Microbial stress can be a boon for young trees.

Saplings grown in soil microbes that have experienced drought, cold or heat are more likely to survive when faced with those same conditions, researchers report in the May 26 Science. And follow-up tests suggest that the microbes’ protective relationship with trees may linger beyond initial planting.

The team’s findings could aid massive tree planting efforts by giving new saplings the best chance of survival over the long run, says Ian Sanders, a plant and fungal ecologist at the University of Lausanne in Switzerland. “If you can control which microbes are put onto tree saplings in a nursery, you can probably help to determine whether they’re going to survive or not when they’re transplanted to the field.”
As climate change pushes global temperatures ever higher, many species must either adapt to new conditions or follow their ideal climate to new places (SN: 1/25/23). While forests’ ranges have changed as Earth’s climate has warmed and cooled over hundreds of millions of years, the pace of current climate change is too fast for trees to keep up (SN: 4/1/20).

Trees live a long time, and they don’t move or evolve very quickly, says Richard Lankau, a forest ecologist at the University of Wisconsin–Madison. They do have close relationships with fast-adapting soil microbes, including fungi, which can help plants survive stressful conditions.

But it was unclear whether microbes that had previously survived various climates and stresses might give inexperienced baby trees encountering a changing climate a leg up. With friends in the soil, “trees might have more tools in their toolkit than we give them credit for” to survive tough conditions, Lankau says.

For the study, Lankau and fellow ecologists Cassandra Allsup and Isabelle George — both also at UW–Madison — collected soil from 12 spots in Wisconsin and Illinois that varied in temperature and amount of rain. The team then used the soils to plant an abundance of 12 native tree species, including white oak (Quercus alba) and silver maple (Acer saccharinum). Overall, “we had thousands of plants we were monitoring,” Allsup says.

Those saplings grew in the soils in a greenhouse for two months before being transplanted in one of two field sites — one warm and one cold. To simulate drought, some trees in each spot were placed under transparent plastic sheets that blocked direct rainfall.

One site in northern Wisconsin was at the northern edge of the trees’ range and represented how trees might take root in a new area that’s getting warm enough for them to grow. There, trees planted in soil containing cold-adapted microbes better survived Wisconsin’s frigid winter temperatures. Plants that faced drought in addition to the cold, on the other hand, didn’t have the same benefit.

The other location, set up in central Illinois, was designed to represent a region where the climate is getting too hot or dry for the tree species to tolerate. Saplings grown in soil with microbes from arid spots were more likely to survive a lack of rain. But those grown in soils with heat-tolerant microbes were only slightly more likely to survive when they received normal rainfall.
Resident species already living in the area didn’t outcompete all of the transplanted microbes. Newly introduced fungi persisted in the soil for three years, a sign that any protective effects might last at least that long, the team found.

It’s still unclear which microbes best aid the trees. Analyses of microbes living in the soil hinted that fungi that live inside plant roots may better help trees survive drought. Cold-adapted soils seem to have fewer fungal species. But soils also contain bacteria, archaea and protists, Sanders says. “We don’t know what it is yet that seems to affect the plant survival in these changing climates.”
Determining which microbes are the important ones and whether there are specific conditions that best suit the soil is next up on the list, Allsup says. For example, can dry-adapted soil from Iowa help when planting trees in Illinois? “We need to think more about soils and combinations and [transplant] success… to actually save the forest.”

One caution, Sanders says, is that transporting microbes from one place to another en masse could bring the bad along with the good. Some microbes might be pathogens in the new place where they’re transplanted. “That’s also a big danger.”

A vaccine to fight Lyme disease, decades in the making, has received a temporary green light from the U.S. Department of Agriculture. But it’s not for people — it’s for mice.

The vaccine isn’t a rodent-sized injection, which wouldn’t work for targeting large populations quickly. Instead, it’s coated onto edible, nutrition-free pellets that mice gobble up.

