One million new galaxies found in fastest radio survey of the sky yet – CNET

racs-small

The most rapid radio survey of the southern sky has been completed by the Australian SKA Pathfinder telescope.

CSIRO

The most detailed and most rapid survey of the southern sky has helped map about a million previously undiscovered galaxies. Using the Australian Square Kilometre Array Pathfinder radio telescope, scientists from the CSIRO, Australia's national science agency, have cut the time to complete such an intense survey of space from years to less than two weeks.

In a study, published in the journal Publications of the Astronomical Society of Australia on Monday, the first results from the CSIRO's Rapid ASKAP Continuum Survey are reported. The agency describes the survey as like a "Google Map" of the universe, providing the most detailed atlas of the southern sky yet. 

The key to the new atlas is ASKAP, which isn't a single telescope but an array of 36 dish-shaped antennas stationed in the West Australian desert. The array listens for radio waves from deep space and can see a region of the sky about 30 times larger than other, contemporary radio arrays.

Taking over 900 images across about 300 hours, the team was able to stitch together a comprehensive map of the southern sky with a higher resolution than previous surveys. The images contain a total of 70 billion pixels and lurking in the data are 3 million galaxies -- a third of which are new to science. 

The map will allow astronomers to study cosmic objects such as supernovas, pulsars and the jets around supermassive black holes in distant galaxies.

"ASKAP is applying the very latest in science and technology to age-old questions about the mysteries of the Universe and equipping astronomers around the world with new breakthroughs to solve their challenges," Larry Marshall, CSIRO chief executive, said in a news release.

It's just the beginning of the journey for ASKAP. RACS was conceived almost as a test bed for what ASKAP will try to achieve. Over the next five years, the radio array will begin to conduct ten major surveys of the sky, which will take about 1,500 hours to complete per project. Some of these projects will probe the most mysterious phenomena at the very edge of the universe. 

"We expect to find tens of millions of new galaxies in future surveys," said David McConnell, astronomer at the CSIRO and lead author on the new study. 

You can take a virtual tour of the impressive map at CSIRO's website.

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China’s Chang’e 5 probe readies for audacious moon rock heist this week – CNET

change5

An animation of the Chang'e 5 probe firing its engines to insert itself into lunar orbit.

China Lunar Exploration Project

China quietly launched its Chang'e 5 spacecraft to the moon last week. The probe has now entered lunar orbit, preparing to touchdown on the moon's surface in the coming days. 

At approximately 4:48 a.m. PT on Saturday, the probe performed a 17-minute burn of its main engine to slow down enough to be captured by the moon's gravity, according to the China Lunar Exploration Project. At 12:40 p.m. PT on Sunday, the lander and its ascent vehicle separated from its module in orbit around the moon. 

The module will continue to zoom around the moon at approximately 125 miles above the surface, while the lander and ascent vehicle autonomously attempts to get to the lunar surface. It will move within 10 miles before descent.

China's Lunar Exploration Program has not released official details of when the landing is scheduled to occur, but China space watchers predict it will be in the next 48 to 72 hours.

Upon touchdown, Chang'e 5 is scheduled to collect around 4.5 pounds of lunar soil from Mons Rumker, a volcanic region shaped like a pimple on the moon's face, before ascending back to orbit and transferring its spoils to an orbiter. Lunar samples were last returned by Soviet spacecraft in 1976.

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China’s Chang’e 5 probe readies for audacious moon rock heist this week – CNET

change5

An animation of the Chang'e 5 probe firing its engines to insert itself into lunar orbit.

China Lunar Exploration Project

China quietly launched its Chang'e 5 spacecraft to the moon last week. The probe has now entered lunar orbit, preparing to touchdown on the moon's surface in the coming days. 

At approximately 4:48 a.m. PT on Saturday, the probe performed a 17-minute burn of its main engine to slow down enough to be captured by the moon's gravity, according to the China Lunar Exploration Project. At 12:40 p.m. PT on Sunday, the lander and its ascent vehicle separated from its module in orbit around the moon. 

The module will continue to zoom around the moon at approximately 125 miles above the surface, while the lander and ascent vehicle autonomously attempts to get to the lunar surface. It will move within 10 miles before descent.

