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Unprecedented collision of heavy and light black holes reveal by Gravitational waves



The gravitational waves from a black-hole merger typically ripple at twice the frequency that the black holes go around each other.


LIGO/T. Pyle

Researchers with the world’s gravitational wave detectors said today they had picked up vibrations from a cosmic collision that harmonized with the opening notes of an Elvis Presley hit. The source was the most exotic merger of two black holes detected yet—a pair in which one weighed more than three times as much as the other. Because of the stark mass imbalance, the collision generated gravitational waves at multiple frequencies, in a harmony Elvis fans would recognize. The chord also confirms a prediction of Einstein’s theory of gravity, or general relativity.

Such mismatched mass events could help theorists figure out how pairs of black holes form in the first place. “Anything that seems to be at the edge of our predictions is most interesting,” says Chris Belczynski, a gravitational theorist at the Polish Academy of Sciences in Warsaw, who was not involved in the observation. But the one event is “not quite in the regime where you can tell the different formation [routes] apart.”

Physicists first detected gravitational waves in 2015, when the Laser Interferometer Gravitational-Wave Observatory (LIGO), a pair of detectors in Washington and Louisiana, spotted two black holes spiraling into each other, generating infinitesimal ripples in spacetime. Two years later, the Virgo detector near Pisa, Italy, joined the hunt, and by August 2017, the detectors had bagged a total of 10 black hole mergers.

All involved pairs of black holes with roughly equal masses, says Maya Fishbach, a physicist and LIGO member at the University of Chicago. But on 12 April 2019, the three detectors detected a black hole merger 2.4 billion light-years away in which one weighed 30 solar masses and the other just eight, says Fishbach, who reported on the event at the American Physical Society’s online April meeting. “This is the first event in which we can confidently say the mass-ratio is not one,” she says.

Ordinarily, two spiraling black holes pump out gravitational waves concentrated at a single frequency: double the rate at which they orbit each other. That doubling arises because of the matched masses of the black holes. Every half orbit they return to a position that’s effectively identical to their original one. But if the black holes have distinctly different masses, then general relativity predicts that they should also generate weaker waves at higher frequencies, or overtones.

The next-strongest note sung by the pair should vibrate at three times the orbital frequency, or one and half times the main gravitational-wave frequency. If the main frequency were a C on a piano, the overtone would be the next higher G—a perfect fifth, and the interval of the first two notes in the melody of Elvis Presley’s hit “I Can’t Help Falling in Love with You.” That is what the LIGO and Virgo researchers detected, says Maximiliano Isi, a physicist and LIGO member at the Massachusetts Institute of Technology, who also spoke at the meeting. The overtone rang roughly as loudly as predicted by general relativity, Isi says. “Einstein prevails again.”

Such oddball events might help researchers figure out how the black holes pair in the first place. That’s a puzzle because it’s not obvious how such big black holes can form so close together. Theorists have two general ideas. The pairs could originate from a pair of orbiting massive stars, which each collapse into black holes at the ends of their lives. Alternatively, in so-called dynamical models, the black holes might form completely separately and find each other across space and time, a scenario more likely in globular clusters, the dense clumps of stars found in the outer reaches of galaxies.

Either scenario can probably account for the mismatched black holes in this event, Belczynski says. “If it [the mass ratio] had been 10-to-1 I would have bet on the dynamical models,” he says, as binary star systems generally don’t form with such skewed ratios. Fishbach agrees that the single event isn’t enough to rule out one scenario or the other. But she says that if LIGO and Virgo spot more mismatched events, the statistical distributions could suggest which scenario is more likely.

However, the event could have a more complex origin, says Emanuele Berti, a gravitational wave astronomer at Johns Hopkins University. The fact that the one black hole is so much heavier than the other and appears to be spinning fast suggest that it, too, was the product of a merger. “It looks quiet like the product of a multiple-generation merger,” he says.

