SAN DIEGO — A sleepless night can leave the brain spinning with anxiety the next day.
In healthy adults, overnight sleep deprivation triggered anxiety the next morning, along with altered brain activity patterns, scientists reported November 4 at the annual meeting of the Society for Neuroscience.
People with anxiety disorders often have trouble sleeping. The new results uncover the reverse effect — that poor sleep can induce anxiety. The study shows that “this is a two-way interaction,” says Clifford Saper, a sleep researcher at Harvard Medical School and Beth Israel Deaconess Medical Center in Boston who wasn’t involved in the study. “The sleep loss makes the anxiety worse, which in turn makes it harder to sleep.” Sleep researchers Eti Ben Simon and Matthew Walker, both of the University of California, Berkeley, studied the anxiety levels of 18 healthy people. Following either a night of sleep or a night of staying awake, these people took anxiety tests the next morning. After sleep deprivation, anxiety levels in these healthy people were 30 percent higher than when they had slept. On average, the anxiety scores reached levels seen in people with anxiety disorders, Ben Simon said November 5 in a news briefing.
What’s more, sleep-deprived people’s brain activity changed. In response to emotional videos, brain areas involved in emotions were more active, and the prefrontal cortex, an area that can put the brakes on anxiety, was less active, functional MRI scans showed.
The results suggest that poor sleep “is more than just a symptom” of anxiety, but in some cases, may be a cause, Ben Simon said.
The cabbage tree emperor moth has wings with tiny scales that absorb sound waves sent out by bats searching for food. That absorption reduces the echoes that bounce back to bats, allowing Bunaea alcinoe to avoid being so noticeable to the nocturnal predators, researchers report online November 12 in the Proceedings of the National Academy of Sciences.
“They have this stealth coating on their body surfaces which absorbs the sound,” says study coauthor Marc Holderied, a bioacoustician at the University of Bristol in England. “We now understand the mechanism behind it.”
Bats sense their surroundings using echolocation, sending out sound waves that bounce off objects and return as echoes picked up by the bats’ supersensitive ears (SN: 9/30/17, p. 22). These moths, without ears that might alert them to an approaching predator, have instead developed scales of a size, shape and thickness suited to absorbing ultrasonic sound frequencies used by bats, the researchers found. The team shot ultrasonic sound waves at a single, microscopic scale and observed it transferring sound wave energy into movement. The scientists then simulated the process with a 3-D computer model that showed the scale absorbing up to 50 percent of the energy from sound waves.
What’s more, it isn’t just wings that help such earless moths evade bats. Other moths in the same family as B. alcinoe also have sound-absorbing fur, the same researchers report online October 18 in the Journal of the Acoustical Society of America. Holderied and his colleagues studied the fluffy thoraxes of the Madagascan bullseye moth and the promethea silk moth, and found that the fur also absorbs sound waves through a different process called porous absorption. In lab tests, the furry-bellied moths absorbed as much as 85 percent of the sound waves encountered. Researchers suspect that the equally fluffy cabbage tree emperor moth also has this ability.
Other moths that have ears can hear bats coming, and can quickly swerve out of the way of their predators, dipping and diving in dizzying directions (SN: 5/26/18, p. 11). Some moths also have long tails on their wings that researchers suspect can be twirled to disrupt bats’ sound waves (SN: 3/21/15, p. 17). Still other moths produce toxins to fend off foes.
Having sound-absorbent fur and scales “might require a lot less energy in terms of protection from the moth’s side,” says Akito Kawahara, an evolutionary biologist at the Florida Museum of Natural History in Gainesville who was not involved with the study. “It’s a very different kind of passive defense system.”
Holderied and his colleagues hope next to study how multiple scales, locked together, respond to ultrasonic sound waves. The findings could one day help in developing better soundproofing technology for sound engineers and acousticians.