China's Lunar Exploration Program has not released official details of when the landing is scheduled to occur, but China space watchers predict it will be in the next 48 to 72 hours.

Upon touchdown, Chang'e 5 is scheduled to collect around 4.5 pounds of lunar soil from Mons Rumker, a volcanic region shaped like a pimple on the moon's face, before ascending back to orbit and transferring its spoils to an orbiter. Lunar samples were last returned by Soviet spacecraft in 1976.

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Half-Life 2’s garden gnome reaches space aboard Rocket Lab’s Electron – CNET

gnome-chompski-3-small

To boldly gnome where no gnome has gnomed before.

Rocket Lab

Rocket Lab's sleek, black Electron rocket is launched from New Zealand's picturesque Māhia Peninsula on Thursday. The mission was a significant step in the plucky spaceflight startup's ambitious plans to recover a rocket booster in midair with a helicopter. But it was also a momentous launch for gnomes and Gabe Newell, founder of video game powerhouse Valve.

A 5-inch titanium garden gnome, dubbed Gnome Chompski, was strapped to the Electron rocket's Kick Stage, a circular platform that drops satellites into orbit and then falls back toward the Earth, for the duration of the mission. 

Chompski will be familiar to Half-Life fans. In Half-Life 2: Episode Two, carrying the gnome from its hiding spot in the communications building to a rocket earns the achievement Little Rocket Man. Fitting, then. Weirdly, to celebrate the flight, Valve updated the achievements for Half-Life 2: Episode Two, a game that's now 13 years old.

And real-world Chompski isn't just a fancy weight to attach to a rocket booster. It's performing science. The gnome was created with a novel 3D printing technique, with support of New Zealand's Weta Workshop, that will be put to the test on its way into the great beyond. 

Chompski's flight wasn't all science and video games though. It also contributed to charity. For every viewer of the launch, Newell pledged to donate $1 to the Pediatric Intensive Care Unit New Zealand's Starship Foundation. It's unclear how many people tuned in live across Twitch and YouTube at present.

What fate ultimately awaits Chompski? Not a pretty one. Eventually, the Kick Stage and Chompski will burn up upon re-entry to Earth's atmosphere. 

Try not to think about that too much and just enjoy the ride.

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Half-Life 2’s garden gnome reaches space aboard Rocket Lab’s Electron – CNET

gnome-chompski-3-small

To boldly gnome where no gnome has gnomed before.

Rocket Lab

Rocket Lab's sleek, black Electron rocket is launched from New Zealand's picturesque Māhia Peninsula on Thursday. The mission was a significant step in the plucky spaceflight startup's ambitious plans to recover a rocket booster in midair with a helicopter. But it was also a momentous launch for gnomes and Gabe Newell, founder of video game powerhouse Valve.

A 5-inch titanium garden gnome, dubbed Gnome Chompski, was strapped to the Electron rocket's Kick Stage, a circular platform that drops satellites into orbit and then falls back toward the Earth, for the duration of the mission. 

Chompski will be familiar to Half-Life fans. In Half-Life 2: Episode Two, carrying the gnome from its hiding spot in the communications building to a rocket earns the achievement Little Rocket Man. Fitting, then. Weirdly, to celebrate the flight, Valve updated the achievements for Half-Life 2: Episode Two, a game that's now 13 years old.

And real-world Chompski isn't just a fancy weight to attach to a rocket booster. It's performing science. The gnome was created with a novel 3D printing technique, with support of New Zealand's Weta Workshop, that will be put to the test on its way into the great beyond. 

Chompski's flight wasn't all science and video games though. It also contributed to charity. For every viewer of the launch, Newell pledged to donate $1 to the Pediatric Intensive Care Unit New Zealand's Starship Foundation. It's unclear how many people tuned in live across Twitch and YouTube at present.

What fate ultimately awaits Chompski? Not a pretty one. Eventually, the Kick Stage and Chompski will burn up upon re-entry to Earth's atmosphere. 

Try not to think about that too much and just enjoy the ride.

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Huge fireball’s spectacular explosion over the ocean captured on film – CNET

The Research Vessel Investigator, operated by Australia's national science agency CSIRO, caught the huge fireball breaking apart over the Southern Ocean.