More peculiar collisions might be waiting among the dozens of recorded events that researchers have yet to analyze. LIGO and Virgo’s observing run 3, which went from 1 April 2019 until 26 March, picked up 56 new gravitational wave events, more than five times the previous total. LIGO and Virgo researchers had hoped to finish a global analysis of roughly half that data set by now, but the coronavirus pandemic delayed them, says Patrick Brady, a physicist at the University of Wisconsin, Milwaukee, and spokesperson for the LIGO scientific collaboration. Belczynski says he’s anxious to see those results. “I’m just sitting here with my students, my entire group, waiting for this paper.”

Edited by Harry Miller

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Neutrinos Yield First Experimental Evidence of the CNO Energy-Production Mechanism of the Universe – SciTechDaily



View into the interior of the Borexino detector. Credit: Borexino Collaboration

Neutrinos Yield First Experimental Evidence of Catalyzed Fusion Dominant in Many Stars

An international team of about 100 scientists of the Borexino Collaboration, including particle physicist Andrea Pocar at the University of Massachusetts Amherst, report in Nature this week detection of neutrinos from the sun, directly revealing for the first time that the carbon-nitrogen-oxygen (CNO) fusion-cycle is at work in our sun.

The CNO cycle is the dominant energy source powering stars heavier than the sun, but it had so far never been directly detected in any star, Pocar explains.

For much of their life, stars get energy by fusing hydrogen into helium, he adds. In stars like our sun or lighter, this mostly happens through the ‘proton-proton’ chains. However, many stars are heavier and hotter than our sun, and include elements heavier than helium in their composition, a quality known as metallicity. The prediction since the 1930’s is that the CNO-cycle will be dominant in heavy stars.

Neutrinos emitted as part of these processes provide a spectral signature allowing scientists to distinguish those from the ‘proton-proton chain’ from those from the ‘CNO-cycle.’ Pocar points out, “Confirmation of CNO burning in our sun, where it operates at only one percent, reinforces our confidence that we understand how stars work.”

Borexino Detector Under Apennine Mountains

The Borexino detector lies deep under the Apennine Mountains in central Italy at the INFN’s Laboratori Nazionali del Gran Sasso. It detects neutrinos as flashes of light produced when neutrinos collide with electrons in 300-tons of ultra-pure organic scintillator. Credit: Borexino Collaboration

Beyond this, CNO neutrinos can help resolve an important open question in stellar physics, he adds. That is, how the sun’s central metallicity, as can only be determined by the CNO neutrino rate from the core, is related to metallicity elsewhere in a star. Traditional models have run into a difficulty – surface metallicity measures by spectroscopy do not agree with the sub-surface metallicity measurements inferred from a different method, helioseismology observations. 

Pocar says neutrinos are really the only direct probe science has for the core of stars, including the sun, but they are exceedingly difficult to measure. As many as 420 billion of them hit every square inch of the earth’s surface per second, yet virtually all pass through without interacting. Scientists can only detect them using very large detectors with exceptionally low background radiation levels. 

The Borexino detector lies deep under the Apennine Mountains in central Italy at the INFN’s Laboratori Nazionali del Gran Sasso. It detects neutrinos as flashes of light produced when neutrinos collide with electrons in 300-tons of ultra-pure organic scintillator. Its great depth, size, and purity make Borexino a unique detector for this type of science, alone in its class for low-background radiation, Pocar says. The project was initiated in the early 1990s by a group of physicists led by Gianpaolo Bellini at the University of Milan, Frank Calaprice at Princeton and the late Raju Raghavan at Bell Labs.

Until its latest detections, the Borexino collaboration had successfully measured components of the ‘proton-proton’ solar neutrino fluxes, helped refine neutrino flavor-oscillation parameters, and most impressively, even measured the first step in the cycle: the very low-energy ‘pp’ neutrinos, Pocar recalls.

Its researchers dreamed of expanding the science scope to also look for the CNO neutrinos – in a narrow spectral region with particularly low background – but that prize seemed out of reach. However, research groups at Princeton, Virginia Tech and UMass Amherst believed CNO neutrinos might yet be revealed using the additional purification steps and methods they had developed to realize the exquisite detector stability required.

Over the years and thanks to a sequence of moves to identify and stabilize the backgrounds, the U.S. scientists and the entire collaboration were successful. “Beyond revealing the CNO neutrinos which is the subject of this week’s Nature article, there is now even a potential to help resolve the metallicity problem as well,” Pocar says.