Screwworms, the first pest to be eliminated on a large scale by the use of the sterile male technique, have shown an alarming increase, according to U.S. and Mexican officials…. The screwworm fly lays its eggs in open wounds on cattle. The maggots live on the flesh of their host, causing damage and death, and economic losses of many millions of dollars. — Science News, November 23, 1968
Update Though eradicated in the United States in 1966, screwworms reemerged two years later, probably coming up from Mexico. Outbreaks in southern U.S. states in 1972 and in Florida in 2016 were both handled with the sterile male technique, considered one of the most successful approaches for pest control. Males are sterilized with radiation, then released into a population to breed with wild counterparts; no offspring result. The method has been used with other pests, such as mosquitoes, which were dropped by drones over Brazil this year as a test before the technology is used against outbreaks like the Zika virus.
A physicist, a gamer and two editors walk into a bar. No, this isn’t the setup for some joke. After work one night, a few Science News staffers tried out a new board game, Subatomic. This deck-building game combines chemistry and particle physics for an enjoyable — and educational — time.
Subatomic is simple to grasp: Players use quark and photon cards to build protons, neutrons and electrons. With those three particles, players then construct chemical elements to score points. Scientists are the wild cards: Joseph J. Thomson, Maria Goeppert-Mayer, Marie Curie and other Nobel laureates who discovered important things related to the atom provide special abilities or help thwart other players. The game doesn’t shy away from difficult or unfamiliar concepts. Many players might be unfamiliar with quarks, a group of elementary particles. But after a few rounds, it’s ingrained in your brain that, for example, two up quarks and one down quark create a proton. And Subatomic includes a handy booklet that explains in easy-to-understand terms the science behind the game. The physicist in our group vouched for the game’s accuracy but had one qualm: Subatomic claims that two photons, or particles of light, can create an electron. That’s theoretically possible, but scientists have yet to confirm it in the lab.
The mastermind behind Subatomic is John Coveyou, who has a master’s degree in energy, environmental and chemical engineering. As the founder and CEO of Genius Games , he has created six other games, including Ion ( SN: 5/30/15, p. 29 ) and Linkage ( SN: 12/27/14, p. 32 ). Next year, he’ll add a periodic table game to the list . Because Science News has reviewed several of his games, we decided to talk with Coveyou about where he gets his inspiration and how he includes real science in his products. The following discussion has been edited for length and clarity. SN: When did you get interested in science?
Coveyou: My mom was mentally and physically disabled, and my dad was in and out of prison and mental institutions. So early on, things were very different for me. I ended up leaving home when I was in high school, hopscotching around from 12 different homes throughout my junior and senior year. I almost dropped out, but I had a lot of teachers who were amazing mentors. I didn’t know what else to do, so I joined the army. While I was in Iraq, I had a bunch of science textbooks shipped to me, and I read them in my free time. They took me out of the environments I was in and became extremely therapeutic. A lot of the issues we face as a society can be worked on by the next generation having a command of the sciences. So I’m very passionate about teaching people the sciences and helping people find joy in them.
SN: Why did you start creating science games?
Coveyou: I was teaching chemistry at a community college, and I noticed that my students were really intimidated by the chemistry concepts before they even came into the classroom. They really struggled with a lot of the basic terminology. At the same time, I’ve been a board gamer pretty much my whole life. And it kind of hit me like, “Whoa, wait a second. What if I made some games that taught some of the concepts that I’m trying to teach my chemistry students?” So I just took a shot at it. The first couple of games were terrible. I didn’t really know what I was doing, but I kept at it.
SN: How do you test the games?
Coveyou: We first test with other gamers. Once we’re ready to get feedback from the general public, we go to middle school or high school students. Once we test a game with people face-to-face, we will send it across the world to about 100 to 200 different play testers, and those vary from your hard-core gamers to homeschool families to science teachers, who try it in the classroom.
SN: How do you incorporate real science into your games?
Coveyou: I pretty much always start with a science concept in mind and think about how can we create a game that best reflects the science that we want to communicate. For all of our upcoming games, we include a booklet about the science. That document is not created by Genius Games. We have about 20 to 30 Ph.D.s and doctors across the globe who write the content and edit each other. That’s been a real treat to actually show players how the game is accurate. We’ve had so many scientists and teachers who are just astonished that we created something like this that was accurate, but also fun to play.
Voyager 2 has entered interstellar space. The spacecraft slipped out of the huge bubble of particles that encircles the solar system on November 5, becoming the second ever human-made craft to cross the heliosphere, or the boundary between the sun and the stars.
