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Super-bright stellar explosion is likely a dying star giving birth to a black hole or neutron star – Phys.org

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In June of 2018, telescopes around the world picked up a brilliant blue flash from the spiral arm of a galaxy 200 million light years away. The powerful burst appeared at first to be a supernova, though it was much faster and far brighter than any stellar explosion scientists had yet seen. The signal, procedurally labeled AT2018cow, has since been dubbed simply “the Cow,” and astronomers have catalogued it as a fast blue optical transient, or FBOT—a bright, short-lived event of unknown origin.

Now an MIT-led team has found strong evidence for the signal’s source. In addition to a bright optical flash, the scientists detected a strobe-like pulse of high-energy X-rays. They traced hundreds of millions of such X-ray pulses back to the Cow, and found the pulses occurred like clockwork, every 4.4 milliseconds, over a span of 60 days.

Based on the frequency of the pulses , the team calculated that the X-rays must have come from an measuring no more than 1,000 kilometers wide, with a mass smaller than 800 suns. By astrophysical standards, such an object would be considered compact, much like a or a neutron star.

Their findings, published today in the journal Nature Astronomy, strongly suggest that AT2018cow was likely a product of a dying star that, in collapsing, gave birth to a compact object in the form of a black hole or neutron star. The newborn object continued to devour surrounding material, eating the star from the inside—a process that released an enormous burst of energy.

“We have likely discovered the birth of a compact object in a supernova,” says lead author Dheeraj “DJ” Pasham, a research scientist in MIT’s Kavli Institute for Astrophysics and Space Research. “This happens in normal supernovae, but we haven’t seen it before because it’s such a messy process. We think this new evidence opens possibilities for finding baby or baby .”

“The core of the Cow”

AT2018cow is one of many “astronomical transients” discovered in 2018. The “cow” in its name is a random coincidence of the astronomical naming process (for instance, “aaa” refers to the very first astronomical transient discovered in 2018). The signal is among a few dozen known FBOTs, and it is one of only a few such signals that have been observed in real-time. Its powerful flash—up to 100 times brighter than a typical supernova—was detected by a survey in Hawaii, which immediately sent out alerts to observatories around the world.

“It was exciting because loads of data started piling up,” Pasham says. “The amount of energy was orders of magnitude more than the typical core collapse supernova. And the question was, what could produce this additional source of energy?”

Astronomers have proposed various scenarios to explain the super-bright signal. For instance, it could have been a product of a black hole born in a supernova. Or it could have resulted from a middle-weight black hole stripping away material from a passing star. However, the data collected by optical telescopes haven’t resolved the source of the signal in any definitive way. Pasham wondered whether an answer could be found in X-ray data.

“This signal was close and also bright in X-rays, which is what got my attention,” Pasham says. “To me, the first thing that comes to mind is, some really energetic phenomenon is going on to generate X-rays. So, I wanted to test out the idea that there is a black hole or compact object at the core of the Cow.”

Finding a pulse

The team looked to X-ray data collected by NASA’s Neutron Star Interior Composition Explorer (NICER), an X-ray-monitoring telescope aboard the International Space Station. NICER started observing the Cow about five days after its initial detection by optical telescopes, monitoring the signal over the next 60 days. This data was recorded in a publicly available archive, which Pasham and his colleagues downloaded and analyzed.

The team looked through the data to identify X-ray signals emanating near AT2018cow, and confirmed that the emissions were not from other sources such as instrument noise or cosmic background phenomena. They focused on the X-rays and found that the Cow appeared to be giving off bursts at a frequency of 225 hertz, or once every 4.4 milliseconds.

Pasham seized on this pulse, recognizing that its frequency could be used to directly calculate the size of whatever was pulsing. In this case, the size of the pulsing object cannot be larger than the distance that the speed of light can cover in 4.4 milliseconds. By this reasoning, he calculated that the size of the object must be no larger than 1.3×108 centimeters, or roughly 1,000 kilometers wide.

“The only thing that can be that small is a compact object—either a neutron star or black hole,” Pasham says.

The team further calculated that, based on the energy emitted by AT2018cow, it must amount to no more than 800 solar masses.

