The left lobe of Pluto’s “heart” is a 600-mile-wide (1,000 kilometers) plain called Sputnik Planitia (formerly known as Sputnik Planum), which astronomers think is an enormous impact crater. This basin has been filling with nitrogen ice over the years and now contains huge amounts of the stuff. Indeed, observations by NASA’s New Horizons spacecraft, which flew by Pluto last year, suggest that Sputnik Planitia’s ice may be up to 6 miles (10 km) thick.
Sputnik Planitia is aligned nicely with Pluto’s “tidal axis” — the line along which the gravitational pull from the dwarf planet’s largest moon, Charon, is the strongest. And that’s probably no coincidence, according to two new studies, both of which were published online today (Nov. 16) in the journal Nature.
In the first study, James Keane, a doctoral student at the University of Arizona’s Lunar and Planetary Laboratory, and his colleagues modeled what happened as nitrogen ice accumulated in Sputnik Planitia. The results were dramatic.
“Once enough ice has piled up, maybe a hundred meters thick, it starts to overwhelm the planet’s shape, which dictates the planet’s orientation,” Keane said in a statement. “And if you have an excess of mass in one spot on the planet, it wants to go to the equator. Eventually, over millions of years, it will drag the whole planet over.”
This tumble brought Sputnik Planitia to the southeast, until the plain faced directly away from Charon as it does today. The team’s models predicted this very orientation: In this spot, near the tidal axis, the additional mass causes the least wobble in Pluto’s spin, the researchers said. (Pluto and Charon are tidally locked, meaning the two bodies always show the same face to each other, just as Earth’s moon always shows just one side to Earth.)
Pluto’s reorientation would have stressed the dwarf planet’s crust, leading to a network of faults and fractures on the surface, Keane and his colleagues report. And New Horizons spotted just such a network, whose characteristics match those predicted by the team’s models, they said.
Those models assume that Pluto harbors a subsurface ocean of liquid water — a notion bolstered by the second study, which was led by Francis Nimmo, a professor of Earth and planetary sciences at the University of California, Santa Cruz.
Nimmo and his team determined that the odds of Sputnik Planitia occurring in its present location, so close to the tidal axis, purely by chance were just 5 percent. So they, too, believe that a substantial reorientation has taken place.
The researchers suggested that the impact that created the basin weakened the crust overlying a buried ocean, causing some of the water to rise close to the surface. This action, along with the deposition of nitrogen ice in Sputnik Planitia, would have created enough of a “positive mass anomaly” to roll the dwarf planet, Nimmo and his colleagues wrote.
It’s hard to imagine Pluto reorienting in this way if it didn’t have an ocean, Nimmo said. For example, the team’s calculations suggest that Sputnik Planitia’s ice layer would have to be 25 miles (40 km) thick if no ocean existed.
“Our view is that 40 kilometers’ thickness of nitrogen ice is not that likely,” Nimmo told Space.com. “So if you want to have another source of dense material down there, then water seemed like a very natural explanation, because water is a lot denser than ice.”
The team also considered the possibility that rock migrated in to make up the extra mass, but that explanation doesn’t seem likely, either, Nimmo said.
“The rock is so far down there, and it’s also pretty strong,” he said. “So it’s hard to figure out how that rock would get moved around in the way that you would need.”
Other research groups also have suggested that Pluto may harbor a subsurface ocean, using other lines of evidence. One such argument points to the dwarf planet’s surface fractures, which may be the result of this ocean gradually freezing over time — a prospect also raised by Keane and his colleagues in their paper. (Water expands as it freezes, which would lead to stresses in overlying rock or ice.) In addition, Nimmo said, Pluto doesn’t have an equatorial bulge — and bodies with oceans can’t maintain such a bulge.
“All these lines of argument are pointing in the same direction,” Nimmo said.
If Pluto does have an ocean, how has it managed to avoid freezing up entirely over the past 4.5 billion years? Pluto is big enough that it may have retained a substantial amount of internal heat, Nimmo said. And the dwarf planet’s water may contain significant amounts of ammonia or other substances that act as an antifreeze, he added.
Astronomers think subsurface oceans exist on the Saturn moons Enceladus and Titan; the Jovian satellites Europa, Ganymede and Callisto; and a number of other solar system bodies. Indeed, such buried water may be abundant in the Kuiper Belt, the ring of frigid objects beyond Neptune’s orbit, Nimmo said.
“My guess is that, on big Kuiper Belt objects, these kinds of oceans are pretty common,” Nimmo said. “One of the lessons of the last 20 years is that oceans pop up in all kinds of unexpected places.”
The asteroid, called 16 Psyche, is one of the most massive in the asteroid belt. Researchers think the 186-mile-wide (300 kilometers) body, made of almost pure nickel-iron, might be the core of a world whose outer layers were blasted off by impacts billions of years ago.
Previous observations of Psyche showed no water on the surface. But according to Vishnu Reddy, an assistant professor at the University of Arizona’s Lunar and Planetary Laboratory, new data from the NASA Infrared Telescope Facility show evidence for water or hydroxyl, a molecule with one hydrogen atom bound to one oxygen atom, on Psyche’s surface. Hydroxyl exists on Earth, but it is very reactive and tends to combine with other compounds — and in fact can remove those compounds from the air.
“We did not expect a metallic asteroid like Psyche to be covered by water and/or hydroxyl,” Reddy said in a statement. “Metal-rich asteroids like Psyche are thought to have formed under dry conditions without the presence of water or hydroxyl, so we were puzzled by our observations at first.”
Reddy presented his results Wednesday (Oct. 20) at the 48th meeting of the American Astronomical Society’s Division for Planetary Sciences and 11th European Planetary Science Congress in Pasadena, California.
The water could have reached Psyche via past impacts from smaller asteroids that contain volatiles such as carbon, hydrogen and water, Reddy said.
NASA is currently reviewing a proposed mission to Psyche, which could tell astronomers whether the signal from the surface comes from water or hydroxyl.
The new research, co-authored by Reddy and led by Driss Takir at the U.S. Geological Survey, has been accepted to the Astronomical Journal, and can be read online here.
A strange and colossal ring system around an alien planet is apparently stuck in reverse, circling opposite to the planet’s own orbit around its parent star. While the arrangement appears unstable, new calculations show the rings could remain for at least 100,000 years.
