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Spacetime ripples reveal black holes gobbling up their neutron star companions – The Weather Network US



Astronomers are reporting an exciting discovery from the depths of the cosmos. Tiny ripples in spacetime have been detected, revealing two separate events where a black hole has swallowed up a neutron star.

A little over five years ago, astronomers announced the very first detection of gravitational waves. These ripples in the very fabric of the universe were the result of two black holes — the most extreme objects in the cosmos — spiralling towards each other and merging in a colossal event.

An artist’s impression of a pair of black holes about to collide to produce an even larger black hole. Credit: Mark Myers, ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav)

Like the aftermath of tossing a pebble in a pond, the merger of these two objects sent ripples radiating outwards through the universe. These ripples were too small to be felt by anyone. Still, they were seen by LIGO — the Laser Interferometer Gravitational-Wave Observatory — which was specifically designed to detect them.

Since that discovery, more gravitational wave detectors have come online, such as the Virgo detector in Italy and the KAGRA detector in Japan. These have led to the discovery of roughly two dozen confirmed mergers and dozens more candidates. Many of the collisions detected have been between black holes. They have also seen mergers between neutron stars.

neutron-star-gravitational-wavesTwo neutron stars spiral in towards one another in this artist impression, setting off ripples through spacetime known as gravitational waves. Credit: R. Hurt/Caltech-JPL

One type of merger that has eluded them so far is between a black hole and a neutron star. There was a possible detection roughly two years ago. Since then, though, it was ruled as more likely a merger between two black holes of different sizes.

Now, an international team of astronomers has made the first confirmed discovery of a black hole-neutron star merger!

Even more remarkable, after years of trying to find just one such merger, the LIGO and Virgo detectors captured two within just 10 days of each other. The first, named GW200105, was spotted on January 5, 2020, where a black hole about nine times the Sun’s mass devoured a neutron star about 1.9 times the Sun’s mass. The second, named GW200115, was seen on January 15, 2020, involving a six-solar-mass black hole and a 1.5-solar-mass neutron star.

black-hole-neutron-star-arcA dense neutron star spirals in towards the maw of a black hole. Credit: Carl Knox/OzGrav ARC Centre of Excellence

The study that details these two discoveries, which involved around 1,400 scientists from across 285 universities and other research organizations, was published in The Astrophysical Journal Letters on June 29, 2021.

“With this new discovery of neutron star-black hole mergers outside our galaxy, we have found the missing type of binary,” Astrid Lamberts, a co-author of the study from Observatoire de la Côte d’Azur, in Nice, France, said in a LIGO press release on Tuesday. “We can finally begin to understand how many of these systems exist, how often they merge, and why we have not yet seen examples in the Milky Way.”

With different detectors in operation in different parts of the world (LIGO Livingston, LIGO Hanford, Virgo, and KAGRA), if they all pick up one of these events, astronomers have a decent chance of locating where it took place in the universe.

For GW200105, though, only LIGO Livingston and Virgo detected it. Furthermore, only LIGO saw a strong signal for it. Thus, while the researchers could narrow down the distance to around 900 million light years away, they couldn’t pinpoint its location. The best they could do was say it occurred in an area of the sky roughly 34,000 times the size of the Moon.

For GW200115, both LIGO detectors and the Virgo detector picked it up. This allowed the astronomers to narrow it down to an area about 3,000 times the size of the Moon and estimate its distance at around 1 billion light years away from us.

When black holes collide, nothing escapes to tip us off. We only detect the ripples through spacetime they produce. However, when neutron stars merge, an explosion of energy and light accompanies it, like the ‘kilonova’ explosion that was detected in 2017.

Watch below: ESO Telescopes Observe ‘Kilonova’ from Gravitational Wave Source

For a black hole devouring a neutron star, however, up until now, there was no telling what we’d see. As it turns out, though, the black holes did not messily tear the neutron stars apart, as a certain blue muppet does with his cookies. Instead, they gobbled up their neutron star companions completely, more like a circular yellow dot-muncher does in his popular video games.

“These were not events where the black holes munched on the neutron stars like the Cookie Monster and flung bits and pieces about,” said co-author Patrick Brady, Spokesperson of the LIGO Scientific Collaboration at the University of Wisconsin-Milwaukee. “That ‘flinging about’ is what would produce light, and we don’t think that happened in these cases.”

“Each collision isn’t just the coming together of two massive and dense objects,” co-author Susan Scott, a Distinguished Professor at Australian National University, said in an ANU press release. “It’s really like Pac-Man, with a black hole swallowing its companion neutron star whole.”


Stars out in the universe come in many different sizes and colours. At the smaller end, there are red dwarfs and yellow Sun-like stars. At the upper limit, there are blue hypergiants and red supergiants, hundreds to thousands of times the size of our Sun. Many of these stars are alone, but they often come in pairs or even groups.

