Magnetars, highly magnetized stellar corpses like the one illustrated here, could be the source of two different cosmic enigmas: fast radio bursts and high-energy neutrinos, a new study suggests. DRACO-ZLAT/ISTOCK/GETTY IMAGES PLUS

The elusive particles would be hard to catch, but they’d be a smoking gun, researchers say

By Lisa Grossman, SEPTEMBER 16, 2020 

For over a decade, astronomers have puzzled over the origins of fast radio bursts, brief blasts of radio waves that come mostly from distant galaxies. During that same period, scientists have also detected high-energy neutrinos, ghostly particles from outside the Milky Way whose origins are also unknown.

A new theory suggests that the two enigmatic signals could come from a single cosmic source: highly active and magnetized neutron stars called magnetars. If true, that could fill in the details of how fast radio bursts, or FRBs, occur. However, finding the “smoking gun” — catching a simultaneous neutrino and radio burst from the same magnetar — will be challenging because such neutrinos would be rare and hard to find, says astrophysicist Brian Metzger of Columbia University. He and his colleagues described the idea in a study posted September 1 at arXiv.org.

Even so, “this paper gives a possible link between what I think are two of the most exciting mysteries in astrophysics,” says astrophysicist Justin Vandenbroucke of the University of Wisconsin–Madison, who hunts for neutrinos but was not involved in the new work.

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Observations of 11 galaxy clusters, such as MACSJ1206.2-0847 (shown), reveal that some globs of dark matter in these clusters are denser than expected. HUBBLE/ESA AND NASA

Not only is the mysterious substance invisible, but it’s also not all where we thought it was

By Maria Temming  September 10, 2020

Dark matter just got even more puzzling.

This unidentified stuff, which makes up most of the mass in the cosmos, is invisible but detectable by the way it gravitationally tugs on objects like stars. (SN: 11/25/19). Dark matter’s gravity can also bend light traveling from distant galaxies to Earth — but now some of this mysterious substance appears to be bending light more than it’s supposed to. A surprising number of dark matter clumps in distant clusters of galaxies severely warp background light from other objects, researchers report in the Sept. 11 Science.

This finding suggests that these clumps of dark matter, in which individual galaxies are embedded, are denser than expected. And that could mean one of two things: Either the computer simulations that researchers use to predict galaxy cluster behavior are wrong, or cosmologists’ understanding of dark matter is.

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Sakkmesterke/Science Photo Library

Massive objects can distort light from distant galaxies, as seen in this illustration.

Charlie Wood  September 8, 2020

The cosmos is starting to look a bit weird. For a few years now, cosmologists have been troubled by a discrepancy in how fast the universe is expanding. They know how fast it should be going, based on ancient light from the early universe, but apparently the modern universe has picked up too much speed — a clue that scientists might have overlooked one of the universe’s fundamental ingredients, or some aspect of how those ingredients stir together.

Now a second crack in the so-called standard model of cosmology may be forming. In late July, scientists announced that the modern universe also looks unexpectedly thin. Galaxies and gas and other matter haven’t clumped together quite as much as they should have. A few earlier studies offered similar hints, but this new analysis of seven years of data represents the cleanest stand-alone indication of the anomaly yet.

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Impression of the Einstein Telescope, a large underground gravitational wave detector. As possible locations the Euro Region near Vaals and Sardinia are considered. IMAGE Nikhef / Thijs Balder

10 September 2020

Supported by the Netherlands, Belgium, Poland and Spain, the Italian government submitted an application on Wednesday to include the Einstein Telescope in a European roadmap for major research infrastructures. The inclusion of the Einstein Telescope in this ESFRI roadmap will be a recognition of the importance of the Einstein Telescope for Europe.

According to advanced plans, the Einstein Telescope will be the largest ever observatory for observing gravitational waves coming from colliding stars and black holes in the Universe. Such observations offer a new window on the cosmos and its history.

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An artist's impression of the last moments before the merger of two black holes. Credit: LIGO-VIRGO COLLABORATION

Jonathan Amos  -- BBC Science Correspondent
2 September 2020

Imagine the energy of eight Suns released in an instant.