These rings could account for bizarre eclipse behavior seen in 2007 for this star, called J1407, researchers on the new study suggested. Back then, astronomers observed an eclipse of the star last for several weeks, varying rapidly in brightness over the course of minutes. In 2015, the team suggested that there could be a planet orbiting this star with rings over a hundred times larger than the rings of Saturn.
In the new simulations conducted this year, the team calculated whether the planet could hang on to its ring system even as the gravitational effect of the star pulls on the rings. Because of the planet’s highly elliptical orbit, the star’s tug could potentially destabilize the rings when the planet approached closer, the researchers said.
According to the simulations, the system can stay stable for more than 10,000 orbits lasting 11 years each, with one stipulation, said lead author Steven Rieder, a postdoctoral fellow at the RIKEN Advanced Institute for Computational Science in Japan.
“The system is only stable when the rings rotate opposite to how the planet orbits the star,” Rieder said in a statement. “It might be far-fetched, massive rings that rotate in opposite direction,” he added, “but we now have calculated that a ‘normal’ ring system cannot survive.” More usually, a planet’s rings circle in the same direction as the planet is traveling, and the planet orbits in the same direction as the star turns.
It’s also possible that the stellar eclipses were created by a free-floating object passing between Earth and the star, but this would be true only if that object’s velocity as measured in the observations was not correct, Rieder said. He added that this would be a strange explanation, as the measurements the team obtained are “very accurate.”
The researchers said they next plan to examine how the ring structure was created, and how it evolves. A paper based on the research will appear shortly in the journal Astronomy and Astrophysics.
The dwarf planet, called 2014 UZ224, measures about 330 miles (530 kilometers) across and is located about 8.5 billion miles (13.7 billion km) from the sun, NPR reported today (Oct. 11). For comparison, Pluto’s largest moon, Charon, is about 750 miles (1,200 km) in diameter, and reaches a maximum distance of about 4.5 billion miles (7.3 billion km) from the sun.
A year on 2014 UZ224 (the time it takes the dwarf planet to orbit the sun) is about 1,100 Earth years. One Pluto year, for c is about 248 Earth years. The new object was also confirmed by NASA.
David Gerdes, a professor of astronomy at the University of Michigan, told NPR that the new dwarf planet was discovered using an instrument called the Dark Energy Camera (DECam). The universe is not only expanding but accelerating in that expansion, and “dark energy” is the name scientists have given the mechanism powering that expansion. The DECam was built to observe the movement of galaxies and supernovas (exploding stars) as they move away from the Earth. The goal is to provide more clues that will help reveal what dark energy actually is or where it comes from.
A project called the Dark Energy Survey is using observations from the DECam to create a map of the universe that provides information relevant to the study of dark energy. The DES maps have already been used to study dark matter (which makes up about eighty percent of all the mass in the universe but whose exact nature is still a mystery) and to find previously unidentified objects.
Part of the DES includes taking images of a few small patches of the sky “roughly” once per week, according to the mission website, and that’s what made this new discovery possible. While stars and galaxies appear in the same place in the sky, an object that is relatively close to Earth and orbiting the sun might appear to move over the course of a week or a few weeks.
A few years ago, Gerdes asked some visiting undergraduates to look for unidentified solar system objects in the galaxy map, according to NPR. The challenge was slightly difficult because the repeated observations would take place at irregular intervals, Gerdes said, but the students developed computer software to work with the irregularities and spot moving objects.
It took two years to confirm the detection of 2014 UZ224, NPR reports, and while its exact orbital path is still unclear, the scientists behind the discovery say they think that 2014 UZ224 is the third most-distant object in the solar system.
The smallest object in the solar system that has earned the title of “dwarf planet” (prior to this new discovery) is Ceres, which lies in the asteroid belt between Jupiter and Mars. Ceres is 590 miles (950 km) across. The object 2014 UZ224 might be too small to be considered a dwarf planet, Gerdes told NPR, but that will have to be decided by the International Astronomical Union (which made the controversial decision to demote Pluto to a dwarf planet). There are four other recognized dwarf planets in the solar system, but scientists think there could be dozens — or even more than 100 — objects that size that have yet to be discovered, according to NASA.
The region beyond Neptune’s orbit is known as the Kuiper Belt, a disk that is believed to contain thousands of icy, rocky bodies. Beyond that is a region known as the Oort Cloud — a sphere of icy, rocky bodies that surrounds the rest of the solar system. Most comets originate in the Kuiper Belt or the Oort Cloud, but their wide orbits bring them close to the sun.
While the outer regions of the solar system are thought to be made up mostly of objects smaller than Pluto, there may be another planet nearly the size of Neptune lurking in this outer territory. Recent research has shown that the movement of known bodies in the outer solar system may point to the existence of this ninth planet (which scientists have dubbed Planet Nine); that research has prompted efforts to spot the new planet with telescopes.
This huge ocean is probably buried about 60 miles (100 kilometers) beneath Dione’s icy shell, according to the study. Intriguingly, Dione’s putative ocean is likely in contact with the moon’s rocky core, team members said.
“The contact between the ocean and the rocky core is crucial,” study co-author Attilio Rivoldini, of the Royal Observatory of Belgium in Brussels, said in a statement. “Rock-water interactions provide key nutrients and a source of energy, both being essential ingredients for life.”
If the researchers are correct, 700-mile-wide (1,120 kilometers) Dione would be the third Saturn moon known to harbor a subsurface ocean, after giant Titan and geyser-spouting Enceladus. Astronomers think the Jupiter moons Europa, Callisto and Ganymede also have buried oceans, and recent research indicates Pluto might as well.
The study team, led by Mikael Beuthe of the Royal Observatory of Belgium, modeled the icy shells of Dione and Enceladus using gravity data gathered by NASA’s Saturn-orbiting Cassini spacecraft during its various flybys of the satellites.
Similar simulations performed by other researchers in the past have suggested that Dione is sea-free and that Enceladus’ ocean is buried deep. But Beuthe and his colleagues added a new wrinkle into their models.
“As an additional principle, we assumed that the icy crust can stand only the minimum amount of tension or compression necessary to maintain surface landforms,” Beuthe said in the same statement. “More stress would break the crust down to pieces.”
