A thick sphere of icy debris known as the Oort cloud shrouds the solar system. Other star systems may harbor similar icy reservoirs, and those clouds may be visible in the universe’s oldest light, researchers report.
Astronomer Eric Baxter of the University of Pennsylvania and colleagues looked for evidence of such exo-Oort clouds in maps of the cosmic microwave background, the cool cosmic glow of the first light released after the Big Bang, roughly 13.8 billion years ago. No exo-Oort clouds have been spotted yet, but the technique looks promising, the team reports November 2 in the Astronomical Journal. Finding exo-Oort clouds could help shed light on how other solar systems — and perhaps even our own — formed and evolved. The Oort cloud is thought to be a planetary graveyard stretching between about 1,000 and 100,000 times as far from the sun as Earth. Scientist think that this reservoir of trillions of icy objects formed early in the solar system’s history, when violent movements of the giant planets as they took shape tossed smaller objects outward. Every so often, one of those frozen planetary fossils dives back in toward the sun and is visible as a comet (SN: 11/16/13, p. 14).
But it’s difficult to observe the Oort cloud directly from within it. Despite a lot of circumstantial evidence for the Oort cloud’s existence, no one has ever seen it.
Ironically, exo-Oort clouds might be easier to spot, Baxter and colleagues thought. The objects in an exo-Oort cloud wouldn’t reflect enough starlight to be seen directly, but they would absorb starlight and radiate it back out into space as heat. For the sun’s Oort cloud, that heat signal would be smeared evenly across the entire sky from Earth’s perspective. But an exo-Oort cloud’s warmth would be limited to a tiny region around its star.
Baxter and colleagues calculated that the expected temperature of an exo-Oort cloud should be about –265° Celsius, or 10 kelvins. That’s right in range for experiments that detect the cosmic microwave background, or CMB, which is about 3 kelvins. The team used data from the CMB-mapping Planck satellite to search for areas across the sky with the right temperature (SN Online: 7/24/18). Then, the researchers compared the results with the Gaia space telescope’s ultraprecise stellar map to see if those regions surrounded stars (SN: 5/26/18, p. 5).
Although the astronomers found some intriguing signals around several bright, nearby stars, it wasn’t enough to declare victory. “That’s pretty interesting, but we can’t definitively say that it’s from an Oort cloud or not,” Baxter says.
Other ongoing CMB experiments with higher resolution, like those with the South Pole Telescope and the Atacama Cosmology Telescope in the Chilean Andes, could confirm if those hints of exo-Oort clouds are real.
“It’s a super clever observational idea,” says astronomer Nicolas Cowan of McGill University in Montreal who was not involved in the new work. “Looking for exo-Oort clouds is looking for a signature of these violent histories in other solar systems.”
Cowan has suggested that the cosmic microwave background could also be used to search for a hypothetical Planet Nine in the sun’s Oort cloud (SN: 7/23/16, p. 7). “The very coolest thing would be if we could get measurements of the exo-Oort clouds and find planets in those systems,” he says.
DNA from a 9,000-year-old baby tooth from Alaska, the oldest natural mummy in North America and remains of ancient Brazilians is helping researchers trace the steps of ancient people as they settled the Americas. Two new studies give a more detailed and complicated picture of the peopling of the Americas than ever before presented.
People from North America moved into South America in at least three migration waves, researchers report online November 8 in Cell. The first migrants, who reached South America by at least 11,000 years ago, were genetically related to a 12,600-year-old toddler from Montana known as Anzick-1 (SN: 3/22/14, p. 6). The child’s skeleton was found with artifacts from the Clovis people, who researchers used to think were the first people in the Americas, although that idea has fallen out of favor. Scientists also previously thought these were the only ancient migrants to South America. But DNA analysis of samples from 49 ancient people suggests a second wave of settlers replaced the Clovis group in South America about 9,000 years ago. And a third group related to ancient people from California’s Channel Islands spread over the Central Andes about 4,200 years ago, geneticist Nathan Nakatsuka of Harvard University and colleagues found. People who settled the Americas were also much more genetically diverse than previously thought. At least one group of ancient Brazilians shared DNA with modern indigenous Australians, a different group of researchers reports online November 8 in Science. Early Americans moved into prehistoric South America in at least three migratory waves, a study proposes. Ancestral people who crossed from Siberia into Alaska first gave rise to groups that settled North America (gray arrows). The first wave of North Americans (blue) were related to Clovis people, represented by a 12,600-year-old toddler from Montana called Anzick-1. They moved into South America at least 11,000 years ago, followed by a second wave (green) whose descendants contributed most of the indigenous ancestry among South Americans today. A third migration wave (yellow) from a group that lived near California’s Channel Island moved into the Central Andes about 4,200 years ago. Dotted areas indicate that people there today still have that genetic ancestry. Genetically related, but distinct groups of people came into the Americas and spread quickly and unevenly across the continents, says Eske Willerslev, a geneticist at the Natural History Museum of Denmark in Copenhagen and a coauthor of the Science study. “People were spreading like a fire across the landscape and very quickly adapted to the different environments they were encountering.”
