It’s unclear whether Planet Nine exists, but astronomers are already digging into the mystery of the hypothetical world’s birth.
In January, Konstantin Batygin and Mike Brown of the California Institute of Technology in Pasadena announced that they had inferred the existence of Planet Nine based on the strange orbits of a half dozen small bodies in the Kuiper Belt beyond Neptune.
Planet Nine, Batygin and Brown suggested, is perhaps 10 times more massive than Earth and orbits the sun at an average distance of about 700 astronomical units (AU). (One AU is the Earth-sun distance — 93 million miles, or 150 million kilometers.) [The Evidence for Planet Nine in Pictures]
Some astronomers are now scanning the sky in an attempt to find the putative planet, while others are tackling another mystery: How did Planet Nine come to be?
There are a number of possible origin stories, researchers say. For example, Planet Nine may be a former exoplanet that was captured by our solar system’s gravity.
This scenario appears to be far-fetched, however. Gongjie Li and Fred Adams, both of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts, performed computer simulations to estimate the odds that Planet Nine was plucked from a passing star system or nabbed as a formerly free-floating “rogue planet.” In both cases, the odds are less than 2 percent, the researchers report in a new study
So it’s likely that Planet Nine is native to our solar system. But did it form in its present location, or begin life much closer to the sun and then get booted into the outer solar system by a gravitational interaction of some kind?
Both scenarios are possible, Scott Kenyon, of the CfA, and Benjamin Bromley, of the University of Utah, report in two new studies of their own, which are also based on computer modeling work.
Given the right initial conditions, Planet Nine could have coalesced near where it’s now thought to lie within 1 billion to 2 billion years of the solar system’s birth, Kenyon and Bromley found. But their simulations also give credence to the idea that interactions with Jupiter and Saturn kicked Planet Nine out from a formerly tighter orbit.
“Think of it like pushing a kid on a swing: If you give them a shove at the right time, over and over, they’ll go higher and higher,” Kenyon said in a statement, adding that this scenario is “the simplest solution.”
The gravitational boot, if it occurred, didn’t have to come from a fellow planet. In their paper, Li and Adams also considered the possibility that Planet Nine was tugged outward by one of the sun’s stellar neighbors. But their simulations pegged the probability of this scenario at 10 percent at best, suggesting that, in most cases, a passing star would have kicked Planet Nine out of our solar system completely.
So the fog of mystery surrounding Planet Nine remains thick. But that fog could clear someday, provided that this mysterious world actually exists — and astronomers are able to get a decent look at it.
“The nice thing about these scenarios is that they’re observationally testable,” Kenyon said. “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.”
The study by Li and Adams has been accepted for publication in The Astrophysical Journal Letters. Kenyon and Bromley have submitted their two papers to The Astrophysical Journal.
Astronomers using NASA’s Hubble Space Telescope have discovered a moon orbiting Makemake, which is the second-brightest object in the distant Kuiper Belt beyond Neptune. (Pluto is the brightest of these bodies.)
The newfound satellite — the first ever spotted around Makemake — is 1,300 times fainter than the dwarf planet and is thought to be about 100 miles (160 kilometers) in diameter, researchers said. The moon was spotted 13,000 miles (20,900 km) from the surface of Makemake, which itself is 870 miles (1,400 km) wide. [See images of the dwarf planet Makemake]
“Makemake is in the class of rare Pluto-like objects, so finding a companion is important,” Alex Parker of the Southwest Research Institute (SwRI) in Boulder, Colorado, who led the image analysis for the Hubble observations, said in a statement today (April 26).
“The discovery of this moon has given us an opportunity to study Makemake in far greater detail than we ever would have been able to without the companion,” Parker added.
For example, further observations of the moon — which has been provisionally named S/2015 (136472) 1, and nicknamed MK 2 — should allow astronomers to calculate the density of Makemake, which should tell them if the dwarf planet and Pluto are made of similar stuff.
Additional Hubble observations should also reveal the shape of MK 2′s orbit around Makemake. If the orbit is tightly circular, the moon was probably created by a long-ago giant impact, just like the five satellites in the Pluto system were, researchers said. A looping, elliptical orbit, on the other hand, would suggest that MK 2 was once a free-flying Kuiper Belt object that Makemake captured.