The team’s results indicate that Enceladus’ ocean is close to the surface, especially near the moon’s south pole — which makes sense, because geysers blast water ice and other material deep into space from this region.
The simulations also suggest Dione has a vast ocean tens of kilometers deep, buried under many miles of ice. This ocean has also probably existed for the moon’s entire history, meaning there has potentially been plenty of time for life to take root and evolve beneath Dione’s battered, icy shell, researchers said.
The new study was published online this week in the journal Geophysical Research Letters.
The skeleton of the Milky Way galaxy is coming into focus: A group of researchers recently dug up a cache galactic “bones” using a method that could answer key questions about these objects.
Galactic “bones” are long, cold, dense filaments of gas that have been discovered running through the center of the Milky Way’s spiral arms. But many other filaments have also been found in the fringes of the galactic arms, or in between them, prompting questions about where these features form.
The new paper reports the identification of 54 galactic filaments, nine of which have been previously identified. This is the first census of a large portion of the galaxy, according to the authors of the new work. The team used a computer algorithm to identify the filaments (previous investigations have searched for these filaments “by eye.”). The authors say the method can help them begin to answer questions about how the filaments formed, how they affect the growth and development of the galaxy, and what happens to them over time.
In 2012, a group of scientists at the Harvard Smithsonian center for Astrophysics (CfA) announced that a cold, dense thread of gas called “Nessie” was actually running straight through the center of one of the Milky Way galaxy’s four main spiral arms. The arms are made up of a sparser collection of gas, dust, stars and other cosmic objects (that could perhaps be considered more “flesh” than the bones). Nessie, which is at least 260 light-years long, was already known to scientists, but no one realized its apparent connection to the spiral arm.
The discovery raised questions about Nessie’s formation: Could the gravitational weight of the arm have formed this “bone”? Did the entire galaxy have a skeleton running through it? Since that discovery, a few other studies have identified a handful of other filaments; while some seem to have definite associations with the structure of the galaxy, some lie in between the arms.
The problem with trying to answer questions about the galactic bone formation is that there haven’t been enough filaments to conduct a comprehensive study, according to Ke Wang, an astronomer with the European Southern Observatory and lead author on the new paper.
With only a small sample of bones to study, it’s difficult to figure out if a particular property is unique to one filament or characteristic of filaments in general. The new study further emphasizes that there is actually tremendous variety among these filaments, and not just their location in the galaxy, Wang told Space.com. The new paper also identifies filaments that are shaped like the letter C, some like the letter S, some like the letter L, and still others like the letter X. What’s more, some of these filaments were “wiggling” and “twisting,” Wang said.
In order to do a characteristic study of the galactic filaments, Wang and his colleagues set out to complete the first large-scale census of the galaxy, and identify as many of these features as possible.
The team built a computer program inspired by something called a “minimum tree spanning” algorithm, which was invented back in the 1920s, and used today to optimize networks, including roads and water pipe systems, Wang told Space.com. The new program looks through a data set that has identified single points in the galaxy that feature the kind of cold, dense gas that defines the filaments. The program then tries to show that groups of those points are connected and make up a single structure.
This first survey used data collected by the Caltech Submillimeter Observatory 10 meter (32.8) telescope, which covered nearly half the galactic plane, as well as data from the Spitzer Space Telescope, Wide-field Infrared Survey Explorer (WISE), and the Arizona Radio Observatory.
The filaments identified in the new paper are between 10 and 276 of parsecs long, where one parsec is about 3.2 light-years, or about 18 trillion miles — in other words, these features are massive. (At 260 light-years long, Nessie is about 79 parsecs). The team identified 54, in a region that covers almost half the galactic plane. In the paper, the authors speculate that there are about 200 filaments of about this size in the entire galaxy.
“By revealing a relatively complete (in the searched region which is about half the Galactic plane) and a statistically significant sample, we are now confident with the statistics,” Wang said in an email. “We find that most large filaments concentrate along major spiral arms, but only about 30% of them run along the center of spiral arms.” Wang defines “bones” as those that lie in the center of a galactic arm.
“[The astrophysical community is] really at the start of revealing the whole population of these kinds of filaments in the entire galaxy,” Wang told Space.com
The new cache of galactic filaments identified by Wang and his team seems to have only opened up more questions about these cosmic objects. While some previous studies have shown that the bones can be found preferentially inside the galactic arms, others have shown that they form preferentially outside the arms, Wang said. But, previous studies only had a few filaments to study, he said. (He noted that various studies have also provided slightly different definitions of what constitutes a galactic filament).
So right now, scientists don’t know how the filaments form of why about 30% of them are showing up in the middle of galactic arms. Wang said scientists have hypothesized that the filaments could be formed by the “differential rotation of of materials in the galactic disk,” by turbulence in the interstellar medium, by magnetic fields, or some combination of factors.
“With the observations so far, including ours and other teams’ work, we are now at the starting of answering this question,” Wang said. “The community is excited about these large filaments, and there are more ongoing observational and theoretical works. I think in a few years’ time we may have an answer.”
Meteorites that crashed onto Earth billions of years ago may have provided the phosphorous essential to the biological systems of terrestrial life.
The meteorites are believed to have contained a phosphorus-bearing mineral called schreibersite, and scientists have recently developed a synthetic version that reacts chemically with organic molecules, showing its potential as a nutrient for life.
Phosphorus is one of life’s most vital components, but it often goes unheralded. It helps form the backbone of the long chains of nucleotides that create RNA and DNA; it is part of the phospholipids in cell membranes; and is a building block of the coenzyme used as an energy carrier in cells, adenosine triphosphate (ATP).
Yet the majority of phosphorus on Earth is found in the form of inert phosphates that are insoluble in water and are generally unable to react with organic molecules. This appears at odds with phosphorus’ ubiquity in biochemistry, so how did phosphorus end up being critical to life?
In 2004, Matthew Pasek, an astrobiologist and geochemist from the University of South Florida, developed the idea that schreibersite [(Fe, Ni)3P], which is found in a range of meteorites from chondrites to stony-iron pallasites, could be the original source of life’s phosphorus. Because the phosphorus within schreibersite is a phosphide, which is a compound containing a phosphorus ion bonded to a metal, it behaves in a more reactive fashion than the phosphate typically found on Earth.
