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Astronomers trace mysterious fast radio burst to extreme, rare star – CNET



Sifting through a trove of radio telescope data in 2007, Duncan Lorimer, an astrophysicist at West Virginia University, spotted something unusual. Data obtained six years earlier showed a brief, energetic burst, lasting no more than 5 milliseconds. Others had seen the blip and looked past it, but Lorimer and his team calculated that it was an entirely new phenomenon: a signal emanating from somewhere far outside the Milky Way.

The team had no idea what had caused it but they published their results in Science. The mysterious signal became known as a “fast radio burst,” or FRB. In the 13 years since Lorimer’s discovery, dozens of FRBs have been discovered outside of the Milky Way — some repeating and others ephemeral, single chirps. Astrophysicists have been able to pinpoint their home galaxies, but they’ve struggled to identify the cosmic culprit, putting forth all sorts of theories, from exotic physics to alien civilizations

On Wednesday, a trio of studies in the journal Nature describes the source of the first FRB discovered within the Milky Way, revealing the mechanism behind at least some of the highly energetic radio blasts.

The newly described burst, dubbed FRB 200428, was discovered and located after it pinged radio antennas in the US and Canada on April 28, 2020. A hurried hunt followed, with teams of researchers around the globe focused on studying the FRB across the electromagnetic spectrum. It was quickly determined that FRB 200428 is the most energetic radio pulse ever detected in our home galaxy. 

In the suite of new papers, astrophysicists outline their detective work and breakthrough observations from a handful of ground- and space-based telescopes. Linking together concordant observations, researchers pin FRB 200428 on one of the most unusual wonders of the cosmos: a magnetar, the hypermagnetic remains of a dead supergiant star. 

It’s the first time astrophysicists have been able to finger a culprit in the intergalactic whodunit — but this is just the beginning. “There really is a lot more to be learned going forward,” says Amanda Weltman, an astrophysicist at the University of Cape Town and author of a Nature news article accompanying the discovery. 

“This is just the first exciting step.”

Under pressure

To understand where FRB 200428 begins, you have to understand where a star ends.

Stars many times larger than the sun are known to experience a messy death. After they’ve exhausted all their fuel, physics conspires against them; their immense size places unfathomable pressure on their core. Gravity forces the star to fold in on itself, causing an implosion that releases huge amounts of energy in an event known as a supernova. 

The star’s crumpled core, born under extreme pressure, is left behind. Except now it’s very small, only about the size of a city, and around 1 million times more dense than the Earth. This stellar zombie is known as a neutron star. 

Some neutron stars have extreme magnetic fields, about 1,000 times stronger than typical neutron stars. They’re a mysterious and intriguing class unto themselves. Astronomers call them “magnetars,” and they’re as curious as FRBs, with only about 30 discovered so far. 

See also: These telescopes work with your phone to show exactly what’s in the sky

One such magnetar in the Milky Way is officially known as SGR 1935+2154, which refers to its position in the sky. To make things easier, let’s nickname it Mag-1. It was first discovered in 2014 and is located around 30,000 light-years from Earth. On April 27, 2020, NASA’s Neil Gehrels Swift Observatory and Fermi Gamma-ray Space Telescope picked up a spike in X-rays and gamma-rays emanating from Mag-1. 

The next day, two huge North American telescopes — the Canadian Hydrogen Intensity Mapping Experiment (CHIME) and the Survey for Transient Astronomical Radio Emission 2 (STARE2) — picked up an extremely energetic radio burst coming from the same region of space: FRB 200428. The FRB and Mag-1 were in the exact same galactic neighborhood. Or rather, they seemed to be in the same galactic house. 

“These observations point to magnetars as a smoking gun of an FRB,” says Lorimer, lead author on the 2007 discovery of the first radio burst. Magnetars had been theorized as potential FRB sources previously, but the data provides direct evidence linking the two cosmic phenomena together.

However, just co-locating the burst with the magnetar doesn’t explain everything.

“Magnetars occasionally produce bursts of bright X-ray emission,” says Adam Deller, an astrophysicist at Swinburne University in Melbourne, Australia, “but most magnetars have never been seen to emit any radio emission.”

Don’t stop me now

Associating Mag-1 with FRB 200428 is just the beginning of a long-term investigation. 

In the cosmic whodunit, astronomers have found a culprit, but they’re not exactly sure of the murder weapon. 

Studying the FRB, researchers were able to determine it was highly energetic but paled in comparison to some deep space FRBs previously discovered. “It was almost as luminous as the weakest FRBs we’ve detected,” says Marcus Lower, an astronomy Ph.D. at Swinburne University studying neutron stars. This suggests magnetars may be responsible for some FRBs but not all of them — some seem far too energetic to be produced in the same way FRB 200428 was.

