Stars, supernovae, black holes and stellar remnants

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weatheriscool
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Stars, supernovae, black holes and stellar remnants

Post by weatheriscool »

I've decided to make a thread centered around stars and what they become...As I don't believe they belong in the space general thread but they're still interesting to discus. The general thread should focus on exploration of man and robots.

New supergiant fast X-ray transient discovered
https://phys.org/news/2022-07-supergian ... sient.html
by Tomasz Nowakowski , Phys.org

Image
An international team of astronomers reports the detection of a new supergiant fast X-ray transient with the Monitor of All-sky X-ray Image (MAXI) instrument. The newfound transient, designated MAXI J0709−159, was identified in the constellation Canis Majoris and lasted about three hours. The finding was detailed in a paper published July 5 on the arXiv pre-print server.

Generally, X-ray binaries are composed of a normal star or a white dwarf transferring mass onto a compact neutron star or a black hole. Based on the mass of the companion star, astronomers divide them into low-mass X-ray binaries (LMXB) and high-mass X-ray binaries (HMXB).

Supergiant fast X-ray transients (SFXTs) are a class of HMXBs with supergiant companions. They showcase significant X-ray flaring activity, experiencing outbursts with very fast rise times and typical durations of a few hours that are associated with supergiant stars.

Now, a group of astronomers led by Mutsumi Sugizaki of National Astronomical Observatories in Beijing, China, has detected a new SFXT—MAXI J0709−159 (or MAXI J0709 for short). The transient, lasting approximately three hours, was identified on January 25, 2022, by the MAXI instrument onboard the International Space Station (ISS). Follow-up observations of this source have been also conducted, using NuSTAR, Swift, and eROSITA, in order to determine its properties.
Last edited by weatheriscool on Fri Jul 15, 2022 6:56 am, edited 2 times in total.
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Re: Stars, Super nova, white dwarfs and black holes news and discussion

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A new measurement record for strongest magnetic field in universe
https://phys.org/news/2022-07-strongest ... verse.html
by Chinese Academy of Sciences
Neutron stars have the strongest magnetic fields in the universe, and the only way to measure their surface magnetic field directly is to observe the cyclotron absorption lines in their X-ray energy spectra. The Insight-HXMT team has recently discovered a cyclotron absorption line with an energy of 146 keV in the neutron star X-ray binary Swift J0243.6+6124, corresponding to a surface magnetic field of more than 1.6 billion Tesla. After direct measurement of the strongest magnetic field in the universe at about 1 billion Tesla in 2020, the world records for the highest energy cyclotron absorption line and direct measurement of the strongest magnetic field in the universe have been broken.

The findings, obtained jointly by the Key Laboratory for Particle Astrophysics at the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences and the Institute for Astronomy and Astrophysics, Kepler Center for Astro and Particle Physics, University of Tübingen (IAAT), were published on June 28 in Astrophysical Journal Letters (ApJL). Dr. Kong Lingda, Prof. Zhang Shu, and Prof. Zhang Shuangnan from IHEP are the corresponding authors of the paper. Dr. Victor Doroshenko and Prof. Andrea Santangelo from the University of Tübingen significantly contributed to the discovery.
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Re: Stars, Super nova, white dwarfs and black holes news and discussion

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International team of astronomers discovers two rare binary star systems
https://phys.org/news/2022-07-internati ... inary.html
by Chris Sasaki, University of Toronto
Image
An international team of astronomers has identified only the second and third examples of a rare type of star system comprising two central stars orbiting each other, encompassed by a remarkable disk of gas and dust.

"If there were a planet in one of these systems, it would be like the planet Tatooine from Star Wars," says Michael Poon, a Ph.D. student in the Faculty of Arts & Science's David A. Dunlap Department of Astronomy & Astrophysics and one of two University of Toronto researchers involved in the discovery.

"You would see two suns in the sky orbiting each other. In addition, there's a disk around the stars. Picture Saturn's rings but much, much larger—with the stars in the middle."