Finding naturally formed schreibersite to use in laboratory experiments can be time-consuming when harvesting from newly fallen meteorites and expensive when buying from private collectors. Instead, it has become easier to produce schreibersite synthetically for use in the laboratory.
Natural schreibersite is an alloy of iron, phosphorous and nickel, but the common form of synthetic schreibersite that has typically been used in experiments is made of just iron and phosphorus, and is easily obtainable as a natural byproduct of iron manufacturing. Previous experiments have indicated it reacts with organics to form chemical bonds with oxygen, the first step toward integrating phosphorous into biological systems.
However, since natural schreibersite also incorporates nickel, some scientific criticism has pointed out that the nickel could potentially alter the chemistry of the mineral, rendering it non-reactive despite the presence of phosphides. If this were the case, it would mean that the experiments with the iron-phosphorous synthetic schreibersite would not represent the behavior of the mineral in nature.
“There was always this criticism that if we did include nickel it might not react as much,” said Pasek.
Pasek and his colleagues have addressed this criticism by developing a synthetic form of schreibersite that includes nickel.
In a recent paper published in the journal Physical Chemistry Chemical Physics, Pasek and lead author and geochemist Nikita La Cruz of the University of Michigan show how a form of synthetic schreibersite that includes nickel reacts when exposed to water. As the water evaporates, it creates phosphorus-oxygen (P-O) bonds on the surface of the schreibersite, making the phosphorus available to life. The findings seem to remove any doubts as to whether meteoritic schreibersite could stimulate organic reactions.
“Biological systems have a phosphorus atom surrounded by four oxygen atoms, so the first step is to put one oxygen atom and one phosphorous atom together in a single P-O bond,” Pasek explained.
Terry Kee, a geochemist at the University of Leeds and president of the Astrobiology Society of Britain, has conducted his own extensive work with schreibersite and, along with Pasek, is one of the original champions of the idea that it could be the source of life’s phosphorus.
“The bottom line of what [La Cruz and Pasek] have done is that it appears that this form of nickel-flavored synthetic schreibersite reacts pretty much the same as the previous synthetic form of schreibersite,” Kee said.
Pasek described how meteors would have fallen into shallow pools of water on ancient Earth. The pools would then have undergone cycles of evaporation and rehydration, a crucial process for chemical reactions to take place. As the surface of the schreibersite dries, it allows molecules to join into longer chains. Then, when the water returns, these chains become mobile, bumping into other chains. When the pool dries out again, the chains bond and build ever larger structures.
“The reactions need to lose water in some way in order to build the molecules that make up life,” said Pasek. “If you have a long enough system with enough complex organics, then, hypothetically, you could build longer and longer polymers to make bigger pieces of RNA. The idea is that at some point you might have enough RNA to begin to catalyze other reactions, starting a chain reaction that builds up to some sort of primitive biochemistry, but there’s still a lot of steps we don’t understand.”
Demonstrating that nickel-flavored schreibersite, of the sort contained in meteorites, can produce phosphorus-based chemistry is exciting. However, Kee said further evidence is needed to show that the raw materials of life on Earth came from space.
“I wouldn’t necessarily say that the meteoric origin of phosphorus is the strongest idea,” he said. “Although it’s certainly one of the more pre-biotically plausible routes.” [Fallen Stars: A Gallery of Famous Meteorites]
Despite having co-developed much of the theory behind schreibersite with Pasek, Kee pointed out that hydrothermal vents could rival the meteoritic model. Deep-sea volcanic vents are already known to produce iron-nickel alloys such as awaruite, and Kee says that the search is now on for the existence of awaruite’s phosphide equivalent in the vents: schreibersite.
“If it could be shown that schreibersite can be produced in the conditions found in vents — and I think those conditions are highly conducive to forming schreibersite — then you’ve got the potential for a lot of interesting phosphorylation chemistry to take place,” said Kee
Pasek agreed that hydrothermal vents could prove a good environment to promote phosphorus chemistry, with the heat driving off the water to allow the P-O bonds to form. “Essentially it’s this driving off of water that you’ve got to look for,” he added.
Pasek and Kee both agreed that it is possible that both mechanisms — the meteorites in the shallow pools and the deep-sea hydrothermal vents — could have been at work during the same time period and provided phosphorus for life on the young Earth. Meanwhile David Deamer, a biologist from the University of California, Santa Cruz, has gone one step further by merging the two models, describing schreibersite reacting in hydrothermal fields of bubbling shallow pools in volcanic locations similar to those found today in locations such as Iceland or Yellowstone National Park.
Certainly, La Cruz and Pasek’s results indicate that schreibersite becomes more reactive as the environment in which it exists gets warmer.
“Although we see the reaction occurring at room temperature, if you increase the temperature to 60 or 80 degrees Celsius [140 or 176 degrees Fahrenheit], you get increased reactivity,” said Pasek. “So, hypothetically, if you have a warmer Earth, you should get more reactivity.”
One twist to the tale is the possibility that phosphorus could have bonded with oxygen in space, beginning the construction of life’s molecules before ever reaching Earth. Schreibersite-rich grains coated in ice and then heated by shocks in planet-forming disks of gas and dust could potentially have provided conditions suitable for simple biochemistry. While Pasek agreed with that idea in principle, he said he has “a hard time seeing bigger things like RNA or DNA forming in space without fluid to promote them.”
The most detailed 3D map yet of a billion stars in the Milky Way galaxy was released today (Sept. 14), along with a sneak peek at brand-new data on millions of stars collected by the European Space Agency’s Gaia spacecraft.
Gaia has been scanning the sky to create a catalog of more than a billion stars in and around the Milky Way since 2014. Today’s first data release includes precise positions and brightness of 1.142 billion stars, plus distances and motions of more than 2 million stars. ESA scientists used the observations to create this stunning fly-through of a packed star cluster.
Just 14 months into its 5-year mission, Gaia’s data release is only the beginning of loads of new information about our galaxy that Gaia is expected to produce. The mission will ultimately build the most comprehensive, detailed and accurate star catalog of all time.
“Gaia is at the forefront of astrometry, charting the sky at precisions that have never been achieved before,” ESA’s Science Director Alvaro Giménez said in a statement.