Before the CNO neutrino discovery, the lab had scheduled Borexino to end operations at the close of 2020. But because the data used in the analysis for the Nature paper was frozen, scientists have continued collecting data, as the central purity has continued to improve, making a new result focused on the metallicity a real possibility, Pocar says. Data collection could extend into 2021 since the logistics and permitting required, while underway, are non-trivial and time-consuming. “Every extra day helps,” he remarks.

Pocar has been with the project since his graduate school days at Princeton in the group led by Frank Calaprice, where he worked on the design, construction of the nylon vessel and the commissioning of the fluid handling system. He later worked with his students at UMass Amherst on data analysis and, most recently, on techniques to characterize the backgrounds for the CNO neutrino measurement.

Reference: “Experimental evidence of neutrinos produced in the CNO fusion cycle in the Sun” by The Borexino Collaboration, 25 November 2020, Nature.
DOI: 10.1038/s41586-020-2934-0

This work was supported in the U.S. by the National Science Foundation. Borexino is an international collaboration also funded by the Italian National Institute for Nuclear Physics (INFN), and funding agencies in Germany, Russia and Poland.

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China's Chang'e-5 probe completes second orbital correction – ecns



China’s lunar probe Chang’e-5 successfully carried out its second orbital correction Wednesday night, according to the China National Space Administration (CNSA).

The probe conducted the orbital correction at 10:06 p.m. (Beijing Time), when its two 150N engines were operational for about six seconds.

Prior to the orbital correction, the lunar probe had traveled for roughly 41 hours in orbit, and was about 270,000 km away from Earth. All of the probe’s systems were in good condition.

The CNSA said that the tracking of the probe by ground monitoring and communication centers and stations is going smoothly.

China launched the lunar probe Tuesday to collect and return samples from the moon. It is the country’s first attempt to retrieve samples from an extraterrestrial body.

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This rocks! Western University student spots never-before-seen asteroid – Belleville Intelligencer



A Western University astronomy student from Chatham, who’s been stargazing since he was a kid, has discovered an asteroid through remote access to a telescope in Spain.

Graduate student Cole Gregg, 22, was using a telescope based at an observatory known as Astrocamp to troll the night sky when he spotted the small, fast-moving, flashing object.

His find — an asteroid estimated to be about 50 to 100 metres long — came after months of seeing nothing notable during his studies. It was, to put it mildly, “unexpected,” Gregg said Wednesday.

“It was quite shocking. You are not really ready for it,” he said. “It takes you by surprise and it was very exciting.”

Using the telescope located on a Spanish mountaintop, Gregg said he observed the asteroid as it sped close to Earth, moving through near-space across Europe.

Gregg’s astronomy professor, Paul Wiegert, called it “a rare treat to be the first person to spot one of these visitors to our planet’s neighbourhood.”

Added Wiegert: “Astronomers around the globe are continuously monitoring near-Earth space for asteroids so this is certainly a feather in Cole’s cap.”

Western astronomy student Cole Gregg monitors the night skies. Gregg discovered the asteroid ALA2xH a week ago.

Gregg spotted the asteroid, given the temporary designation ALA2xH, on Nov. 18. Data collected about the asteroid was sent to the Minor Planet Center in Cambridge, Mass., to determine whether the observation was unique or not.

From there, it goes on their near-Earth object confirmation page.

Gregg used a website called Itelescope, which allows the public to access telescopes via the internet.

“A lot of people use them for the pretty astrophotography pictures, but they are quite capable of science as well,” Gregg said. “My project is proving that these small telescopes are quite capable of science.”

Despite their efforts, Gregg said they have not spotted the asteroid again “due to weather and unavailability of the telescopes.”

Gregg said he has been fascinated with space since he was camping as a boy and relished looking up at stars in the dark skies. “It sparked my interest.”

After completing his PhD in astronomy, he hopes to continue his research and teach.

“I’m interested in asteroids and comets and how they move, how they exist in the solar system and where they come from,” he said. “And how we can learn from our own solar system to understand . . . other solar systems in the galaxy.”

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