Coming in second place is no mean achievement. Voyager 1 became the first spacecraft to exit the solar system in 2012. But that craft’s plasma instrument stopped working in 1980, leaving scientists without a direct view of the solar wind, hot charged particles constantly streaming from the sun (SN Online: 9/12/13). Voyager 2’s plasma sensors are still working, providing unprecedented views of the space between stars.
“We’ve been waiting with bated breath for the last couple of months for us to be able to see this,” NASA solar physicist Nicola Fox said at a Dec. 10 news conference at the American Geophysical Union meeting in Washington, D.C.
NASA launched the twin Voyager spacecraft in 1977 on a grand tour of the solar system’s planets (SN: 8/19/17, p. 26). After that initial tour was over, both spacecraft continued travelling through the bubble of plasma that originates at the sun. “When Voyager was launched, we didn’t know how large the bubble was, how long it would take to get [to its edge] and whether the spacecraft could last long enough to get there,” said Voyager project scientist Edward Stone of Caltech.
For most of Voyager 2’s journey, the spacecraft’s Plasma Science Experiment measured the speed, density, temperature, pressure and other properties of the solar wind. But on November 5, the experiment saw a sharp drop in the speed and the number of solar wind particles that hit the detector each second. At the same time, another detector started picking up more high-energy particles called cosmic rays that originate elsewhere in the galaxy. Those measurements suggest that Voyager 2 has reached the region where the solar wind slams into the colder, denser population of particles that fill the space between stars. Voyager 2 is now a little more than 18 billion kilometers from the sun.
Intriguingly, Voyager 2’s measurements of cosmic rays and magnetic fields — which Voyager 1 could still make when it crossed the boundary — did not exactly match up with Voyager 1’s observations. “That’s what makes it interesting,” Stone said. The variations are probably from the fact that the two spacecraft exited the heliosphere in different places, and that the sun is at a different part of its 11-year activity cycle than it was in 2012. “We would have been amazed if they had looked the same.”
The Voyagers probably have between five and 10 years left to continue exploring interstellar space, said Voyager project manager Suzanne Dodd from NASA’s Jet Propulsion Laboratory in Pasadena, Calif.
“Both spacecraft are very healthy if you consider them senior citizens,” Dodd said. The biggest concern is how much power they have left and how cold they are — Voyager 2 is currently about 3.6° Celsius, close to the freezing point of its hydrazine fuel. In the near future, the team will have to turn off some of the spacecraft’s instruments to keep the craft operating and sending data back to Earth.
“We do have difficult decisions ahead,” Dodd said. She added that her personal goal is to see the spacecraft last until 2027, for a total of 50 years in space. “That would be fantastic.”
WASHINGTON – A months-long heat wave that scorched the Tasman Sea beginning in November of 2017 is the latest example of an extreme event that would not have happened without human-caused climate change.
Climate change also increased the likelihood of 15 other extreme weather events in 2017, from droughts in East Africa and the U.S. northern Plains states to floods in Bangladesh, China and South America, scientists reported December 10 at a news conference at the American Geophysical Union’s fall meeting. The findings were also published online December 10 in a series of studies in a special issue of the Bulletin of the American Meteorological Society. One study, of wildfires in Australia, was inconclusive on whether climate change influenced the event. And for the first time, none of the extreme events studied was determined to be the product of natural climate variability.
The findings mark the second year in a row — and only the second time — that scientists contributing to this special issue have definitively linked human-caused climate change with specific extreme weather events (SN: 1/20/18, p. 6). To the editors of the special issue, this latest tally is representative of the new normal in which the world finds itself.
“Many events were found to have appreciable climate change input; that’s not itself a surprise,” said Martin Hoerling, a special editor of the issue, at the news conference. “We are in a world that is warmer than it was in the 20th century, and we keep moving away from that baseline….”
“Nature is unfolding itself in front of our eyes,” added Hoerling, a research meteorologist with the U.S. National Oceanic and Atmospheric Administration in Boulder, Colo. Marine heat waves Several marine heat waves have struck the Tasman Sea, located between Australia and New Zealand, in the last decade, including a severe heat wave during the Southern Hemisphere summer of 2015 to 2016. But the 2017–2018 event extended across a much broader area, encompassing the entire sea. At its most severe point, temperatures increased to at least 2 degrees Celsius above average in the ocean, devastating the region’s iconic kelp forests and contributing to record-breaking summer temperatures in New Zealand.