The vaccine makes mice develop antibodies that neutralize Borrelia burgdorferi, the bacterium that causes most U.S. cases of Lyme disease. When ticks imbibe the blood of a vaccinated mouse, the idea goes, they won’t get an active infection and so can’t transmit the bacteria to people or other animals.
“Mice are probably one of the most important reservoir hosts for Lyme disease,” especially in the Eastern United States where Lyme disease is rampant, says Jean Tsao, a disease ecologist at Michigan State University in East Lansing who was not involved in developing the new vaccine. Reservoir hosts are animals with B. burgdorferi in their blood (SN: 2/5/21).

The vaccine has a conditional license, granted on May 9. That means it is available on request by groups such as federal and state health agencies under certain conditions for roughly one year, with the possibility of renewal.

The first well-documented case of Lyme disease in a person in the United States was in 1970. A vaccine for humans was available from 1998 to 2002, but it was taken off the market due to low consumer demand, likely related to fears over the vaccine’s safety. Some vaccinated people reported developing arthritis, but the U.S. Food and Drug Administration found no meaningful difference in joint problems in vaccinated versus control groups.

Both the mouse and human vaccines use a protein called OspA, found on the surface of B. burgdorferi, to spur antibody production and prevent infection.

Biologist Maria Gomes-Solecki co-led the early development of the new mouse vaccine. Her team distributed an early version of the vaccine to areas in upstate New York from 2007 to 2011. B. burgdorferi has a two-year life cycle in ticks. This and other factors mean it takes time to see meaningful reductions in infections, says Gomes-Solecki, of the University of Tennessee Health Science Center in Memphis. After two and five years of vaccination, the researchers found that tick infections were reduced by 23 and 76 percent, respectively, compared with control sites.

That early vaccine used live Escherichia coli bacteria to deliver the OspA protein. But the current, green-lighted version of the vaccine uses inactive E. coli. A 2020 study of the new vaccine found a 30 percent reduction in the proportion of infected ticks in residential areas after two years, compared with control sites. Several coauthors on that study work for US Biologic, the company Gomes-Solecki cofounded to develop the vaccine.
“The vaccine they have works, but it’s not spectacular” in terms of the rate of reducing B. burgdorferi–infected ticks, says Sam Telford III, an epidemiologist at Tufts University in Medford, Mass., who was involved in the development of the human vaccine and led research in the 1990s for vaccinating mice.

Edible vaccines targeted at hosts have worked well for other diseases and species. For instance, vaccinating prairie dogs against the plague has decreased levels of the disease. For now, it remains to be seen whether vaccinating mice will result in lower Lyme risks for humans. “With additional studies as the product rolls out … we’ll see more data on how well it does,” Telford says. “It’s certainly a step in the right direction.”

Researchers are studying many approaches to controlling Lyme disease, including genetically engineered mice that produce B. burgdorferi antibodies without the need for vaccination (SN: 8/9/17). Tsao and Telford are studying how to limit tick populations by controlling deer numbers. And a new vaccine for humans is in late-phase testing in several thousand people.

Vaccines that target wildlife hosts will remain one tool among many for managing exposure to Lyme disease, the researchers say. Showering after being in areas with ticks, wearing long sleeves and pants and doing tick checks will still be important.

“We have to continue to be vigilant,” Gomes-Solecki says.

SEATTLE — Tyrannosaurus rex may have had small arms, but it was no pushover.

This fierce dinosaur is known for its giant head, powerful jaws and overall fearsome appearance — except for those comical-looking arms. But the roughly meter-long limbs weren’t just vestigial reminders of a longer-armed past, paleontologist Steven Stanley of the University of Hawaii at Manoa said October 23 at the Geological Society of America’s annual meeting. Instead, the limbs were well-adapted for vicious slashing at close quarters, he argued.
T. rex ancestors had longer arms that the dinos used for grasping. But at some point, T. rex and other tyrannosaurs began to use their giant jaws for grasping instead, and the limbs eventually atrophied. Many people have hypothesized that the shrunken arms were, at best, used for mating or perhaps pushing the animal up off the ground; at worst, they were completely functionless.

But Stanley noted that the arms were quite strong, with robust bones that could sustain the impact of slashing. Each arm ended in two sharp claws about 10 centimeters long. Two claws give more slashing power than three, because each one can apply heavier pressure. Furthermore, the edges of the claws are beveled and sharp like those of a bear rather than flat like the grasping claws of an eagle. Those traits support the slasher hypothesis, Stanley concluded.