Every one of these stars has a limited life span. Eventually, they all expend the last of the nuclear fuel in their core and die. Their outer layers are blasted out into space, and they leave behind their core as the final remnant of their existence. When this happens to our Sun, the result will be a white dwarf. This remnant will be roughly the size of the Earth but with nearly all the mass of the Sun.

Neutron Star Montreal  NASA's Goddard Space Flight CenterThis illustration compares the size of a neutron star to the area around Montreal. Credit: NASA’s Goddard Space Flight Center

Larger stars have enough mass to crush their cores down almost as far as they can go. In these cases, the leftover remnant is a neutron star — a glowing sphere just 20 kilometres across but packed with more mass than is contained in our Sun.

When the largest stars die, their extreme mass can compress their core past the breaking point of physics. The force of gravity blows past any resistance the matter in the core may muster, collapsing it down to an infinitely small singularity. Surrounding that singularity is a region of space under such extremes that not even light can escape from within it.

Watch below: See the first-ever photo taken of a black hole

When a pair of massive stars have both died and left behind their remnants, the end result can be two neutron stars orbiting each other, or two black holes, or a black hole and a neutron star. This situation isn’t often a stable one, though. The powerful gravitational pull between objects like this causes them to draw closer to one another. They spiral in, getting closer and closer until they eventually collide.

Astrophysicists figured out that if there was such a collision, the titanic forces involved would actually cause the fabric of the universe to warp and ripple. In the moments leading up to the final merger, these ripples would become so extreme that they would radiate outwards from the event, like waves on the surface of a pond. They called these ripples ‘gravitational waves’.

Dual detectors with arrow and stns labeledThe LIGO Hanford Observatory, in Washington State. Credit: Caltech/MIT/LIGO Lab

This led to the invention of LIGO, the Laser Interferometer Gravitational-Wave Observatory. This pair of detectors each fire a laser beam down a set of perpendicular 4 km-long tunnels and watch for tiny wiggles in the point the laser makes on the end target. These wiggles can be as small as the width of a single proton, so gravitational wave astronomers rely on very sensitive instruments to spot them.

The first detection of gravitational waves by LIGO, in 2015, earned a group of scientists the 2017 Nobel Prize in Physics. The Virgo detector in Italy came online shortly after that to aid in searching for more gravitational wave events. KAGRA was built in Japan for the same reason.

“The detector groups at LIGO, Virgo, and KAGRA are improving their detectors in preparation for the next observing run scheduled to begin in summer 2022,” Brady said. “With the improved sensitivity, we hope to detect merger waves up to once per day and to better measure the properties of black holes and super-dense matter that makes up neutron stars.”

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Lake Huron sinkhole surprise: The rise of oxygen on early Earth linked to changing planetary rotation rate –



A scuba diver observes the purple, white and green microbes covering rocks in Lake Huron’s Middle Island Sinkhole. Credit: Phil Hartmeyer, NOAA Thunder Bay National Marine Sanctuary.

The rise of oxygen levels early in Earth’s history paved the way for the spectacular diversity of animal life. But for decades, scientists have struggled to explain the factors that controlled this gradual and stepwise process, which unfolded over nearly 2 billion years.

Now an international research team is proposing that increasing on the early Earth—the spinning of the young planet gradually slowed over time, making the days longer—may have boosted the amount of oxygen released by photosynthetic cyanobacteria, thereby shaping the timing of Earth’s oxygenation.

Their conclusion was inspired by a study of present-day microbial communities growing under extreme conditions at the bottom of a submerged Lake Huron sinkhole, 80 feet below the water’s surface. The water in the Middle Island Sinkhole is rich in sulfur and low in oxygen, and the brightly colored bacteria that thrive there are considered good analogs for the single-celled organisms that formed mat-like colonies billions of years ago, carpeting both land and seafloor surfaces.

The researchers show that longer day length increases the amount of oxygen released by photosynthetic microbial mats. That finding, in turn, points to a previously unconsidered link between Earth’s oxygenation history and its . While the Earth now spins on its axis once every 24 hours, day length was possibly as brief as 6 hours during the planet’s infancy.

The team’s findings are scheduled for publication Aug. 2 in the journal Nature Geoscience.

Lead authors are Judith Klatt of the Max Planck Institute for Marine Microbiology and Arjun Chennu of the Leibniz Centre for Tropical Marine Research. Klatt is a former postdoctoral researcher in the lab of University of Michigan geomicrobiologist Gregory Dick, who is one of the study’s two corresponding authors. The other co-authors are from U-M and Grand Valley State University.