Climate change was also responsible for another marine heat wave off the coast of East Africa that lasted from March to June 2017, according to a separate study. That marine heat wave, which the researchers found could not have happened in a preindustrial climate, also may have contributed to a drought in East Africa that caused food shortages for millions of people in the Horn of Africa, including 6 million in Somalia alone. The hot sea surface temperatures, the researchers found, doubled the probability that such a drought would occur.
“Any given extreme event might occur, but the severity of the events, that’s really what has changed. And it’s going to continue to change,” says Karsten Haustein, a climate scientist at the University of Oxford who is part of a research group that specializes in such climate attribution studies. Haustein is a coauthor on a study included in the collection that found that climate change dramatically increased the likelihood — by as much as 100 percent — of a six-day rainstorm that inundated Bangladesh in March 2017. The rainfall, which caused a flash flood, occurred before the onset of the monsoon season and proved devastating to farmers, Haustein says.
Legal liability The new issue highlights how the field of climate attribution science overall has crossed a critical threshold when it comes to liability, Lindene Patton, a strategic advisor at the Earth & Water Law Group in Washington, D.C., who specializes in climate attribution, said at the news conference. Although climate change was not found to be definitively to blame in most of the studies, it very likely was responsible for or intensified the impacts of nearly every extreme event examined in the issue — and that level of statistical certainty is enough to be legally important, Patton said. “The sufficiency of certainty differs in a court of law and in science. Perfection is not required; you just need to know if it’s more likely than not.”
The threat of liability may not be the ideal way to achieve more environment-friendly policies — but there is a precedent for it, she noted. “We clearly saw the emergence of liability in the 1970s with pollution” as a precursor to pollutant legislation.
BAMS Editor in Chief Jeff Rosenfeld acknowledges that in a world where real-time attribution studies of events such as 2018’s Hurricane Florence are becoming more common (SN Online: 9/13/18), the detailed, retrospective analyses of the BAMS special issue that lag by a year may seem a bit slow. “The funny thing is, initially, we considered it fast response,” he says.
But he thinks the looming question of climate liability highlights why the slower, more deliberate BAMS studies will continue to remain relevant, even in the swiftly changing climate of attribution science. “The people who are decision makers want numbers. They want risk factors.”
A new soft, wireless implant may someday help people who suffer from overactive bladder get through the day with fewer bathroom breaks.
The implant harnesses a technique for controlling cells with light, known as optogenetics, to regulate nerve cells in the bladder. In experiments in rats with medication-induced overactive bladders, the device alleviated animals’ frequent need to pee, researchers report online January 2 in Nature.
Although optogenetics has traditionally been used for manipulating brain cells to study how the mind works, the new implant is part of a recent push to use the technique to tame nerve cells throughout the body (SN: 1/30/10, p. 18). Similar optogenetic implants could help treat disease and dysfunction in other organs, too. “I was very happy to see this,” says Bozhi Tian, a materials scientist at the University of Chicago not involved in the work. An estimated 33 million people in the United States have overactive bladders. One available treatment is an implant that uses electric currents to regulate bladder nerve cells. But those implants “will stimulate a lot of nerves, not just the nerves that control the bladder,” Tian says. That can interfere with the function of neighboring organs, and continuous electrical stimulation can be uncomfortable.
The new optogenetic approach, however, targets specific nerves in only one organ and only when necessary. To control nerve cells with light, researchers injected a harmless virus carrying genetic instructions for bladder nerve cells to produce a light-activated protein called archaerhodopsin 3.0, or Arch. A stretchy sensor wrapped around the bladder tracks the wearer’s urination habits, and the implant wirelessly sends that information to a program on a tablet computer. If the program detects the user heeding nature’s call at least three times per hour, it tells the implant to turn on a pair of tiny LEDs. The green glow of these micro light-emitting diodes activates the light-sensitive Arch proteins in the bladder’s nerve cells, preventing the cells from sending so many full-bladder alerts to the brain. John Rogers, a materials scientist and bioengineer at Northwestern University in Evanston, Ill., and colleagues tested their implants by injecting rats with the overactive bladder–causing drug cyclophosphamide. Over the next several hours, the implants successfully detected when rats were passing water too frequently, and lit up green to bring the animals’ urination patterns back to normal.