Many scientists aren’t convinced. While an interesting idea, it’s still unlikely that an adult T. rex would have used its arms as a primary weapon, says vertebrate paleontologist Thomas Holtz of the University of Maryland in College Park, who was not involved in the study. Although strong, the arm of a fully grown T. rex would barely reach past its chest, greatly reducing its potential strike zone. But a T. rex’s arms grew more slowly than its body, so younger dinos would have had proportionally longer arms. It’s possible the juveniles might have found them useful for slashing prey, he says.

At the beginning of 2017, parents and pediatricians got new peanut guidelines that, for most kids, are very pro-peanut. My colleague and fellow mom Meghan Rosen wrote about the recommendations, issued from the National Institute of Allergy and Infectious Diseases.

This “let them eat nuts” advice is based in part on a large and unusually clear dataset from a study that looked at babies at high risk of developing an allergy to peanuts. In the study, some of the children were regularly fed peanut-containing foods until their fifth birthdays. The others avoided any food with peanuts. By the end of the study, the kids who regularly ate peanut-containing food were way less likely to have a peanut allergy than the kids who had avoided the nut, the researchers found.
In a nutshell, parents of low-risk babies (infants without an egg allergy or severe eczema) should feel free to put peanut-containing food in the rotation as soon as their babies are ready for solid foods, around 4 to 6 months of age.

Whole peanuts and peanut butter are both choking hazards and shouldn’t be fed to babies. Instead, peanut butter (or peanut flour or peanut butter powder) can be mixed into breast milk, formula, fruit, yogurt or purees.

Babies with severe eczema or who are allergic to eggs ought to be seen by an allergist who can help guide the introduction of peanuts to the diet. Those appointments may reveal that some babies are in fact already allergic to peanuts. For those kids, peanuts may need to be avoided altogether.

When the recommendations were released, health officials were optimistic that the advice would lead to a reduction in peanut allergy in kids, given the study that found an early peanut introduction curbed this allergy. But that intro may not be happening as early or often as officials had hoped.
Bryce Hoffman, an allergist in New York City, suspected that the guidelines weren’t being used. Anecdotally, he and his colleagues hadn’t seen many infants coming into his allergy office with referrals for peanut allergy testing.

To get an idea of whether the guidelines were being applied (or not), Hoffman and his colleagues surveyed pediatricians about their advice to parents on peanuts. The results, which he presented October 30 at the annual meeting of the American College of Allergy, Asthma and Immunology, were discouraging.

Of the 79 pediatricians who responded, 30, or 38 percent, were not using the new guidelines in their practice. What’s more, 61, or 77 percent, of the pediatricians recommended high-risk patients eat peanuts later than ages 4 to 6 months, instead of sending those children to an allergist first for testing. Close to half (44 percent) of the pediatricians said they didn’t routinely test high-risk patients for allergy or send them to an allergist for testing.

This reluctance to test poses a problem for infants who “may have a dangerous anaphylactic reaction if given peanut,” Hoffman says. Testing can help clear up whether these infants should strictly avoid peanuts or be exposed to the nut first in an allergist’s office.

Peanuts got a bad rap for a long time, so it’s not surprising that parents and pediatricians might not jump at the chance to get peanut-containing food on the menu. The survey suggested that pediatricians aren’t familiar enough with the guidelines and, what’s more, are often too rushed to delve into the details during checkups. But for the new guidelines to do any good, they need to be used.

NASA’s New Horizons mission needs a catchier nickname for its next destination. The bar isn’t exactly high.

On New Year’s Day 2019, the spacecraft will fly by the tiny Kuiper Belt world that bears the official designation of (486958) 2014 MU69. NASA announced Monday that it is asking the public for an easier-to-remember nickname. The SETI Institute is hosting the contest.