This is the gravitational "shockwave" that spread out from the biggest merger yet observed between two black holes.
The signal from this event travelled for some seven billion years to reach Earth but was still sufficiently strong to rattle laser detectors in the US and Italy in May last year.
Researchers say the colliding black holes produced a single entity with a mass 142 times that of our Sun.
This is noteworthy. Science has long traced the presence of black holes on the sky that are quite a bit smaller or even very much larger. But this new observation inaugurates a novel class of so-called intermediate-sized black holes in the range of 100-1,000 Sun (or solar) masses.
The analysis is the latest to come out of the international LIGO-VIRGO collaboration, which operates three super-sensitive gravitational wave-detection systems in America and Europe.

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The link for the article in PRL 

© Carl Knox, ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav)

23 June 2020

Scientists puzzle over the mysterious astrophysical object: have they discovered the heaviest neutron star or the lightest black hole ever observed?

An international team of scientists including Lancaster University have discovered a compact object lying between neutron stars and black holes in terms of mass.

When the most massive stars die, they collapse under their own gravity and leave behind black holes; when stars that are a bit less massive die, they explode in a supernova and leave behind dense, dead remnants of stars called neutron stars.

For decades, astronomers have been puzzled by a gap that lies between neutron stars and black holes: the heaviest known neutron star is no more than 2.5 times the mass of our sun, or 2.5 solar masses, and the lightest known black hole is about 5 solar masses.

The question remained: does anything lie in this so-called mass gap?

Now, in a new study from the National Science Foundation's Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo detector in Europe, scientists have announced the discovery of an object of 2.6 solar masses, placing it firmly in the mass gap.

The object was found on August 14, 2019, as it merged with a black hole of 23 solar masses, generating a splash of gravitational waves detected back on Earth by LIGO and Virgo. A paper about the detection has been accepted for publication in The Astrophysical Journal Letters.

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See the same news from Virgo website

See the same news from LIGO website

© Jeremy Sanders, Hermann Brunner and the eSASS team (MPE); Eugene Churazov, Marat Gilfanov (on behalf of IKI)

By Jonathan Amos

BBC Science Correspondent

Behold the hot, energetic Universe.
A German-Russian space telescope has just acquired a breakthrough map of the sky that traces the heavens in X-rays.
The image records a lot of the violent action in the cosmos - instances where matter is being accelerated, heated and shredded.
Feasting black holes, exploding stars, and searingly hot gas.
The data comes from the eRosita instrument mounted on Spektr-RG.
This orbiting telescope was launched in July last year and despatched to an observing position some 1.5 million km from Earth. Once commissioned and declared fully operational in December, it was left to slowly rotate and scan the depths of space.
eRosita's first all-sky data-set, represented in the image at the top of this page, was completed only last week. It records over a million sources of X-rays.
"That's actually pretty much the same number as had been detected in the whole history of X-ray astronomy going back 60 years. We've basically doubled the known sources in just six months," said Kirpal Nandra, who heads the high-energy astrophysics group at the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, Germany.
"The data is truly stunning and I think what we're doing here will revolutionise X-ray astronomy," he told BBC News.

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See also Max-Planck webpage

A bright radio burst generated by a magnetar (one illustrated) in our galaxy hints that similar objects are responsible for at least some of the fast radio bursts in other galaxies, which have puzzled astronomers for over a decade. L. CALÇADA/ESO

High-energy event nearby could help explain mystery signals from distant galaxies

By Maria Temming

Astronomers think they’ve spotted the first example of a superbright blast of radio waves, called a fast radio burst, originating within the Milky Way.

Dozens of these bursts have been sighted in other galaxies — all too far away to see the celestial engines that power them (SN: 2/7/20). But the outburst in our own galaxy, detected simultaneously by two radio arrays on April 28, was close enough to see that it was generated by a highly magnetic neutron star called a magnetar.