Data from Gaia will be used not just for constructing a gigantic and unprecedented 3D map of the Milky Way, but it will also inspire new research. For example, knowing the stars’ positions, movements and other physical qualities could help researchers study the structure and history of the Milky Way galaxy.
While this may be the biggest and most ambitious galaxy-mapping endeavor yet, the vast amount of stars observed in this mission will represent only about 1 percent of all of the stars in the Milky Way galaxy.
A massive ice giant may be traveling through the outer solar system. Dubbed “Planet Nine,” the hypothetical world was proposed to exist after scientists noticed that a handful of objects beyond Pluto had been shaken up in unusual orbits. Search parties have formed to find the unseen planet, with optimistic hopes of spotting it within a year.
“It’s not crazy; this is the kind of stuff people are finding all the time,” co-discoverer Mike Brown, at the California Institute of Technology, told Space.com earlier this year. Brown and lead author Konstantin Batygin, also at CalTech, published a paper in January 2016 suggesting that a massive planet could be stirring up the icy bodies of the Kuiper Belt, a ring of material at the edge of the solar system.
“We just need to go out and cover a good swath of the sky.”
An unseen planet
Pluto makes its home at the edge of the Kuiper Belt, a region of ice-covered rocks left over from the formation of the solar system. Batygin and Brown noticed that several of the objects had similarities in their orbits, which suggested they were affected by a massive body. The usual suspects would be the solar system’s giant planets, but the objects the pair spotted were too far away to be affected by the behemoths.
By analyzing the strange orbits of the objects, Batygin and Brown proposed the presence of a new planet in the solar system, an object four times as large as Earth and 10 times as massive. They traced the possible orbit of the unseen giant, which they called “Planet Nine.” To create the observed disturbances, they mapped an orbit that comes as close as 200 astronomical units (AU) from the sun and travel as far away as 1,200 AU. (One AU is the distance from Earth to the sun — about 93 million miles, or 150 million kilometers.)
Not everyone is convinced that an enormous giant is skulking around the edges of the solar system. Ann-Marie Madigan, a postdoctoral researcher at the University of California Berkeley, found that the objects could “self-organize,” pushing and pulling one another into their unusual orbits. Working with co-author Michael McCourt of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts, the pair found that if the objects in the scattered disk roughly equal the mass of Earth, they could have dragged themselves to their current orbits within about 600 million years of the solar system’s birth, omitting the need for Planet Nine’s interference.
According to Batygin and Brown, however, the Planet Nine scenario is more probable, because current surveys suggest there isn’t enough mass in the region. In their research, they note that the disk of material that birthed the planets may have started out with enough mass, but interactions with the giant planets would have quickly tossed it out of the solar system.
Another study suggested that Planet Nine could be tugging on NASA’s Cassini probe, orbiting Saturn. Agnès Fienga at the Côte d’Azur Observatory in France and her colleagues added Planet Nine to a theoretical model to see if the proposed world could solve the mystery of tiny changes in the spacecraft’s orbit that existing solar system objects cannot account for. If the missing planet lies about 600 AUs away toward the constellation Cetus, the puzzling perturbations can be accounted for.
According to Cassini’s mission managers, however, the spacecraft isn’t actually experiencing any mysterious anomalies.
“Although we’d love it if Cassini could help detect a new planet in the solar system, we do not see any perturbations in our orbit that we cannot explain with our current models,” said Earl Maize, Cassini project manager at JPL, in a statement.
Other objects in the Kuiper Belt may help nail down the case for the world. Research by Renu Halhotra, Kathryn Volk and Xianyu Wang, all at the University of Arizona, reveal half a dozen ice-cover rocks whose orbits appear to fit with the presence of a distant planet.
“It’s a different line of evidence than Mike Brown and Konstantin Batygin proposed,” Volk told Space.com.
Where did it come from?
A planet in the outer solar system today has to come from somewhere. Without directly seeing it, scientists can only model possibilities for the massive world.
One possibility is that the sun somehow managed to gravitationally grab onto a free-floating world or a planet orbiting another star and add it to the solar system’s crown. Computer simulations performed by Gongjie Li and Fred Adams, both of the CfA, suggest that the odds of this happening are less than 2 percent.
If Planet Nine didn’t come from outside the solar system, then it must have come from within. Models performed by Scott Kenyon of the CfA and Benjamin Bromely of the University of Utah suggest there’s a good chance the hypothetical world could have been born where it was, or been booted into the outer solar system by interactions with the giant planets.
“The nice thing about these scenarios is that they’re observationally testable,” Kenyon said in a statement.
“A scattered gas giant will look like a cold Neptune, while a planet that formed in place will resemble a giant Pluto with no gas.”
Not everyone is waiting to see the planet before trying to dive inside of it. Astrophysics professor Christoph Mordasini and his doctoral student Esther Linder, both of the University of Bern in Switzerland, modeled what astronomers might see when they spot Planet Nine.
Assuming that it is a smaller version of the ice giants Uranus and Neptune, with hydrogen and helium dominating its atmosphere, the pair calculated that a 10-Earth-mass Planet Nine would be about 3.7 times wider than our planet. Temperatures would average minus 375 degrees Fahrenheit (minus 226 degrees Celsius).
“This means that the planet’s emission is dominated by the cooling of its core,” Linder said in a statement.
Sunlight would contribute very little to the light of the planet, making it brighter in the infrared wavelengths than in visible light.
Although the world remains unseen, that doesn’t mean we should fear it. Reports by the New York Post published in April claimed that Planet Nine could hurl asteroids and comets toward Earth, with potentially devastating consequences. The video, which had several factual errors, was dismissed by Brown.
“Hey, so … fun fact? Planet Nine is not going to cause the Earth’s destruction. If you read that it will, you have discovered idiotic writing!” Brown said via his Twitter account, @plutokiller.
He also dismissed the idea that the world played a role in mass extinctions of the past. While the planet orbits a significant distance from the sun, it isn’t quite far enough out to stir up the Oort Cloud, the region of icy comets beyond the Kuiper Belt. With a 10,000-year orbit, it would also constantly bombard the Earth, Brown said.
“I suspect it has something like zero effect on us, he told Space.com previously.