“This rules out the idea that the signal is from an intermediate black hole,” Pasham says.

Apart from pinning down the source for this particular signal, Pasham says the study demonstrates that X-ray analyses of FBOTs and other ultrabright phenomena could be a new tool for studying infant black holes.

“Whenever there’s a new phenomenon, there’s excitement that it could tell something new about the universe,” Pasham says. “For FBOTs, we have shown we can study their pulsations in detail, in a way that’s not possible in the optical. So, this is a new way to understand these newborn compact objects.”


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More information:
Dheeraj Pasham, Evidence for a compact object in the aftermath of the extragalactic transient AT2018cow, Nature Astronomy (2021). DOI: 10.1038/s41550-021-01524-8. www.nature.com/articles/s41550-021-01524-8

Citation:
Super-bright stellar explosion is likely a dying star giving birth to a black hole or neutron star (2021, December 13)
retrieved 13 December 2021
from https://phys.org/news/2021-12-super-bright-stellar-explosion-dying-star.html

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Consistent Asteroid Collisions Rock Previous Thinking on Mars Impact Craters – SciTechDaily

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This image provides a perspective view of a triple crater in the ancient Martian highlands. Credit: ESA/DLR/FU Berlin

New Curtin University research has confirmed the frequency of asteroid collisions that formed impact craters on <span aria-describedby="tt" class="glossaryLink" data-cmtooltip="

Mars
Mars is the second smallest planet in our solar system and the fourth planet from the sun. Iron oxide is prevalent in Mars’ surface resulting in its reddish color and its nickname "The Red Planet." Mars’ name comes from the Roman god of war.

“>Mars has been consistent over the past 600 million years.

New Curtin University research has confirmed the frequency of asteroid collisions that formed impact craters on Mars has been consistent over the past 600 million years.

The study, published in Earth and Planetary Science Letters, analyzed the formation of more than 500 large Martian craters using a crater detection algorithm previously developed at Curtin, which automatically counts the visible impact craters from a high-resolution image.

Despite previous studies suggesting spikes in the frequency of asteroid collisions, lead researcher Dr. Anthony Lagain, from Curtin’s School of Earth and Planetary Sciences, said his research had found they did not vary much at all for many millions of years.

Impact Craters on Mars

One of the 521 large craters that has been dated in the study. The formation age of this 40km crater has been estimated using the number of small craters accumulated around it since the impact occurred. A portion of these small craters are shown on the right panel and all of them have been detected using the algorithm. In total, more than 1.2 million craters were used to date the Martian craters. Credit: Curtin University

Dr. Lagain said counting impact craters on a planetary surface was the only way to accurately date geological events, such as canyons, rivers, and volcanoes, and to predict when, and how big, future collisions would be.

“On Earth, the erosion of plate tectonics erases the history of our planet. Studying planetary bodies of our Solar System that still conserve their early geological history, such as Mars, helps us to understand the evolution of our planet,” Dr. Lagain said.

“The crater detection algorithm provides us with a thorough understanding of the formation of impact craters including their size and quantity, and the timing and frequency of the asteroid collisions that made them.”

Past studies had suggested that there was a spike in the timing and frequency of asteroid collisions due to the production of debris, Dr. Lagain said.

“When big bodies smash into each other, they break into pieces or debris, which is thought to have an effect on the creation of impact craters,” Dr. Lagain said.

“Our study shows it is unlikely that debris resulted in any changes to the formation of impact craters on planetary surfaces.”

Co-author and leader of the team that created the algorithm, Professor Gretchen Benedix, said the algorithm could also be adapted to work on other planetary surfaces, including the Moon.

“The formation of thousands of lunar craters can now be dated automatically, and their formation frequency analyzed at a higher resolution to investigate their evolution,” Professor Benedix said.

“This will provide us with valuable information that could have future practical applications in nature preservation and agriculture, such as the detection of bushfires and classifying land use.”