Both studies offer details that help fill out an oversimplified narrative of the prehistoric Americas, says Jennifer Raff, an anthropological geneticist at the University of Kansas in Lawrence who was not involved in the work. “We’re learning some interesting, surprising things,” she says.
For instance, Willerslev’s group did detailed DNA analysis of 15 ancient Americans different from those analyzed by Nakatsuka and colleagues. A tooth from Trail Creek in Alaska was from a baby related to a group called the ancient Beringians, who occupied the temporary land mass between Alaska and Siberia called Beringia. Sometimes called the Bering land bridge, the land mass was above water before the glaciers receded at the end of the last ice age. The ancient Beringians stayed on the land bridge and were genetically distinct from the people who later gave rise to Native Americans, Willerslev and colleagues found.
The link between Australia and ancient Amazonians also hints that several genetically distinct groups may have come across Beringia into the Americas.
The Australian signature was first found in modern-day indigenous South Americans by Pontus Skoglund and colleagues (SN: 8/22/15, p. 6). No one was sure why indigenous Australians and South Americans shared DNA since the groups didn’t have any recent contact. One possibility, says Skoglund, a geneticist at the Francis Crick Institute in London and a coauthor of the Cell paper, was that the signature was very old and inherited from long-lost ancestors of both groups.
So Skoglund, Nakatsuka and colleagues tested DNA from a group of ancient Brazilians, but didn’t find the signature. Willerslev’s group, however, examined DNA from 10,400-year-old remains from Lagoa Santa, Brazil, and found the signature, supporting the idea that modern people could have inherited it from much older groups. And Skoglund is thrilled. “It’s amazing to see it confirmed,” he says.
How that genetic signature got to Brazil in the first place is still a mystery, though. Researchers don’t think early Australians paddled across the Pacific Ocean to South America. “None of us really think there was some sort of Pacific migration going on here,” Skoglund says.
That leaves an overland route through Beringia. There’s only one problem: Researchers didn’t find the Australian signature in any of the ancient remains tested from North or Central America. And no modern-day indigenous North or Central Americans tested have the signature either.
Still, Raff thinks it likely that an ancestral group of people from Asia split off into two groups, with one heading to Australia and the other crossing the land bridge into the Americas. The group that entered the Americas didn’t leave living descendants in the north. Or, because not many ancient remains have been studied, it’s possible that scientists have just missed finding evidence of this particular migration.
If Raff is right, that could mean that multiple groups of genetically distinct people made the Berigian crossing, or that one group crossed but was far more genetically diverse than researchers have realized.
The studies may also finally help lay to rest a persistent idea that some ancient remains in the Americas are not related to Native Americans today.
The Lagoa Santans from Brazil and a 10,700-year-old mummy from a place called Spirit Cave in Nevada had been grouped as “Paleoamericans” because they both had narrow skulls with low faces and protruding jaw lines, different from other Native American skull shapes. Some researchers have suggested that Paleoamericans — including the so-called Kennewick Man, whose 8,500-year-old remains were found in the state of Washington (SN: 12/26/15, p. 30) — weren’t Native Americans, but a separate group that didn’t have modern descendants.
But previous studies of Paleoamericans and Willerslev’s analysis of the Spirit Cave mummy’s DNA provide evidence that, despite their skull shapes, the Paleoamericans were not different from other Native Americans of their time. And the ancient people are more closely related to present-day Native Americans than any other group.