As with similar crowdsourced naming campaigns, the name options vary widely. Current candidates range from Mjölnir (the hammer of the Norse god Thor) to Z’ha’dum (a planet from Babylon 5) to Peanut, Almond and Cashew — multiple name options may be necessary if the object is a binary pair. Whatever the object is named, it will be the most distant solar system body ever visited.
NASA will submit a formal name (or names) to the International Astronomical Union after the flyby, based on whether MU69 turns out to be a single body, binary pair or other system.

While anyone is welcome to submit a name or vote on existing options, SETI must approve any options before they appear on the ballot. So the odds don’t look good for Planet McPlanetface.

The naming campaign will close at 3 p.m. EST on December 1. The winner will be announced in early January.

Immigrants, they get the job done — eventually. Among dwarf mongooses, it takes newcomers a bit to settle into a pack. But once these immigrants become established residents, everyone in the pack profits, researchers from the University of Bristol in England report online December 4 in Current Biology.

Dwarf mongooses (Helogale parvula) live in groups of around 10, with a pecking order. The alphas — a top male and female — get breeding priority, while the others help with such group activities as babysitting and guard duty. But the road to the top of the social hierarchy is linear and sometimes crowded. So some individuals skip out on the group they were born into to find one with fewer members of their sex with which to compete —“effectively ‘skipping the queue,’” says ecologist Julie Kern.
Kern and her colleague Andrew Radford tracked mongoose immigration among nine packs at Sorabi Rock Lodge Reserve in Limpopo, South Africa. The researchers focused on guard duty, in which sentinels watch for predators and warn foragers digging for food.

Dwarf mongoose packs gain about one member a year. Among pack animals, higher group numbers are thought to come with the benefit of better access to shared social information like the approach of prowling predators. But upon arrival, new individuals are less likely to pitch in and serve as sentinels, Kern and Radford found. One possible reason: Immigrants lose weight during their transition from one pack to another and may not have the energy required for guard duty.
Pack residents don’t exactly put out a welcome mat for strangers, either. On the rare occasions when newcomers take a guard shift, residents tend to ignore their warning calls. Newbies may be seen as less reliable guards, or packs may have signature alarm calls that immigrants must learn. But after five months, these immigrants have come far. “Given time to recuperate following dispersal and a period of integration,” Kern says, “they contribute equally to their new group.”

Science came out of the lab and touched people’s lives in some awe-inspiring and alarming ways in 2017. Science enthusiasts gathered to celebrate a total solar eclipse, but also to march on behalf of evidence-based policy making. Meanwhile, deadly natural disasters revealed the strengths and limitations of science. Here’s a closer look at some of the top science events of the year.

Great American Eclipse
On August 21, many Americans witnessed their first total solar eclipse, dubbed the “Great American Eclipse.” Its path of totality stretched across the United States, passing through 14 states — with other states seeing a partial eclipse. This was the first total solar eclipse visible from the mainland United States since 1979, and the first to pass from coast to coast since 1918 (SN: 8/20/16, p. 14).
As people donned protective glasses to watch, scientists used telescopes, spectrometers, radio receivers and even cameras aboard balloons and research jets in hopes of answering lingering questions about the sun, Earth’s atmosphere and the solar system. One of the biggest: Why is the solar atmosphere so much hotter than the sun’s surface (SN Online: 8/20/17)? Data collected during the event may soon provide new insights.

March for Science
On April 22, Earth Day, more than 1 million people in over 600 cities around the world marched to defend science’s role in society. Called the first-ever March for Science, the main event was in Washington, D.C. Featured speakers included Denis Hayes, coordinator of the first Earth Day in 1970, and science advocate Bill Nye (SN Online: 4/22/17). Attendees advocated for government funding for scientific research and acceptance of the scientific evidence on climate change.

The march came on the heels of the Trump administration’s first budget proposal, released in March, which called for cutting federal science spending in fiscal year 2018 (SN: 4/15/17, p. 15). Some scientists worried that being involved with the march painted science in a partisan light, but others said science has always been political since scientists are people with their own values and opinions (SN Online: 4/19/17).

Climate deal announcement
On June 1, President Donald Trump announced that the United States would pull out of the Paris climate accord (SN Online: 6/1/17) — an agreement the United States and nearly 200 other countries signed in 2015 pledging to curb greenhouse gas emissions to combat global warming. With the announcement, Trump made good on one of his campaign promises. He said during a news conference that the agreement “is less about the climate and more about other countries gaining a financial advantage over the United States.”

