Stars, supernovae, black holes and stellar remnants

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caltrek
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Re: Stars, supernovae, black holes and stellar remnants

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Surprise Magnetic Signal May Finally Solve The Mystery of Fast Radio Bursts
by Shi Dai
May 12, 2023

Introduction:
(Science Alert) Fast radio bursts – intense, milliseconds-long flashes of radio energy from outer space – have puzzled astronomers since they were first spotted in 2007. A single burst can emit as much energy in its brief life as the Sun does in a few days.

The great majority of the short-lived pulses originate outside our Milky Way galaxy. We don't know what produces most of them, or how.

In new research published in Science, we observed a repeating fast radio burst for more than a year and discovered signs it is surrounded by a strong but highly changeable magnetic field.

Our results suggest the source of this cosmic explosion may be a binary system made up of a neutron star whirling through winds of dense, magnetized plasma produced by a massive companion star or even a black hole.

Read more here: https://www.sciencealert.com/surprise- ... o-bursts
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Re: Stars, supernovae, black holes and stellar remnants

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Biggest cosmic explosion ever seen: 100x the width of our solar system
By Michael Irving
May 14, 2023
https://newatlas.com/space/biggest-cosm ... ever-seen/
Astronomers have captured the biggest cosmic explosion ever detected. About 100 times bigger than the solar system and two trillion times brighter than the Sun at its peak, the mysterious miasma has remained visible for three years.

The universe is full of extreme events – stars go supernova with some regularity, black holes swallow objects with powerful burps, and cosmic collisions give off so much energy they distort the very fabric of space and time.

But this new event is more energetic than anything else ever seen. Designated somewhat anticlimactically as AT2021lwx, the explosion has been visible since 2020 in the constellation Vulpecula, about 8 billion light-years away.

It was first detected by the Zwicky Transient Facility (ZTF) and then the Asteroid Terrestrial-impact Last Alert System (ATLAS), both of which are designed to pick up signals from space that change in brightness over time. Usually this includes things like supernova going off or asteroids and comets whizzing around, but this was obviously something different.

“We came upon this by chance, as it was flagged by our search algorithm when we were searching for a type of supernova,” said Dr Philip Wiseman, lead researcher on the study. “Most supernovae and tidal disruption events only last for a couple of months before fading away. For something to be bright for two plus years was immediately very unusual.”
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Re: Stars, supernovae, black holes and stellar remnants

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Latest research provides scientists close-up views of energetic particle jets ejected from the sun
https://phys.org/news/2023-05-latest-sc ... getic.html
Image
by Southwest Research Institute
Southwest Research Institute (SwRI) scientists observed the first close-ups of a source of energetic particles expelled from the sun, viewing them from just half an astronomical unit (AU), or about 46.5 million miles. The high-resolution images of the solar event were provided by ESA's Solar Orbiter, a sun-observing satellite launched in 2020.

"In 2022, the Solar Orbiter detected six recurrent energetic ion injections. Particles emanated along the jets, a signature of magnetic reconnection involving field lines open to interplanetary space," said SwRI's Dr. Radoslav Bucik, the lead author of a new study published this month in Astronomy & Astrophysics Letters. "The Solar Orbiter frequently detects this type of activity, but this period showed very unusual elemental compositions."

In one ion injection, the intensity of the rare isotope Helium-3 exceeded the amount of hydrogen, the most abundant element on the sun, and the levels of iron were similar to the isotope Helium-4, the second most abundant element on the sun. In another injection two days later, the amount of Helium-3 had significantly decreased to an almost negligible amount.

"Our analysis shows that the elemental and spectral variations in recurrent injections are associated with the shape of the jet, the size of the jet source and the distribution of the underlying photospheric field that evolved over time," Bucik said. "We believe that understanding the variability in recurrent events from a single source sheds light on the acceleration mechanism in solar flares."

