No matter what planet you’re on, physics remains the same. For clouds, that means they follow a peculiar law – they form only around a seed of some sort, usually a fleck of dust or salt. On Earth, with its thick atmosphere and strong air currents, it’s possible to find these lightweight particles throughout the atmosphere, forming clouds at all different altitudes.
On Mars, this process is more difficult. Scientists have struggled to understand the high-altitude clouds they routinely see in Mars’ skies, since models predict that it’s difficult to lift even Mars’ prolific dust high enough into the atmosphere to form the clouds.Read More
A massive clump of dark matter may have plowed through a conga line of stars streaming around the Milky Way, according to new research presented Tuesday at the 234th Meeting of the American Astronomical Society.
The research, led by Ana Bonaca of the Harvard-Smithsonian Center for Astrophysics, reveals a curious abnormality in an otherwise uniform stream of stars orbiting in the Milky Way’s outer halo. Specifically, the researchers found an odd kink within the stream that they think was caused by a “close encounter with a massive and dense perturber,” according to the presentation’s abstract.
Because there are no obvious culprits made of normal matter that fit the bill, the researchers believe the intervening object could be a 5 million-solar-mass blob of dark matter that ripped through the stream at over 500,000 miles (800,000 kilometers) per hour roughly half a billion years ago.
Although this theory is far from confirmed, the unique observation does open the door to the possibility of using stellar streams like this one to constrain the properties of dark matter in the Milky Way. For example, if it was truly dark matter that tore through this stellar stream, Bonaca says it would suggest dark matter is “cold,” meaning it’s heavy, relatively slow moving (non-relativistic), and effectively clumps together.
To carry out the study, Bonaca and her team used data from the ESA’s Gaia space observatory, which has observed over a billion objects with unparalleled precision. Using this data, they mapped the positions and motions of stars in the stellar stream GD-1, which astronomers believe is the remains of a 70,000-solar-mass collection of old stars (called a globular cluster) that was shredded by past gravitational interactions with the Milky Way.
After noticing that GD-1 has an impact scar — a line of ejected stars — that indicates a past interaction, the researchers ran simulations to try to reproduce what they saw. After testing a variety of models, they found that the gravity of an object millions of times more massive than the Sun would do the trick.
The team naturally went searching for the object responsible. “Any massive and dense object orbiting in the halo could be the perturber,” Bonaca told Astronomy, “so a wandering supermassive black hole is definitely a possibility.” But so far, the team has failed to find any objects, black holes or otherwise, with the right trajectory and mass.
According to a preprint of their paper, “Orbit integrations back in time show that the stream encounter could not have been caused by any known globular cluster or dwarf galaxy.” This led the team to conclude the “most plausible explanation” is that GD-1 had a past encounter with a clump of dark matter, like those expected to reside in the halos of galaxies.
Bonaca admits the current research is not conclusive. “However, if we can locate where the perturber is now, that would open new research directions, including searching for additional observational evidence [indicating it is dark matter].” Such evidence could take the form of other stars or gas clouds being jostled around by the dark matter’s gravity, or even gamma-rays associated with dark matter annihilations, which occur when two dark matter particles slam into and destroy each other, releasing a flash of energy.
Bonaca says her team recently obtained measurements of the motion of stars in the disrupted part of the stream. By mapping out where the stars are now and how they are moving, the team should be able to better calculate where the perturber could be now to locate it. That would tell them were on the sky to look for that additional evidence that the cosmic cannonball is indeed dark matter.
Dark matter, the invisible material that so far shows itself only through the pull of its gravity, was first proposed nearly a century ago. It took another half-century to truly ignite the physics community. But at this point, a plethora of highly advanced projects have gone hunting for dark matter and come up empty.
Now scientists around the world are turning to new methods, and searching for dark matter that may look different than theory originally predicted. In the past, those hunts have focused largely on what physicists think are the most likely kind of dark matter particles, known as weakly interacting massive particles, or WIMPs. These tiny particles only interact with our universe through gravity, and they’re the easiest form of dark matter to reconcile with physics as we know it.
But it’s possible, in the absence of such particles so far, that physicists’ guesses about these WIMPs aren’t quite correct. So now they’re expanding their guesses, and trying to stay nimble in their search.