Another paper in Nature on Wednesday sees researchers using China’s Five-hundred-meter Aperture Spherical radio Telescope (FAST) to study Mag-1 during one of its X-ray outbursts. The telescope did not pick up any radio emission from the magnetar during its outbursts. That means it’s unlikely such an outburst, alone, is responsible for spewing highly energetic FRBs. “It’s definite that not every magnetar X-ray burst fires off an accompanying radio burst,” says Deller. 

Deller also notes that FRB 200428 shows characteristics similar to those seen in repeating FRBs from outside the Milky Way.

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This is important because, at present, astronomers have observed two types of FRBs in other galaxies. There are those that  flash to life and disappear, and others that appear to be repeating with regular rhythm. FRB 200428 looks like a repeater, but much weaker. Further observations by the CHIME telescope in October detected more radio bursts from the magnetar, though this work hasn’t yet been published.

All in all, there’s still some uncertainty. “We cannot say for certain if magnetars are the sources of all of the FRBs observed to date,” Weltman notes. 

Another question: How did Mag-1 generate the FRB? Two different mechanisms have been proposed. 

One suggestion is magnetars produce radio waves just as they do X-rays and gamma-rays in their magnetosphere, the huge region of extreme magnetic fields surrounding the star. The other is a little more complex. “The magnetar could live in a cloud of material hanging around from previous outflows,” says Adelle Goodwin, an astrophysicist at Curtin University who was not affiliated with the study. This cloud of material, Goodwin notes, could then be slammed into by an X-ray or gamma-ray outburst, transferring energy into radio waves. Those waves then travel through the cosmos and ping Earth’s detectors as an FRB. 

It’s not clear which mechanism resulted in FRB 200428 — or if something more exotic might be happening. Other researchers have suggested FRBs may even be caused by asteroids slamming into a magnetar, for instance. But one thing now seems certain: it’s not alien civilizations trying to contact us. Sorry.

Radio ga-ga

There’s still a great deal of work to be done in unraveling the mystery of fast radio bursts. 

For Deller, the hunt continues. Part of his work is focused on where FRBs originate. He says his team still needs to collect more data, but there’s a chance that repeating FRBs may inhabit different types of galaxies from those FRBs which don’t repeat. Weltman notes the search for other signals will also intensify, with astronomers looking for electromagnetic radiation and neutrinos that are generated from any magnetar-produced FRB. 

The investigation will, ultimately, change the way we see the universe. Duncan Lorimer notes that if FRBs can be definitively linked to neutron stars, it would provide a way to take a census of those extreme cosmic entities. Current methods can’t identify neutron star types with great specificity — but FRBs could change that. And FRBs are already changing the way we see things. A study published in Nature earlier this year used FRBs to solve a decades-old problem about the universe’s “missing matter.” 

Lorimer says many of the predictions his team made after discovering the first FRB in 2007 “have been realized in some way” and he always hoped FRBs could become part of the mainstream. As the mysteries deepen, they’ve surpassed his expectations. They’ve become one of astrophysics’ most perplexing but intriguing phenomena. 

“It continues to be a fascinating adventure,” he says.

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Earth Is a Whole Lot Closer to Our Galaxy's Supermassive Black Hole Than We Thought – ScienceAlert



It seems that Earth has been misplaced.

According to a new map of the Milky Way galaxy, the Solar System’s position isn’t where we thought it was. Not only is it closer to the galactic centre – and the supermassive hole therein, Sagittarius A* – it’s orbiting at a faster clip.

It’s nothing to be concerned about; we’re not actually moving closer to Sgr A*, and we’re in no danger of being slurped up. Rather, our map of the Milky Way has been adjusted, more accurately identifying where we have been all along.

And the survey beautifully demonstrates how tricky it is to map a galaxy in three dimensions from inside it.

It’s a problem that has long devilled our understanding of space phenomena. It’s relatively easy to map the two-dimensional coordinates of stars and other cosmic objects, but the distances to those objects is a lot harder to figure out.

And distances are important – they help us determine the intrinsic brightness of objects. A good recent example of this is the red giant star Betelgeuse, which turned out to be closer to Earth than previous measurements suggested. This means that it’s neither as large nor as bright as we thought.

Another is the object CK Vulpeculae, a star that exploded 350 years ago. It’s actually much farther away, which means that the explosion was brighter and more energetic, and requires a new explanation, since previous analyses were performed under the assumption it was relatively low energy.

But we’re getting better at calculating those distances, with surveys using the best available technology and techniques working hard to refine our three-dimensional maps of the Milky Way, a field known as astrometry. And one of these is the VERA radio astronomy survey, conducted by the Japanese VERA collaboration.

VERA stands for VLBI (Very Long Baseline Interferometry) Exploration of Radio Astrometry, and it uses a number of radio telescopes across the Japanese archipelago, combining their data to effectively produce the same resolution as a telescope with a 2,300 kilometre- (1,430 mile-) diameter dish. It’s the same principle behind the Event Horizon Telescope that produced our very first direct image of a black hole’s shadow.