Hunting the unseen
Planet Nine remains hypothetical; no one has actually seen the world. But that doesn’t mean scientists aren’t searching for it. Batygin and Brown started off by searching through previous skymaps, hunting their unseen world.
“We dumpster-dived into the existing observational data to search for Planet Nine,” Batygin said.” Because we didn’t find it we were able to rule out parts of its orbit.”
Exoplanet researcher Nicolas Cowan of McGill University in Montreal thinks Planet Nine might show up in present and future surveys of the cosmic microwave background. Depending on the planet’s orbit, it could also be picked up by the Dark Energy Survey, a project in the Southern Hemisphere designed to probe the acceleration of the universe. NASA’s WISE instrument should also be able to spot the giant, helping to narrow down the potential paths of the planet.
Linder and Mordasini remain cautious. According to their models, existing surveys would likely be incapable of spotting the world if it weighs in at less than 20 Earth masses, especially if it was far enough away.
Batygin and Brown are trying to obtain telescope time on the Subaru Telescope on Mauna Kea in Hawaii. They’re asking for roughly 20 nights of observing, a significant amount of time on a powerful instrument that is constantly in use.
“It’s a pretty big request compared to what other people generally get on the telescope,” Brown told Space.com.
“We’ll see if they bite.”
If they do, he estimated that the planet could be spotted within a year.
Astronomers have discovered another dwarf planet in the Kuiper Belt, the ring of icy objects beyond Neptune. But this newfound world, dubbed 2015 RR245, is much more distant than Pluto, orbiting the sun once every 700 Earth years, scientists said. (Pluto completes one lap around the sun every 248 Earth years.) You can see an animation of the new dwarf planet’s orbit here.
“The icy worlds beyond Neptune trace how the giant planets formed and then moved out from the sun,” discovery team member Michele Bannister, of the University of Victoria in British Columbia, said in a statement. “They let us piece together the history of our solar system.” [Meet the Solar System’s Dwarf Planets]
“But almost all of these icy worlds are painfully small and faint; it’s really exciting to find one that’s large and bright enough that we can study it in detail,” Bannister added.
The exact size of 2015 RR245 is not yet known, but the researchers think it’s about 435 miles (700 kilometers) wide. Pluto is the largest resident of the Kuiper Belt, with a diameter of 1,474 miles (2,371 km).
The research team first spotted 2015 RR245 in February of this year, while poring over images that the Canada-France-Hawaii Telescope in Hawaii took in September 2015 as part of the ongoing Outer Solar System Origins Survey (OSSOS).
“There it was on the screen — this dot of light moving so slowly that it had to be at least twice as far as Neptune from the sun,” Bannister said.
OSSOS has discovered more than 500 objects beyond Neptune’s orbit, but 2015 RR245 is the first dwarf planet that the survey has found, the scientists said.
Dwarf planets are massive enough to be crushed into spheres by their own gravity, but they have not “cleared their neighborhood” of other objects, which differentiates them from “normal” planets such as Earth and Saturn. This definition, which was devised by the International Astronomical Union in 2006, led to Pluto’s controversial reclassification as a dwarf planet.
Astronomers are still working out the details of 2015 RR245’s highly elliptical orbit, but the object appears to come as close to the sun as 34 astronomical units (AU), and farther away than 120 AU. (One AU is the average Earth-sun distance — about 93 million miles, or 150 million km.)
2015 RR245 — which will get a catchier, official name at some point — will make its closest approach to the sun in 2096, the researchers said.
Other confirmed dwarf planets in the Kuiper Belt region include Pluto, Eris, Haumea and Makemake. Several other objects in this distant realm, including Sedna, Quaoar and 2007 OR10, probably meet the dwarf-planet criteria as well, scientists have said.
Saturn’s biggest moon, Titan, may possess the kind of chemistry that could eventually lead to life, albeit without water, a new study finds.
Titan is larger than the planet Mercury, making it the biggest of the more than 60 known moons orbiting Saturn. The moon’s surface is covered in rivers, lakes and oceans of methane, which also rains from the sky. This methane cycle, similar to Earth’s water cycle, can make Titan seem like an equally familiar and alien location.
Now, using computer models, a group of researchers has shown that a chemical on Titan’s surface could lay the groundwork for the formation of life. In Titan’s cold atmosphere, this ingredient can act as a catalyst for chemical reactions, and potentially absorb energy from sunlight, even through Titan’s thick clouds. [Photos of Saturn’s moon Titan]
Although Earth and Titan have major differences — for instance, Titan is much colder, is poor in oxygen and lacks surface water — Titan has a surface atmospheric pressure similar to Earth’s, and is the only place in the solar system except Earth where rainfall erodes the landscape.
On Earth, water flows in a cycle, raining from the sky, pouring down rivers and streams to oceans and lakes, and evaporating under sunlight into mist, forming clouds that eventually rain down. Probes sent to Titan have revealed that methane flows in a similar cycle of rivers, lakes and clouds over an ice crust.
The methane cycle, frigid climate and lack of liquid water on Titan’s surface make it a window into what life might be like on a world radically different from — and yet, in some ways, very similar to — Earth. In the new research paper, Jonathan Lunine, a planetary scientist at Cornell University in Ithaca, New York, and his colleagues investigated what prebiotic chemistry — the kinds of reactions that might lead to life — might be like on Titan-like worlds.
The scientists focused on a chemical known as hydrogen cyanide, which previous research has suggested might be central to the origin of life on Earth, the researchers said. (A cyanide is any molecule that contains a group made of a carbon atom and a nitrogen atom bonded together. Hydrogen cyanide is made of hydrogen, carbon and nitrogen, all linked together in a row. Cyanides are generally extremely toxic.)
Hydrogen cyanide can serve as a precursor to amino acids and nucleic acids, which are the building blocks of key molecules of Earth life, such as proteins and DNA. Prior work found that hydrogen cyanide is the most abundant hydrogen-containing molecule in Titan’s atmosphere.
Previous experiments suggested that hydrogen cyanide molecules often link together to form a compound known as polyimine. Now, the research team’s computer models show that polyimine has interesting properties that might support prebiotic chemistry in the kind of ultracold temperatures seen on Titan.
The scientists found that polyimine can absorb a wide spectrum of light, including wavelengths that can penetrate Titan’s smoggy atmosphere. This suggests that it can soak up energy from the sun that polyimine could then use in chemical reactions on Titan’s surface, they said.