Experts in the field of dark matter recently collaborated to form a new report put out by the Department of Energy, called “Basic Research Needs for Dark Matter Small Projects New Initiatives.” Their work suggests scientists should cast many smaller nets for dark matter, both in terms of trying many different things, and in searching for even tinier particles. The DOE has also offered $24 million in small grants over the next four years to develop new ideas in the dark matter hunt.Read More
Billions of hoverflies from Europe descend on southern Britain each spring. The black and yellow striped bugs are no more than half an inch in length but make the long trek to Britain for the summer.
Once they arrive, the hoverflies pollinate flowers and lay eggs. The fly populations have remained stable unlike those of honeybees and other insects, which have dropped in recent years, researchers find in a new study. The discovery suggests the bugs may become increasingly important for pollinating crops.Read More
The Milky Way likely collided with a recently discovered dwarf galaxy called Antlia 2 less than a billion years ago, according to new research presented Wednesday at the 234th Meeting of the American Astronomical Society.
The research, spearheaded by Sukanya Chakrabarti of the Rochester Institute of Technology, supports a prediction she made a decade ago about how the Milky Way picked up a unique “ripple” pattern in its outer disk. If confirmed, researchers think the discovery will make Antila 2 an ideal natural laboratory for investigating the elusive substance known as dark matter. The work has been submitted for publication to the Astrophyical Journal Letters; a preprint is currently available.
Back in 2006, researchers revealed the Milky Way has a strange set of ripples percolating through its outer gas disk. In 2009, Chakrabarti published a study that analyzed these ripples, showing a collision between a dark-matter dominated dwarf galaxy and the Milky Way could explain how they formed.
To find the culprit, her team first rounded up the usual suspects: known satellites of the Milky Way like the Magellanic Clouds and the Sagittarius Dwarf Galaxy. However, the Magellanic Clouds are too far away and Sagittarius Dwarf has too little heft to explain the fingerprints left in our galaxy. This led Chakrabarti to predict that another dwarf galaxy — one that hadn’t been found at the time — was responsible for the galactic drive-by.
Fast forward to last year, when researchers using the second release of data from the Gaia satellite (called Gaia DR-2) uncovered a previously unknown, faint dwarf galaxy orbiting near the outskirts of the Milky Way: Antlia 2. The galaxy, which is located about 400,000 light-years away and is about as wide as the Large Magellanic Cloud, is also basically invisible. In fact, according to Chakrabarti, it’s currently the galaxy with the lowest known surface brightness (a measure of a galaxy’s light per area of the sky that it covers).
Chakrabarti set out to see whether this newly found galaxy could truly be the elusive dark matter-dominated dwarf she predicted nearly a decade ago. To test her theory, she calculated the past trajectory of Antlia 2 based on its movement and location now. Lo and behold, Antlia 2 does indeed appear to have smashed into the Milky Way in the past.
“The orbit of Antlia 2, as derived from Gaia DR-2 data, does bring it within [about 32,000 light-years] of the galactic center,” Chakrabarti said in an interview. “The outer parts of the Milky Way then show the perturbations [ripples] for about 500 million years or so.”
But just how well do the real ripples compare to those produced by a simulated collision between our galaxy and Antlia 2? “It’s almost dead on,” Chakrabarti says.
But before she and her team can be certain, though, they will need to wait for the next batch of data from the European Space Agency’s Gaia mission, which is working to map over a billion stars in the Milky Way. The new data will let researchers test their “hand-on-the-cutting-board kind of prediction,” Chakrabarti says, for how the stars within Antlia 2 should currently be moving.
If the motions line up with the predictions, it should clinch the case for Antlia 2 as the cause of our galaxy’s ripples.
NASA’s Spitzer Space Telescope was launched in 2003 on a mission to spend five years exploring the cosmos in infrared light. That means it excels at capturing images and chemical signatures of warm objects, like the glow of gas in nebulas and galaxies, or the composition of planets in still-forming alien solar systems. It even found a new ring of Saturn.
In recent years, it’s been operating with just one instrument, as the other two succumbed to the elements and ceased functioning. Despite its diminished capacity, the telescope is still delivering ground-breaking science. Now, NASA has finally decided to shut down the aging telescope. It will be switched off on January 30, 2020.
That the telescope has lasted this long is a testament to the engineers at the Jet Propulsion Laboratory, who have adapted with the telescope’s age to keep it functioning as best they could.
As with other infrared telescopes, Spitzer is sensitive to heat. Even the tiny amount of heat generated by its own electronics, and the glare of sunlight as it orbits, can create noise in its images. That’s why the telescope was designed to fly far from Earth’s own warmth, and reflect sunlight back without absorbing any more energy than it needs to power itself.