That observation is a smoking gun that magnetars are behind at least some of the extragalactic fast radio bursts, or FRBs, that have defied explanation for over a decade (SN: 7/25/14). Researchers describe the magnetar’s radio burst online at arXiv.org on May 20 and May 21.

“When I first heard about it, I thought, ‘No way. Too good to be true,’” says Ben Margalit, an astrophysicist at the University of California, Berkeley, who wasn’t involved in the observations. “Just, wow. It’s really an incredible discovery.”

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You may have a look also in a recent TAT paper  

The Australian Square Kilometre Array Pathfinder helped detect the universe's missing matter.(Supplied: Kirsten Gottschalk, COMET)

28.05.2020

By science, technology and environment reporter Michael Slezak and the Specialist Reporting Team's Penny

After an intergalactic search lasting more than two decades, an Australian-led team of scientists say they have finally found the universe's "missing matter", solving a mystery that has long stumped astronomers.

Since the mid-90s, scientists have been trying to locate half of the universe's ordinary matter. They believed it was out there because of clues left over from the Big Bang, but it had never been seen.

"What we're talking about here is what scientists call baryonic matter, which is the normal stuff that you and I are made of," said Associate Professor Jean-Pierre Macquart, from the Curtin University node of the International Centre for Radio Astronomy Research.

Astronomy is full of missing stuff. Most of the universe is understood to be "dark matter" and "dark energy", which nobody has ever directly seen. But even more of a mystery for astronomers was that they couldn't find about half the ordinary matter in the universe.

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Do you understand enough about the Big Bang theory to challenge it? GETTY

Jamie Carter,  May 14, 2020

In cosmology, the Big Bang theory is king. It wasn’t always that way, but over the years the evidence has mounted and, for the most part, astronomers are convinced it’s the best we have.

So why do many people hate it? Black holes, invisible dark matter and the idea of the cosmos being born in a millisecond defy plain common sense.

Frustrated by people telling them how to do their job, two astronomers set-out to answer the questions and criticism they are so frequently sent. The result is The Cosmic Revolutionary’s Handbook (Or: How to Beat the Big Bang), which sets out exactly what any Big Bang theory-hater needs to explain before a new theory can even begin to take hold.

“As cosmologists, our job is to explain the Universe as a whole—it’s structure, constituents and evolution,” said Dr Luke A. Barnes is a postdoctoral researcher at Western Sydney University. “People email us with their ideas about how the Universe works, and while we love their enthusiasm, we found ourselves sending the same kind of reply over and over again.”

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Marek Abramowicz, Michał Bejger, Éric Gourgoulhon & Odele Straub

Our existence in the Universe resulted from a rare combination of circumstances. The same must hold for any highly developed extraterrestrial civilisation, and if they have ever existed in the Milky Way, they would likely be scattered over large distances in space and time. However, all technologically advanced species must be aware of the unique property of the galactic centre: it hosts Sagittarius A* (Sgr A*), the closest supermassive black hole to anyone in the Galaxy. A civilisation with sufficient technical know-how may have placed material in orbit around Sgr A* for research, energy extraction, and communication purposes. In either case, its orbital motion will necessarily be a source of gravitational waves. We show that a Jupiter-mass probe on the retrograde innermost stable circular orbit around Sgr A* emits, depending on the black hole spin, at a frequency of fGW = 0.63–1.07 mHz and with a power of PGW = 2.7 × 10^36–2.0 × 10^37 erg/s. We discuss that the energy output of a single star is sufficient to stabilise the location of an orbiting probe for a billion years against gravitational wave induced orbital decay. Placing and sustaining a device near Sgr A* is therefore astrophysically possible. Such a probe will emit an unambiguously artificial continuous gravitational wave signal that is observable with LISA-type detectors.

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A visualization of a collision between two differently sized black holes.