Moreover, polyimine has a flexible backbone, meaning that it can adopt several different structures, from sheets to more coiled shapes. The researchers suggested that some of these structures might act like catalysts to accelerate prebiotic chemical reactions. In addition, other shapes could interact to form more complex structures that could host prebiotic chemistry — for instance, porous stacks of sheets could form. These stacks of sheets, in turn, could support delicate chemical reactions in them and let molecules drift in and out, the researchers said.
“We are not saying we created Titan life in a computer, or even structures that might be in life on Titan,” Lunine told Space.com. “We are saying that the early steps toward structures, catalysis and absorption of energy might be possible on Titan with polymers like those we modeled.”
The researchers noted that polyimine might be present on Titan and might have escaped detection because Titan’s murky atmosphere would make it difficult to identify. They added that future missions to Titan could be designed to look for polyimine and learn more about a potentially exotic kind of biochemistry.
“We need to go back to Titan and analyze the surface composition and search for polymers,” Lunine said.
The scientists detailed their findings online July 4 in the journal Proceedings of the National Academy of Sciences.
If Pluto’s subsurface ocean had frozen over completely, it would have formed highly pressurized ice that would have caused the dwarf planet to shrink, according to new research. The canyons and valleys on Pluto seem to have formed as the dwarf planet swelled up, rather than as it shrank, indicating that a liquid ocean most likely sits beneath the thick ice crust today, researchers said in the study.
“Thanks to the incredible data returned by [NASA’s New Horizons mission], we were able to observe tectonic features on Pluto’s surface [and] update our thermal evolution model with new data,” Noah Hammond, a graduate student at Brown University, said in a statement from the school. Hammond worked with his advisers — Amy Barr, of the Planetary Science Institute, and Marc Parmentier, also at Brown — to study the likelihood that a liquid ocean hides beneath Pluto’s .
When the New Horizons probe flew past Pluto last July, its images of the dwarf planet’s surface revealed deep faults, or fractures in the surface, hundreds of kilometers long, according to the statement from Brown. The long canyons appeared to form as Pluto’s crust expanded, Hammond said. “A subsurface ocean that was slowly freezing over would cause this kind of expansion,” he said.
It didn’t take long for scientists to conclude that Pluto once housed an ocean, but the question of whether it had already frozen over remained. Using updated measurements of Pluto’s diameter and density, Hammond’s model revealed that a frozen ocean beneath the crust would have changed from conventional water ice to a more compact, crystallized structure known as “ice II.” As the ice changed, the frozen ocean would have shrunk, creating an entirely different type of feature known as compressional fractures, which are not seen on Pluto’s surface.
“We don’t see the things on the surface we’d expect if there had been a global contraction,” Hammond said. “So we conclude that ice II has not formed, and therefore that the ocean hasn’t completely frozen.”
Ice II would have formed only if the dwarf planet’s outer shell were at least 160 miles (260 kilometers) thick, putting sufficient pressure on the underlying ice, the statement said. Under the thinner shell, the ocean could have remained regular ice, not shrinking at all.
Hammond’s model suggests that the shell might be closer to 190 miles (300 km) thick, thanks to high temperatures in the core, according to the paper. The addition of nitrogen and methane ice spotted on the surface of the tiny world may also help keep the water warm.
“Those exotic ices are actually good insulators,” Hammond said.
That means oceans could lie not only inside tiny Pluto but also in other similar worlds in the far reaches of the Kuiper Belt, the sphere of ice and rock at the edge of the solar system.
“That’s amazing to me,” Hammond said. “The possibility that you could have vast liquid water ocean habitats so far from the sun on Pluto — and that the same could also be possible on other Kuiper Belt objects as well — is absolutely incredible.”
The research was published online on June 15 in the journal Geophysical Research Letters.
Researchers studied the properties of nearly 9,000 near-Earth objects (NEOs) — asteroids and other bodies that come within 1.3 Earth-sun distances of our planet — to build a model of the overall NEO population.
This model seemed to have a problem, however: It predicted that astronomers should be seeing 10 times more NEOs that closely approach the sun — come within 9 million miles (15 million kilometers) or so of the star — than they actually observe.
The research team spent a year puzzling over this outcome before coming to a surprising conclusion: The missing NEOs are actually being destroyed as they get close to the sun, but long before they actually dive into the star.
“The discovery that asteroids must be breaking up when they approach too close to the sun was surprising, and that’s why we spent so much time verifying our calculations,” study co-author Robert Jedicke, of the University of Hawaii Institute for Astronomy, said in a statement.
The team’s work should help scientists better understand the NEO population in a variety of ways. For example, many meteors that light up Earth’s night skies are pieces of debris shed by parent NEOs on their laps around the sun. Such debris clouds travel on the same orbits as their parent bodies, but astronomers generally have trouble finding these NEOs. The new study suggests that this is because the parent objects have already been destroyed, the researchers said.
In addition, study team members determined that darker NEOs die farther from the sun than brighter ones do, which helps explain something astronomers already knew: Asteroids that approach the sun closely tend to be quite bright.
This finding implies that dark and bright asteroids may differ significantly in structure and composition, the researchers said.
“Perhaps the most intriguing outcome of this study is that it is now possible to test models of asteroid interiors simply by keeping track of their orbits and sizes,” lead author Mikael Granvik, of the University of Helsinki in Finland, said in the same statement. “This is truly remarkable and was completely unexpected when we first started constructing the new NEO model.”
Granvik and his colleagues built their model by studying nearly 100,000 images of NEOs acquired by the Catalina Sky Survey in Arizona over an eight-year period.
To date, scientists have identified and tracked almost 14,000 NEOs, but the overall population is thought to number in the millions. Astronomers think that most of these bodies begin their lives in the main asteroid belt between Mars and Jupiter, and then veer inward after experiencing gravitational nudges by Jupiter and/or Saturn. The new study was published online today (Feb. 17) in the journal Nature.
Invisible “plasma lenses” shaped like noodles, lasagna sheets or hazelnuts might lurk between stars in the Milky Way, researchers say.
This finding could help solve the longstanding mystery of where a major part of the galaxy’s matter is hiding, the scientists added.