Nicaragua and Syria signed on to the agreement in late 2017. A withdrawal from the United States would leave it as the only United Nations–recognized country to reject the global pact. President Trump left the door open for the United States to stay in the climate deal under revised terms. A U.S. climate assessment released in November by 13 federal agencies said it is “extremely likely” that humans are driving warming on Earth (SN Online: 11/3/17). Whether that report — the final version of which is due to be released in 2018 — will have an impact on U.S. involvement in the global accord remains to be seen.

North Korea nuclear test
On September 3, North Korea reported testing a hydrogen bomb, its sixth confirmed nuclear detonation, within a mountain at Punggye-ri. That test, along with the launch of intercontinental ballistic missiles this year, increased hostilities between North Korea and other nations, raising fears of nuclear war. As a result of these tests, the United Nations Security Council passed a resolution strengthening sanctions against North Korea to discourage the country from more nuclear testing.

As the international community waits to see what’s next, scientists continue to study the seismic waves that result from underground explosions in North Korea. These studies can help reveal the location, depth and strength of a blast (SN: 8/5/17, p. 18).

Natural disasters
The 2017 Atlantic hurricane season saw hurricanes Harvey, Irma and Maria devastate areas of Texas, Florida and the Caribbean. More than 200 people died from these three massive storms, and preliminary estimates of damage are as high as hundreds of billions of dollars. The National Oceanic and Atmospheric Administration had predicted that the 2017 season could be extreme, thanks to above-normal sea surface temperatures. The storms offered scientists an opportunity to test new technologies that might save lives by improving forecasting (SN Online: 9/21/17) and by determining the severity of flooding in affected regions (SN Online: 9/12/17).

In addition to these deadly storms, two major earthquakes rocked Mexico in September, killing more than 400 people. More than 500 died when a magnitude 7.3 earthquake shook Iran and Iraq in November. And wildfires raged across the western United States in late summer and fall. In California, fires spread quickly thanks to record summer heat and high winds. At least 40 people died and many more were hospitalized in California’s October fires. Rising global temperatures and worsening droughts are making wildfire seasons worldwide last longer on average than in the past, researchers have found (SN Online: 7/15/15).

Not so long ago, the lives of sea turtles were largely a mystery. From the time that hatchlings left the beaches where they were born to waddle into the ocean until females returned to lay their eggs, no one really knew where the turtles went or what they did.

Then researchers started attaching satellite trackers to young turtles. And that’s when scientists discovered that the turtles aren’t just passive ocean drifters; they actively swim at least some of the time.
Now scientists have used tracking technology to get some clues about where South Atlantic loggerhead turtles go. And it turns out that those turtles are traveling to some unexpected places.

Katherine Mansfield, a marine scientist and turtle biologist at the University of Central Florida in Orlando, and colleagues put 19 solar-powered satellite tags on young (less than a year old), lab-reared loggerhead sea turtles. The turtles were then let loose into the ocean off the coast of Brazil at various times during the hatching season, between November 2011 and April 2012.

The tags get applied to the turtles in several steps. Turtle shells are made of keratin, like your fingernails, and this flakes off and changes shape as a turtle grows. Mansfield’s team had figured out, thanks to a handy tip from a manicurist, that a base layer of manicure acrylic deals with the flaking. And then some strips of neoprene along with aquarium silicone attach the tag to the shell. With all that prep, the tag can stay on for months. The tags transmit while a turtle is at the water’s surface. A loss of the signal indicates that either the tag has fallen off and sunken into the water, “or something ate the turtle,” Mansfield says.
The trackers revealed that not all Brazilian loggerhead sea turtles stay in the South Atlantic. Turtles released in the early- to mid-hatching season stay in southern waters. But then the off-coast currents change direction, which brings later-season turtles north, across the equator. Their trajectories could take them as far as the Caribbean, the Gulf of Mexico or even farther north, which would explain genetic evidence of mixing between southern and northern loggerhead populations. And it may help to make the species, which is endangered, more resilient in the face of environmental and human threats, the researchers conclude December 6 in the Proceedings of the Royal Society B.

