Stars, supernovae, black holes and stellar remnants

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Re: Stars, supernovae, black holes and stellar remnants

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

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Scientists map gusty winds in a far-off neutron star system
https://phys.org/news/2023-04-scientist ... -star.html
by Massachusetts Institute of Technology
An accretion disk is a colossal whirlpool of gas and dust that gathers around a black hole or a neutron star like cotton candy as it pulls in material from a nearby star. As the disk spins, it whips up powerful winds that push and pull on the sprawling, rotating plasma. These massive outflows can affect the surroundings of black holes by heating and blowing away the gas and dust around them.

At immense scales, "disk winds" can offer clues to how supermassive black holes shape entire galaxies. Astronomers have observed signs of disk winds in many systems, including accreting black holes and neutron stars. But to date, they've only ever glimpsed a very narrow view of this phenomenon.

Now, MIT astronomers have observed a wider swath of winds, in Hercules X-1, a system in which a neutron star is drawing material away from a sun-like star. This neutron star's accretion disk is unique in that it wobbles, or "precesses," as it rotates. By taking advantage of this wobble, the astronomers have captured varying perspectives of the rotating disk and created a two-dimensional map of its winds, for the first time.

The new map reveals the wind's vertical shape and structure, as well as its velocity—around hundreds of kilometers per second, or about a million miles per hour, which is on the milder end of what accretion disks can spin up.
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Re: Stars, supernovae, black holes and stellar remnants

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First Y brown dwarf binary system discovered

by Tomasz Nowakowski , Phys.org
https://phys.org/news/2023-04-brown-dwarf-binary.html
Using the Near Infrared Camera (NIRCam) onboard the James Webb Space Telescope (JWST), an international team of astronomers has discovered the first known binary system composed of two Y-type brown dwarfs. The finding was reported in a research paper published March 29 on the arXiv pre-print repository.

Brown dwarfs are intermediate substellar objects between planets and stars with masses below the hydrogen burning limit—about 80 Jupiter masses. One subclass of brown dwarfs (with effective temperatures lower than 500 K) is known as Y dwarfs, and represents the coolest and least luminous substellar objects so far detected.

WISE J033605.05−014350.4 (or W0336 for short) is a nearby brown dwarf of spectral type Y0 detected in 2012 with NASA's Wide-field Infrared Survey Explorer (WISE). The object is located some 32.7 light years away in the constellation Eridanus and has an effective temperature of about 460 K.

Now, new observations conducted by a group of astronomers led by Per Calissendorf of the University of Michigan in Ann Arbor, unveiled the presence of a companion object to W0336. The brown dwarf was observed in September 2022 as part of a JWST Cycle 1 GO program—a survey of 20 Y dwarfs.

"We report the discovery of the first brown dwarf binary system with a Y dwarf primary, WISE J033605.05−014350.4, observed with NIRCam on JWST with the F150W and F480M filters. We employed an empirical point spread function binary model to identify the companion, located at a projected separation of 0.''084, position angle of 295 degrees, and with contrast of 2.8 and 1.8 magnitudes in F150W and F480M, respectively," the researchers wrote in the paper.
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Re: Stars, supernovae, black holes and stellar remnants

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Metal-poor stars are more life-friendly, suggests study
https://phys.org/news/2023-04-metal-poo ... endly.html
by Max Planck Society

Stars that contain comparatively large amounts of heavy elements provide less favorable conditions for the emergence of complex life than metal-poor stars, as scientists from the Max Planck Institutes for Solar System Research and for Chemistry as well as from the University of Göttingen have now found.

The team showed how the metallicity of a star is connected to the ability of its planets to surround themselves with a protective ozone layer. Crucial to this is the intensity of the ultraviolet light that the star emits into space, in different wavelength ranges. The study provides scientists searching the sky with space telescopes for habitable star systems with important clues as to where this endeavor could be particularly promising.

It also suggests a startling conclusion: as the universe ages, it becomes increasingly unfriendly to the emergence of complex life on new planets.

In the search for habitable or even inhabited planets orbiting distant stars, researchers have in the past years increasingly focused on the gas envelopes of these worlds. Do observational data show evidence of an atmosphere? Does it perhaps even contain gases such as oxygen or methane, which on Earth are produced almost exclusively as metabolic products of lifeforms?
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Re: Stars, supernovae, black holes and stellar remnants

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Astronomers capture first image of jet being launched from edge of black hole

Wed 26 Apr 2023 16.56 BST

Astronomers have captured the first image showing a powerful jet being launched from the edge of a black hole’s event horizon into intergalactic space.

The observations of the black hole at the centre of the galaxy Messier 87 (M87) could help reveal how black hole jets, which are among the brightest objects in the universe, are created.

“We know that jets are ejected from the region surrounding black holes, but we still do not fully understand how this actually happens,” said Dr Ru-Sen Lu, the lead author of the Shanghai Astronomical Observatory.

“To study this directly we need to observe the origin of the jet as close as possible to the black hole.”

https://www.theguardian.com/science/202 ... black-hole


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Re: Stars, supernovae, black holes and stellar remnants

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Study finds J0049−2525 is the most massive pulsating white dwarf
https://phys.org/news/2023-05-j00492525 ... dwarf.html
by Tomasz Nowakowski , Phys.org
Astronomers have conducted photometric observations of a white dwarf known as J004917.14−252556.81. Results of the observational campaign detected photometric variability of this object, making J004917.14−252556.81 the most massive pulsating white dwarf known to date. The finding is reported in a paper published April 18 in Monthly Notices of the Royal Astronomical Society.

