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X marks the spot for fast radio bursts – Nature.com

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In 2007, astronomers detected a flash of radio waves that was much shorter in duration than the blink of an eye1. Such signals, now called fast radio bursts (FRBs), are thought to have been produced billions of years ago in distant galaxies2. If so, the sources of FRBs must be spectacularly energetic and, quite possibly, unlike anything that has ever been observed in our Galaxy. Pinpointing the galaxies that host FRBs is the key to unlocking the mysterious origins of these signals. Writing in Nature, Ravi et al.3 report the discovery of the likely host galaxy of an FRB that travelled for 6 billion years before reaching Earth. The properties of this galaxy suggest that active star formation is not essential for making an FRB source.

The maxim ‘location, location, location’ applies to FRBs: knowing where these signals originate is crucial to understanding what generates them. Although astronomers have detected almost 100 FRB sources so far2, the measured positions of these sources on the sky have typically been too inaccurate to identify their host galaxies. One exception is the first FRB source observed to produce repeat bursts4. This source was localized to a region of active star formation in a puny ‘dwarf’ galaxy5. The finding supported theories that ascribe the origin of FRBs to the extremely condensed remnants of powerful stellar explosions called supernovae. For example, the repeating FRBs could originate from young and hyper-magnetized neutron stars — the collapsed remnants of massive stars6.

However, most FRB sources have not been seen to produce repeat bursts. Astronomers have therefore questioned whether these apparently one-off events have a different origin from that of the repeating FRBs2. From a practical point of view, one-off FRBs are much more challenging to study than repeaters. In the case of a repeating FRB, a patient observer can wait for further bursts and refine the measured position of the source. But for a one-off FRB, the position needs to be pinpointed by capturing the necessary high-resolution data at the same time as the burst is discovered.

Ravi and colleagues achieved this feat using an array of ten relatively small (4.5-metre-diameter) radio dishes spread across an area of roughly one square kilometre in Owens Valley, California. This distributed telescope network, known as the Deep Synoptic Array 10-antenna prototype (DSA-10), can scan a broad swathe of sky for FRBs (Fig. 1a). It can also provide enough spatial resolution to determine the position of a burst on the sky with high precision7. This precision must indeed be extremely high: unless the position is known to 1,000th of a degree, robustly associating an FRB with a specific host galaxy is impossible8. Even though Ravi et al. determined the position of their FRB to this level of precision (Fig. 1b), there is still some uncertainty as to whether or not the identified galaxy is the true host.

Figure 1 | Localization of a fast radio burst (FRB). a, Ravi et al.3 report observations from an array of radio telescopes known as the Deep Synoptic Array 10-antenna prototype (DSA-10). The field of view of DSA-10 is roughly 40 square degrees7, which is about 200 times the area on the sky that is covered by the full Moon when viewed from Earth’s surface. b, Ravi and colleagues used DSA-10 to precisely determine the position of an FRB — a millisecond-duration flash of radio waves. The broken white ellipse shows the region in which the FRB could be located. The authors then identified a massive galaxy (indicated by the yellow circle) that is the likely host of the FRB.

The authors demonstrate that this likely host galaxy is markedly different from the host5 of the well-localized source of the repeating FRB. It is 1,000 times more massive, and shows none of the prodigious star formation that is associated with the environment of the repeating-FRB source. Only a week before Ravi and colleagues’ work was published online, a similar breakthrough was reported9 using the Australian Square Kilometre Array Pathfinder (ASKAP) telescope. The authors of that paper achieved an even more precise localization of another one-off FRB, and also demonstrated that it originates from a massive galaxy that shows little signs of active star formation.

So, do these results mean that one-off FRBs and repeaters come from different galaxy types, and that they have physically different origins? Do astronomers have two puzzles on their hands? Perhaps, but with only three FRB host galaxies identified so far, many alternatives remain open. For instance, it is possible that all FRBs are generated by hyper-magnetized neutron stars, but that there are various ways in which such neutron stars can be produced10. Some might form directly through the collapse of a massive star, whereas others might be made from old neutron stars in a binary system that smash into each other as the orbital distance between them decreases. This difference could explain why some FRBs seem to originate from star-forming regions and others do not10.

Excitingly, we will soon know a lot more. The mystery of FRBs has driven many teams worldwide to tune radio telescopes towards discovering and localizing these signals, and many thousands of FRBs are thought to happen somewhere on the sky each day2. The fact that fewer than 100 FRB sources have been detected is a reflection of the small fields of view of existing radio telescopes. If a sensitive radio telescope could be built that has a continuous view of the entire sky, FRBs would look like a fireworks display. However, wide-field telescopes such as the Canadian Hydrogen Intensity Mapping Experiment11 (CHIME) are starting to change the game. It might not be long before astronomers have catalogued thousands of FRB sources and pinpointed at least dozens of them.

