possible by technological breakthroughs, innovative new algorithms, and of course, connecting several of the world’s best radio observatories. The image confirmed that the object at the center of M87 is indeed a black hole.
The EHT captured photons trapped in orbit around the black hole, swirling around at near the speed of light, creating a bright ring around it. From this, astronomers were able to deduce that the black hole is spinning clockwise. The imaging also revealed the shadow of the black hole, a dark central region within the ring. That shadow is as close as astronomers can get to taking a picture of the actual black hole, from which light cannot escape once it crosses the event horizon. And just as the size of the event horizon is proportional to the black hole’s mass, so, too, is the black hole’s shadow: the more massive the black hole, the larger the shadow. (The M87 black hole’s mass is 6.5 billion times that of our Sun.) It was a stunning confirmation of the general theory of relativity, showing that those predictions hold up even in extreme gravitational environments.
However, what was lacking was insight into the process behind the powerful twin jets produced by the black hole gobbling up matter, ejecting a portion of the material falling into it away at nearly light speed. (The black hole at the center of our Milky Way is less ravenous, i.e., relatively quiet, compared to M87’s black hole.) For example, astronomers don’t yet agree about how those jets get accelerated to such high speeds. These new results place additional constraints around the various competing theories, narrowing the possibilities.
In much the same way that polarized sunglasses reduce glare from bright surfaces, the polarized light around a black hole provides a sharper view of the region around it. In this case, the polarization of light isn’t due to special filters (like the lenses in sunglasses) but the presence of magnetic fields in the hot region of space surrounding the black hole. That polarization enables astronomers to map the magnetic field lines at the inner edge and to study the interaction between matter flowing in and being blown outward.
“The observations suggest that the magnetic fields at the black hole’s edge are strong enough to push back on the hot gas and help it resist gravity’s pull. Only the gas that slips through the field can spiral inwards to the event horizon,” said co-author Jason Dexter of the University of Colorado Boulder, who is also coordinator of the EHT Theory Working Group. That means that only theoretical models that incorporate the feature of a strongly magnetized gas accurately describe what the EHT collaboration has observed.
DOI: “First M87 Event Horizon Telescope Results VII: polarization of the ring,” Astrophysical Journal Letters, 2021. 10.3847/2041-8213/abe71d.
DOI: “First M87 Event Horizon Telescope Results VIII: Magnetic Field Structure Near The Event Horizon,” Astrophysical Journal Letters, 2021. 10.3847/2041-8213/abe4de.
New species of crested dinosaur identified in Mexico
A team of palaeontologists in Mexico have identified a new species of dinosaur after finding its 72 million-year-old fossilized remains almost a decade ago, Mexico’s National Institute of Anthropology and History (INAH) said on Thursday.
The new species, named Tlatolophus galorum, was identified as a crested dinosaur after 80% of its skull was recovered, allowing experts to compare it to other dinosaurs of that type, INAH said.
The investigation, which also included specialists from the National Autonomous University of Mexico, began in 2013 with the discovery of an articulated tail in the north-central Mexican state of Coahuila, where other discoveries have been made.
“Once we recovered the tail, we continued digging below where it was located. The surprise was that we began to find bones such as the femur, the scapula and other elements,” said Alejandro Ramírez, a scientist involved in the discovery.
Later, the scientists were able to collect, clean and analyze other bone fragments from the front part of the dinosaur’s body.
The palaeontologists had in their possession the crest of the dinosaur, which was 1.32 meters long, as well as other parts of the skull: lower and upper jaws, palate and even a part known as the neurocranium, where the brain was housed, INAH said.
The Mexican anthropology body also explained the meaning of the name – Tlatolophus galorum – for the new species of dinosaur.
Tlatolophus is a mixture of two words, putting together a term from the indigenous Mexican language of Nahuatl that means “word” with the Greek term meaning “crest”. Galorum refers to the people linked to the research, INAH said.
(Reporting by Abraham Gonzalez; Writing by Drazen Jorgic; Editing by Ana Nicolaci da Costa)
Alberta family searches for answers in teen's sudden death after COVID exposure, negative tests – CBC.ca
A southern Alberta mother and father are grappling with the sudden, unexplained death of their 17-year-old daughter, and with few answers, they’re left wondering if she could be the province’s youngest victim of COVID-19.
Sarah Strate — a healthy, active Grade 12 student at Magrath High School who loved singing, dancing and being outdoors — died on Monday, less than a week after being notified she’d been exposed to COVID-19.
While two tests came back negative, her parents say other signs point to the coronavirus, and they’re waiting for more answers.
“It was so fast. It’s all still such a shock,” said Sarah’s mother, Kristine Strate. “She never even coughed. She had a sore throat and her ears were sore for a while, and [she had] swollen neck glands.”
Kristine said Sarah developed mild symptoms shortly after her older sister — who later tested positive for COVID-19 — visited from Lethbridge, one of Alberta’s current hot spots for the virus.
The family went into isolation at their home in Magrath on Tuesday, April 20. They were swabbed the next day and the results were negative.
‘Everything went south, super-fast’
By Friday night, Sarah had developed fever and chills. On Saturday, she started vomiting and Kristine, a public health nurse, tried to keep her hydrated.
“She woke up feeling a bit more off on Monday morning,” Kristine said. “And everything went south, super-fast.”