It also carried coolant to keep its instrumentation chilled, though it needed less than previous telescopes due to its clever design and orbit. Still, that coolant ran out back in 2009, rendering two of its instruments useless. Since then, it’s been running in what engineers call “warm mode,” with only two of the original four light wavelength windows available on its remaining instrument.
Due to its distant, Earth-trailing orbit, Spitzer has also drifted farther from Earth over time. It’s now about 600 times the Earth-Moon distance from us, and the angles between Spitzer, Earth, and the sun have shifted since the mission’s start. That makes sending data back to Earth a problem.
The telescope can’t charge its solar panels and communicate with Earth at the same time due to a geometric mismatch between its solar and communication arrays, and it only has so much battery life. So it can only point to Earth for 2.5 hours at a time before it must turn back to the sun and recharge. And that window will only grow shorter as the spacecraft continues to drift farther behind Earth.
On top of the time limitation, the angle Spitzer must turn to talk to Earth at all these days is beyond its original limits. Engineers have had to turn off certain safety protocols to tilt the spacecraft toward Earth as the angle between them has changed. If the spacecraft were to put itself in safe mode, engineers worry it might never emerge, thanks to aging systems and the increasing difficulty of communicating with the spacecraft.
In its time, Spitzer was one of NASA’s premiere space telescopes, classified among the space agency’s “Great Observatories” alongside Hubble, Compton Gamma Ray Observatory, and the Chandra X-Ray Observatory. Spitzer revealed breathtaking views of otherwise invisible materials swirling through the cosmos. It captured galaxies from the early days of the universe, their light shifted and stretched over the eons from bright ultraviolet light then to a dimmer infrared glow now. For nearer galaxies, Spitzer has helped pinpoint where rich dust lanes lay, and where star formation is churning out piles of baby stars.
Spitzer was also the first telescope to directly detect an exoplanet, picking up the light from HD 209458b in 2005. Until then, every exoplanet detection had been indirect, based on the wobble or transit of the star.
While generally considered a successor to Hubble, the upcoming James Webb Space Telescope is mostly an infrared instrument, and will pick up where Spitzer leaves off. With a primary mirror 7.5 times larger than Spitzer’s, JWST will see the universe though much of the same light, but with far greater precision.
“There have been times when the Spitzer mission could have ended in a way we didn’t plan for,” said Bolinda Kahr, Spitzer’s mission manager, in a press release. “I’m glad that in January we’ll be able to retire the spacecraft deliberately, the way we want to do it.”
(Inside Science) — A gangrene-inducing bite in Africa, 40 years of curiosity, and backyard experiments her daughters still complain about have all come together to tell Alison Cobb one thing: Stripes help zebras keep their cool. New research published this week in the Journal of Natural History shows stripes may create air flows that give zebras a kind of natural air conditioning system that helps them ward off the blazing sun.
“It’s about thermoregulation to avoid the heat and cold,” said Cobb, a retired amateur naturalist, who conducted the research with her zoologist husband, Stephen Cobb. Other scientists argue the main reason for stripes is to deter biting insects.
When she was four years old, Cobb, now 85, first wondered about zebra stripes after reading Rudyard Kipling’s story “How the Leopard Got His Spots.” A nature documentary she watched claimed zebra stripes were a type of camouflage. But camouflage seemed a poor explanation to Cobb in light of her own observations in Africa of lions prowling up and down herds of zebras deciding which one to eat. She had also witnessed zebras spending a great deal of time grazing in the hot midday sun — more than the antelopes which lived in the same area — and believed the stripes might be helping them deal with the heat.
Forty years ago she did her first experiment by draping different colored felt coats on water-filled oil drums out in the sun and taking the temperature of the water inside. Without direct access to research animals, she enlisted the help of her three daughters, aged 8, 9 and 10. She made them wear rugby shirts she sewed with zebra stripes and had her “experimental animals” crawl around on their hands and knees in the sun in England.
“They still complain about it. They are now in their early 60s,” Cobb said.
But when she touched the different stripes on their backs, they could tell her which was black and which was white without seeing. But this still didn’t give her a full explanation: If the white spots were cooler, why did they have black bits at all? Plus, she knew from extensive experience with horses that the animals sweat a lot, and she was still unsure how sweat would interact with the different colored stripes.