The precise localizations from DSA-10 and ASKAP are shedding light on the origins of FRBs, but they are also teaching us about the potential use of these signals as astronomical probes. FRBs are delayed in their arrival at Earth by the otherwise invisible material between galaxies2. By measuring the magnitude of this time delay, and comparing this measurement with the distance to the host galaxy, astronomers can map the density of ionized material in intergalactic space and thereby weigh the Universe in a unique way. The localizations of one-off FRBs suggest that FRB host galaxies will only slightly skew such measurements. Moreover, the results indicate that, with the detection and localization of thousands of FRBs, a 3D map of the material between galaxies could be made.

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The weird, repeating signals from deep space just tripled – CNET

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We’re picking up more signals from deep space.


Danielle Futselaar

Scientists suddenly have a whole lot more data on one of the strangest and most recent mysteries in the cosmos, so-called fast radio bursts (FRBs). First discovered in 2007, these fleeting blasts of radio waves originate thousands, millions or even billions of light years from Earth. 

FRBs have influenced the design of new radio telescopes like the Canadian Hydrogen Intensity Mapping Experiment (CHIME). And now a team of Canadian and American researchers using CHIME has reported a major new set of FRB detections that could fine-tune our understanding of where these enigmatic signals come from and what produces them. 

The group says it’s discovered eight new FRBs that repeat.


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“Repeating FRBs are highly valuable from an observational perspective since their repeating nature make them better candidates for localizing their host galaxies and multi-wavelength follow-up observations that can help determine if FRBs emit at wavelengths other than radio,” said Ryan McKinven, one of the researchers who is based at the University of Toronto and co-author of a paper about the FRBs.

Those follow-up observations could provide details about the origins of the strange bursts, he added. A larger sample size of repeating FRBs to study could also help scientists answer one of the obvious questions about non-repeating FRBs: Could they actually be repeating FRBs that just haven’t been recorded as repeating yet?

While dozens of FRBs have been detected and cataloged over the past 12 years, few of those deep space signals had been known to repeat themselves. Two have been documented so far in published, peer-reviewed journals. Two others — one via a Russian radio telescope, the other via Australia — have been reported but not yet reviewed. 

So with this batch of bursts, the number of reported repeaters has tripled — from four to 12. 

The team laid out its findings in a draft paper that’s been submitted to the Astrophysical Journal and was posted this month on the Arxiv pre-print site

Discovering different types of FRBs at an unexpected rate, we will soon open new windows into understanding the cosmological origin of these high-energy astrophysical phenomena,” said co-author Masoud Rafiei-Ravandi of the Perimeter Institute for Theoretical Physics. 

In addition to the sheer number of repeating FRBs discovered in one haul, one of the newfound repeaters appears to be much closer to Earth than the handful of fast radio bursts that have been traced back to a source galaxy. So far, traceable FRBs seem to come from sources on the other side of the universe — we’re talking billions of light years away.

However, in the new paper, the authors suggest that one of the repeating FRBs could actually originate near the edge of our own Milky Way galaxy but caution that more study is needed to better localize the signal. 

“Knowing that we are observing every patch of sky visible to CHIME once every day, it was only a matter of time before we detected a very nearby source,” co-author Pragya Chawla of McGill University said.

Studying relatively nearby FRBs will hopefully allow scientists to get a better idea of just what the heck is throwing off these signals, which could be anything from far-fetched notions like alien starships to the less fantastic but literally more powerful sources, like neutron stars.

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Climate Crisis: Hurricanes Are Making Some Spiders More Aggressive – Inverse

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In the most uncomfortable piece of climate crisis-related news yet, a team of scientists believe that the increasing tropical cyclones may be changing the temperament of a “super abundant” spider. As the storms continue to increase in tandem with the planet’s temperature, some of our eight-legged friends are starting to get more aggressive, report scientists in a paper published Monday in Nature Ecology and Evolution.

Specifically, these findings refer to a species of group-dwelling spiders called Anelosimus studiosus. They’re “hardly majestic,” lead study author Jonathan Pruitt, Ph.D., an associate professor at the University of California Santa Barbara, tells Inverse, but they happen to have very intricate social lives. Along the Gulf Coast, the spiders form multi-female groups that hunt in packs, dwell in group webs, and sometimes rear each other’s children. But the climate crisis may be shifting these old spider traditions toward a less interconnected lifestyle.

In the paper, Pruitt and his team show that hurricanes are actually changing the social and behavior dynamics of these spider colonies. The aggressive spiders in the colonies are well-equipped to handle the chaos, but the less aggressive ones are not. That inequality, he explains, may reshape life in the colony.

“There’s a behavioral tipping point when very very aggressive colonies stop working together, start killing each other, and the group wisely disbands,” he says. “Combine hurricane increases with global warming and I think you could get something like that.”

Anelosimus studiosus, a social cobweb spider, can live in groups, but if the group becomes too aggressive it can disband. 

The species as a whole will fare just fine, he says, in case you’re worried about losing even more animal and insect species to climate change. But the spiders are a good example of the way incomprehensibly large events — say, increases in large storms — can cause minute but significant changes too, like the behavior of a five-millimeter-long spider.