Willerslev presented the results about the Spirit Cave mummy to the Fallon Paiute-Shoshone tribe when the data became available. Based on the genetic results, the tribe was able to claim the mummy as an ancestor and rebury the remains.
What do you get when you flip a fossilized “jellyfish” upside down? The answer, it turns out, might be an anemone.
Fossil blobs once thought to be ancient jellyfish were actually a type of burrowing sea anemone, scientists propose March 8 in Papers in Palaeontology.
From a certain angle, the fossils’ features include what appears to be a smooth bell shape, perhaps with tentacles hanging beneath — like a jellyfish. And for more than 50 years, that’s what many scientists thought the animals were. But for paleontologist Roy Plotnick, something about the fossils’ supposed identity seemed fishy. “It’s always kind of bothered me,” says Plotnick, of the University of Illinois Chicago. Previous scientists had interpreted one fossil feature as a curtain that hung around the jellies’ tentacles. But that didn’t make much sense, Plotnick says. “No jellyfish has that,” he says. “How would it swim?”
One day, looking over specimens at the Field Museum in Chicago, something in Plotnick’s mind clicked. What if the bell belonged on the bottom, not the top? He turned to a colleague and said, “I think this is an anemone.”
Rotated 180 degrees, Plotnick realized, the fossils’ shape — which looks kind of like an elongated pineapple with a stumpy crown — resembles some modern anemones. “It was one of those aha moments,” he says. The “jellyfish” bell might be the anemone’s lower body. And the purported tentacles? Perhaps the anemone’s upper section, a tough, textured barrel protruding from the seafloor.
Plotnick and his colleagues examined thousands of the fossilized animals, dubbed Essexella asherae, unearthing more clues. Bands running through the fossils match the shape of some modern anemones’ musculature. And some specimens’ pointy protrusions resemble an anemone’s contracted tentacles. “It’s totally possible that these are anemones,” says Estefanía Rodríguez, an anemone expert at the American Museum of Natural History in New York City who was not involved with the work. The shape of the fossils, the comparison with modern-day anemones — it all lines up, she says, though it’s not easy to know for sure.
Paleontologist Thomas Clements agrees. Specimens like Essexella “are some of the most notoriously difficult fossils to identify,” he says. “Jellyfish and anemones are like bags of water. There’s hardly any tissue to them,” meaning there’s little left to fossilize. Still, it’s plausible that the blobs are indeed fossilized anemones, says Clements, of Friedrich-Alexander-Universität Erlangen-Nürnberg in Germany. He was not part of the new study but has spent several field seasons at Mazon Creek, the Illinois site where Essexella lived some 310 million years ago. Back then, the area was near the shoreline, Clements says, with nearby rivers dumping sediment into the environment – just the kind of place ancient burrowing anemones may have once called home.
Disinfection of public drinking water is one of the great public health success stories of the 20th century. In 1900, outbreaks of cholera and typhoid, both caused by waterborne bacteria, were common in American cities. In 1908, Jersey City, N.J., became the first U.S. city to routinely disinfect community water. Other cities and towns quickly followed, and by 1920, the typhoid rate in the United States had dropped by 66 percent.
But that battle isn’t over. Around the world, more than 2 billion people lack reliable access to safe water (SN: 8/18/18, p. 14), and half a million people die each year from diarrhea caused by contaminated water, according to the World Health Organization. And in the United States, challenges remain. The management failures that caused the 2014 lead contamination crisis in Flint, Mich., were a wake-up call (SN: 3/19/16, p. 8), but Flint is hardly alone. Systems in other big cities are also falling short. In October, officials in Newark, N.J., scrambled to hand out home water filters after it became clear that efforts to prevent lead from leaching into drinking water were not getting the job done. In the first six months of 2017, more than 22 percent of water samples in that city exceeded federal limits for lead, according to news reports.
If big cities are struggling, small towns with skimpy budgets as well as the many people who get their water from private wells often have it harder, lacking access to the infrastructure or technology to make water reliably safe. But science can help.