The Hubble discovery images suggest that MK 2 is as dark as charcoal, which seems surprising given that Makemake is so bright. One possible explanation is that the moon’s gravity is too weak to hold onto reflective ices, which sublimate off MK 2′s surface into space, researchers said.
Makemake orbits the sun at an average distance of 45.7 astronomical units (AU) and completes one lap around the star every 309 Earth years. (One AU is the Earth-sun distance — about 93 million miles, or 150 million km.) The dwarf planet is even farther away than Pluto, which lies 39.5 AU from the sun on average and orbits once every 248 Earth years.
Makemake is one of five objects officially recognized as a dwarf planet by the International Astronomical Union (IAU). The others are the Kuiper Belt denizens Pluto, Eris and Haumea, and Ceres, which lies in the main asteroid belt between Mars and Jupiter.
Ceres is the only one of these five that doesn’t have at least one moon.
The IAU defines a dwarf planet as an object that orbits the sun and is massive enough to have been forced into a spherical shape by its own gravity but has not “cleared its neighborhood” of other orbiting material. (Pluto falls short on this last count, according to IAU officials, which is why the former ninth planet was reclassified as a dwarf planet in 2006.)
MK 2 was spotted in observations made by Hubble’s Wide Field Camera 3 in April 2015, after several previous Makemake observation campaigns had failed to turn up any satellites.
“Our preliminary estimates show that the moon’s orbit seems to be edge-on, and that means that often when you look at the system you are going to miss the moon because it gets lost in the bright glare of Makemake,” Parker said.
Stephen Hawking, Yuri Milner and Mark Zuckerberg helm the board for a new initiative, Breakthrough Starshot, whose technology could be used to someday reach Earth’s neighboring star Alpha Centauri after just a 20-year journey. Besides being an easy target — it’s among the closest stars to the sun — astronomers have been eying our stellar neighbors for potential Earth-like planets.
“This is Alpha Centauri, our neighboring star,” Milner said in a news conference yesterday (April 12). “But in space, neighboring does not mean very near. Alpha Centauri is over 4 light-years away […] that’s 25 trillion miles. And the problem is, space travel as we know it is slow. If [humanity's fastest-moving spacecraft] Voyager had left our planet when humans first left Africa, travelling at 11 miles a second, it would be arriving at Alpha Centauri just about now
Milner said that his proposed Starshot technology could get a tiny spacecraft to the system, traveling at 20 percent the speed of light, in around 20 years. But barring that, it would be a long trip indeed.
The stars of Alpha Centauri lie 4.3 light-years from us, which is around 270,000 times the distance from the Earth to the sun. Milner said that to travel that distance within a generation, a chemical rocket like the ones we use today would need fuel equivalent to the weight of all the stars in the Milky Way. A fusion rocket could reach the system in 50 years, but the technology is still far from viable. His proposed Starshot technology could make it there in 20.
This chart shows most of the stars visible with the unaided eye on a clear night. The star Alpha Centauri is one of the brightest stars in the southern sky (marked with a red circle). It lies just 4.3 light-years from the Earth and one component in a triple star system. Image released Oct. 17. 2012.
Astronomers have discovered an Earth-size planet orbiting one of the nearest stars in our galaxy. Learn more about Alpha Centauri in our full infographic.
From Earth, Alpha Centauri appears as a single point of light: It’s one of the brightest stars in the southern sky. Through a telescope, one can make out the system’s two stars Alpha Centauri A and its smaller, dimmer companion Alpha Centauri B. Each has a mass that is about the same as the Earth’s sun, and they orbit one another at about the same distance that Uranus orbits the sun.
A third star, Proxima Centauri, is slightly closer to Earth — it’s actually the nearest star outside the Earth’s solar system. That star is much smaller and dimmer: it’s just 0.12 times the mass of the sun, or 1.5 times the size of Jupiter, and it shines faintly at a cautious distance from the other two. In fact, some astronomers question whether it’s part of the system at all, or just passing through.
Astronomers first realized the bright star Alpha Centauri was a tightly orbiting pair in 1689, and Proxima Centauri was first spotted in 1915.
