Physicists believe they have detected a striking asymmetry in the arrangements of galaxies in the sky. If confirmed, the finding would point to features of the unknown fundamental laws that operated during the Big Bang.
“If this result is real, someone’s going to get a Nobel Prize,” said Marc Kamionkowski, a physicist at Johns Hopkins University who was not involved in the analysis.
As if playing a cosmic game of Connect the Dots, the researchers drew lines between sets of four galaxies, constructing four-cornered shapes called tetrahedra. When they had built every possible tetrahedron from a catalog of 1 million galaxies, they found that tetrahedra oriented one way outnumber their mirror images.
A hint of the imbalance between tetrahedra and their mirror images was first reported by Oliver Philcox, an astrophysicist at Columbia University in New York, in a paper published in Physical Review D in September. In an independent analysis conducted simultaneously that’s now undergoing peer review, Jiamin Hou and Zachary Slepian of the University of Florida and Robert Cahn of Lawrence Berkeley National Laboratory detected the asymmetry with a level of statistical certainty that physicists usually consider definitive.
But with such a blockbuster finding — and one that’s still under review — experts say caution is warranted.
“There’s no obvious reason that they’ve made a mistake,” said Shaun Hotchkiss, a cosmologist at the University of Auckland. “That doesn’t mean that there isn’t a mistake.”
The putative imbalance violates a symmetry called “parity,” an equivalence of left and right. If the observation withstands scrutiny, physicists think it must reflect an unknown, parity-violating ingredient in the primordial process that sowed the seeds of all the structure that developed in our universe.
“It’s an incredible result — really impressive,” Kamionkowski said. “Do I believe it? I’m going to wait to really celebrate.”
Parity was once a cherished symmetry of physics. But then, in 1957, the Chinese American physicist Chien-Shiung Wu’s nuclear decay experiments revealed that our universe indeed has a slight handedness to it: Subatomic particles involved in the weak nuclear force, which causes nuclear decay, are always magnetically oriented in the opposite direction from the one they move in, so that they spiral like the threads of a left-handed screw. The mirror-image particles — the ones like right-handed screws — don’t feel the weak force.
Wu’s revelation was shocking. “We are all rather shaken by the death of our well-beloved friend, parity,” the physicist John Blatt wrote in a letter to Wolfgang Pauli.
The left-handedness of the weak force has subtle effects that couldn’t have influenced the cosmos on galactic scales. But ever since Wu’s discovery, physicists have sought other ways in which the universe differs from its mirror image.
If, for instance, some primordial parity violation was in effect when the universe was in its infancy, it might have imprinted a twist onto the structure of the cosmos.
At or near the time of the universe’s birth, a field known as the inflaton is thought to have permeated space. A roiling, boiling medium where inflaton particles continuously bubbled up and disappeared, the inflaton field was also repulsive; for the brief time it may have existed, it would have caused our universe to rapidly expand to 100 trillion trillion times its original size. All of those quantum fluctuations of particles in the inflaton field were flung outward and frozen into the cosmos, becoming variations in the density of matter. The denser pockets continued to gravitationally coalesce to produce the galaxies and large-scale structure we see today.
In 1999, researchers including Kamionkowski considered what would happen if more than one field was present before this explosion. The inflaton field could have interacted with another field that could produce right-handed and left-handed particles. If the inflaton treated right-handed particles differently than the left-handed ones, then it could have preferentially created particles of one handedness over the other. This so-called Chern-Simons coupling would have imbued the early quantum fluctuations with a preferred handedness, which would have evolved into an imbalance of left-handed and right-handed tetrahedral arrangements of galaxies.
As for what the additional field might be, one possibility is the gravitational field. In this scenario, a parity-violating Chern-Simons interaction would occur between inflaton particles and gravitons — the quantum units of gravity — which would have popped up in the gravitational field during inflation. Such an interaction would have created a handedness in the density variations of the early universe and, consequently, in today’s large-scale structure.
In 2006, Stephon Alexander, a physicist now at Brown University, suggested that Chern-Simons gravity could also potentially solve one of the biggest mysteries in cosmology: why our universe contains more matter than antimatter. He surmised that the Chern-Simons interaction could have yielded a relative abundance of left-handed gravitons, which would in turn preferentially create left-handed matter over right-handed antimatter.
Alexander’s idea remained relatively obscure for years. When he heard about the new findings, he said, “that was a big surprise.”