In this issue, Science News staff writer Laurel Hamers digs into the latest research on water treatment technology and finds a focus on efforts to invent affordable, scalable solutions. There’s a lot of engineering and chemistry involved, not surprisingly, and also physics — it’s hard to move water efficiently through a filter while also catching the bad stuff. Her story is a testament to researcher ingenuity, and a helpful primer on how a typical municipal water treatment plant works.
As I read Hamers’ story, I realized that I didn’t know how our water is treated here in Washington, D.C., even though I live barely a mile from one of the city’s two treatment plants. (I at least get credit for knowing the water comes from the Potomac River.) So I Googled it and found a description of how that process works. Plus I found data on potential contaminants such as Giardia and Cryptosporidium, as well as information on how residents can get their water tested for lead, which can leach from pipes or fixtures. I also learned that each spring, the Washington Aqueduct briefly switches disinfectants from chloramine to chlorine while the agency cleans the water pipes. That might explain the short-lived swimming pool smell in the tap water.
For me, this became a double win; I learned a lot about advances in water treatment technology from Hamers’ reporting, and I was motivated to seek out information about my local water supply.
If other readers feel inspired by our work to learn more, count me as a happy journalist.
A newly designed airplane prototype does away with noisy propellers and turbines.
Instead, it’s powered by ionic wind: charged molecules, or ions, flowing in one direction and pushing the plane in the other. That setup makes the aircraft nearly silent. Such stealth planes could be useful for monitoring environmental conditions or capturing aerial imagery without disturbing natural habitats below.
The aircraft is the first of its kind to be propelled in this way, researchers report in the Nov. 22 Nature. In 10 indoor test flights the small plane, which weighs about as much as a Chihuahua, traveled 40 to 45 meters for almost 10 seconds at a steady height, even gaining about half a meter of altitude over the course of a flight. Most planes rely on spinning parts to move forward. In some, an engine turns a propeller that pushes the plane forward. Or a turbine sucks in air with a spinning fan, and then shoots out jets of gas that propel the plane forward.
Ionic wind is instead generated by a high-voltage electric field around a positively charged wire, called an emitter. The electricity, often supplied by batteries, makes electrons in the air collide with atoms and molecules, which then release other electrons. That creates a swarm of positively charged air molecules around the emitter, which are drawn to a negatively charged wire. The movement of molecules between the two wires, the ionic wind, can push a plane forward. The current design uses four sets of these wires. Moving ions have helped other things to fly through the air, such as tiny airborne robots. But conventional wisdom said that using the approach to move something through the air as big as an airplane wasn’t possible, because adding enough battery power to propel a plane this way would make it too heavy to stay aloft. (The ion thrusters that propel spacecraft through the vacuum of space work in a very different way and aren’t functional in air.) Attempts to build ion-propelled aircraft in the 1960s weren’t very successful. MIT aeronautics researcher Steven Barrett thought differently. With the right aircraft design and light enough batteries, flight might be possible, his initial calculations suggested. So he and his team used mathematical equations to optimize various features of the airplane — its shape, materials, power supply — and to predict how each version would fly. Then the researchers built prototypes of promising designs and tested the planes at the MIT indoor track, launching them via a bungee system. “The models and the reality of construction don’t always match up perfectly,” Barrett says, so finding the right design took a lot of tries. But in the new study, he and his collaborators report success: 10 flights of the aircraft, which has a 5-meter wingspan and weighs just under 2.5 kilograms.
Barrett’s team isn’t the only one who thought the ionic wind method might take off. Based on calculations done in his lab, “we were confident that this could be done,” says Franck Plouraboue of the Toulouse Fluid Mechanics Institute in France, who wasn’t part of the research. “Here they’ve done it — which is fantastic!”
It’s an example of distributed electric propulsion, says Plouraboue — spreading out the thrust-generating parts of the plane, instead of having one centralized source. That’s a hot area for aircraft research right now. NASA’s X-57 Maxwell plane, for example, bears 14 battery-operated motors along its wings. Increasing the number of propellers makes the plane go farther on the same amount of energy, says Plouraboue, but also increases the drag. With ionic wind propulsion, increasing the number of wires doesn’t increase drag very much.
The plane still needs some upgrades before it’s ready for the real world: Its longest flight was only 12 seconds. And while the aircraft can maintain steady flight for a short time once launched, it can’t actually get off the ground using ionic wind.