CSIRO

An enormous, spectacular fireball blazing a trail across the sky off the southern coast of Tasmania, Australia, has been captured on film. 

A livestream camera fitted to the research vessel Investigator, operated by Australia's national science agency CSIRO, spotted the fireball at 9:21 p.m. local time on Nov. 18. The vessel is designed to "look" down, performing mapping of the seafloor and conducting oceanographic studies about 60 miles south of Australia, but it was the meteor that flew by overhead that excited the crew on Wednesday.

"What we saw on reviewing the livestream footage astounded us, the size and brightness of the meteor was incredible," John Hooper, voyage manager onboard the vessel, said in a press release.

The local media was "flooded with reports of sightings," but no additional photos or vision have turned up at this stage, according to CSIRO. The International Meteor Organization, which tracks meteors, doesn't contain any reports of the fireball over the ocean. The research vessel investigator seems to have had the only good view of the burning rock as it made its death dive, with chunks likely to have fallen into the sea.

"We were very fortunate that we captured it all on the ship livestream," Hooper said. 

You can catch a glimpse of the fireball above and find the full video here.

Meteors are giant chunks of rocks that are known to put on quite a show when they collide with the Earth's atmosphere. In July, a fireball exploded over the skies of Tokyo with the force of 165 tons of TNT -- enough to create a sonic boom. 

And while you may have missed out on seeing those rocks clangin' and bangin' into the Earth, you can catch the Leonid meteor shower right now, which will remain active until Monday, Nov. 30. Plenty of chances to catch the stunning celestial events.

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SpaceX, NASA Crew-1 mission docks with ISS for six-month stay – CNET

The Crew Dragon Resilience on approach to the International Space Station, backed by the Earth.

NASA TV

At exactly 4:27 p.m. PT on Sunday, a SpaceX Falcon 9 booster burst to life at the Kennedy Space Center's Launch Complex 39A, its engines lighting up the Florida coast. The picture-perfect launch of the gumdrop-shaped Crew Dragon spacecraft, nicknamed Resilience, marked a historic moment in US spaceflight

Not since the end of the Space Shuttle program in 2011 has NASA sent humans to orbit from American soil in an operational mission. The launch for this particular mission has been delayed, pushed back and postponed multiple times -- the original timeline included a launch date of November 2016. Four years and a few technical stumbles later, Resilience has now docked with the International Space Station.

"By working together through these difficult times, you've inspired the nation, the world, and in no small part, the name of this incredible vehicle, Resilience," Michael Hopkins, spacecraft commander of Crew-1, said prior to launch.  

The docking was scheduled to take place at 8 p.m. PT and was essentially right on time. However, shadows obscured the crew's view of the space station, and the astronauts decided to make a short hold 20 meters from the docking adapter. After waiting for "sunset" and the shadows to move away, Resilience made contact with the ISS and officially performed a "soft capture" at 8:01 p.m PT and docked at approximately 8:15 p.m. PT. 

"This is a new era of operational flights to the International Space Station from the Florida coast," said Hopkins upon docking. 

The Crew Dragon carried an international assembly of astronauts: HopkinsVictor Glover and Shannon Walker of NASA, plus Soichi Noguchi of Japanese space agency, JAXA. After a handful of safety checks and a welcoming ceremony in the early hours of Tuesday morning, the team will get to work on science experiments and maintenance. They are expected to spend the next six months on the station. The Dragon is capable of autonomous and the Dragon is rated to remain at the station for 210 days, as per NASA requirements.   

The launch was celebrated by NASA and SpaceX representatives at a post-launch conference Sunday. "This is a great day for the United States of America and a great day for Japan," NASA Administrator Jim Bridenstine said. "The big milestone here is that we are now moving away from development and tests and into operational flights." 

"I am looking forward to enjoy the new era and going together for the future," said Hiroshi Sasaki, vice president at JAXA. 

Less than 10 minutes after launch, the first stage Falcon 9 booster landed safely on the Just Read The Instructions droneship stationed in the Atlantic. It was the first time the reusable rocket was utilized in a mission and the plan is for it to be reused on the next operational flight of the SpaceX's Crew Dragon, Crew-2. 

The launch of Crew-2 is slated to occur in March 2021 and will again carry four astronauts. It will reuse the Crew Dragon Endeavour, which was first used in the SpaceX Demo-2 mission in May.

