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Astronomical News

2104.03902.pdf (arxiv.org)

The Autodidactic Universe

We present an approach to cosmology in which the Universe learns its own physical laws. It does so by exploring a landscape of possible laws, which we express as a certain class of matrix models.

We discover maps that put each of these matrix models in correspondence with both a gauge/gravity theory and a mathematical model of a learning machine, such as a deep recurrent, cyclic neural network. This establishes a correspondence between each solution of the physical theory and a run of a neural network. This correspondence is not an equivalence, partly because gauge theories emerge from N → ∞ limits of the matrix models, whereas the same limits of the neural networks used here are not well-defined. We discuss in detail what it means to say that learning takes place in autodidactic systems, where there is no supervision.

We propose that if the neural network model can be said to learn without supervision, the same can be said for the corresponding physical theory. 1 arXiv:2104.03902v1 [hep-th] 29 Mar 2021We consider other protocols for autodidactic physical systems, such as optimization of graph variety, subset-replication using self-attention and look-ahead, geometrogenesis guided by reinforcement learning, structural learning using renormalization group techniques, and extensions. These protocols together provide a number of directions in which to explore the origin of physical laws based on putting machine learning architectures in correspondence with physical theories.
 
2104.03902.pdf (arxiv.org)

The Autodidactic Universe

We present an approach to cosmology in which the Universe learns its own physical laws. It does so by exploring a landscape of possible laws, which we express as a certain class of matrix models.

We discover maps that put each of these matrix models in correspondence with both a gauge/gravity theory and a mathematical model of a learning machine, such as a deep recurrent, cyclic neural network. This establishes a correspondence between each solution of the physical theory and a run of a neural network. This correspondence is not an equivalence, partly because gauge theories emerge from N → ∞ limits of the matrix models, whereas the same limits of the neural networks used here are not well-defined. We discuss in detail what it means to say that learning takes place in autodidactic systems, where there is no supervision.

We propose that if the neural network model can be said to learn without supervision, the same can be said for the corresponding physical theory. 1 arXiv:2104.03902v1 [hep-th] 29 Mar 2021We consider other protocols for autodidactic physical systems, such as optimization of graph variety, subset-replication using self-attention and look-ahead, geometrogenesis guided by reinforcement learning, structural learning using renormalization group techniques, and extensions. These protocols together provide a number of directions in which to explore the origin of physical laws based on putting machine learning architectures in correspondence with physical theories.
Imagine.jpg
 
Lyrid Meteor Shower peaking on the morning of the 22nd. Nice clear skies here at the moment so I'll be having a look (if I'm not sleeping!).
2021 Lyrid meteor shower: All you need to know
Posted by Bruce McClure and Deborah Byrd in ASTRONOMY ESSENTIALS | TONIGHT | April 20, 2021
The Lyrids are an Earth Day meteor shower, peaking on the morning of April 22. Also, try the next morning, April 23. The moon is waxing – staying out longer after dark each night – so you’ll want to watch the time of moonset carefully.

The annual Lyrid meteor shower always brings an end to the meteor drought, which happens each year between January and mid-April. There are no major meteor showers during that time, as you can see by looking at EarthSky’s meteor shower guide. The Lyrids are active each year from about April 16 to 25. In 2021, we expect the shower to peak in the predawn hours on Thursday, April 22. The following morning (April 23) might be good too, if you’re game.
etc

https://earthsky.org/astronomy-essentials/everything-you-need-to-know-lyrid-meteor-shower
 
The closest black hole to Earth has been christened "The Unicorn".

Astronomers have discovered one of the smallest black holes to date, sitting just 1,500 light-years away which also makes it the closest one to Earth found so far. And they have called it "the Unicorn."

The black hole was given the nickname in part because it's so rare but also because it was discovered in the constellation Monoceros, which means unicorn, according to a release from the Ohio State University.

Though it's roughly three times the mass of our sun, the size is considered tiny for a black hole.