“An enduring question in the Earth sciences has been how did Earth’s atmosphere get its oxygen, and what factors controlled when this oxygenation took place,” Dick said from the deck of the R/V Storm, a 50-foot NOAA research vessel that carried a team of scientists and scuba divers on a sample-collection trip from the town of Alpena, Michigan, to the Middle Island Sinkhole, several miles offshore.

“Our research suggests that the rate at which the Earth is spinning—in other words, its day length—may have had an important effect on the pattern and timing of Earth’s oxygenation,” said Dick, a professor in the U-M Department of Earth and Environmental Sciences.

The researchers simulated the gradual slowing of Earth’s rotation rate and showed that longer days would have boosted the amount of oxygen released by early cyanobacterial mats in a manner that helps explain the planet’s two great oxygenation events.

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The project began when co-author Brian Arbic, a physical oceanographer in the U-M Department of Earth and Environmental Sciences, heard a public lecture about Klatt’s work and noted that day length changes could play a role, over geological time, in the photosynthesis story that Dick’s lab was developing.

Cyanobacteria get a bad rap these days because they are the main culprits behind the unsightly and toxic algal blooms that plague Lake Erie and other water bodies around the world.

But these microbes, formerly known as blue-green algae, have been around for billions of years and were the first organisms to figure out how to capture energy from sunlight and use it to produce organic compounds through photosynthesis—releasing oxygen as a byproduct.

Masses of these simple organisms living in primeval seas are credited with releasing oxygen that later allowed for the emergence of multicellular animals. The planet was slowly transformed from one with vanishingly small amounts of oxygen to present-day atmospheric levels of around 21%.

At the Middle Island Sinkhole in Lake Huron, purple oxygen-producing cyanobacteria compete with white sulfur-oxidizing bacteria that use sulfur, not sunlight, as their main energy source.

In a microbial dance repeated daily at the bottom of the Middle Island Sinkhole, filmy sheets of purple and white microbes jockey for position as the day progresses and as environmental conditions slowly shift. The white sulfur-eating bacteria physically cover the purple cyanobacteria in the morning and evening, blocking their access to sunlight and preventing them from carrying out oxygen-producing photosynthesis.

But when sunlight levels increase to a critical threshold, the sulfur-oxidizing bacteria migrate back down below the photosynthetic cyanobacteria, enabling them to start producing oxygen.

New theory: Earth's longer days kick-started oxygen growth
This June 19, 2019 photo provided by NOAA Thunder Bay National Marine Sanctuary shows purple microbial mats in the Middle Island Sinkhole in Lake Huron, Mich. Small hills and “fingers” like this one in the mats are caused by gases like methane and hydrogen sulfide bubbling up beneath them. Feel like days are just getting longer? They are and it’s a good thing because we wouldn’t have much to breathe if they weren’t, according to a new explanation for how Earth’s oxygen rich atmosphere may have developed because of Earth’s rotation slowing. Scientists provided evidence for this new hypothesis by lab testing gooey smelly purple bacteria from a deep sinkhole in Lake Huron. Credit: Phil Hartmeyer/NOAA Thunder Bay National Marine Sanctuary

The vertical migration of sulfur-oxidizing bacteria has been observed before. What’s new is that the authors of the Nature Geoscience study are the first to link these microbial movements, and the resultant rates of oxygen production, to changing day length throughout Earth’s history.

“Two groups of microbes in the Middle Island Sinkhole mats compete for the uppermost position, with sulfur-oxidizing bacteria sometimes shading the photosynthetically active cyanobacteria,” Klatt said while processing a core sample from Middle Island Sinkhole microbial mats in an Alpena laboratory. “It’s possible that a similar type of competition between microbes contributed to the delay in oxygen production on the early Earth.”

A key to understanding the proposed link between changing day length and Earth’s oxygenation is that longer days extend the afternoon high-light period, allowing photosynthetic cyanobacteria to crank out more oxygen.

“The idea is that with a shorter day length and shorter window for high-light conditions in the afternoon, those white sulfur-eating bacteria would be on top of the photosynthetic bacteria for larger portions of the day, limiting oxygen production,” Dick said as the boat rocked on choppy waters, moored a couple hundred yards from Middle Island.

The present-day Lake Huron microbes are believed to be good analogs for ancient organisms in part because the extreme environment at the bottom of the Middle Island Sinkhole likely resembles the harsh conditions that prevailed in the shallow seas of early Earth.

Lake Huron is underlain by 400-million-year-old limestone, dolomite and gypsum bedrock that formed from the saltwater seas that once covered the continent. Over time, the movement of groundwater dissolved some of that bedrock, forming caves and cracks that later collapsed to create both on-land and submerged sinkholes near Alpena.

Cold, oxygen-poor, sulfur-rich groundwater seeps into the bottom of the 300-foot-diameter Middle Island Sinkhole today, driving away most plants and animals but creating an ideal home for certain specialized microbes.