She didn’t get the chance to get close to zebras again until her 70th birthday, when she and her husband traveled back to Africa to test her idea on a couple of captive zebras living on private ranches in Kenya in December 2003. They measured the temperatures of adjacent black and white stripes on various parts of the zebras every 15 minutes throughout the day, as well as taking ambient air temperatures near the animals. They also took similar measurements of a zebra hide wrapped around clothes in the shape of a horse left in the sun on the ranch.
The research didn’t come without casualties — Stephen Cobb got bit by a territorial male stallion, and his wound later turned to gangrene. “He still has a scar,” Alison Cobb said.
But their research proved enlightening. They found the temperature of the black and white stripes differed greatly on the living animals, with greater differences at the hottest points of the day. The stripes on the inanimate hide had a similar difference between black and white stripes, but the highest temperatures of the black stripes were 15 degrees Celsius hotter than the peak black stripe temperatures of living zebras.
The research couple believes that these differences in temperature are enough to cause small air eddies. In the living zebras, these air flows could help to cool the zebras in the hottest times of the day by speeding up the evaporation of sweat.
The Cobbs also noted that the living zebras were able to stick their black hairs straight up in the air, and did so at some of the hottest times of the day. They hypothesize this behavior may also help in heat regulation, though the mechanism is still unclear.
Gabor Horvath, a researcher at Eotvos Lorand University in Budapest who has studied zebra stripes, but was not involved in the Cobbs’ research, does not believe that thermoregulation is the primary function of zebra stripes.
“Such alleged convective air eddies could be formed exclusively above horizontal striped surfaces,” he said in an email. “If the main function of zebra stripes were cooling by these air eddies, then only the nearly horizontal areas of the back of zebras should be striped.”
Tim Caro, a wildlife biologist at the University of California, Davis who has also studied zebra stripes but was not involved in the Cobbs’ research, said that “it’s an interesting descriptive study” about the differences in temperature between black and white zebra stripes. However, he doesn’t think the article advances our understanding of the principal evolutionary drivers of these stripe patterns in the animals. His research and that of Horvath and others indicates the stripes could deter insects from landing.
“We’re absolutely sure that it’s about thwarting biting flies,” Caro said, adding that tsetse and horseflies that pester the zebras in Africa can carry deadly diseases like African horse sickness, equine influenza and a form of horse sleeping sickness called nagana. “They just cannot afford to let these biting flies land on their coats.”
At the same time, Caro still believes that the stripes have thermal consequences for zebras. He, Horvath and the Cobbs all agree that there likely isn’t one single reason zebras have evolved stripes.
Let’s say I have an idea for a great invention one day — a series of pneumatic tubes that would shoot pods with people inside between cities at hundreds of miles an hour. My “Superloop” sounds like a sure-fire hit, but I don’t have the resources to pull the project off, and what’s more, the technology to build it isn’t actually there yet.
But I don’t want someone with more money to come along and snag the invention from me — I did do the hard work of having the idea, after all. If I lived anywhere else but the U.S., I might be out out of luck. But here, where bootstraps (even imaginary ones) are the upwardly mobile tool of choice, there’s a way to secure the rights to inventions and processes that don’t actually exist yet. It’s called a prophetic patent.Read More
Since Cassini plunged into Saturn’s atmosphere in 2017, ending its 13-year mission, scientists have continued to comb through the rich store of data it sent back, especially during its last year, when it dove closer to Saturn’s rings than ever before.
Among the findings are a deep look at the complex ring system, which hid more structure than scientists expected, including “straw-like” texture, tiny gaps shaped like propellers, and wavy, sculpted edges to the rings. Scientists still don’t know what causes some of these structures, something we may need to wait until the next big Saturn mission to find out.
Among the more concrete findings, scientists have realized the rings are less massive by half than they thought, and also that the rings are possibly quite young – maybe as young as 10 million years. This has big implications for how the ring system formed, and how it continues to evolve.Read More
Nearly 200 years ago Charles Darwin voyaged to the Galapagos islands and began to formulate his theory of evolution — largely thanks to his observations of how finches’ beaks varied in shape from island to island. But now, the finches’ famous beaks might be in trouble, thanks to a small, blood-sucking visitor.
An invasive insect, called Philornis downsi, is finding a home in the nests of almost every species of ground bird on the islands, causing serious damage to their populations. The birds are dying in alarming numbers and suffering malformations to one of their most defining qualities — their beaks.Read More