Astronomers first detected clues of these mysterious structures 30 years ago as they monitored quasarsquasars, the brightest objects in the universe. Quasars are the most energetic form of active galactic nuclei, which are supermassive black holes in the centers of distant galaxies that release extraordinarily large amounts of light as they rip apart stars and gobble matter
Previous research found that radio waves from quasars could vary wildly in strength, a phenomenon technically known as an extreme scattering event. Astronomers suggested these events were due to clouds of plasma — that is, electrically charged particles. These clouds are essentially lumps in the thin gas that fills the space between the stars in the Milky Way.
“Lumps in this gas work like lenses, focusing and defocusing the radio waves, making them appear to strengthen and weaken over a period of days, weeks or months,” study lead author Keith Bannister, an astronomer at the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Australia, said in a statement.
Previous research suggested these “plasma lenses” are huge — about 620 million miles (1 billion kilometers) wide, a distance nearly seven times the distance between Earth and the sun. Ones detected so far lie about 3,200 light-years away, nearly 800 times farther than the nearest star to Earth, Proxima Centauri.
Plasma lenses among the stars
Plasma lenses have been difficult to find, so much about them is a mystery. For instance, estimates suggested the pressures within these plasma lenses are about 1,000 times greater than the surrounding interstellar gas. It was uncertain how these structures could form and survive long enough for astronomers to detect as often as they have.
In addition, until now, scientists knew nothing about the shape of these plasma lenses. This made it difficult to figure out what these structures were or what their origins were.
Now astronomers have for the first time successfully detected a lensing event while it was happening. This helped them conduct follow-up analyses that permitted the first estimates of plasma lens shapes.
Researchers used the Australia Telescope Compact Array to scan about 1,000 active galactic nuclei for sudden changes in their radio waves. They detected a lensing event in 2014 that went on for a year in connection with the quasar PKS 1939-315, located in the constellation Sagittarius. Whereas old analyses of lensing events only monitored two radio frequencies, “our new method gave us 9,000 frequencies at once,” Bannister told Space.com. “It was like going from black-and-white TV to color.”
Based on their findings, the researchers suggest this plasma lens could neither be a spherical cloud nor a corrugated or bent sheet.
“We could be looking at a flat sheet, edge on,” study co-author Cormac Reynolds at CSIRO said in a statement. “Or we might be looking down the barrel of a hollow cylinder like a noodle, or at a spherical [hollow] shell like a hazelnut.”
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Detecting more of these plasma lenses could reveal their shapes, which could in turn shed light on their origins. Previous research suggested two potential origins for these plasma lenses. One involves plasma sheets, perhaps the remains of shock waves from supernovas, Bannister said. Another involves cold clouds pulled together by the force of their own gravity.
If the plasma lenses are shaped like sheets, they may be plasma sheets. If they are spherical hollow shells, then they may be cold clouds held together by their own gravity. If they are hollow tubes, they may be flux tubes, structures formed by magnetic fields in the interstellar medium, Bannister said.
If the plasma lenses are made up of cold clouds, that suggests that cold clouds must make up a substantial fraction of the Milky Way, Bannister said. If so, they could help solve the so-called “missing baryon problem.”
Normal matter is made up mostly of particles known as baryons, which include protons and neutrons found in the atoms making up planets, stars and galaxies. Normal matter only makes up about one-sixth of all matter in the universe, with the rest consisting of dark matter, a mysterious invisible substance detectable via its gravitational influence on normal matter.
However, even normal matter presents a puzzle, since theories of the formation and evolution of the universe predict there should be about two times more baryons than astronomers see. Cold clouds might help solve the missing baryon problem, but “proving that is still a long way off though,” Bannister said.
In the future, the Australian Square Kilometre Array Pathfinder (ASKAP) should find plasma lenses “in droves,” Bannister said. This may help solve the mystery of what these structures are, he noted.
The scientists detailed their findings in the Jan. 22 issue of the journal Science.
A previously unidentified highway of dust extends across the Milky Way, between the sun and the central bulge of the galaxy, scientists have found.
Called the “Great Dark Lane” by the astronomers who announced it, the dusty road twists in front of the bulge of the galaxy.
“For the first time, we could map this dust lane at large scales, because our new infrared maps cover the whole central region of the Milky Way,” Dante Minniti, a researcher at Universidad Andres Bello in Chile and lead author of a study describing the findings, told Space.com by email.
Mapping the Milky Way
The center of a spiral galaxy contains a collection of stars that bulge above and below the flatter spirals, much like an egg yolk. The arms that give the galaxies their classification twist around the bulge, often in a beautiful spiral (although sometimes they are more elongated). Lanes of dust often lie between these arms, which present a particular challenge to map out.
“It is very difficult to mapthe structure of our galaxy because we are inside, and it is very large and covered with dust clouds that are opaque in the optical,” Minniti said.
Working with a team of astronomers, Minniti used the European Space Observatory’s Vista Variables in the Via Lactea Survey (VVV), a project to scan the Milky Way using the VISTA telescope in Chile, to study the galaxy in the near-infrared. At this wavelength, telescopes are able to peer through the clouds of dust to a group of objects known as red clump (RC) stars lying within the bulge.
Red clump stars have helium-burning cores that generate a similar brightness no matter what their age or composition is. This makes them reliable distance indicators for astronomers.
Based on the measurement of 157 million stars, Minniti and his team found that the RC stars of the Milky Way’s bulgewere split into two colors — a difference they determined was caused by dust between the stars and the observers. The astronomers could see a sharp transition between the two distinct groups — the dusty Great Dark Lane dividing them.
The Great Dark Lane extends approximately 20 degrees across the sky, reaching both above and below the plane of the galaxy. It sits roughly 15,000 light-yearsfrom the solar system, although the team is still working to refine the distance. It lies outside of the bulge rather than being contained within it, they said.
If the dust passed through the bulge itself, the red clump stars of the center would have a patchier distribution, rather than a clean break, as some of the stars at a certain height above the plane would be in front of the dust and others would be behind it, the researchers said. Instead, all of the red clump stars contained within the bulge lie behind the dust, according to the study.
“Detailed maps and modeling are needed in order to test this important galactic feature,” the researchers wrote in their paper, which appeared in the journal Astronomy & Astrophysics last year.