Even with improvements, ion-propelled aircraft won’t find their niche as passenger planes, predicts Daniel Drew, an aerodynamics researcher at the University of California, Berkeley, who was not involved in the work. (Drew has designed miniature flying bots that fly using ionic propulsion.) It’s probably not feasible to scale up to something the size of a 747 — there are efficiency trade-offs as planes get bigger, he says. But down the road, the approach might be useful for small, uncrewed planes or drones.
Devices that eavesdrop on neural activity can help paralyzed people command computer tablets to stream music, text friends, check the weather or surf the internet.
Three people with paralysis below the neck were able to navigate off-the-shelf computer tablets using an electrode array system called BrainGate2. The results, published November 21 in PLOS One, are the latest to show that neural signals can be harnessed to directly allow movement (SN: 6/16/12, p. 5).
The two men and one woman had electrode grids implanted over part of the motor cortex, an area of the brain that helps control movement. The brain implants picked up neural activity indicating that the participants were thinking about moving a cursor. Those patterns were then sent to a virtual mouse that was wirelessly paired to the tablet. Using nothing more than their intentions to move a cursor, the three participants performed seven common digital tasks, including web browsing and sending e-mail. One participant looked up orchid care, ordered groceries online and played a digital piano. “The tablet became second nature to me, very intuitive,” she told the researchers when asked about her experience, according to the study.
Another participant enjoyed texting friends, “especially because I could interject some humor,” he told the scientists. The system even allowed two of the participants to chat with each other in real time.
For the study, the researchers used tablets with standard settings, without installing any shortcuts or features to make typing or navigation easier.
SAN DIEGO — Getting goose bumps doesn’t just make hairs stand on end; it may also help hair grow.
Nerves and muscles that raise goose bumps also stimulate stem cells in the skin to make hair follicles and grow hair. Ya-Chieh Hsu, a stem cell researcher at Harvard University, reported the unpublished findings December 9 at the joint meeting of the American Society for Cell Biology and the European Molecular Biology Organization. Getting goose bumps when it’s cold may encourage animals’ fur to grow thicker, Hsu said. Nerves that are part of the sympathetic nervous system — which controls pupil dilation, heart rate and other automatic processes — nestle next to stem cells that will create hair follicles, Hsu and her colleagues found. Usually nerves are wrapped in a protective coating called myelin, like electrical wire sheathed in plastic. But Hsu’s group found that the nerves’ ends were naked where they meet hair follicle stem cells, like wires stripped at the tips to make contacts with electrical nodes.
The nerves secrete the hormone norepinephrine. That hormone is necessary for hair growth, the researchers found. Those findings might help explain why hair loss is a side effect of drugs known as beta-blockers, which interfere with norepinephrine’s action.
Sympathetic nerves next to hair follicles are also wrapped around tiny arrector pili muscles, which contract to make hair cells stand on end, causing goose bumps. Mice with mutations that prevented the muscles from growing also lacked the sympathetic nerves and didn’t grow hair normally. Men with male pattern baldness also lack arrector pili muscles in their scalps, Hsu said, suggesting that sympathetic nerves and goose bump–raising muscles may also be important in that type of baldness. Restoring the nerves and muscles may lead to new hair growth, she said.
From tales about whales to enthralling scientific histories and the memoir of a frustrated astrophysicist, 2018 was a banner year for science books. Here are Science News’ picks for the titles that should be on any science lover’s bookshelf. Find detailed reviews of many of these books in the links below and in our Editor’s Pick: Favorite books of 2018.