VERA, which started observing in 2000, is designed to help us calculate the distances to radio-emitting stars by calculating their parallax. With its incredible resolution, it observes these stars for over a year, and watches how their position changes relative to stars that are much farther away as Earth orbits the Sun.

(National Astronomical Observatory of Japan)

This change in position can then be used to calculate how far a star is from Earth, but not all parallax observations are created equal. VLBI can produce much higher resolution images; VERA has a breathtaking angular resolution of 10 millionths of an arcsecond, which is expected to produce extraordinarily high precision astrometry measurements.

And this is what astronomers have used to refine our Solar System’s position in the Milky Way. Based on the first VERA Astrometry Catalog of 99 objects released earlier this year, as well as other observations, astronomers created a position and velocity map of those objects.

From this map, they calculated the position of the galactic centre.

In 1985, the International Astronomical Union defined the distance to the galactic centre as 27,700 light-years. Last year, the GRAVITY collaboration recalculated it and found it closer, just 26,673 light-years away.

solar system gc(National Astronomical Observatory of Japan)

The VERA-based measurements bring it closer still, to a distance of just 25,800 light-years. And the Solar System’s orbital speed is faster, too – 227 kilometres (141 miles) per second, rather than the official velocity of 220 kilometres (137 miles) per second.

That change may not seem like much, but it could have an impact on how we measure and interpret activity in the galactic centre – ultimately, hopefully, leading to a more accurate picture of the complex interactions around Sgr A*.

Meanwhile, the VERA collaboration is forging ahead. Not only is it continuing to make observations of objects in the Milky Way, it’s joining up with an even larger project, the East Asian VLBI Network. Together, astronomers hope, the telescopes involved in this project could provide measurements of unprecedented accuracy.

The Vera Astrometry Catalog was published in the Publications of the Astronomical Society of Japan.

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Earth just got 2,000 light-years closer to Milky Way's supermassive black hole – CNET




Earth is a little closer to the supermassive black hole at the center of the Milky Way than we believed.


At the center of the our galaxy there’s a supermassive black hole called Sagittarius A*. It has a mass roughly 4 million times that of our sun.

Great news! It turns out scientists have discovered that we’re 2,000 light-years closer to Sagittarius A* than we thought.

This doesn’t mean we’re currently on a collision course with a black hole. No, it’s simply the result of a more accurate model of the Milky Way based on new data.

Over the last 15 years, a Japanese radio astronomy project, VERA, has been gathering data. Using a technique called interferometry, VERA gathered data from telescopes across Japan and combined them with data from other existing projects to create what is essentially the most accurate map of the Milky Way yet. 

By pinpointing the location and velocity of around 99 specific points in our galaxy, VERA has concluded that the supermassive black hole Sagittarius A, at the center of our galaxy, is actually 25,800 light-years from Earth — almost 2,000 light-years closer than what we previously believed. 

In addition, the new model calculates Earth is moving faster than we believed. Older models clocked Earth’s speed at 220 kilometers (136 miles) per second, orbiting around the galaxy’s centre. VERA’s new model has us moving at 227 kilometers (141 miles) per second.

Not bad!

VERA is now hoping to increase the accuracy of its model by increasing the amount of points it’s gathering data from by expanding into EAVN (East Asian VLBI Network) and gathering data from a larger suite of radio telescopes located throughout Japan, Korea and China. 

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Scientists find neutrinos from star fusion for the first time – Engadget



Neutrino detection in INFN Gran Sasso Laboratories' facility


Researchers have effectively confirmed one of the most important theories in star physics. NBC News reports that a team at the Italian National Institute for Nuclear Physics has detected neutrinos traced back to star fusion for the first time. The scientists determined that the elusive particles passing through its Borexino detector stemmed from a carbon-nitrogen-oxygen (CNO) fusion process at the heart of the Sun.

This kind of behavior had been predicted in 1938, but hadn’t been verified until now despite scientists detecting neutrinos in 1956. Borexino’s design was crucial to overcoming that hurdle — its “onion-like” construction and ongoing refinements make it both ultra-sensitive and resistant to unwanted cosmic radiation.

It’s a somewhat surprising discovery, too. CNO fusion is much more common in larger, hotter stars. A smaller celestial body like the Sun only produces 1 percent of its energy through that process. This not only confirms that CNO is a driving force behind bigger stars, but the universe at large.

That, in turn, might help explain some dark matter, where neutrinos could play a significant role. Scientist Orebi Gann, who wasn’t involved in these findings, also told NBC that an asymmetry between neutrinos and their relevant antiparticles might explain why there isn’t much known antimatter in the universe. To put it another way, the findings could help answer some of the most basic questions about the cosmos.

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