Such disks are referred to as protoplanetary disks because they eventually form into families of planets like our solar system. The newly discovered systems are rare because their disks lie at an angle to the orbits of their central stars.
Last edited by weatheriscool on Fri Jul 15, 2022 6:56 am, edited 1 time in total.
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Re: Stars, supernovae, black holes and stellar remnants

Post by wjfox »

Hope you don't mind, but I changed the thread title slightly, to include a wider range of objects.

Edit: Also, would be nice to have some pictures included with these articles, as they tend to be visually interesting. :)
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Re: Stars, supernovae, black holes and stellar remnants

Post by Lorem Ipsum »

wjfox wrote: Wed Jul 13, 2022 9:04 pm Hope you don't mind, but I changed the thread title slightly, to include a wider range of objects.
Space Phenomena News and Discussions?
weatheriscool
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Re: Stars, supernovae, black holes and stellar remnants

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Sounds awesome wjfox

Modeling the merger of a black hole with a neutron star and the subsequent process in a single simulation
https://phys.org/news/2022-07-merger-bl ... -star.html
by Max Planck Society
Image
Using supercomputer calculations, scientists at the Max Planck Institute for Gravitational Physics in Potsdam and from Japan show a consistent picture for the first time: They modeled the complete process of the collision of a black hole with a neutron star. In their studies, they calculated the process from the final orbits through the merger to the post-merger phase in which, according to their calculations, high-energy gamma-ray bursts may occur. The results of their studies have now been published in the journal Physical Review D.

Almost seven years have passed since the first detection of gravitational waves. On September 14, 2015, the LIGO detectors in the U.S. recorded the signal of two merging black holes from the depths of space. Since then, a total of 90 signals have been observed: from binary systems of two black holes or neutron stars, and also from mixed binaries. If at least one neutron star is involved in the merger, there is a chance that not only gravitational-wave detectors will observe the event, but also telescopes in the electromagnetic spectrum.

When two neutron stars merged in the event detected on August 17, 2017 (GW170817), about 70 telescopes on Earth and in space observed the electromagnetic signals. In the two mergers of neutron stars with black holes observed so far (GW200105 and GW200115), no electromagnetic counterparts to the gravitational waves were detected. But when more such events are measured with the increasingly sensitive detectors, the researchers expect electromagnetic observations here as well. During and after the merger, matter is ejected from the system and electromagnetic radiation is generated. This probably also produces short gamma-ray bursts, as observed by space telescopes.
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Re: Stars, supernovae, black holes and stellar remnants

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'Black hole police' discover a dormant black hole outside the Milky Way galaxy
https://phys.org/news/2022-07-black-hol ... milky.html
by Harvard-Smithsonian Center for Astrophysics
A team of international experts who are known for debunking black hole discoveries have found a dormant stellar-mass black hole in the Large Magellanic Cloud, a galaxy that neighbors the Milky Way. The team includes Kareem El-Badry—nicknamed by fellow astronomers as the "black hole destroyer"—of the Center for Astrophysics | Harvard & Smithsonian (CfA).

"For the first time, our team got together to report on a black hole discovery, instead of rejecting one," says study lead Tomer Shenar, a Marie-Curie Fellow at Amsterdam University in the Netherlands.

The team found that the star that gave rise to the black hole vanished without any sign of a powerful explosion.

"We identified a needle in a haystack," says Shenar. Though other similar black hole candidates have been proposed, the team claims this is the first "dormant" stellar-mass black hole to be unambiguously detected outside of the Milky Way galaxy. The work was published today in the journal Nature Astronomy.

Stellar-mass black holes form when massive stars reach the end of their lives and collapse under their own gravity. In a binary, a system of two stars revolving around each other, this process leaves behind a black hole in orbit with a luminous companion star. The black hole is "dormant" if it does not emit high levels of X-ray radiation, which is how such black holes are typically detected
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Re: Stars, supernovae, black holes and stellar remnants

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Supermassive black hole influences star formation
https://phys.org/news/2022-07-supermass ... ation.html
by University of Cologne
A European team of astronomers led by Professor Kalliopi Dasyra of the National and Kapodistrian University of Athens, Greece, under participation of Dr. Thomas Bisbas, University of Cologne modeled several emission lines in Atacama Large Millimeter Array (ALMA) and Very Large Telescope (VLT) observations to measure the gas pressure in both jet-impacted clouds and ambient clouds. With these unprecedented measurements, published recently in Nature Astronomy, they discovered that the jets significantly change the internal and external pressure of molecular clouds in their path.