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Through the smoke, the first stage of the Falcon 9 on the droneship in the Atlantic.

NASA

Around 12 minutes later, Resilience separated from the second stage and headed on its way.

It's not the first time a Falcon 9 rocket has delivered a Crew Dragon spacecraft to space. In May, NASA astronauts Bob Behnken and Doug Hurley were the first two humans to be carried to orbit via SpaceX's workhorse rocket. But that was a test mission, the final box to be ticked before operations officially begin for NASA's Commercial Crew Program. 

Crew-1 signals the return of operational flights to US soil and the first flight in the CCP. Until recently, NASA was purchasing flights on the Russian Soyuz spacecraft. Flying SpaceX, NASA will save around $25 million per seat. 

NASA has also contracted Boeing to deliver astronauts to the ISS, but the company's crewed spacecraft, Starliner, ran into technical issues during its first uncrewed demonstration launch.

You can watch the replay of the launch below.

Updated Nov. 17: Added docking success, changed headline

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Explosive neutron star collision may have created a rare, extreme star – CNET

When two neutron stars collide, the universe winces. The extreme crash is explosive and creates a "kilonova," which sends out a bright, rapid burst of gamma rays. It also sends ripples through the fabric of space-time. Then, scientists believe, the cosmic smash likely creates a newly merged object that quickly collapses into a black hole. But... what if it survives? 

A new study, set to be published in The Astrophysical Journal but available as a preprint on arXiv, describes the brightest kilonova yet and suggests a neutron star collision might sometimes give rise to a magnetar, an extreme neutron star with dense magnetic fields.

On May 22, NASA's Neil Gehrels Swift Observatory, a space telescope, spotted a gamma-ray burst in an extremely distant corner of space, dubbed GRB 200522A. Scientists believe these types of short bursts occur when two neutron stars collide, so when a telescope sees one, there's a mad scramble to obtain observations at other wavelengths on the electromagnetic spectrum. The collision in question occurred some 5.5 billion years ago but our telescopes only now picked up the signals.

In the new study, the research team pointed a number of different space- and ground-based telescopes at GRB 200522A, including NASA's Hubble Space Telescope, and observed the fallout after the bright gamma-ray burst. 

Using X-ray, radio and near-infrared data, the team were able to measure the brightness of the gamma-ray burst. But there was one particular observation that didn't fit in. The near-infrared images from Hubble showed an extremely bright burst -- about 10 times brighter than any kilonova ever seen (though only a handful have been observed so far). 

"We scratched our heads for awhile and pored through all possible models at our disposal," says Wen-fai Fong, an astrophysicist at Northwestern University and lead author of the new research. "The near-infrared light we saw from GRB 200522A was far too bright to be explained by a standard radioactively powered kilonova."

Fong and her team eventually settled on a model they dubbed a "magnetar-boosted kilonova" to explain the extreme brightness.

Two neutron stars colliding in deep space may have given rise to a magnetar. If confirmed, it would be the first time astronomers have spotted the birth of these extreme stars.

Northwestern University

Kilonova are created when two dense cosmic objects -- like neutron stars and black holes -- crash into each other. The process of merging ejects a ton of subatomic material into space, including generating the gamma-ray burst. Fong says you can think of it like a smoothie in a blender that you forgot to put the lid on, with "neutron-rich" material streaming out into the cosmos. 

The team's model suggests the creation of a magnetar, a highly magnetized type of neutron star, may have been able to supercharge the kilonova event, making it far brighter than astronomers predicted.

"If confirmed, this would be the first time we were able to witness the birth of a magnetar from a pair of neutron stars," Fong says.

But there's some work to be done. Continuing to observe GRB 200522A with radio telescopes will help more clearly determine exactly what happened around the gamma-ray burst. The radio waves from the event should be able to confirm what was seen at infrared wavelengths, but how long those waves take to reach the Earth depends on the environment around GRB 200522A. The model suggests it could be around six years until we pick up such a signal, and Fong says the team will monitor for radio emissions for years to come.