In 2012, researchers used an instrument called the High Accuracy Radial velocity Planet Searcher to detect a planet around Alpha Centauri B. The instrument, which is part of the European Space Agency’s La Silla Observatory in Chile, measured tiny wobbles in the star that suggested that a planet was orbiting it — likely just a bit bigger than Earth, orbiting its star every 3.24 days.
Since then, researchers have tried to verify the planet’s existence using transits — a slight dimming in the star as the planet passes by — but haven’t found additional, conclusive evidence. And a re-examination of the original study suggested that the planet might be an artifact of the data processing, according to a report by the deep-space exploration site Centauri Dreams.
Regardless, because of their nearness, the Alpha Centauri twins and Proxima Centauri offer a promising location to look for planets at a distance — especially using direct imaging — if researchers can filter out the complexities of the double star. And they also seem to be a good place to visit. The distance may be vast, but it could be relatively easy for Starshot’s nanocraft or other interstellar travelers to blast through and beam back information to Earth about the system with a bit more than a four-year delay. While planets orbiting those stars would see a starscape that is quite different from Earth’s, the stars’ similarity to the sun would make their habitable zones an intriguing place to look for Earth analogues.
“Astronomers estimate that there is a reasonable chance of an Earth-like planet existing in the ‘habitable zones’ of Alpha Centauri’s three-star system,” Breakthrough Starshot representatives said in a statement. “A number of scientific instruments, ground-based and space-based, are being developed and enhanced, which will soon identify and characterize planets around nearby stars.”
And then it could be time to go take a look.
The hunt is on to find “Planet Nine” — a large undiscovered world, perhaps 10 times as massive as Earth and four times its size — that scientists think could be lurking in the outer solar system. After Konstantin Batygin and Mike Brown, two planetary scientists from the California Institute of Technology, presented evidence for its existence this January, other teams have searched for further proof by analyzing archived images and proposing new observations to find it with the world’s largest telescopes. Just this month, evidence from the Cassini spacecraft orbiting Saturn helped close in on the missing planet.
Many experts suspect that within as little as a year someone will spot the unseen world, which would be a monumental discovery that changes the way we view our solar system and our place in the cosmos. “Evidence is mounting that something unusual is out there — there’s a story that’s hard to explain with just the standard picture,” says David Gerdes, a cosmologist at the University of Michigan who never expected to find himself working on Planet Nine.
He is just one of many scientists who leapt at the chance to prove — or disprove — the team’s careful calculations. Batygin and Brown made the case for Planet Nine’s existence based on its gravitational effect on several Kuiper Belt objects — icy bodies that circle the sun beyond Neptune’s orbit. Theoretically, though, its gravity should also tug slightly on the planets, moons and even any orbiting spacecraft. With this in mind, Agnès Fienga at the Côte d’Azur Observatory in France and her colleagues checked whether a theoretical model (one that they have been perfecting for over a decade) with the new addition of Planet Nine could better explain slight perturbations seen in Cassini’s orbit. Without it, the eight planets in the solar system, 200 asteroids and five of the most massive Kuiper Belt objects cannot perfectly account for it. The missing puzzle piece might just be a ninth planet. So Fienga and her colleagues compared the updated model, which placed Planet Nine at various points in its hypothetical orbit, with the data. They found a sweet spot—with Planet Nine 600 astronomical units (about 90 billion kilometers) away toward the constellation Cetus — that can explain Cassini’s orbit quite well.
Although Fienga is not yet convinced that she has found the culprit for the probe’s odd movements, most outside experts are blown away. “It’s a brilliant analysis,” says Greg Laughlin, an astronomer at Lick Observatory, who was not involved in the study. “It’s completely amazing that they were able to do that so quickly.” Gerdes agrees: “That’s a beautiful paper.” The good news does not end there. If Planet Nine is located toward the constellation Cetus, then it could be picked up by the Dark Energy Survey, a Southern Hemisphere observation project designed to probe the acceleration of the universe. “It turns out fortuitously that the favored region from Cassini is smack dab in the middle of our survey footprint,” says Gerdes, who is working on the cosmology survey. “We could not have designed our survey any better.”