Credit: N. Fischer, H. Pfeiffer, A. Buonanno (Max Planck Institute for Gravitational Physics), Simulating eXtreme Spacetimes (SXS) Collaboration

Davide Castelvecchi,  20 APRIL 2020

Gravitational-wave astronomers have for the first time detected a collision between two black holes of substantially different masses — opening up a new vista on astrophysics and on the physics of gravity. The event offers the first unmistakable evidence from these faint space-time ripples that at least one black hole was spinning before merging, giving astronomers rare insight into a key property of these these dark objects.

“It’s an exceptional event,” said Maya Fishbach, an astrophysicist at the University of Chicago in Illinois. Similar mergers on which data have been published all took place between black holes with roughly equal masses, so this new one dramatically upsets that pattern, she says. The collision was detected last year, and was unveiled on 18 April by Fishbach and her collaborators at a virtual meeting of the American Physical Society, held entirely online because of the coronavirus pandemic.

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Galaxy cluster glows with x-rays from hot gas (shown here in purple). Surveys of such clusters across the sky are revealing what may be curious anomalies in cosmic structure. Credit: ESA and XMM-Newton (x-rays); CFHTLS (optical); XXL Survey

Lee Billings on April 15, 2020

A new study of galaxy clusters suggests the cosmos may not be the same in all directions

If your life sometimes seems directionless, you might legitimately blame the universe.

According to the key tenets of modern physics, the cosmos is “isotropic” at multi-billion-light-year scales—meaning it should have the same look and behavior in every direction. Ever since the big bang nearly 14 billion years ago, the universe ought to have expanded identically everywhere. And that expectation matches what astronomers see when they observe the smooth uniformity of the big bang’s all-sky afterglow: the cosmic microwave background (CMB). Now, however, an x-ray survey of distances to galaxy clusters across the heavens suggests some are significantly closer or farther away than isotropy would predict. This finding could be a sign that the universe is actually “anisotropic”—expanding faster in some regions than it does in others. With apologies to anyone seeking a cosmic excuse for personal woes, maybe the universe is not so directionless after all.

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A star's rosette-shaped path around a black hole confirms Einstein's theory of gravity. Rather than tracing out a single ellipse (red), its orbit rotates over time (blue, rotation exaggerated in this illustration for emphasis). L. CALÇADA/ESO

Decades of observations revealed the rotation of the star’s elliptical orbit

Emily Conover - ScienceNews

The first sign that Albert Einstein’s theory of gravity was correct has made a repeat appearance, this time near a supermassive black hole.

In 1915, Einstein realized that his newly formulated general theory of relativity explained a weird quirk in the orbit of Mercury. Now, that same effect has been found in a star’s orbit of the enormous black hole at the heart of the Milky Way, researchers with the GRAVITY collaboration report April 16 in Astronomy & Astrophysics.

The star, called S2, is part of a stellar entourage that surrounds the Milky Way’s central black hole. For decades, researchers have tracked S2’s elliptical motion around the black hole. The researchers previously had used observations of S2 to identify a different effect of general relativity, the reddening of the star’s light due to what’s called gravitational redshift (SN: 7/26/18).

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A map showing the rate of the expansion of the Universe in different directions across the sky based on data from ESA's XMM-Newton, NASA's Chandra and the German-led ROSAT X-ray observatories.

08/04/2020

Astronomers have assumed for decades that the Universe is expanding at the same rate in all directions. A new study based on data from ESA’s XMM-Newton, NASA’s Chandra and the German-led ROSAT X-ray observatories suggests this key premise of cosmology might be wrong.

Konstantinos Migkas, a PhD researcher in astronomy and astrophysics at the University of Bonn, Germany, and his supervisor Thomas Reiprich originally set out to verify a new method that would enable astronomers to test the so-called isotropy hypothesis. According to this assumption, the Universe has, despite some local differences, the same properties in each direction on the large scale.

Widely accepted as a consequence of well-established fundamental physics, the hypothesis has been supported by observations of the cosmic microwave background (CMB). A direct remnant of the Big Bang, the CMB reflects the state of the Universe as it was in its infancy, at only 380 000 years of age. The CMB’s uniform distribution in the sky suggests that in those early days the Universe must have been expanding rapidly and at the same rate in all directions.

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