So Dwyer and his team turned to the Low Frequency Array (LOFAR), a network of thousands of small radio telescopes mostly in the Netherlands. LOFAR usually gazes at distant galaxies and exploding stars. But according to Dwyer, “it just so happens to work really well for measuring lightning, too.”
When thunderstorms roll overhead, there’s little useful astronomy that LOFAR can do. So instead, the telescope tunes its antennas to detect a barrage of a million or so radio pulses that emanate from each lightning flash. Unlike visible light, radio pulses can pass through thick clouds.
Using radio detectors to map lightning isn’t new; purpose-built radio antennas have long observed storms in New Mexico. But those images are low-resolution or only in two dimensions. LOFAR, a state-of-the-art astronomical telescope, can map lighting on a meter-by-meter scale in three dimensions, and with a frame rate 200 times faster than previous instruments could achieve. “The LOFAR measurements are giving us the first really clear picture of what’s happening inside the thunderstorm,” said Dwyer.
A materializing lightning bolt produces millions of radio pulses. To reconstruct a 3D lightning image from the jumble of data, the researchers employed an algorithm similar to one used in the Apollo moon landings. The algorithm continuously updates what’s known about an object’s position. Whereas a single radio antenna can only indicate the rough direction of the flash, adding data from a second antenna updates the position. By steadily looping in thousands of LOFAR’s antennas, the algorithm constructs a clear map.
When the researchers analyzed the data from the August 2018 lightning flash, they saw that the radio pulses all emanated from a 70-meter-wide region deep inside the storm cloud. They quickly inferred that the pattern of pulses supports one of the two leading theories about how the most common type of lightning gets started.
One idea holds that cosmic rays—particles from outer space—collide with electrons inside thunderstorms, triggering electron avalanches that strengthen the electric fields.
The new observations point to the rival theory. It starts with clusters of ice crystals inside the cloud. Turbulent collisions between the needle-shaped crystals brush off some of their electrons, leaving one end of each ice crystal positively charged and the other negatively charged. The positive end draws electrons from nearby air molecules. More electrons flow in from air molecules that are farther away, forming ribbons of ionized air that extend from each ice crystal tip. These are called streamers.
Each crystal tip gives rise to hordes of streamers, with individual streamers branching off again and again. The streamers heat the surrounding air, ripping electrons from air molecules en masse so that a larger current flows onto the ice crystals. Eventually a streamer becomes hot and conductive enough to turn into a leader—a channel along which a fully fledged streak of lightning can suddenly travel.
“This is what we’re seeing,” said Christopher Sterpka, first author on the new paper. In a movie showing the initiation of the flash that the researchers made from the data, radio pulses grow exponentially, likely because of the deluge of streamers. “After the avalanche stops, we see a lightning leader nearby,” he said. In recent months, Sterpka has been compiling more lightning initiation movies that look similar to the first.
Scientists study trajectory of meteorite that landed in B.C. in October – Red Deer Advocate
VANCOUVER — Scientistsstudying a meteorite that landed next to a British Columbia woman’s head last year say it was diverted to that path about 470 million years ago.
The small meteorite broke through a woman’s ceiling in Golden, B.C., in October, landing on her pillow, next to where she had been sleeping moments earlier.
Philip McCausland,a lead researcher mapping the meteorite’s journey, said Monday they know the 4.5-billion-year-old rock collided with something about 470 million years ago, breaking into fragments and changing the trajectory of some of the pieces.
McCausland, who’s an adjunct professor at Western University in London, Ont., said the meteorite is of scientific significance because it will allow scientists to study how material from the asteroid belt arrives on Earth.
“There’s 50,000 to 60,000 identified meteorites now in the world, but most have no context. We don’t know really where they came from,” he said.
“In cases where we have known orbits, where they were observed coming in well enough that we can reconstruct what the orbit was before it hit the Earth’s atmosphere, we can actually (determine) where they came from in the asteroid belt. Golden is one of those,” he said, referring to the location of where the meteorite landed.
Researchers determined the meteorite is an L chondrite, one of the most commonly found types of meteorites to fall to Earth. Despite this, he said only about five L chondrites have known orbits.
He said the Canadian team is now working with scientists in Switzerland, the U.K., U.S. and Italy to learn more about the meteorite and its path to Golden.
“We know we’re still going to get something interesting out of this,” McCausland said. “We actually do want to get a good handle on how things get delivered from the asteroid belt, and this is a useful part of putting that together.”
Most of the meteorite has been returned to Ruth Hamilton, the woman who had the close call, and McCausland said it’s up to her to decide what to do with it.
Whether she decides to keep, sell or donate the rock, he said there is cultural significance of the rock to Canada. If she sells it to an international buyer, she would be required to go through the exportation process, he said.
Hamilton said she hasn’t yet made up her mind on what to do with the meteor. It’s currently sitting in a safety deposit box.
“I don’t have any plans for it right now, but once they’re done analyzing it, I’ll get all the documentation that proves it’s a meteorite,” she said. “It’s going to be officially named the Golden Meteorite.”
Before her roof is permanently repaired this spring, Hamilton said she intends to remove the section where the meteorite crashed through to keep it preserved alongside the rock.
McCausland said the research will likely conclude in May, and the scientists will then publish their work in an academic journal.
“Whenever something like this happens, I like to tell people it could happen to any of us; anyone can find a meteorite. It’s unlikely one will crash through your roof, but it can happen,” McCausland said. “It’s nature and, if anything, it’s a reminder that we’re part of something bigger.”
Elon Musk’s Starlink Is Causing More Streaks to Appear in Space Images – Gizmodo
Researchers at the Zwicky Transient Facility in California have analyzed the degree to which SpaceX’s Starlink satellite constellation is affecting ground-based astronomical observations. The results are mixed.