The Truth About Animals Lucy Cooke
A zoologist debunks myths about bats, pandas, Adélie penguins and many other misunderstood creatures, recounting surprising stories from the animal kingdom (SN: 4/14/18, p. 26). Basic Books, $28
Spying On Whales Nick Pyenson
In this captivating look at whales, a paleontologist dives into the animals’ past, exploring how some of Earth’s most intelligent species came to be, and their uncertain future (SN: 7/7/18, p. 29). Viking, $27
Eager Ben Goldfarb
Some people see beavers as pests. But a science writer explains how the dam-building rodents are actually vital ecosystem engineers that can create or expand habitats that benefit the entire wildlife community (SN: 8/4/18, p. 28). Chelsea Green Publishing, $24.95
The Rise and Fall of the Dinosaurs Steve Brusatte
In this memoir, a paleontologist blends experiences from his career with evolutionary science to take readers on an engrossing journey through time, from the beginnings of the dinosaurs to their ultimate extinction. William Morrow, $29.99
The Big Ones Lucy Jones
A seismologist examines past catastrophic natural disasters, including volcanic eruptions, earthquakes and floods, and their impact on culture, politics and society (SN: 3/31/18, p. 26). With the past as a guide, the author warns readers to be prepared for when the next disaster strikes. Doubleday, $26.95
Losing the Nobel Prize Brian Keating
An astrophysicist’s dream of winning a Nobel Prize turned to dust after a promising experiment failed to find the first definitive evidence of cosmic inflation. The experience revealed how the prize can hamper scientific progress (SN: 4/14/18, p. 27). W.W. Norton & Co., $27.95
The Poisoned City Anna Clark
Weaving together history, science and reporting, a journalist explores the public health crisis that began in Flint, Mich., when lead started leaching into residents’ drinking water (SN: 7/21/18, p. 28). Metropolitan Books, $30
The Poison Squad Deborah Blum
A Pulitzer Prize–winning journalist tells the story of a government chemist at the turn of the 20th century and his mission to make food safe in the United States. Penguin Press, $28
Aroused Randi Hutter Epstein
The history of endocrinology makes for a strange and fascinating read, from the scientists who discovered the effects of hormones to the people whose lives have been irrevocably changed by these powerful substances (SN: 7/7/18, p. 28). W.W. Norton & Co., $26.95
Nine Pints Rose George
Blood, the feared as well as revered substance that flows throughout the human body, has a rich historical and scientific past (SN: 10/27/18, p. 28). Metropolitan Books, $30
She Has Her Mother’s Laugh Carl Zimmer
This comprehensive history recounts how researchers have come to understand genetic inheritance. Looking to the future, the author considers risks of gene manipulation (SN: 6/9/18, p. 29). Dutton, $30
Genetics in the Madhouse Theodore M. Porter
Using archival records, a science historian traces the origins of the study of human heredity to insane asylums in the 1800s (SN: 7/7/18, p. 29). Princeton Univ., $35
The Tangled Tree David Quammen
In chronicling the lives of researchers who made important advances in molecular biology and genetics, this book shows how recent findings shake up our understanding of evolution and the tree of life. Simon & Schuster, $30
An orbital oopsie has led to new proof of Albert Einstein’s physics prowess.
In 2014, two satellites intended for Europe’s Galileo network, the equivalent of the United States’ GPS network, were placed into orbit incorrectly, causing them to travel around Earth in ellipses rather than circles. That wasn’t ideal for the satellites’ originally intended navigational use, but scientists realized the wayward satellites were perfect for another purpose: testing Einstein’s theory of gravity, the general theory of relativity.
According to general relativity, gravity affects not just space, but also time. The deeper within a gravitational field you are, the slower time passes (SN: 10/17/15, p. 16). So a clock at a higher altitude will tick faster than one closer to Earth’s surface, where Earth’s gravity is stronger. The satellites’ orbital mishap allowed the most precise test yet of this effect, known as gravitational redshift, two teams of scientists report in a pair of papers in the Dec. 7 Physical Review Letters.
As the two misplaced satellites move in their elliptical orbits, their distance from Earth periodically increases and decreases by about 8,500 kilometers. Using the precise atomic clocks on the satellites, the scientists studied how that altitude change affected the flow of time. The clocks sped up and slowed down by tiny fractions of a second as expected, agreeing with the predictions of general relativity within a few thousandths of a percent, the teams report.
SEATTLE — The next generation exoplanet hunter is coming into its own. NASA’s Transiting Exoplanet Survey Satellite, or TESS, has already found eight confirmed planets in its first four months of observing — and some are unlike anything astronomers have seen before.
“The torrent of data is starting to flow already,” TESS principal investigator George Ricker of MIT said January 7 in a news conference at a meeting of the American Astronomical Society.