1619256147502.jpeg


"The Unicorn" appears to be a companion to a red giant star, which is how scientists were able to find it. Since black holes aren't visible, researchers were able to locate this one after analyzing data documenting certain changes in the companion star. After noticing something was causing the red giant's intensity and appearance to change, researchers noticed something was pulling at the star, an effect known as a tidal distortion.

https://eu.usatoday.com/story/news/...n-may-smallest-one-discovered-yet/7349740002/

maximus otter
 
Proxima Centauri shoots out humongous flare

Scientists have spotted one of the largest stellar flares ever recorded in our galaxy. The jets of plasma shot outward from the sun's nearest neighbor, the red dwarf star Proxima Centauri. The flare, which was around 100 times more powerful than any experienced in our solar system, could change the way scientists think about solar radiation and alien life.

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Stock image

Proxima Centauri is a red dwarf — the smallest, dimmest and most common type of main sequence stars in the galaxy — located approximately 4.25 light-years from Earth. Its mass is only one-eighth of the sun's, and it is orbited by two exoplanets. One of these planets, Proxima Centauri b, is considered to be Earth-like and lies within the star's habitable zone — the distance from a star that could support the development of life, according to the researchers.

On May 1, 2019, the team captured the mega flare, which shone for just 7 seconds and was mainly visible in the ultraviolet spectrum.

"The star went from normal to 14,000 times brighter when seen in ultraviolet wavelengths over the span of a few seconds," [said] Meredith MacGregor, an astrophysicist at the University of Colorado, Boulder.

https://www.space.com/proxima-centauri-emits-largest-stellar-flare.html

maximus otter
 
Scientists Spot Yet Another Unexplained Ring-Shaped Radio Structure In Space

Scientists have spotted yet another bizarre, gigantic, and unexplained circle-shaped radio structure in outer space, a discovery that contributes to “exciting times in astronomy.”


The bubble is the latest example of an Odd Radio Circle (ORC), an aptly named type of spectral ring that debuted in a 2020 paper led by Western Sydney University astrophysicist Ray Norris. Norris and his colleagues detected four of these enormous circles eerily glowing in faint radio wavelengths far beyond our galaxy.

Now, scientists led by Bärbel Koribalski, a research scientist at CSIRO's Australia Telescope National Facility, have discovered a fifth ORC that appears to span about one million light years.

1619725369184-untitled-design-17.jpeg


ASKAP images of the new ORC. Image: Koribalski et al. 2021

This structure, named ORC J0102–2450, also looks like it has an elliptical galaxy at its center, a feature it shares with two of the ORCs found by Norris’ team.

The team suggests that “a giant blast wave in the central galaxy” that produces “a spherical shell of radio emission” might be the progenitor of ORCs, according to the study. One possible trigger of such a large-scale spherical shock could be the merger of two supermassive black holes during a galactic collision.

https://www.vice.com/en/article/5db...xplained-ring-shaped-radio-structure-in-space

maximus otter
 
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Scientists say they have solved the riddle of why Betelgeuse appeared to dim.

"Astronomers say they've put to bed the mystery of why one of the most familiar stars in the night sky suddenly dimmed just over a year ago.

Betelgeuse, a red supergiant in the constellation of Orion, abruptly darkened in late 2019, early 2020.

The behaviour led many to speculate that it might be about to explode.

But a team using the Very Large
Telescope (VLT) in Chile say the cause was almost certainly a giant dust cloud between us and the star."

https://www.bbc.com/news/science-environment-57501416
 
Nice! Reminds me of this:

Extrasolar Enigmas: From Disintegrating Exoplanets to Exoasteroids​

Thousands of transiting exoplanets have been discovered to date, thanks in great part to the Kepler space mission. As in all populations, and certainly in the case of exoplanets, one finds unique objects with distinct characteristics. Here we will describe the properties and behaviour of a small group of ‘disintegrating’ exoplanets discovered over the last few years (KIC 12557548b, K2-22b, and others). They evaporate, lose mass unraveling their naked cores, produce spectacular dusty comet-like tails, and feature highly variable asymmetric transits. Apart from these exoplanets, there is observational evidence for even smaller ‘exo-’objects orbiting other stars: exoasteroids and exocomets. Most probably, such objects are also behind the mystery of Boyajian’s star. Ongoing and upcoming space missions such as TESS and PLATO will hopefully discover more objects of this kind, and a new era of the exploration of small extrasolar systems bodies will be upon us.
 