The observations made by Solar Orbiter are unique as the propagation effects that can affect abundances could be minimal near the sun. The distance of just 0.5 AU has given the scientific team a remarkably detailed view of solar events.
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Re: Stars, supernovae, black holes and stellar remnants

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James Webb Telescope finds evidence of 'celestial monster' stars the size of 10,000 suns lurking at the dawn of time


By Ben Turner published about 5 hours ago
The James Webb Space Telescope has found key chemical fingerprints of supermassive stars just 440 million years after the Big Bang.



Globular clusters like this one contain hundreds of thousands to millions of stars -- including some of the oldest in the universe. (Image credit: NASA Goddard)

The James Webb Space Telescope (JWST) has discovered the first evidence that millions of supermassive stars up to 10,000 times the mass of the sun may be hiding at the dawn of the universe.

Born just 440 million years after the Big Bang, the stars could shed light on how our universe was first seeded with heavy elements. Researchers, who dubbed the giant stars "celestial monsters," published their findings May 5 in the journal Astronomy and Astrophysics.

"Today, thanks to the data collected by the James Webb Space Telescope, we believe we have found a first clue of the presence of these extraordinary stars," lead study author Corinne Charbonnel, an astronomy professor at the University of Geneva in Switzerland, said in a statement.

The researchers found chemical traces of the gigantic stars inside globular clusters — clumps of tens of thousands to millions of tightly packed stars, many of which are among the most ancient to have ever formed in our universe. Roughly 180 globular clusters dot our Milky Way galaxy and, because they are so old, serve astronomers as windows through time into the earliest years of our universe.
More:
https://www.livescience.com/space/cosmo ... wn-of-time
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Re: Stars, supernovae, black holes and stellar remnants

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Strange star system may hold first evidence of an ultra-rare 'dark matter star'
By Paul Sutter published 23 May 2023
In a distant star system, a sunlike star orbits an invisible object that may be the first example of a 'boson star' made of dark matter, new research suggests.

Astronomers long thought that a peculiar star system observed by the European Space Agency's Gaia satellite was a simple case of a star orbiting a black hole. But now, two astronomers are challenging that claim, finding that the evidence suggests something far stranger: possibly, a never-before-seen type of star made of invisible dark matter. Their research, which has yet to be peer-reviewed, was published April 18 on the preprint server arXiv.

The system itself consists of a sunlike star and, well, something else. The star weighs a little less than the sun (0.93 solar mass) and has roughly the same chemical abundance as our star. Its mysterious companion is much more massive — around 11 solar masses. The objects orbit each other at a distance of 1.4 astronomical units, about the distance at which Mars orbits the sun, making a complete orbit every 188 days.

What could that dark companion be? One possibility is that it's a black hole. While that would easily fit the bill in terms of the orbital observations, that hypothesis has challenges. Black holes form from the deaths of very massive stars, and for this situation to arise, a sunlike star would have to form in companionship with one of those monsters. While not outright impossible, that scenario requires an extraordinary amount of fine-tuning to make the match happen and to keep these objects in orbit around each other for millions of years.

So perhaps that dark orbital companion is something much more exotic, as researchers propose in the new study. Maybe, they suggest, it's a clump of dark matter particles.
More:
https://www.livescience.com/space/black ... atter-star
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Re: Stars, supernovae, black holes and stellar remnants

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Black hole evaporation: Theoretical study proves Stephen Hawking partially correct
https://phys.org/news/2023-06-black-hol ... ephen.html
by Radboud University Nijmegen
New theoretical research by Michael Wondrak, Walter van Suijlekom and Heino Falcke of Radboud University has shown that Stephen Hawking was right about black holes, although not completely. Due to Hawking radiation, black holes will eventually evaporate, but the event horizon is not as crucial as had been believed. Gravity and the curvature of spacetime cause this radiation too. This means that all large objects in the universe, like the remnants of stars, will eventually evaporate.

Using a clever combination of quantum physics and Einstein's theory of gravity, Stephen Hawking argued that the spontaneous creation and annihilation of pairs of particles must occur near the event horizon (the point beyond which there is no escape from the gravitational force of a black hole).