Although the survey was not planned to search for solar system objects, Gerdes has discovered some (including one of the icy objects that led Batygin and Brown to conclude Planet Nine exists in the first place). Laughlin thinks this survey has the best immediate chance of success. He is also excited by the fact that Planet Nine could be so close. Although 600 AUs—roughly 15 times the average distance to Pluto—does sound far, Planet Nine could theoretically hide as far away as 1,200 AUs. “That makes it twice as easy to get to, twice as soon,” Laughlin says. “And not just twice as bright but 16 times as bright.”
And the Dark Energy Survey is not the only chance to catch the faint world. It should be possible to look for the millimeter-wavelength light the planet radiates from its own internal heat. Such a search was proposed by Nicolas Cowan, an exoplanet astronomer at McGill University in Montreal, who thinks that Planet Nine might show up in surveys of the cosmic microwave background (CMB), the pervasive afterglow of the big bang. “CMB experiments have historically used solar system giant planets to calibrate their instruments, so we know that current and planned CMB experiments are sensitive enough to measure the flux from Planet Nine if it is as bright as we think it is,” Cowan says. Already, cosmologists have started to comb through data from existing experiments, and astronomers with many different specialties have also joined in on the search. “I love that we can take this four-meter telescope and find a rock 100 kilometers in diameter that is a billion kilometers past Neptune with the same instrument that we are using to do extragalactic stuff and understand the acceleration of the universe,” Gerdes says. In the meantime Batygin and Brown are proposing a dedicated survey of their own.
In a recent study they searched through various sky maps to determine where Planet Nine cannot be. “We dumpster-dived into the existing observational data to search for Planet Nine, and because we didn’t find it we were able to rule out parts of the orbit,” Batygin says. The zone where the planet makes its farthest swing from the sun as well as the small slice of sky where Fienga thinks the planet could be now, for example, have not been canvassed by previous observations. To search the unmapped zones, Batygin and Brown have asked for roughly 20 observing nights on the Subaru Telescope on Mauna Kea in Hawaii. “It’s a pretty big request compared to what other people generally get on the telescope,” Brown says. “We’ll see if they bite.” If they do, Brown is convinced he will have his planet within a year. “I really want to see what it looks like,” says Batygin, who adds that his aspiration drives him to search for the unseen world. But Laughlin takes it a step further: “I think [the discovery] would provide amazing inspiration for the next stage of planetary exploration,” he says. We now have another opportunity to see one of the worlds of our own solar system for the first time. “If Planet Nine isn’t out there, we won’t have that experience again.”
Supermassive black holes are the most extreme objects in the known universe, with masses millions or even billions of times the mass of our sun. Now astronomers have been able to study one of these behemoths inside a strange, distant quasar and they’ve made an astonishing discovery — it’s spinning one-third the speed of light.
Studying a supermassive black hole some 3.5 billion light-years away is no easy feat, but this isn’t a regular object: it’s a quasar that shows quasi-periodic brightening events every 12 years or so — a fact that has helped astronomers reveal its extreme nature.
Quasars are extremely bright accretion disks in galactic cores driven by copious quantities of matter falling into the central supermassive black hole. The vast majority of galaxies are thought to contain supermassive black holes, though modern galaxies have calmed down and quasars no longer shine. But it’s a different story for galaxies that are billions of light-years away.
The object at the center of the strange quasar called OJ287 “weighs in” at 18 billion solar masses and is one of the biggest supermassive (or ultramassive?) black holes in the known universe. Interestingly, it is also one of the most well-studied quasars as it is located very close to the apparent path of the sun’s motion across the sky as seen from Earth — a region where historic searches for asteroids and comets are regularly carried out. Therefore, astronomers have over 100 years of serendipitous brightness data for OJ287, allowing them to predict when the next flaring event would be.
On closer inspection of the flaring events that occurred in recent decades, astronomers realized that rather than a single brightening event occurring every 12 years, the brightening is actually a double peak, providing a clue as to what might be causing it. ANALYSIS: Black Holes Slug it Out in Quasar Deathmatch Mauri Valtonen of University of Turku, Finland, and his international team used several optical telescopes around the world in conjunction with NASA’s SWIFT X-ray space telescope to realize that these 12-year double-brightening events are triggered by a smaller black hole in orbit around OJ287.