Sarah had grown very weak and her parents decided to call 911 when she appeared to become delirious.
“She had her blanket on and I was talking to her and, in an instant, she was unresponsive,” said Kristine, who immediately started performing CPR on her daughter.
When paramedics arrived 20 minutes later, they were able to restore a heartbeat and rushed Sarah to hospital in Lethbridge, where she died.
“I thought there was hope once we got her heart rate back. I really did,” recalled Sarah’s father, Ron.
“He was praying for a miracle, and sometimes miracles don’t come,” said Kristine.
Searching for answers
At the hospital, the family was told Sarah’s lungs were severely infected and that she may have ended up with blood clots in both her heart and lungs, a condition that can be a complication of COVID-19.
But a second test at the hospital came back negative for COVID-19.
“There really is no other answer,” Ron said. “When a healthy 17-year-old girl, who was sitting up in her bed and was able to talk, and within 10 minutes is unconscious on our floor — there was no reason [for it].”
The province currently has no record of any Albertans under the age of 20 who have died of COVID-19.
According to the Strate family, the medical examiner is running additional blood and tissue tests, in an effort to uncover the cause of Sarah’s death.
‘Unusual but not impossible’
University of Alberta infectious disease specialist Dr. Lynora Saxinger, who was not involved in Sarah’s treatment, says it is conceivable that further testing could uncover evidence of a COVID-19 infection, despite two negative test results.
However, she hasn’t seen a similar case in Alberta.
“It would be unusual but not impossible because no test is perfect. We have had cases where an initial test is negative and then if you keep on thinking it’s COVID and you re-test, you then can find COVID,” she said.
According to Saxinger, the rate of false negatives is believed to be very low. But it can happen if there are problems with the testing or specimen collection.
She says people are more likely to test positive after symptoms develop.
“The best sensitivity of the test is around day four or five of having symptoms,” she said. “So you can miss things if you test very, very early. And with new development of symptoms, it’s always a good time to re-test because then the likelihood of getting a positive test is a little higher. But again, no test is perfect.”
Sarah deteriorated so quickly — dying five days after she first developed symptoms — she didn’t live long enough to make it to her follow-up COVID-19 test. Instead, it was done at the hospital.
‘An amazing kid’
The Strate family now faces an agonizing wait for answers — one that will likely take months — about what caused Sarah’s death.
But Ron, who teaches at the school where Sarah attended Grade 12, wants his daughter to be remembered for the life she lived, not her death.
Sarah was one of five children. Ron says she was strong, active and vibrant and had plans to become a massage therapist after graduating from high school.
She played several sports and loved to sing and dance as part of a show choir. She was a leader in the school’s suicide prevention group and would stand up for other students who were facing bullying.
“She’s one of the leaders in our Hope Squad … which goes out and helps kids to not be scared,” he father said.
“She’s an amazing kid.”
Sarah would often spend hours helping struggling classmates, and her parents hope her kindness is not forgotten.
“She’d done so many good things. Honestly, I’ve got so many messages from parents saying, ‘You have no idea how much your daughter helped our kid,'” said Ron.
“This 17-year-old girl probably lived more of a life in 17 years than most adults will live in their whole lives. She was so special. I love her so much.”
China launches key module of space station planned for 2022
BEIJING (Reuters) -China launched an unmanned module on Thursday containing what will become living quarters for three crew on a permanent space station that it plans to complete by the end of 2022, state media reported.
The module, named “Tianhe”, or “Harmony of the Heavens”, was launched on the Long March 5B, China’s largest carrier rocket, at 11:23 a.m. (0323 GMT) from the Wenchang Space Launch Centre on the southern island of Hainan.
Tianhe is one of three main components of what would be China’s first self-developed space station, rivalling the only other station in service – the International Space Station (ISS).
The ISS is backed by the United States, Russia, Europe, Japan and Canada. China was barred from participating by the United States.
“(Tianhe) is an important pilot project in the building of a powerful nation in both technology and in space,” state media quoted President Xi Jinping as saying in a congratulatory speech.
Tianhe forms the main living quarters for three crew members in the Chinese space station, which will have a life span of at least 10 years.
The Tianhe launch was the first of 11 missions needed to complete the space station, which will orbit Earth at an altitude of 340 to 450 km (211-280 miles).
In the later missions, China will launch the two other core modules, four manned spacecraft and four cargo spacecraft.
Work on the space station programme began a decade ago with the launch of a space lab Tiangong-1 in 2011, and later, Tiangong-2 in 2016.
Both helped China test the programme’s space rendezvous and docking capabilities.
China aims to become a major space power by 2030. It has ramped up its space programme with visits to the moon, the launch of an uncrewed probe to Mars and the construction of its own space station.
In contrast, the fate of the ageing ISS – in orbit for more than two decades – remains uncertain.
The project is set to expire in 2024, barring funding from its partners. Russia said this month that it would quit the project from 2025.
Russia is deepening ties with China in space as tensions with Washington rise.
Moscow has slammed the U.S.-led Artemis moon exploration programme and instead chosen to join Beijing in setting up a lunar research outpost in the coming years.
(Reporting by Ryan Woo and Liangping Gao; Editing by Christian Schmollinger, Simon Cameron-Moore and Lincoln Feast.)
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