But, Mansfield cautions, “these are just a handful of satellite tracks for a handful of turtles off the coast of Brazil.” She and other scientists “are just starting to build a story” about what happens to these turtles out in the ocean. “There’s still so much we don’t know,” she says.

Mansfield hopes the tracking data will help researchers figure out where the young turtles can be found out in the open ocean so scientists can catch, tag and track wild turtles. And there’s a need for even tinier tags that can be attached to newly hatched turtles to see exactly where they go and how many actually survive those first vulnerable weeks and months at sea. Eventually, Mansfield would like to have enough data to make comparisons between sea turtle species.

“The more we’re tracking, the more we’re studying them, we’re starting to realize [the turtles] behave differently than we’ve historically assumed,” Mansfield says.

It’s like having “an elephant stand on your thumb.”

That’s how deep-sea physiologist and ecologist Mackenzie Gerringer describes the pressure squeezing down on the deepest known living fish, some 8 kilometers down. What may help these small, pale Mariana snailfish survive elephantine squashing, says Gerringer of the University of Washington’s Friday Harbor Labs, is a body bulked up, especially at the rump, with a watery goo.

The snailfish family gets its nickname from the way some shallow-water species in thundering tides grip a rock with a little suction cup on the belly and curl up. “Quite cute,” Gerringer says, and maybe, if you squint, somewhat like a snail.
She and colleagues discovered the deepest fish in 2014 in the western Pacific Ocean’s Mariana Trench and described the newly named Psuedoliparis swirei November 28 in Zootaxa. To catch specimens, Gerringer and colleagues turned to extreme trapping. They weighted a boxy, mesh-sided trap with steel plates to sink it. It took about four hours to fall to the bottom.

The scientists baited traps with mackerel, which snailfish don’t eat. But the fish do eat the underwater amphipods that mob a mackerel feast. Remotely related to harmless garden pill bugs, trench amphipods clean mackerel to the bones, Gerringer says. “I certainly wouldn’t swallow a live amphipod after seeing what they can do.” A snailfish, however, has a second set of jaws at the back of its throat that render crustaceans safe to swallow.

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For animals that live in such extreme pressures and temperatures (1° or 2° Celsius), snailfish don’t “look very robust … or very armored,” she says. “You can actually see the brain through the skull.”

Skimping on dense muscles and bones may improve snailfish buoyancy and save energy. These fish also lack air pockets that give a little lift to some other fishes, but that would get squashed to nothing so far down. Instead, the snailfish have inner deposits of a watery goo, more buoyant than muscles and bones and less compressible than air.

The goo also may aid swimming efficiency by offering a cheap shape improvement, Gerringer and colleagues proposed December 6 in Royal Society Open Science. To test the idea, she 3-D printed and motorized a robo-snailfish. Easier than catching a real one, Gerringer says.

A latex sleeve around the robot tail let her add or subtract water as an approximation of the gelatinous tissue. With an empty sleeve, the wide fish body pinches in to a thin tail, inviting vortices that cause drag. With this abrupt narrowing, robo-swimming proved a struggle. Filling the tail-sleeve to create a tapering rear let the robo-snailfish swim faster.

This goo is cheap tissue to grow, Gerringer says. It’s mostly water, one thing a fish living underneath eight kilometers of ocean has in abundance.

OXON HILL, Md. — Fast radio bursts could come from a turbulent home. At least one source of these bright, brief blasts of radio energy may be a young neutron star assisted by a nearby massive black hole, new research suggests.

“The biggest mystery around fast radio bursts is how such powerful and short-duration bursts are emitted,” says astronomer Daniele Michilli of the University of Amsterdam. The latest observations, reported online January 10 in Nature and at a meeting of the American Astronomical Society, suggest the bursts are coming from an environment with an unusually strong magnetic field. That field leaves a signature mark on the radio waves, twisting them into spirals, Michilli and his colleagues report.
Only a few fast radio bursts have ever been detected, and most appear as one-off events. Few known processes in the universe can explain them. But one burst, FRB 121102, has been seen repeating over the past decade or so (SN Online: 12/21/16). That repetition let astronomers follow up on the burst, and track it to a dwarf galaxy some 2.5 billion light-years away (SN: 2/4/17, p. 10).