In the ending part of solar cycle 24 in 2020, the sun went to sleep with hardly any sun spots.

We are now in solar cycle 25 with the middle being 2025 through 2027, and no one can agree about anything.

Some scientists are calling for another non sun spot time with blizzard conditions on earth.

Some scientists are calling for the opposite, a rash of sun spots with oppressive heat.

If I am around in 2027, I will let you know !
 
Some scientists are calling for the opposite, a rash of sun spots with oppressive heat.
Well, it seems according to American reports that they are suffering powerful tornadoes, and searing heat right now!
 
Astronomers have worked out when the first stars began shining.

They say that this period, known as the "cosmic dawn," occurred between 250 to 350 million years after the Big Bang.

The results indicate that the first galaxies will be bright enough to be seen by Nasa's James Webb Space Telescope, which is set to be launched later this year.

The study is published in the Monthly Notices of the Royal Astronomical Society.

The Universe came into being 13.8 billion years ago in the Big Bang. After an initial flash, it went through a period known as the cosmic dark ages. According to the new study, 250 to 350 million years after the Big Bang, the first stars emerged, bringing light to the cosmos.

Critically, the new analysis also indicates that the first galaxies are bright enough and within the range where they can be seen by the James Webb Space Telescope - the successor to the venerable Hubble Space Telescope.

The researchers analysed starlight from the galaxies using both Hubble and the Spitzer Space Telescope. They estimated the age of the galaxies by examining the proportion of hydrogen atoms in the atmosphere of their stars. The older the stars, the greater the proportion of hydrogen atoms.

The team then calculated how far away the galaxies were. Because light from these galaxies takes time to reach us, the further away they are, the further back in time astronomers are observing them.

Because the six galaxies the team studied are at the limits of objects that can be observed by telescopes, they are also among the earliest known.

The team needed 70 hours of observing time, using four of the largest ground-based telescopes to estimate their distances. These were the Atacama Large Millimetre Array (Alma), the Very Large Telescope (VLT) and the Gemini South Telescope - all located in Chile - as well as the twin Keck telescopes in Hawaii.

These measurements enabled the team to confirm that they were observing these galaxies when the Universe was 550 million years old. Knowing the age of the galaxies and when they existed enabled the team to calculate when the first stars were born.
Similar estimates have been made using just single galaxies, but this is the first meaningful estimate based on a representative group of them.
 
Exoplanets in 2,034 star-systems get cosmic front-row seat to see Earth

Cornell University/sciencedaily.com
23 June, 2021

Scientists at Cornell University and the American Museum of Natural History have identified 2,034 nearby star-systems -- within the small cosmic distance of 326 light-years -- that could find Earth merely by watching our pale blue dot cross our sun.

That's 1,715 star-systems that could have spotted Earth since human civilization blossomed about 5,000 years ago, and 319 more star-systems that will be added over the next 5,000 years.

Exoplanets around these nearby stars have a cosmic front-row seat to see if Earth holds life, the scientists said in research published June 23 in Nature.

"From the exoplanets' point-of-view, we are the aliens," said Lisa Kaltenegger, professor of astronomy and director of Cornell's Carl Sagan Institute, in the College of Arts and Sciences.

"We wanted to know which stars have the right vantage point to see Earth, as it blocks the Sun's light," she said. "And because stars move in our dynamic cosmos, this vantage point is gained and lost."

Kaltenegger and astrophysicist Jackie Faherty, a senior scientist at the American Museum of Natural History and co-author of "Past, Present and Future Stars That Can See Earth As A Transiting Exoplanet," used positions and motions from the European Space Agency's Gaia eDR3 catalog to determine which stars enter and exit the Earth Transit Zone -- and for how long.