White dwarfs (WDs) are stellar cores left behind after a star has exhausted its nuclear fuel. Although their atmospheres are mainly composed of hydrogen or helium, between 25% and 50% of all known white dwarfs show traces of metals in their spectra. In general, the majority of WDs have primary spectral classification DA—they showcase hydrogen-dominated atmospheres.

Located some 325 light years away, J004917.14−252556.81 (or J0049−2525 for short) is a DA white dwarf with an effective temperature of 13,020 K and an estimated mass of approximately 1.3 solar masses. Previous studies have suggested that J0049−2525 may be a pulsating WD of the ZZ Ceti type, however, due to the lack of time-series photometric data, it was difficult to confirm this hypothesis.

That is why a team of astronomers led by Mukremin Kilic of the University of Oklahoma in Norman, Oklahoma, decided to conduct time-series photometric observations of J0049−2525. For this purpose, they employed the Apache Point Observatory (APO) in New Mexico and the Gemini South telescope in Chile.
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Star "superflare" is one of largest ever seen

6th May 2023

A giant flare in the binary star system V1355 Orionis is one of the largest ever observed in the history of astronomy.

Read more: https://www.futuretimeline.net/blog/202 ... rflare.htm


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Astronomers solve a 60-year mystery of quasars – the most powerful objects in the Universe

26 April 2023

Scientists have unlocked one of the biggest mysteries of quasars – the brightest, most powerful objects in the Universe – by discovering that they are ignited by galaxies colliding.

First discovered 60 years ago, quasars can shine as brightly as a trillion stars packed into a volume the size of our solar system. In the decades since they were first observed, one of the biggest mysteries puzzling experts has been what could trigger such powerful activity. New work led by scientists at the Universities of Hertfordshire and Sheffield has now revealed that they are the consequence of galaxies crashing together.

The collisions were discovered when researchers, using deep imaging observations from the Isaac Newton Telescope in La Palma, observed the presence of distorted structures in the outer regions of the galaxies that are home to quasars.

Most galaxies have supermassive black holes at their centres, lurking in the nuclei. They also contain prodigious amounts of gas – but most of the time this gas is orbiting at large distances from the galaxy centres, out of reach of the black holes. Collisions between galaxies drive the gas towards the black hole at the galaxy centre; just before the gas is consumed by the black hole, it releases prodigious amounts of energy in the form of radiation, resulting in the characteristic quasar brilliance.

The ignition of a quasar can have dramatic consequences for entire galaxies – it can drive the rest of the gas out of the galaxy, which prevents it from forming new stars for billions of years into the future.

https://www.herts.ac.uk/about-us/news-a ... e-universe


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Re: Stars, supernovae, black holes and stellar remnants

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A Supermassive Black Hole Ripped Apart a Star and Wore Its Remains Like a Scarf
by Kiona Smith
May 10, 2023

Introduction:
(Inverse) Astronomers recently watched a supermassive black hole rip apart an unwary star much like our Sun.

Just before a star falls into a black hole, the tremendous gravity of the black hole pulls the star apart and stretches it into a thin stream of blazing hot gas. Astronomers call this act of cosmic destruction a tidal disruption event. The gas wraps around the black hole, forming what’s called an accretion disk; it’s as if the black hole is wearing the star’s skin as a battle trophy before finally swallowing it up. As the gas spirals inward, it heats up and emits enough light to be visible even against the bright light of an entire galaxy.

A team of astronomers led by University of Turku astronomer Yannis Liodakis recently caught a supermassive black hole in a nearby galaxy in the act of ripping apart a star. The spaghettified plasma that had once been a Sun-like star didn’t behave in quite the way Liodakis and his colleagues expected, though — which sheds some light on how much we still have to learn about the huge, violent things that happen at the edge of a black hole.

They published their findings in the journal Science.

FISHING EXPEDITION

Liodakis and his colleagues were on a fishing expedition when they spotted the bright flare of light from a galaxy roughly a billion light years away. A “fishing expedition” is what Liodakis calls just looking into space to see what’s out there — it’s space, after all, so there’s bound to be something cool happening — and it’s a rare opportunity for astronomers.

Read more here: https://www.inverse.com/science/this-i ... t-a-star
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Astronomers Reveal the Largest Cosmic Explosion Ever Seen
May 11, 2023

Introduction:
(Eurekalert) A team of astronomers led by the University of Southampton have uncovered the largest cosmic explosion ever witnessed.
The explosion is more than ten times brighter than any known supernova (exploding star) and three times brighter than the brightest tidal disruption event, where a star falls into a supermassive black hole.

The explosion, known as AT2021lwx, has currently lasted over three years, compared to most supernovae which are only visibly bright for a few months. It took place nearly 8 billion light years away, when the universe was around 6 billion years old, and is still being detected by a network of telescopes.

The researchers believe that the explosion is a result of a vast cloud of gas, possibly thousands of times larger than our sun, that has been violently disrupted by a supermassive black hole. Fragments of the cloud would be swallowed up, sending shockwaves through its remnants, as well as into a large dusty ‘doughnut’ surrounding the black hole. Such events are very rare and nothing on this scale has been witnessed before.

Last year, astronomers witnessed the brightest explosion on record - a gamma-ray burst known as GRB 221009A. While this was brighter than AT2021lwx, it lasted for just a fraction of the time, meaning the overall energy released by the AT2021lwx explosion is far greater.

Read more here: https://www.eurekalert.org/news-releases/988665
Don't mourn, organize.

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