Tetrahedra in the Sky
Cahn thought the possibility of solving the matter-antimatter asymmetry puzzle with parity violation in the early universe was “speculative, but also provocative.” In 2019, he decided to look for parity violation in a catalog of galaxies in the Sloan Digital Sky Survey. He didn’t expect to find anything but thought it would be worth a check.
To test whether the galaxy distribution respects or violates parity, he and his collaborators knew they needed to study tetrahedral arrangements of four galaxies. This is because the tetrahedron is the simplest three-dimensional shape, and only 3D objects have a chance at violating parity. To understand this, consider your hands. Because hands are 3D, there’s no way to rotate a left one to make it look like a right one. Flip your left hand over so that the thumbs of both hands are on the left, and your hands still look different — the palms face opposite ways. By contrast, if you trace a left hand on a sheet of paper and cut out the 2D image, flipping the cutout over makes it look like a right hand. The cutout and its mirror image are indistinguishable.
In 2020, Slepian and Cahn came up with a way of defining the “handedness” of a tetrahedral arrangement of galaxies in order to compare the number of left-handed and right-handed ones in the sky. First they took a galaxy and looked at the distances to three other galaxies. If the distances increased in the clockwise direction like a right-handed screw, they called the tetrahedron right-handed. If the distances increased going counterclockwise, it was left-handed.
To determine whether the universe as a whole has a preferred handedness, they had to repeat the analysis for all tetrahedra constructed from their database of 1 million galaxies. There are nearly 1 trillion trillion such tetrahedra — an intractable list to handle one at a time. But a factoring trick developed in earlier work on a different problem allowed the researchers to look at the parity of tetrahedra more holistically: Rather than assembling one tetrahedron at a time and determining its parity, they could take each galaxy in turn and group all other galaxies according to their distances from that galaxy, creating layers like the layers of an onion. By expressing the relative positions of galaxies in each layer in terms of mathematical functions of angles called spherical harmonics, they could systematically combine sets of three layers to make collective tetrahedra.
The researchers then compared the results to their expectations based on parity-preserving laws of physics. Hou led this step, analyzing fake catalogs of galaxies that had been generated by simulating the evolution of the universe starting from tiny, parity-preserving density variations. From these mock catalogs, Hou and her colleagues could determine how the tally of left- and right-handed tetrahedra randomly varies, even in a mirror-symmetric world.
The team found a “seven-sigma” level of parity violation in the real data, meaning that the imbalance between left- and right-handed tetrahedra was seven times as large as could be expected from random chance and other conceivable sources of error.
Kamionkowski called it “incredible that they were able to do that,” adding that “technically, it’s absolutely astounding. It’s a really, really, really complicated analysis.”
Philcox used similar methods (and had co-authored some earlier papers proposing such an analysis with Hou, Slepian and Cahn), but he made some different choices — for example, grouping the galaxies into fewer layers than Hou and colleagues, and omitting some problematic tetrahedra from the analysis — and therefore found a more modest 2.9-sigma violation of parity. The researchers are now studying the differences between their analyses. Even after extensive efforts to understand the data, all parties remain cautious.
The surprising finding hints at new physics that could potentially answer long-standing questions about the universe. But the work has only just begun.
First physicists need to verify (or falsify) the observation. New, ambitious galaxy surveys on which to repeat the analysis are already underway. The ongoing Dark Energy Spectroscopic Instrument survey, for instance, has logged 14 million galaxies so far and will contain more than 30 million when it’s completed. “That’ll give us an opportunity to look at this in much greater detail with much better statistics,” said Cahn.
Moreover, if the parity-violating signal is real, it could show up in data other than the distribution of galaxies. The oldest light in the sky, for example — a bath of radiation known as the cosmic microwave background, left over from the early universe — provides our earliest snapshot of spatial variations in the cosmos. The dappled pattern of this light should contain the same parity-violating correlations as the galaxies that formed later. Physicists say it should be possible to find such a signal in the light.
Another place to look will be the pattern of gravitational waves that may have been generated during inflation, called the stochastic gravitational wave background. These corkscrew-like ripples in the space-time fabric can be right-handed or left-handed, and in a parity-preserving world, they would contain equal amounts of each. So if physicists manage to measure this background and find that one handedness is favored, this would be an unambiguous, independent check of parity-violating physics in the early universe.
As the search for corroborating evidence begins, theorists will study models of inflation that could have produced the signal. With Giovanni Cabass, a theoretical physicist at the Institute for Advanced Study in Princeton, New Jersey, Philcox recently used his measurement to test a slew of parity-violating models of inflation, including those of the Chern-Simons type. (They can’t yet say with certainty which model, if any, is correct.)