TESS launched in April and began science observations in July (SN: 5/12/18, p. 7). It was designed to be a follow-up to the prolific Kepler space telescope, which went dark in October after almost a decade of observing (SN Online: 10/30/18). Like Kepler, TESS searches for planets by watching for dips in starlight as planets cross, or transit, in front of their stars. Unlike Kepler, which stared unblinkingly at a single patch of sky for years, TESS scans a new segment of sky every month. Over two years, TESS will cover the entire 360 degrees of sky visible from Earth’s orbit.
In the first four segments, TESS has already spotted eight confirmed planets and more than 320 unconfirmed candidates, said Xu Chelsea Huang of MIT. And several of them are downright strange. Take the third-found planet, HD 21749b. Only 52 light-years away, it has the lowest temperature known for a planet orbiting a bright, nearby star, astronomers reported at the meeting and in a paper posted at arXiv.org on January 1. That makes it a great candidate for follow-up observations with future telescopes like the James Webb Space Telescope, scheduled to launch in 2021. Webb will use starlight filtering through the atmospheres of planets like this one to measure those atmospheres’ properties and search for signs of life (SN: 4/30/16, p. 32).
“If we want to study atmospheres of cool planets, this is the one to start with,” Huang said.
“Cool” is a relative term. This particular planet is still probably too hot and gassy to host life. Its orbit takes 36 Earth days, the longest known orbital period for planets transiting bright stars within 100 light-years of the sun.
That leaves it at a distance from the star that should heat the planet’s surface to about 150° Celsius, too hot for liquid water. And at 2.84 times Earth’s size and 23.2 times Earth’s mass, its density suggests it must have a thick atmosphere, unlike Earth’s life-friendly one.
But it’s still worth checking out, says astronomer Diana Dragomir of MIT, a member of the TESS team. Despite its heat, this planet is “tepid” compared with most of the scorched worlds whose atmospheres astronomers can probe right now, she says, so closer to an Earthlike system. Smaller, cooler, more Earthlike worlds are few and far between, and may not orbit such bright stars.
Finding more longer-period planets “helps you explore the diversity of planets that are out there,” says astronomer Paul Dalba of the University of California, Riverside, who studies exoplanet atmospheres but was not involved in the TESS discovery. Because TESS spends such a short stretch of time looking at each segment of the sky, astronomers expect most of its planets to have shorter years than an Earth month. “The fact that we’re already getting one that’s longer period I think is just really exciting, showing that TESS isn’t just for the shortest-period exoplanets.” The other planets in TESS’s first haul are equally exotic. TESS’s first find, Pi Mensae c, was reported in September ( SN Online: 9/18/18 ). The planet orbits its star every 6.27 days, and is about 2.14 times Earth’s size and 4.8 times Earth’s mass, giving it a density similar to pure water. The weirdest thing about that super-Earth is the company it keeps, Huang said. Previous observations showed that the star Pi Mensae also has a planet 10 times the mass of Jupiter that orbits every 5.7 years. That planet, Pi Mensae b, revolves on a wildly eccentric orbit, swinging between the distance of Earth and the distance of Jupiter from its star.
“This is the most extreme system we know of that has this type of architecture,” Huang said.
Theories of how planets develop such wonky orbits suggest that this super-Jupiter should have booted Pi Mensae c out of the system (SN: 5/12/18, p. 28). “We are really surprised that the inner super-Earth actually survived that disruptive event,” Huang said. “It’s a mystery we really want to understand.”
The second planet found by TESS, LHS 3844b, has a radius just 1.3 times Earth’s. But it swings around its star every 11 hours, giving it a surface temperature of about 540° C, Huang said. “It’s likely a lava world.”
TESS has completed about one-twelfth of its first sky survey, but Ricker is already writing proposals to extend its initial two-year mission. TESS’s orbit is held stable by the moon’s gravity, so it doesn’t need to spend any fuel to stay put. The fuel on board, used to change the direction the telescope points, is enough to last for 300 years.
“The orbit itself was designed to be extremely stable on timescales of decades to centuries,” Ricker said. “TESS is really going to be an important part of our astronomical efforts for the next decade and for more to come.”
Editor’s note: This story was updated January 29, 2019, to correct the description of the planet LHS 3844b’s orbit. It orbits a star, not a planet.