The new paper, published in The Astrophysical Journal Letters and led by former Caltech postdoctoral scholar Przemek Mróz, offers some good news and some bad news. The good news is that Starlink is not currently causing problems for scientists at the Zwicky Transient Facility (ZTF), which operates out of Caltech’s Palomar Observatory near San Diego. ZTF, using both optical and infrared wavelengths, scans the entire night sky once every two days in an effort to detect sudden changes in space, such as previously unseen asteroids and comets, stars that suddenly go dim, or colliding neutron stars.
But that doesn’t mean Starlink satellites, which provide broadband internet from low Earth orbit, aren’t having an impact. The newly completed study, which reviewed archival data from November 2019 to September 2021, found 5,301 satellite streaks directly attributable to Starlink. Not surprisingly, “the number of affected images is increasing with time as SpaceX deploys more satellites,” but, so far, science operations at ZTF “have not yet been severely affected by satellite streaks, despite the increase in their number observed during the analyzed period,” the astronomers write in their study.
The bad news has to do with the future situation and how satellite megaconstellations, whether Starlink or some other fleet, will affect astronomical observations in the years to come, particularly observations made during the twilight hours. Indeed, images most affected by Starlink were those taken at dawn or dusk. In 2019, this meant satellite streaks in less than 0.5% of all twilight images, but by August 2019 this had escalated to 18%. Starlink satellites orbit at a low altitude of around 324 miles (550 km), causing them to reflect more sunlight during sunset and sunrise, which creates a problem for observatories at twilight.
Astronomers perform observations at dawn and dusk when searching for near-Earth asteroids that might appear next to the Sun from our perspective. Two years ago, ZTF astronomers used this technique to detect 2020 AV2—the first asteroid entirely within the orbit of Venus. A concern expressed in the new paper is that, when Starlink gets to 10,000 satellites—which SpaceX expects to achieve by 2027—all ZTF images taken during twilight will contain at least one satellite streak. Following yesterday’s launch of a Falcon 9 rocket, the Starlink megaconstellation consists of over 2,000 satellites.
In a Caltech press release, Mróz, now at the University of Warsaw in Poland, said he doesn’t “expect Starlink satellites to affect non-twilight images, but if the satellite constellation of other companies goes into higher orbits, this could cause problems for non-twilight observations.” A pending satellite constellation managed by OneWeb, a UK-based telecommunications firm, will orbit at an operational altitude of 745 miles (1,200 km), for example.
The researchers also estimated the fraction of pixels that are lost as a result of a single satellite streak, finding it to be “not large.” By “not large” they mean 0.1% of all pixels in a single ZTF image.
That said, “simply counting pixels affected by satellite streaks does not capture the entirety of the problem, for example resources that are required to identify satellite streaks and mask them out or the chance of missing a first detection of an object,” the scientists write. Indeed, as Thomas Prince, an astronomer at Caltech and a co-author of the study pointed out in the press release, a “small chance” exists that “we would miss an asteroid or another event hidden behind a satellite streak, but compared to the impact of weather, such as a cloudy sky, these are rather small effects for ZTF.”
SpaceX has not responded to our request for comment.
The scientists also looked into the measures taken by SpaceX to reduce the brightness of Starlink satellites. Implemented in 2020, these measures include visors that prevent sunlight from illuminating too much of the satellite’s surface. These measures have served to reduce the brightness of Starlink satellites by a factor of 4.6, which means they’re now at a 6.8 magnitude (for reference, the brightest stars shine at a magnitude 1, and human eyes can’t see objects much dimmer than 6.0). This marks a major improvement, but it’s still not great, as members of the 2020 Satellite Constellations 1 workshop asked that satellites in LEO have magnitudes above 7.
The current study only considered the impacts of Starlink on the Zwicky Transient Facility. Every observatory will be affected differently by Starlink and other satellites, including the upcoming Vera C. Rubin Observatory, which is expected to be badly affected by megaconstellations. Observatories are also expected to experience problems as a result of radio interference, the appearance of ghost-like artifacts, among other potential issues.
Earth's core is rapidly cooling, study reveals. Is our planet becoming 'inactive'? – USA TODAY
Planet Earth hits 6th warmest year on record
Earth simmered to the sixth hottest year on record in 2021, according to several newly released temperature measurements. (Jan. 13)
Earth’s interior is cooling faster than we previously estimated, according to a recent study, prompting questions about how long people can live on the planet.
There’s no exact timetable on the cooling process, which could eventually turn Earth solid, similar to Mars. But results from a new study, published in the peer-reviewed journal Earth and Planetary Science Letters, focuses on how quickly the core may cool by studying bridgmanite, a heat-conducting mineral commonly found at the boundary between the Earth’s core and mantle.
“Our results could give us a new perspective on the evolution of the Earth’s dynamics,” ETH Zurich professor Motohiko Murakami, the lead author of the study, said in a press release. “They suggest that Earth, like the other rocky planets Mercury and Mars, is cooling and becoming inactive much faster than expected.”
While the process may be moving quicker than previously thought, it’s a timeline that “should be hundreds of millions or even billions of years,” Murakami told USA TODAY.
The boundary between the Earth’s outer core and mantle is where the planet’s internal heat interaction exists. The scientific team studied how much bridgmanite conducts from the Earth’s core and found higher heat flow is coming from the core into the mantle, dissipating the overall heat and cooling much faster than initially thought.
“This measurement system let us show that the thermal conductivity of bridgmanite is about 1.5 times higher than assumed,” Murakami said in the press release. “We still don’t know enough about these kinds of events to pin down their timing.”
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