Alexander has also refocused his efforts on understanding Chern-Simons gravity. With collaborators including Kamionkowski and Cyril Creque-Sarbinowski of the Flatiron Institute’s Center for Computational Astrophysics, Alexander has begun working out subtle details about how Chern-Simons gravity in the early universe would influence the distribution of today’s galaxies.
“I was kind of like the lone soldier pushing this stuff for a while,” he said. “It’s good to see people taking an interest.”
Editor’s Note: The Flatiron Institute is funded by the Simons Foundation, which also supports this editorially independent magazine. In addition, Oliver Philcox receives funding from the Simons Foundation.
Green comet making its closest approach to Earth in 50,000 years – Yahoo Movies Canada
A rare green comet, that has not been seen for 50,000 years, is about to make its closest pass by Earth, becoming visible in a once-in-a-lifetime opportunity.
Called C/2022 E3 (ZTF), this celestial object hails from the Oort cloud at the outermost edge of the solar system.
Its green glow is a result of ultraviolet radiation from the sun lighting up the gases surrounding the comet’s surface.
The icy ball orbits the sun once every 50,000 years, which means the last time it went past the planet was during the Stone Age – when Neanderthals roamed the Earth.
It is due to pass closest to the planet – still some 42 million kilometres away – on Wednesday night, into the early hours of Thursday and in a very dark sky will appear as a faint smudge to those looking for it with the naked eye.
However, even if the moon is too bright for stargazers to spot the comet on Wednesday night, they might be able to catch a glimpse of it a week later when it passes Mars.
Professor Don Pollacco, from the department of physics at the University of Warwick, told the PA news agency: “Comet C/2022 E3 passes closest to Earth tonight, on 1 February.
“It has been christened the “Green Comet” as pictures show the head of the Comet to have a striking colour.
“We understand this as due to light emitted from carbon molecules ejected from the nucleus due to the increase in heat etc during its closest approach to the sun, which happened around 12 January.
“Some comets approach the sun much closer and are completely evaporated by the intense radiation.”
He added: “As the comet approaches Earth (it’s still 42 million km away, so no chance of a collision) it appears to move more quickly across the sky on a night-by-night basis.
“Tonight the comet is about halfway between the pole star and the bright star Capella, overhead about 11pm.
“However, the waxing moon will make the Comet much harder to spot. To see it you’ll need a clear sky, binoculars and a bit of luck.
“Alternately, if you wait a few days to around 10 February, the moon will be less bright and the comet will be clearer to see in the southern part of the sky, passing Mars.”
The Greenwich Royal Observatory says that from the northern hemisphere, the comet is already visible in the night sky using a telescope or some binoculars.
It adds: “Comet C/2022 E3 (ZTF) will be closest to Earth on February 1. This will also be the moment the comet appears at its brightest, and currently it is expected to reach a brightness magnitude of +6. That would mean it would be visible to the naked eye.
“It’s worth noting, however, that comets can be unpredictable, and it’s hard to say with accuracy how bright the comet will be or what it will look like ahead of time.
“The comet looks like a fuzzy green ball or smudge in the sky. This green glow is a result of UV radiation from the sun lighting up the gases streaming off of the comet’s surface.”
Advising on where the comet can be seen in the night sky, the Observatory says: “When it passes near Earth in February, the green comet will be in the constellation of Camelopardalis.
“After its closest approach, the green comet will move through Auriga and end up in Taurus mid-February.
“The comet will dim over the month as it moves away from us, and the time that it will be up in the sky during the night will get shorter and shorter.”
New AI algorithm helps find 8 radio signals from space
A new artificial intelligence algorithm created by a Toronto student is helping researchers search the stars for signs of life.
Peter Xiangyuan Ma, a University of Toronto undergraduate student and researcher, said he started working on the algorithm while he was in Grade 12 during the pandemic.
“I was just looking for projects and I was interested in astronomy,” he told CTV News Toronto.
The idea was to help distinguish between technological radio signals created by human technologies and signals that were potentially coming from other forms of life in space.
“What we’re looking for is signs of technology that signifies if the sender is intelligent or not. And so unsurprised to us, we keep on finding ourselves,” Ma explained. “We don’t want to be looking at our own noisy signals.”
Using this algorithm, Ma said researchers were able to discover eight new radio signals being emitted from five different stars about 30 to 90 light years away from the Earth.
These signals, Ma said, would disappear when researchers looked away from it, which rules out, for the most part, interference from a signal originating from Earth. When they returned to the area, the signal was still there.