Valtonen is the lead author of the study published in the Astrophysical Journal. The massive black hole possesses a very hot accretion disk, a key component of a quasar.
The material accumulates in the disk and gets pulled into the black hole, feeding it. Along the way, the disk material is heated and emits powerful electromagnetic radiation. OJ287′s smaller black hole partner, which itself is still 100 solar masses (still a huge black hole!) has a highly elongated orbit, swinging close to the more massive black hole every 12 years.
During closest approach, the smaller black hole “splashes” into OJ287′s accretion disk once during the incoming swing and once more as it swings around the black hole’s far side, creating 2 distinct flaring events, as this diagram demonstrates: An illustration of the binary black hole system in OJ287. The predictions of the model are verified by observations.
This periodic close encounter stirs up the supermassive black hole’s accretion disk material, rapidly heating it twice in rapid succession. This is what causes OJ287′s strange brightenings every 12 years. With this binary black hole model in mind, the researchers were able to predict when the latest event was due to occur.
The last brightening happened on Nov. 18, 2015, only a few days before Valtonen’s prediction, confirming his team’s binary black hole model. But through these observations, the supermassive black hole’s spin could also be calculated and it’s fast. The team’s observations show that it is spinning at a third of the speed of light. Interestingly, from the historical data of OJ287, the team was also able to calculate how much energy is being lost from the system via gravitational waves. Of course, gravitational waves are currently a very hot topic, having been directly detected for the first time by the US-based Laser Interferometer Gravitational-wave Observatory (LIGO) and announced last month.
That LIGO detection was the signature produced by 2 orbiting and merging black holes, a discovery that not only confirmed one of Einstein’s final predictions of general relativity, but also directly confirmed the existence of 2 black holes merging as one. ANALYSIS: We Just Heard the Spacetime ‘Chirp’ of Black Hole Rebirth Though the gravitational waves of the OJ287 black hole binary are too weak to be detected by the current generation of gravitational wave detectors (as the source is far too distant), the Nov. 18 brightening
This periodic close encounter stirs up the supermassive black hole’s accretion disk material, rapidly heating it twice in rapid succession. This is what causes OJ287′s strange brightenings every 12 years. With this binary black hole model in mind, the researchers were able to predict when the latest event was due to occur.
The last brightening happened on Nov. 18, 2015, only a few days before Valtonen’s prediction, confirming his team’s binary black hole model. But through these observations, the supermassive black hole’s spin could also be calculated and it’s fast. The team’s observations show that it is spinning at a third of the speed of light. Interestingly, from the historical data of OJ287, the team was also able to calculate how much energy is being lost from the system via gravitational waves. Of course, gravitational waves are currently a very hot topic, having been directly detected for the first time by the US-based Laser Interferometer Gravitational-wave Observatory (LIGO) and announced last month. That LIGO detection was the signature produced by 2 orbiting and merging black holes, a discovery that not only confirmed one of Einstein’s final predictions of general relativity, but also directly confirmed the existence of 2 black holes merging as one.
We Just Heard the Spacetime ‘Chirp’ of Black Hole Rebirth Though the gravitational waves of the OJ287 black hole binary are too weak to be detected by the current generation of gravitational wave detectors (as the source is far too distant), the Nov. 18 brightening of the quasar serves as a fitting celebration for Einstein’s theory that he presented almost exactly 100 years before on Nov. 25, 1915.
Infant stars may release bursts of light when they collide with and devour dense clumps of matter that otherwise might have gone on to form planets, new research suggests. The new finding has larger implications for understanding how stars grow and evolve early in their lives — specifically, that stars may grow through chaotic series of violent events, instead of steadily getting larger, as previously thought, the authors of the new work noted.
Stars coalesce from vast clouds of gas and dust, and planets emerge from whirling disks of leftover matter that surround newborn stars. Young stars that are still feeding on their parent clouds are known as protostars, while the disks of material that give rise to planets are known as protoplanetary disks.