How Storms Change Spider Behavior

Anelosimus studiosus have two “behavioral” phenotypes (traits) that seem to be heritable, suggesting that they each have a genetic underpinning.

Some individuals are naturally more aggressive, which means that they swiftly attack in large numbers, kill their mates, are more wasteful their their prey, and are prone to fight among themselves; they also happen to be better at foraging when resources are scarce. The other individuals tend to be more docile, so they’re better at coexisting. To survive in a colony, you need a balance of both.

But Pruitt’s work suggests that tropical cyclones are selecting for the aggressive spiders. He observed 240 colonies before and after Hurricane Florence, Hurricane Michael, and tropical storm Alberto in the fall of 2018, finding that, while roughly 75 percent of each colony survived the storm, the colonies with more aggressive foraging responses produced more egg cases than the colonies with less aggressive tendencies.

Over time, this process shifts the nature of the colony toward the more aggressive types.

What Aggressive Behavior Means For the Species

While this shift likely won’t impact the species’ chances of survival, it does edge in on a “behavioral” tipping point. A colony of overly aggressive spiders, honed by the hostile summer cyclones of the Southern USA, is unlikely to cohabitate, says Pruitt. So if this trend continues, these spiders, which traditionally live in tight communities, may each decide to go it alone.

“I think the species as a whole will fare fine. But, if tropical cyclones start striking some regions all of the time (e.g., annually), then we might see this species revert back to is ancestral solitary state, where females no longer work together and they go it alone,” he explains.

Already, we know that extreme environmental disturbances (like the once predicted with increasing global temperature), will profoundly affect which species will live and die. But Pruitt’s work also shows a more nuanced approach to how climate change will impact species, as Eric Ameca, an ecologist who studies biodiversity and response to extreme climate events, adds in a commentary accompanying the new paper. While some species do have adaptive responses (so they’ll probably make it out okay), Ameca writes, they may look or behave a lot differently due to these extreme weather events.

Pruitt for one, sees the changing behavior of his spiders as a puzzle to be solved — and maybe applied across species in the future.

“It also means that the future of life, how it operates, and who prevails in the face of changing environments is going to be a very difficult puzzle to solve. Thankfully, humans like puzzles,” he says.

Abstract:

Extreme events, such as tropical cyclones, are destructive and influential forces. However, observing and recording the ecological effects of these statistically improbable, yet pro- found ‘black swan’ weather events is logistically difficult. By anticipating the trajectory of tropical cyclones, and sampling populations before and after they make landfall, we show that these extreme events select for more aggressive colony phe- notypes in the group-living spider Anelosimus studiosus. This selection is great enough to drive regional variation in colony phenotypes, despite the fact that tropical cyclone strikes are irregular, occurring only every few years, even in particularly prone regions. These data provide compelling evidence for tropical cyclone-induced selection driving the evolution of an important functional trait and show that black swan events contribute to within-species diversity and local adaptation.

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Hurricanes, spiders and Waffle Houses: How a McMaster evolutionary biologist spent his summer – TheSpec.com

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The findings might seem relevant only to spider colonies, but in a broader sense, studying the evolutionary tendencies of species following extreme weather events could have wide-ranging applications, Pruitt suggested, given climate models predicting more violent storms in the future.

“The fact is, we know surprisingly little about what kind of species do better after these storms; how it affects diversity, how storms can cause the evolution of certain collective traits, or individual traits … It hints that tropical storms could drive the evolution of aggressiveness in other species.”

Anelosimus studiosus spiders are not harmful to humans. Pruitt, an engaging and often humorous speaker — and a Canada 150 Research Chair — said that the spiders are just five millimetres long and, while terrifying to, say, a fly, “I could put some on your Red Lobster salad, and they would drown in the dressing before you would ever know they were there.”


He chased results in the field following hurricanes Florence, Michael and Alberto.

In the process, Pruitt said he observed more than 1,000 spiders in 240 colonies, listened to four fantasy novels in his car while logging 33,000 km on the road and ate frequently at U.S. road-trip staple Waffle House, which never seems to close.

He recorded spider behaviour by putting a little piece of paper in the webbed colony, and then used a mechanical toothbrush with a metal thread attached to vibrate the paper and coax spiders out of their home, as though food, like a moth, was waiting.

Docile spiders “take their sweet time” coming out, and aggressive ones emerge quickly. He noted his findings on the spot.

He laughs imagining the sight he must have been for locals who spotted him poking around a large silken web, wearing his beat-up Pokemon T-shirt (a childhood enthusiasm) and holding a toothbrush “that looks like a narwhal.”

Next up for the insect/storm chaser — McMaster colleagues call him a “swarm chaser’ — is Northern Australia for three months, starting in January, to examine cyclonic storm impact on spiders and a wide range of other insects.

“I’m narrowly missing what could be a cold winter here,” said Pruitt, who grew up in Florida.

“I chase summer.”

jwells@thespec.com

905-526-3515 | @jonjwells

jwells@thespec.com

905-526-3515 | @jonjwells

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