Magnetars have long been mysterious cosmic bodies, but in the last week, astronomers have begun to shed some light on the elusive dead stars. Last week, a team astrophysicists reported the discovery of a fast radio burst (FRB) from a magnetar inside the Milky Way. The momentous discovery suggests magnetars may be able to create these mysterious radio signals sometimes, though the jury is out on whether they can create all FRBs. GRB 200522A may provide an opportunity to test that hypothesis again.

"If we were able to associate an FRB with the location of GRB 200522A, that would be an astounding discovery and would indeed be a smoking gun linking this particular event to a magnetar," Fong says. However, she cautions it would be surprising if there's a connection between short gamma-ray bursts themselves and FRBs.

But gamma-ray bursts do keep throwing up new mysteries and cosmic puzzles to solve. "I have studied the same type of explosion for a decade now, and short gamma-ray bursts can still surprise and amaze me," Fong notes.

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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.

Now playing: Watch this: How much of our solar system should be protected wilderness?

3:46

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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Astronomers probe black hole origins after 39 new cosmic collisions detected – CNET

The number of gravitational wave events, caused by massive collisions between black holes and neutron stars, has quadrupled. In a suite of new papers, researchers from the LIGO and Virgo collaborations cataloged 39 "new" events, adding to the 11 already detected since the LIGO and Virgo gravitational wave detectors were switched on in 2015. 

Gravitational waves are ripples in space-time caused by collisions between black holes and other extreme cosmic phenomena. When massive cosmic bodies merge, they release exceptional amounts of energy, causing a wave to ripple out from their location. Eventually, that wave washes over the Earth, pinging detectors in the US (LIGO) and Italy (Virgo). Gravitational wave detections have revolutionized the way we see the universe, helping scientists to understand some of the most mystifying objects in space.

The new catalog, announced on Wednesday, is known as GWTC-2 and features 50 total events, including black hole mergers, neutron star mergers and, potentially, collisions between a black hole and neutron star. Thirty-nine events were detected between April 1 and Sept. 30, 2019 after the LIGO and Virgo facilities received a number of upgrades, increasing their sensitivity. 

The catalog update includes some of the most extreme cosmic collisions ever detected, including one revealed in September which created a black hole 150 times more massive than the sun -- the biggest yet -- and a particularly unusual merger between a black hole and a "mysterious object" that doesn't seem to fit in with previous discoveries.   

But the merger motherlode has excited gravitational wave astronomers because it gives them a ton of new data with which to probe the very nature of these extreme cosmic collisions.

An animation displaying all 50 gravitational wave events detected since 2015.

Zoheyr Doctor/University of Oregon/LIGO-Virgo Collaboration

"It's kind of like the difference between finding a single Iguanodon bone and finding hundreds of Iguanodon fossils," explains Eric Thrane, an astrophysicist at Monash University in Melbourne, Australia, and chief investigator with OzGrav, an Australian research center studying gravitational waves.

In one new preprint paper, submitted to the Astrophysical Journal Letters, the collaboration studied 47 of the 50 events and analyzed the physical properties of black hole mergers.

"Black holes are fascinating objects because they're very simple," says Thrane. "They only have two numbers describing them: their mass and their spin."

The spin of a black hole can be determined by the gravitational wave signal. This gives scientists a window into how black holes meet and fall into each other in deep space, revealing how they met.

Black holes are created when huge stars collapse in on themselves. Sometimes, two stars have been orbiting each other for eons in what is known as a "binary." Over time, they lose their mass and eventually die, collapsing to form black holes. But they continue orbiting each other until they collide and form a much larger black hole. In this instance, the spin doesn't change -- it points in the same direction. 

On the other hand, if the black holes have been wandering the cosmos in dense clusters of stars, all alone, then bump into one another, theory suggests this would mess with their spin. "When that happens, you'd expect the spin to be pointed in different directions," says Thrane.

Importantly, with the truckload of new observations, the LIGO and Virgo collaboration are seeing both types of black holes. 

"We're getting at the origin of where the black holes come from where [and] how they get together and merge," says Thrane.

The last observation run by LIGO and Virgo, O3b, took place between Nov. 1 2019 and March 27, 2020 before being stopped due to the coronavirus pandemic. Data from this period is currently being analyzed and will expand the catalog of gravitational wave events, once again furthering our understanding of extreme cosmic collisions.

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