Shriya Srinivasan, a medical engineer at MIT not involved in the work, is impressed with the short-term effectiveness of the implant. But, she says, longer-term studies may reveal complications with the treatment.
For instance, a patient might develop an immune reaction to the foreign Arch protein, which would cripple the protein’s ability to block signals from bladder nerves to the brain. But if proven safe and effective in the long term, similar optogenetic implants that sense and respond to organ motion may also help treat heart, lung or muscle tissue problems, she says.
Optogenetic implants could also monitor other bodily goings-on, says study coauthor Robert Gereau, a neuroscientist at Washington University in St. Louis. Hormone levels and tissue oxygenation or hydration, for example, could be tracked and used to trigger nerve-altering LEDs for medical treatment, he says.
There’s no sorrier sight than a puking preschooler. That’s the conclusion I recently reached around 2 a.m. as my poor 4-year-old heaved into the dim abyss. Luckily, her bout with the stomach flu was brief, and she was feeling better by the next day.
Stomach flu, also known as gastroenteritis, is a common affliction caused by bacteria or viruses that inflame the gut. Though mercifully short, the misery this brings is complete, for both the sufferer and the person charged with scrubbing chunks out of sheets, carpet and a stuffed toy cupcake. So when presented with something that could potentially cut short the puking, any parent would jump at the chance. That’s the promise of probiotics, “good” bacteria (typically in pill form) that some people think might help restore the irritated gut and get kids feeling better faster. But according to two big studies (here and here) of puking kids and probiotics, parents should save their money for something else.
For both studies, scientists studied kids ages 3 months to 4 years who came to an emergency department with acute gastroenteritis. In addition to receiving regular care, these kids took either a probiotic or placebo for five days. Then the researchers tallied up the kids’ symptoms to see if those who got the live bugs fared better than those who received a placebo. Long story short, the scientists found absolutely no differences.
The trials used different bacteria as probiotics. One used Lactobacillus rhamnosus, sold as products such as Culturelle, and the other used that bacteria plus Lactobacillus helveticus, a combination sold as Lacidofil. Neither of the formulations cut puking or other symptoms short. The kids had about the same duration of diarrhea (about two days) and missed the same amount of daycare (two days on average).
As far as studies go, these results, both published November 22 in the New England Journal of Medicine, are pretty clear: Probiotics didn’t help puking kids feel better faster. Of course, it’s possible that certain types of probiotics are good for other things, as an editorial in the same issue of the NEJM points out. Scientists have been studying whether probiotics can curb colic in babies, with some hints that helpful bacteria may reduce crying in breastfed babies (though the jury is still out). Other bacteria might also help newborns at risk of developing dangerous infections, as a recent study on babies in rural India suggests.
But when it comes to gastroenteritis in kids, probiotics’ benefits don’t seem to be there. If you’re desperate and willing to throw money at the problem, go ahead and buy your poor puking kid some probiotics. There’s no evidence they hurt, and it might make you feel like you’re doing something. Still, you’re probably better off spending your money on juice and popsicles.
Data from NASA’s now-defunct Cassini spacecraft show that five odd-shaped moons embedded in Saturn’s rings are different colors, and that the hues come from the rings themselves, researchers report. That observation could help scientists figure out how the moons were born.
“The ring moons and the rings themselves are kind of one and the same,” says planetary scientist Bonnie Buratti of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “For as long as the moons have existed, they’ve been accreting particles from the rings.” Saturn has more than 60 moons, but those nearest to the planet interact closely with its main band of rings. Between December 2016 and April 2017, Cassini passed close to five of these ring-dwelling moons: ravioli-shaped Pan and Atlas (SN Online: 3/10/17), ring-sculpting Daphnis and Pandora (SN: 9/2/17, p. 16) and potato-shaped Epimetheus. The flybys brought Cassini between two and 10 times closer to the moons than it had ever been, before the spacecraft deliberately crashed into Saturn in September 2017 (SN Online: 9/15/17).