Reference: “Has the impact flux of small and large asteroids varied through time on Mars, the Earth and the Moon?” by Anthony Lagain, Mikhail Kreslavsky, David Baratoux, Yebo Liu, Hadrien Devillepoix, Philip Bland, Gretchen K. Benedix, Luc S. Doucet and Konstantinos Servis, 7 January 2022, Earth and Planetary Science Letters.
DOI: 10.1016/j.epsl.2021.117362

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B.C. researchers uncover mechanism that keeps large whales from drowning while feeding on krill – CTV News Vancouver

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Vancouver –

New research from the University of British Columbia is shedding light on the ways that whales feed underwater without flooding their airways with seawater.

The research, published this month in Current Biology, shows that lunge-feeding whales – the type that lunge and gulp at large schools of krill – have a special mechanism in the back of their mouths that stops water from entering their lungs when eating.

“It’s kind of like when a human’s uvula moves backwards to block our nasal passages, and our windpipe closes up while swallowing food,” says lead author Dr. Kelsey Gil, a postdoctoral researcher in the department of zoology, in a statement.

Specifically, a fleshy bulb acts as a plug, to close off upper airways, while a larynx closes to block lower airways.

The humpback whale and the blue whale are both lunge-feeders, but the scientists’ research focused on fin whales, thanks in part to being able to travel to Iceland in 2018 and examine carcass remains at a commercial whaling station.

“We haven’t seen this protective mechanism in any other animals, or in the literature. A lot of our knowledge about whales and dolphins comes from toothed whales, which have completely separated respiratory tracts, so similar assumptions have been made about lunge-feeding whales,” Gil said.

Lunge-feeders are impressive, Gil said, because sometimes the amount of food and water they consume is larger than their bodies. After snapping at krill, and while blocking the water from their airways, the whales then drain the ocean water through their baleen, leaving behind the tasty fish.

The study’s senior author Dr. Robert Shadwick, a professor in the UBC department of zoology, says the efficiency of the whales’ feeding is a key factor in their evolution.

“Bulk filter-feeding on krill swarms is highly efficient and the only way to provide the massive amount of energy needed to support such a large body size. This would not be possible without the special anatomical features we have described,” he said in a statement. 

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Study confirmed the frequency of asteroid collisions that formed Mars craters – Tech Explorist

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Mapping and counting impact craters are the most commonly used technique to derive detailed insights on geological events and processes shaping the surface of terrestrial planets. Scientists from Curtin University have used a crater detection algorithm to analyze the formation of more than 500 large Martian craters.

The algorithm they used automatically counts the visible impact craters from a high-resolution image. Scientists found that the frequency of asteroid collisions that formed Mars craters has been consistent for over 600 million years.

Lead scientist Dr. Anthony Lagain from Curtin’s School of Earth and Planetary Sciences said, “Despite previous studies suggesting spikes in the frequency of asteroid collisions, this research had found they did not vary much at all for many millions of years.”

“Counting impact craters on a planetary surface was the only way to accurately date geological events, such as canyons, rivers, and volcanoes, and to predict when, and how big, future collisions would be.”

“On Earth, the erosion of plate tectonics erases the history of our planet. Studying planetary bodies of our Solar System that still conserve their early geological history, such as Mars, helps us to understand the evolution of our planet.”

“The crater detection algorithm provides us with a thorough understanding of the formation of impact craters, including their size and quantity, and the timing and frequency of the asteroid collisions that made them.”

“Past studies had suggested that there was a spike in the timing and frequency of asteroid collisions due to the production of debris.”

“When big bodies smash into each other, they break into pieces of debris, which is thought to affect the creation of impact craters.”

“Our study shows it is unlikely that debris resulted in any changes to the formation of impact craters on planetary surfaces.”

Co-author and leader of the team that created the algorithm, Professor Gretchen Benedix, said“the algorithm could also be adapted to work on other planetary surfaces, including the Moon.”

“The formation of thousands of lunar craters can now be dated automatically, and their formation frequency analyzed at a higher resolution to investigate their evolution.”

“This will provide us with valuable information that could have future practical applications in nature preservation and agriculture, such as the detection of bushfires and classifying land use.”

Journal Reference:

  1. Anthony Lagain et al. Has the impact flux of small and large asteroids varied through time on Mars, the Earth, and the Moon? DOI: 10.1016/j.epsl.2021.117362

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