"Gaia has provided us with a precise map of the Milky Way galaxy," Faherty said, "allowing us to look backward and forward in time, and to see where stars had been located and where they are going."

Of the 2,034 star-systems passing through the Earth Transit Zone over the 10,000-year period examined, 117 objects lie within about 100 light-years of the sun and 75 of these objects have been in the Earth Transit Zone since commercial radio stations on Earth began broadcasting into space about a century ago.

(...)

https://www.sciencedaily.com/releases/2021/06/210623113905.htm
 
The discovery of a new type of supernova illuminates a medieval mystery

University of California - Santa Barbara/phys.org
28 June, 2021

A worldwide team led by UC Santa Barbara scientists at Las Cumbres Observatory has discovered the first convincing evidence for a new type of stellar explosion—an electron-capture supernova. While they have been theorized for 40 years, real-world examples have been elusive. They are thought to arise from the explosions of massive super-asymptotic giant branch (SAGB) stars, for which there has also been scant evidence. The discovery, published in Nature Astronomy, also sheds new light on the thousand-year mystery of the supernova from A.D. 1054 that was visible all over the world in the daytime, before eventually becoming the Crab Nebula.

Historically, supernovae have fallen into two main types: thermonuclear and iron-core collapse. A thermonuclear supernova is the explosion of a white dwarf star after it gains matter in a binary star system. These white dwarfs are the dense cores of ash that remain after a low-mass star (one up to about 8 times the mass of the sun) reaches the end of its life. An iron core-collapse supernova occurs when a massive star—one more than about 10 times the mass of the sun—runs out of nuclear fuel and its iron core collapses, creating a black hole or neutron star. Between these two main types of supernovae are electron-capture supernovae. These stars stop fusion when their cores are made of oxygen, neon and magnesium; they aren't massive enough to create iron.

While gravity is always trying to crush a star, what keeps most stars from collapsing is either ongoing fusion or, in cores where fusion has stopped, the fact that you can't pack the atoms any tighter. In an electron capture supernova, some of the electrons in the oxygen-neon-magnesium core get smashed into their atomic nuclei in a process called electron capture. This removal of electrons causes the core of the star to buckle under its own weight and collapse, resulting in an electron-capture supernova.

(...)

https://phys.org/news/2021-06-supernova.html
 
Rare cosmic collisions spotted twice in 10 days.

"Scientists have detected two collisions between a neutron star and a black hole in the space of 10 days.

Researchers predicted that such collisions would occur, but did not know how often.

The observations could mean that some ideas of how stars and galaxies form may need to be revised.

Prof Vivien Raymond, from Cardiff University, told BBC News that the surprising results were fantastic.

"We have to go back to the drawing board and rewrite our theories," he said effusively."

https://www.bbc.com/news/science-environment-57639520
 
What happens when a neutron star collides with a black hole - does the neutron star disappear into the black hole or does it bounce off somehow? @eburacum may have some insight..
 
https://www.bbc.co.uk/news/science-environment-57639520
In the first collision, which was detected on 5 January 2020, a black hole six-and-a-half times the mass of our Sun crashed into a neutron star that was 1.5 times more massive than our parent star. In the second collision, picked up just 10 days later, a black hole of 10 solar masses merged with a neutron star of two solar masses.
When objects as massive as these collide they create ripples in the fabric of space called gravitational waves. And it is these ripples that the researchers have detected.
The researchers looked back at earlier observations with fresh eyes and many of them are likely to to have been similar mismatched collisions.
The Neutron Star would be disrupted as it enters the black hole, and some of its mass would escape explosively, but neutron stars are very tightly bound, so this escape would be minimal. Most of the mass of the neutron star would enter the black hole, and extreme gravitational waves would carry a significant amount of mass-energy away for us to detect.
 