Depending on which of the two pressures changes the most, both compression of clouds and triggering of star formation and dissipation of clouds and delaying of star formation are possible in the same galaxy. "Our results show that supermassive black holes, even though they are located at the centers of galaxies, could affect star formation in a galaxy-wide manner," said Professor Dasyra. "Studying the impact of pressure changes in the stability of clouds was key to the success of this project. Once few stars actually form in a wind, it is usually very hard to detect their signal on top of the signal of all other stars in the galaxy hosting the wind."

It is believed that supermassive black holes lie at the centers of most galaxies in our universe. When particles that were infalling onto these black holes are trapped by magnetic fields, they can be ejected outwards and travel far inside galaxies in the form of enormous and powerful jets of plasma. These jets are often perpendicular to galactic disks. In IC 5063 however, a galaxy 156 million light years away, the jets are actually propagating within the disk, interacting with cold and dense molecular gas clouds. From this interaction, compression of jet-impacted clouds is theorized to be possible, leading to gravitational instabilities and eventually star formation due to the gas condensation.
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Re: Stars, supernovae, black holes and stellar remnants

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Astronomers develop novel way to 'see' the first stars through the fog of the early universe
https://phys.org/news/2022-07-astronome ... verse.html
by University of Cambridge
A team of astronomers has developed a method that will allow them to "see" through the fog of the early universe and detect light from the first stars and galaxies.

The researchers, led by the University of Cambridge, have developed a methodology that will allow them to observe and study the first stars through the clouds of hydrogen that filled the universe about 378,000 years after the Big Bang.

Observing the birth of the first stars and galaxies has been a goal of astronomers for decades, as it will help explain how the universe evolved from the emptiness after the Big Bang to the complex realm of celestial objects we observe today, 13.8 billion years later.

The Square Kilometre Array (SKA)—a next-generation telescope due to be completed by the end of the decade—will likely be able to make images of the earliest light in the universe, but for current telescopes the challenge is to detect the cosmological signal of the stars through the thick hydrogen clouds.
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Re: Stars, supernovae, black holes and stellar remnants

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Distant Galaxy Hosted One of the Most Powerful Explosions Since the Big Bang
by Kiona Smith
July 27, 2022

Introduction:
(Inverse) THE SMALL, dim, red dot in the center of a newly-released image of a distant galaxy shows it endured one of the most powerful explosions since the Big Bang.

Astronomer Brendan O’Connor and his colleagues recently discovered this still-unnamed galaxy 9 billion light years away in data from the Gemini North Telescope in Hawai’i, and they say it’s the source of a brief, brilliant flare of gamma radiation that dazzled NASA’s Swift Observatory in late 2015.
Imagine an explosion releasing as much energy as our Sun will produce in 10 billion years – compressed into a burst of less than two seconds.

Astronomers call this almost unimaginable cataclysm a short gamma-ray burst, and the universe hasn’t witnessed a brighter or more powerful explosion since the Big Bang. What could cause such an event? The answer seems to involve two neutron stars colliding.

Binary star systems aren’t vanishingly rare in the universe; one of our nearest neighbors, Alpha Centauri, is actually a pair of stars fairly similar to our Sun. On the other hand, binaries involving two neutron stars — the dense ball of neutrons left behind by the death of a star massive enough to cause a supernova, but not quite massive enough to collapse into a black hole — seem to be much rarer.

But every once in a while, a binary pair of neutron stars will pull each other into a gravitational death spiral, eventually colliding with enough force to release a brief burst of gamma rays brighter than a whole galaxy. Astrophysicists say this happens, in most galaxies, a few times every million years.
Read more here: https://www.inverse.com/science/this-g ... cataclysm
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