Examining those close-ups, Buratti and her colleagues noticed that the moons’ colors vary depending on the objects’ distances from Saturn. And the moon hues are similar to the colors of the rings that the objects are closest to, the team reports online March 28 in Science. Close-in Pan was the reddest moon, while the farthest-out Epimetheus was the bluest. The researchers think the red material comes from Saturn’s dense main rings, and mostly consists of organics and iron (SN Online: 10/4/18). The blue material is probably water ice from Saturn’s more distant E ring, which is created by plumes erupting from the larger, icy moon Enceladus. The team thinks that the rings are continually depositing material onto the moons. “It’s an ongoing process,” Buratti says. She notes that “skirts” of material at Atlas and Pan’s equators are probably made of accreted ring debris, too.
The overall similarity between the moons and rings led the researchers to conclude that these small moons are leftover shards of a destructive event that created the rings in the first place. But it’s unknown whether that event was a collision between long-gone, larger moons, the shredding of one moon by Saturn’s gravity, or some other occurrence (SN: 1/20/18, p. 7).
Saturn, its rings and its moons are “very dynamic,” says planetary scientist Matija Ćuk of the SETI Institute in Mountain View, Calif. The idea that the rings are still shedding material onto the moons today “sounds perfectly reasonable.” He isn’t sure the moons formed at the same time as the rings, though. It’s possible “they formed from the rings since that catastrophic event,” he says.
Editor’s note: On April 10, the Event Horizon Telescope collaboration released a picture of the supermassive black hole at the center of galaxy M87. Read the full story here.
We’re about to see the first close-up of a black hole.
The Event Horizon Telescope, a network of eight radio observatories spanning the globe, has set its sights on a pair of behemoths: Sagittarius A*, the supermassive black hole at the Milky Way’s center, and an even more massive black hole 53.5 million light-years away in galaxy M87 (SN Online: 4/5/17). In April 2017, the observatories teamed up to observe the black holes’ event horizons, the boundary beyond which gravity is so extreme that even light can’t escape (SN: 5/31/14, p. 16). After almost two years of rendering the data, scientists are gearing up to release the first images in April.
Here’s what scientists hope those images can tell us.
What does a black hole really look like? Black holes live up to their names: The great gravitational beasts emit no light in any part of the electromagnetic spectrum, so they themselves don’t look like much.
But astronomers know the objects are there because of a black hole’s entourage. As a black hole’s gravity pulls in gas and dust, matter settles into an orbiting disk, with atoms jostling one another at extreme speeds. All that activity heats the matter white-hot, so it emits X-rays and other high-energy radiation. The most voraciously feeding black holes in the universe have disks that outshine all the stars in their galaxies (SN Online: 3/16/18). The EHT’s image of the Milky Way’s Sagittarius A, also called SgrA, is expected to capture the black hole’s shadow on its accompanying disk of bright material. Computer simulations and the laws of gravitational physics give astronomers a pretty good idea of what to expect. Because of the intense gravity near a black hole, the disk’s light will be warped around the event horizon in a ring, so even the material behind the black hole will be visible. And the image will probably look asymmetrical: Gravity will bend light from the inner part of the disk toward Earth more strongly than the outer part, making one side appear brighter in a lopsided ring.
Does general relativity hold up close to a black hole? The exact shape of the ring may help break one of the most frustrating stalemates in theoretical physics.
The twin pillars of physics are Einstein’s theory of general relativity, which governs massive and gravitationally rich things like black holes, and quantum mechanics, which governs the weird world of subatomic particles. Each works precisely in its own domain. But they can’t work together.
“General relativity as it is and quantum mechanics as it is are incompatible with each other,” says physicist Lia Medeiros of the University of Arizona in Tucson. “Rock, hard place. Something has to give.” If general relativity buckles at a black hole’s boundary, it may point the way forward for theorists.