Dick’s team, in collaboration with co-author Bopaiah Biddanda of the Annis Water Resources Institute at Grand Valley State University, has been studying the microbial mats on the floor of Middle Island Sinkhole for several years, using a variety of techniques. With the help of scuba divers from NOAA’s Thunder Bay National Marine Sanctuary—which is best known for its shipwrecks but is also home to the Middle Island Sinkhole and several others like it—the researchers deployed instruments to the lake floor to study the chemistry and biology there.

They also brought mat samples to the lab to conduct experiments under controlled conditions.

Klatt hypothesized that the link between day length and oxygen release can be generalized to any given mat ecosystem, based on the physics of oxygen transport. She teamed up with Chennu to conduct detailed modeling studies to relate microbial mat processes to Earth-scale patterns over geological timescales.

The modeling studies revealed that day length does, in fact, shape oxygen release from the mats.

“Simply speaking, there is just less time for the oxygen to leave the mat in shorter days,” Klatt said.

This led the researchers to posit a possible link between longer day lengths and increasing atmospheric oxygen levels. The models show that this proposed mechanism might help explain the distinctive stepwise pattern of Earth’s oxygenation, as well as the persistence of low-oxygen periods through most of the planet’s history.

Throughout most of Earth’s history, atmospheric oxygen was only sparsely available and is believed to have increased in two broad steps. The Great Oxidation Event occurred about 2.4 billion years ago and has generally been credited to the earliest photosynthesizing cyanobacteria. Nearly 2 billion years later a second surge in , known as the Neoproterozoic Oxygenation Event, occurred.

Earth’s rotation rate has been slowly decreasing since the planet formed about 4.6 billion years ago due to the relentless tug of the moon’s gravity, which creates tidal friction.

Explore further

Researchers find oxygen spike coincided with ancient global extinction

More information:
Possible link between Earth’s rotation rate and oxygenation, Nature Geoscience (2021). DOI: 10.1038/s41561-021-00784-3 ,

Lake Huron sinkhole surprise: The rise of oxygen on early Earth linked to changing planetary rotation rate (2021, August 2)
retrieved 2 August 2021

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information purposes only.

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Astronomers spot light behind a black hole for the first time, reaffirming Einstein's theory of general relativity – TechSpot



Something to look forward to: An international team of astronomers have observed light from behind a black hole for the first time. Future observatories, like the Advanced Telescope for High Energy Astrophysics (Athena) should provider even higher resolution images with much shorter observation times.1

Led by Stanford University’s Dan Wilkins, the team focused on a black hole that is 10 million times as massive as our sun and located 1,800 million light years away in a galaxy called I Zwicky.

Armed with the European Space Agency’s XMM-Newton and NASA’s NuSTAR space telescopes, the astronomers observed bright flares of X-ray light coming from around the black hole. The X-ray flares echoed off of gas that was falling into the black hole, and as the flares were subsiding, the telescopes were remarkably able to pick up smaller flashes of X-rays that were different “colors.” These were the echoes bouncing off the gas behind the black hole.

“Any light that goes into that black hole doesn’t come out, so we shouldn’t be able to see anything that’s behind the black hole,” Wilkins said. “The reason we can see that is because that black hole is warping space, bending light and twisting magnetic fields around itself,” he added.

The black hole’s gravitational pull is responsible for the warping of space.

This is the first time that astronomers have directly observed light from behind a black hole, and it also matches Einstein’s theory of general relativity, yet again confirming his predictions.

The team’s findings were recently published in the scientific journal Nature.

Image credit Dan Wilkins

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Russian cosmonauts give video tour of module that jolted space station – Euronews



MOSCOW – Russian cosmonauts have given a video tour of the interior of a research module which briefly threw the International Space Station out of control on Thursday a few hours after docking.

Russian space officials said a software glitch and possible lapse in human attention were to blame for the mishap that caused the entire space station to pitch out of its normal flight position 250 miles above the Earth with seven crew members aboard.

Footage published late on Saturday showed cosmonauts Oleg Novitsky and Pyotr Dubrov opening the hatches and giving a short tour inside the Nauka module, the Russian space agency Roscosmos said.

According to NASA‘s account of Thursday’s incident, the mission flight director immediately declared a spaceflight emergency as engineers on the ground struggled to restore stability to the sprawling research satellite.

NASA and Roscosmos each said that the seven crew members – two Russian cosmonauts, three U.S. astronauts and two others from Japan and France – were never in any immediate danger.

Roscosmos, which this week spoke of plans to launch another Russian module to the station in November, has suffered a series of mishaps and corruption scandals, including during the construction of the Vostochny Cosmodrome in the country’s far east where contractors were accused of embezzling state funds.

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