'There may not be a conflict after all' in expanding universe debate

University of Chicago/phys.org
30 June, 2021

Our universe is expanding, but our two main ways to measure how fast this expansion is happening have resulted in different answers. For the past decade, astrophysicists have been gradually dividing into two camps: one that believes that the difference is significant, and another that thinks it could be due to errors in measurement.

If it turns out that errors are causing the mismatch, that would confirm our basic model of how the universe works. The other possibility presents a thread that, when pulled, would suggest some fundamental missing new physics is needed to stitch it back together. For several years, each new piece of evidence from telescopes has seesawed the argument back and forth, giving rise to what has been called the 'Hubble tension.'

Wendy Freedman, a renowned astronomer and the John and Marion Sullivan University Professor in Astronomy and Astrophysics at the University of Chicago, made some of the original measurements of the expansion rate of the universe that resulted in a higher value of the Hubble constant. But in a new review paper accepted to the Astrophysical Journal, Freedman gives an overview of the most recent observations. Her conclusion: the latest observations are beginning to close the gap.

That is, there may not be a conflict after all, and our standard model of the universe does not need to be significantly modified.

(...)

University of Chicago graduate student Taylor Hoyt, who has been making measurements of the red giant stars in the anchor galaxies, added, "We keep measuring and testing the red giant branch stars in different ways, and they keep exceeding our expectations."

The value of the Hubble constant Freedman's team gets from the red giants is 69.8 km/s/Mpc—virtually the same as the value derived from the cosmic microwave background experiment. "No new physics is required," said Freedman.

The calculations using Cepheid stars still give higher numbers, but according to Freedman's analysis, the difference may not be troubling. "The Cepheid stars have always been a little noisier and a little more complicated to fully understand; they are young stars in the active star-forming regions of galaxies, and that means there's potential for things like dust or contamination from other stars to throw off your measurements," she explained.

(...)

https://phys.org/news/2021-06-conflict-universe-debate.html
 
Astronomers Detect a Lurking Cosmic Cloud, Bigger Than The Entire Milky Way

MICHELLE STARR
5 JULY 2021


In the yawning vacuum of intergalactic space, something large is lurking.

Not a galaxy, although it's of a comparable size: A vast cloud of hot, faintly glowing gas, bigger than the Milky Way, in the space between galaxies congregating in a huge cluster.

Scientists believe this cloud may have been unceremoniously stripped from a galaxy in the cluster, the first gas cloud of this kind we've ever seen. Even more surprisingly, it hasn't dissipated, but has remained clumped together for hundreds of millions of years.

This not only tells us something new about the environments inside galaxy clusters, it suggests a new way to explore and understand these colossal structures.

"This is an exciting and also a surprising discovery. It demonstrates that new surprises are always out there in astronomy, as the oldest of the natural sciences," said physicist Ming Sun of the University of Alabama in Huntsville.

(...)

https://www.sciencealert.com/a-myst...he-milky-way-is-just-hanging-out-in-space/amp
 
Astronomers Detect a Lurking Cosmic Cloud, Bigger Than The Entire Milky Way

MICHELLE STARR
5 JULY 2021


In the yawning vacuum of intergalactic space, something large is lurking.

Not a galaxy, although it's of a comparable size: A vast cloud of hot, faintly glowing gas, bigger than the Milky Way, in the space between galaxies congregating in a huge cluster.

Scientists believe this cloud may have been unceremoniously stripped from a galaxy in the cluster, the first gas cloud of this kind we've ever seen. Even more surprisingly, it hasn't dissipated, but has remained clumped together for hundreds of millions of years.

This not only tells us something new about the environments inside galaxy clusters, it suggests a new way to explore and understand these colossal structures.

"This is an exciting and also a surprising discovery. It demonstrates that new surprises are always out there in astronomy, as the oldest of the natural sciences," said physicist Ming Sun of the University of Alabama in Huntsville.

(...)

https://www.sciencealert.com/a-myst...he-milky-way-is-just-hanging-out-in-space/amp
No Mass = No gravity perhaps? Only a less than amateur theory!
 
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