“We’re all very suspicious and scratching our heads,” he said. “We proved that we found things that we wanted to find … now, what do we do with all these? That’s another separate issue.”
Steve Croft, Project Scientist for Breakthrough Listen on the Green Bank Telescope, the institute whose open source data was the inspiration for Ma’s algorithm, said that finding radio signals in space is like trying to find a needle in a haystack.
“You’ve got to recognize the haystack itself and make sure that you don’t throw the needle away as you’re looking at the individual pieces of hay,” Croft, who collaborated on Ma’s research, told CTV News Toronto.
Croft said algorithms being used to discover these signals have to account for multiple characteristics, including the position they are coming from in the sky and whether or not the transmission changes over time, which could indicate if it’s coming from a rotating planet or star.
“The algorithm that Peter developed has enabled us to do this more efficiently,” he said.
The challenge, Croft says, is recognizing that false positives may exist despite a signal meeting this criteria. What could be signs of extraterrestrial life may also just be a “weirdly shaped bit of a haystack,” he added.
“And so that’s why we have to go back and look again and see if the signal still there. And with these particular examples that Peter found with his algorithm, the signal was not there when we pointed the telescope back again. And so we sort of can’t say one way or another, is this genuine?”
Researchers have been searching the sky for technologically-generated signals since the 1960s, searching thousands of stars and galaxies for signs of intelligent life. The process is called “SETI,” or “the Search for Extraterrestrial Intelligence.”
But interference from our own radio signals has always proven to be a challenge. Croft says most pieces of technology have some kind of Bluetooth or wireless wave element that creates static, resulting in larger amounts of data needed to be collected.
“That’s a challenge but also computing provides the solution,” he said.
“So the computing and particularly the machine-learning algorithms gives us the power to search through this big haystack, looking for the needle of an interesting signal.”
Ma said that while we may not have found a “technosignal” just yet, we shouldn’t give up. The next step would be to employ multiple kinds of search algorithms to find more and more signals to study.
While the “dream” is to find evidence of life, Ma says he is more focused on the scientific efforts of actively looking for it.
This sentiment is echoed by Croft, who said he is most fascinating in working towards answering the question of whether humans are alone in this universe.
“I don’t show up to work every day, thinking I’m going to find aliens, but I do show up for work. So you know, I’ve got sort of some optimism.”
How to spot the green comet in Manitoba
Space enthusiasts in the province will get the chance to potentially see a rare green comet over the next couple of days.
The comet was discovered by astronomers in southern California last year and it was determined the last time it passed Earth was around 50,000 years ago.
Mike Jensen, the planetarium and science gallery program supervisor at the Manitoba Museum, said the time between appearances and the colour of the comet makes this unique compared to others.
“The last time it would have appeared anywhere within the region of visibility to Earth, we’re talking primitive humans walking the Earth,” said Jensen. “And then yes, its colour. Most people associate comets, they’re often referred to as ghosts of the night sky because they often have a bit of a whitish-blue appearance. This one’s got a bit of green to it. Comets are all made up of different types of material, this just happens to have a bit more of some carbon elements in it.”
Jensen notes the green tint on the comet will be subtle, comparing it to the subtle red that surrounds Mars in the night sky.
Wednesday and Thursday are the best days to see the comet as Jensen said that’s when it will be closest to Earth – 42 million kilometres away.
“That proximity to us means it does get to its best visibility for us. The added advantage is it’s also appearing sort of high up in the northern sky, which puts it amongst the circumpolar stars of our night sky. In other words, the stars that are circling around the North Star.”
Now, just because the comet is close enough to be visible doesn’t mean it will be the easiest to see in the night sky according to Jensen. He said there are a few factors that play into having a successful sighting.
First, he suggests getting out of the city and away from the lights, noting, the darker it is, the better. If people head outside city limits, Jensen recommends people dress warmly, saying comet watching in the winter is not for the “faint of heart.”
Secondly, he said even though it might be possible to see the comet with the naked eye, he still suggests bringing binoculars to improve people’s chances. He also recommends checking star maps before leaving to get the most accurate location of where the comet may be.
Lastly, even if all of that is achieved, Jensen notes people will have to battle with the light of the moon, as it is close to a full moon.
“I’m not trying to dissuade anybody from going out to see it, but certainly, there’s going to be some hurdles to overcome in order to be able to spot it on your own.”
If people don’t want to go outside to see it, he said there are plenty of resources online to find digital views.
– With files from CTV News’ Michael Lee
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