Now, Michilli and his colleagues have used the Arecibo radio telescope in Puerto Rico to show that the burst’s source is embedded in an extremely strong magnetic field, 200 times stronger than the average magnetic field in the Milky Way.

The team measured the radio waves from 16 distinct bursts over three two-hour observational runs spanning several months. The bursts were exceptionally brief, the shortest lasting just 30 microseconds. That means that whatever emitted it must be just 10 kilometers wide, Michilli says.

“To emit a short burst you need a small region,” he says. “Therefore compact objects such as neutron stars are strongly favored by this result.”
The team also analyzed the radio waves in a new way, revealing that what looked like individual bursts were actually composed of many smaller sub-bursts, says astronomer Andrew Seymour of the Universities Space Research Association at Arecibo. That complicates the picture even further. The sub-bursts might be intrinsic to the object that creates them, or they might be the result of the waves passing through blobs of plasma, he says.

Finally, the observations showed that the waves were polarized, all oriented in the same direction. But something had twisted the waves, forcing them to rotate in corkscrews on their way from the dwarf galaxy to Earth. Follow-up observations with the Green Bank Telescope in West Virginia confirmed the twists were really there.

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The only phenomenon that is known to create such a rotation is a strong magnetic field, Michilli says. There are two main hypotheses for the bursts’ behavior. One is that they are from a young, energetic neutron star called a magnetar that’s sitting inside a shell of magnetized gas, which the magnetar itself expelled in a supernova explosion. The magnetar emits radio waves, and the shell makes them rotate.

“If you have young magnetars that have just been born in supernova explosions, only a few decades old, they could be very bursty objects, have very violent youths, and that could give rise to repeating fast radio bursts,” says astronomer Brian Metzger of Columbia University, who was not involved in the new study.

But Michilli points out that in order to drive such strong magnetic fields, the supernova remnant would have to be a million times brighter than even the brightest remnant in the Milky Way, the Crab nebula (SN: 1/1/11, p. 11). Instead, the bursts could come from a young neutron star orbiting the dwarf galaxy’s dominant black hole, which probably has between 10,000 and 1 million times the mass of the sun, he says.

Such large black holes are already known to have strong magnetic fields and to make polarized light rotate. And a neutron star nestling up next to a black hole is a plausible setup: There’s one orbiting the supermassive black hole at the center of the Milky Way. Although this neutron star’s radio waves don’t come in brief bright bursts, they are also twisted, the researchers say.

If not for that neutron star, “this would seem very contrived to me,” Metzger says. “That combines two unlikely things.”

More exotic explanations remain possible, too, Michilli’s team says.

“The joke is there are far more theories than there are observed bursts,” said coauthor Jason Hessels of the University of Amsterdam in a news conference January 10. “In the coming weeks we expect that very creative theorists will come up with explanations for our observations we haven’t thought of yet.”

Questions remain about whether all fast radio bursts, including the ones that don’t repeat, come from such exciting neighborhoods. “We cannot say yet if there are two classes with different properties, or if it’s one class of fast radio bursts and they just happen to be seen in different configurations,” Michilli says.

It’s also still unknown whether any other bursts have twisted waves at high frequencies — the smoking gun for strong magnetic fields. Measuring the rotation of the waves in FRB 121102 required hacking Arecibo with new hardware that let it detect higher frequencies than before. “We weren’t able to do that until recently,” Seymour says. “I stayed up on Christmas evening [2016] and made these observations, and luckily it paid off.” Maybe other fast radio bursts that Arecibo observed didn’t show the same rotation signature because the telescope wasn’t ready to measure it yet.

Hessels thinks “the prospects are quite good” for figuring out what fast radio bursts are in the near future. Several new radio observatories around the world are due to come online in the next few years. “These are going to be FRB factories,” Hessels said. He expects to find other repeating bursts, if they exist. “Then we can see if this repeating source is really a complete oddball, or part of a distribution of sources.”