A particle and its anti-particle are created very briefly from the quantum field, after which they immediately annihilate. But sometimes a particle falls into the black hole, and then the other particle can escape: Hawking radiation. According to Hawking, this would eventually result in the evaporation of black holes.
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Re: Stars, supernovae, black holes and stellar remnants

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The Birth of a Black Hole Created the Brightest Space Explosion Ever Seen
by Michele Starr
June 8, 2023

Introduction:
(Science Alert) A record-breaking space explosion that lit up the sky with the most power we've ever seen was caused by a structured jet carrying massive amounts of exploded star guts pointing directly at Earth, scientists have determined.

The gamma-ray burst GRB 221009A, detected in October of last year, was so bright that our instruments struggled to measure it. But when the first hints of it came through, scientists scrambled to point telescopes in its direction, and with the wealth of data collected, an international team of scientists has finally figured out how the supernova generated such a powerful kaboom.

GRB 221009A, nicknamed the BOAT (for Brightest of All Time), was the result of the death of a massive star a relatively close 2.4 billion light-years away, collapsing down into a black hole after expelling its outer envelope. The gamma-ray burst produced by this collapse contained a narrow, structured jet surrounded by a wider outflow of gas.

This is unexpected; our current models predict that the explosion would produce just a jet. The findings have implications for our understanding of the formation of black holes, and how the brightest explosions in the Universe take place.

"GRB 221009A represents a massive step forward in our understanding of gamma-ray bursts, and demonstrates that the most extreme explosions do not obey the standard physics assumed for garden variety gamma-ray bursts," says astronomer Brendan O'Connor of George Washington University, lead author on the new paper.

Read more here: https://www.sciencealert.com/astronome ... ver-seen


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Re: Stars, supernovae, black holes and stellar remnants

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This collapsed star is turning into an gigantic diamond before our eyes
published 1 day ago

Scientists have discovered a star that is in the process of crystallizing into a celestial diamond.

The star is a white dwarf — the shriveled husk of a sun-like star that burned off most of its fuel before collapsing. For stars with cores made mostly of metallic oxygen and carbon, the cooling process that follows the collapse into a white dwarf will ultimately result in the star crystallizing into a giant diamond. However, this process is so slow that researchers don't think any star in the universe has actually become an enormous orb of bling; scientists estimate such a transition would take one quadrillion years, and the universe is only 13.6 billion years old. (A quadrillion is a thousand trillions, and a trillion is a thousand billions.)

Now, though, researchers think they've found a star that is at the early stages of this transition. The star, dubbed HD 190412 C, is about 104 light-years away in a quadruple star system called HD 190412. The researchers calculated the star's temperature — about 11,420 degrees Fahrenheit (6,300 degrees Celsius) — which puts it into the range of a crystallizing white dwarf. Because the system has other stars that have not yet collapsed into the white dwarf state, the researchers were able to use those still-burning star compositions to determine how much metal is in the white dwarf's core. They also calculated the star's age at about 4.2 billion years.
https://www.space.com/collapsed-star-gi ... ents-61780
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Re: Stars, supernovae, black holes and stellar remnants

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Re: Stars, supernovae, black holes and stellar remnants

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Astronomers Capture Space-Squishing Echoes of Merging Supermassive Black Holes
by Kiona Smith
June 28, 2023

Introduction:
(Inverse) There’s a monster lurking at the center of every galaxy, millions of miles wide and millions of times more massive than our Sun: a supermassive black hole. When two of these cosmic leviathans meet, they fall into a million-year death spiral that ends in a dramatic merger.

The motion of these cosmic leviathans creates long, low-frequency waves in the fabric of spacetime, called nanohertz gravitational waves.

Astronomers just measured these extremely low-frequency gravitational waves for the first time — by turning a whole quadrant of our galaxy into a giant astronomical instrument.

“We’re using a gravitational wave detector the size of the galaxy that’s made out of exotic stars, which just blows my mind,” says the National Radio Astronomy Observatory’s Scott Ransom in a statement.

The U.S.-based NANOGrav collaboration published their findings in a series of papers in The Astrophysical Journal Letters. Other research groups based in Australia, China, Europe, and India made the same discovery independently and are publishing their own papers at the same time. You can read the papers here https://iopscience.iop.org/article/10. ... al-waves
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