Scientists have discovered stardust that formed five to seven billion years ago in a meteorite that fell fifty years ago in Australia.
It’s the oldest solid material ever found on Earth—and it has a pungent smell, with one student describing it as resembling “rotten peanut butter.”
These so-called “presolar grains” come from a time before the Sun—and therefore our solar system—existed.
At around seven billion years old, these grains are around 2.5 billion years older than the solar system.
“These are the oldest solid materials ever found, and they tell us about how stars formed in our galaxy,” says Dr. Philipp Heck, a curator at the Field Museum in Chicago, associate professor at the University of Chicago, and lead author of a paper describing the findings in Proceedings of the National Academy of Sciences (PNAS). “They’re solid samples of stars, real stardust.”
It’s a major discovery since presolar grains are found only in about five percent of meteorites that fall to Earth. The research was partly funded by NASA.
What is the Murchison meteorite?
It’s an especially chemically primitive carbonaceous chondrite meteorite that fell near the town of Murchison in Victoria, Australia, on September 28, 1969. It’s one of the most studied meteorites of all because it contains 90 different amino acids, only 19 of which are found on our planet. The Field Museum has the largest portion of the Murchison meteorite.
Why is the Murchison meteorite important?
It’s a wellspring of presolar grains, which are essentially time capsules of the period before the solar system existed. Trapped in meteorites, these grains of stardust have remained unchanged for billions of years.
How were the presolar grains found?
“It starts with crushing fragments of the meteorite down into a powder,” says Jennika Greer, a graduate student at the Field Museum and the University of Chicago and co-author of the study. “Once all the pieces are segregated, it’s a kind of paste, and it has a pungent characteristic-it smells like rotten peanut butter.” That paste was then dissolved with acid to isolate the presolar grains.
Where is the stardust from?
Presolar grains are formed when a star dies. By measuring their exposure to cosmic rays—high-energy particles that fly through our galaxy and penetrate solid matter—using isotopes of Neon, the scientists figured out how old the presolar grains are. Most are 4.6-4.9 billion years old, some are older than 5.5 billion years, but the oldest are 7.5 billion years old.
What does the stardust tell us?
Contrary to the theory that stars form at a steady rate, this study provides evidence that there was a period of intense star formation seven billion years ago. “We have more young grains that we expected,” says Heck. “Our hypothesis is that the majority of those grains, which are 4.9 to 4.6 billion years old, formed in an episode of enhanced star formation … we now have direct evidence for a period of enhanced star formation. This is one of the key findings of our study.”
“It’s so exciting to look at the history of our galaxy,” says Heck. “Stardust is the oldest material to reach Earth, and from it, we can learn about our parent stars, the origin of the carbon in our bodies, the origin of the oxygen we breathe.
Heck and his colleagues hope that their discoveries of the lifetimes of stardust can be used to develop models of the “galactic life cycle.”
Wishing you clear skies and wide eyes.
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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