Since black holes are the most extreme gravitational environments in the universe, they’re the best environment to crash test theories of gravity. It’s like throwing theories at a wall and seeing whether — or how — they break. If general relativity does hold up, scientists expect that the black hole will have a particular shadow and thus ring shape; if Einstein’s theory of gravity breaks down, a different shadow.
Medeiros and her colleagues ran computer simulations of 12,000 different black hole shadows that could differ from Einstein’s predictions. “If it’s anything different, [alternative theories of gravity] just got a Christmas present,” says Medeiros, who presented the simulation results in January in Seattle at the American Astronomical Society meeting. Even slight deviations from general relativity could create different enough shadows for EHT to probe, allowing astronomers to quantify how different what they see is from what they expect. Do stellar corpses called pulsars surround the Milky Way’s black hole? Another way to test general relativity around black holes is to watch how stars careen around them. As light flees the extreme gravity in a black hole’s vicinity, its waves get stretched out, making the light appear redder. This process, called gravitational redshift, is predicted by general relativity and was observed near SgrA* last year (SN: 8/18/18, p. 12). So far, so good for Einstein.
An even better way to do the same test would be with a pulsar, a rapidly spinning stellar corpse that sweeps the sky with a beam of radiation in a regular cadence that makes it appear to pulse (SN: 3/17/18, p. 4). Gravitational redshift would mess up the pulsars’ metronomic pacing, potentially giving a far more precise test of general relativity.
“The dream for most people who are trying to do SgrA* science, in general, is to try to find a pulsar or pulsars orbiting” the black hole, says astronomer Scott Ransom of the National Radio Astronomy Observatory in Charlottesville, Va. “There are a lot of quite interesting and quite deep tests of [general relativity] that pulsars can provide, that EHT [alone] won’t.”
Despite careful searches, no pulsars have been found near enough to SgrA* yet, partly because gas and dust in the galactic center scatters their beams and makes them difficult to spot. But EHT is taking the best look yet at that center in radio wavelengths, so Ransom and colleagues hope it might be able to spot some.
“It’s a fishing expedition, and the chances of catching a whopper are really small,” Ransom says. “But if we do, it’s totally worth it.” How do some black holes make jets? Some black holes are ravenous gluttons, pulling in massive amounts of gas and dust, while others are picky eaters. No one knows why. SgrA* seems to be one of the fussy ones, with a surprisingly dim accretion disk despite its 4 million solar mass heft. EHT’s other target, the black hole in galaxy M87, is a voracious eater, weighing in at between about 3.5 billion and 7.22 billion solar masses. And it doesn’t just amass a bright accretion disk. It also launches a bright, fast jet of charged subatomic particles that stretches for about 5,000 light-years.
“It’s a little bit counterintuitive to think a black hole spills out something,” says astrophysicist Thomas Krichbaum of the Max Planck Institute for Radio Astronomy in Bonn, Germany. “Usually people think it only swallows something.”
Many other black holes produce jets that are longer and wider than entire galaxies and can extend billions of light-years from the black hole. “The natural question arises: What is so powerful to launch these jets to such large distances?” Krichbaum says. “Now with the EHT, we can for the first time trace what is happening.”
EHT’s measurements of M87’s black hole will help estimate the strength of its magnetic field, which astronomers think is related to the jet-launching mechanism. And measurements of the jet’s properties when it’s close to the black hole will help determine where the jet originates — in the innermost part of the accretion disk, farther out in the disk or from the black hole itself. Those observations might also reveal whether the jet is launched by something about the black hole itself or by the fast-flowing material in the accretion disk.
Since jets can carry material out of the galactic center and into the regions between galaxies, they can influence how galaxies grow and evolve, and even where stars and planets form (SN: 7/21/18, p. 16).
“It is important to understanding the evolution of galaxies, from the early formation of black holes to the formation of stars and later to the formation of life,” Krichbaum says. “This is a big, big story. We are just contributing with our studies of black hole jets a little bit to the bigger puzzle.”
Editor’s note: This story was updated April 1, 2019, to correct the mass of M87’s black hole; the entire galaxy’s mass is 2.4 trillion solar masses, but the black hole itself weighs in at several billion solar masses. In addition, the black hole simulation is an example of one that uphold’s Einstein’s theory of general relativity, not one that deviates from it.