Previous research often envisioned protostars growing in a simple manner, steadily accumulating or accreting fuel from surrounding clouds. However, protostars are often far dimmer than expected, given their estimated average rates of accretion. With the new finding, scientists now have evidence that protostars may evolve in an extremely chaotic way, sporadically accreting dense clumps of gas from their surrounding protoplanetary disks.
For the new work, astronomers focused on protostars known as FU Orionis objects. These young stars, also known as FUors, are known to experience dramatic spikes in brightness, the researchers said. Previous work suggested that FUors brightened because their accretion rates suddenly increased by a factor of 1,000 or more, and staying that way for decades or longer. To learn more about these outbursts, scientists used the Subaru Telescope, located at the Mauna Kea Observatories in Hawaii, to analyze four of the 11 confirmed FUors, located between 1,500 and 3,500 light-years from the Milky Way.
The new images of the flaring newborn stars “were surprising and fascinating, and nothing like anything previously observed around young stars,” representativesofthe National Institutes of Natural Sciences (NINS) in Japan said in a statement. (NINS is one of the managing institutions of the National Astronomical Observatory of Japan, where some of the paper’s authors are based.) The researchers discovered “tails” projecting from the protoplanetary material around the young stars, as well as spikes of gas and dust.
The researchers created computer simulations that suggested that the proto-planetary disks of newly formed stars could be gravitationally unstable and can fragment, creating dense clumps of gas that can collide with the stars, helping them grow and creating those bright bursts of light. “We suggest a previously unrecognized evolutionary stage in the formation of stars and protoplanetary disks,” study lead author Hauyu Baobab Liu, an astronomer at the Academia Sinica Institute of Astronomy and Astrophysics in Taipei, Taiwan, told Space.com.
These observations may reveal that clumps of gas and dust fall into the stars (helping them grow) in a more chaotic fashion than once thought. Credit: Science Advances, H. B. Liu This unstable phase of a protostar’s life might last several hundred thousand years, the scientists added. “Although more simulations are required to match the simulations to the observed images, these images show that this is a promising explanation for the nature of FU Ori[onis]outbursts,” NINS representatives said in the statement. The scientists detailed their findings online Feb. 5 in the journal Science Advances.
A powerful greenhouse effect can destroy a planet’s chances of hosting life, a new study suggests.
Until proven otherwise, scientists on Earth assume water is necessary for life to arise on other planets. In the search for life outside the solar system, scientists focus on a “habitable zone” around other stars. Inside such a habitable zone, Earth-like planets are neither too hot nor too cold for liquid water to exist on the surface.
A planet that orbits too close to its sun may become parched because of the solar heat. But now, scientists think an extreme greenhouse effect can also push a planet into dry conditions — similar to what happened on Venus.
The new research shows that warming due to carbon dioxide is as powerful as solar heat due to orbit when it comes to drying out a planet. The modeling study was published today (Feb. 9) in the journal Nature Communications.
“This is interesting because it tells you that you need to know more than just the position of a planet to know whether it might be habitable or not,” said Max Popp, lead author of the study and a postdoctoral researcher at the Max Planck Institute for Meteorology in Hamburg, Germany.
In the case of hot, hellish Venus, water that evaporated from the planet’s surface built up high in the planet’s atmosphere and eventually escaped into space. This is called a “moist greenhouse.” Today, the atmosphere of Venus is almost entirely carbon dioxide. (Earth is able to keep its water because this planet’s upper atmosphere is quite dry.)
To better understand the conditions that trigger such extreme greenhouse effects, Popp and his colleagues created a 3D model of an Earth-like planet that was entirely covered by water. This simulated water-world meant the scientists could ignore the complicated effects of continents and seasons.
The researchers discovered that once carbon dioxide levels in the model reached 1,520 parts per million, the planet’s climate was unstable. The surface temperatures rapidly jumped to about 135 degrees Fahrenheit (57 degrees Celsius), creating a warm, moist greenhouse regime, the study reported. (The measurement means there are 1,520 molecules of carbon dioxide for every 1 million air molecules.)
“A planet like Earth will eventually change to a very warm climate, and it will occur relatively abruptly,” Popp told Live Science.
The researchers think changes in large-scale cloud patterns drive the warm, moist greenhouse effect, Popp said. The location and thickness of cloud cover can change how much solar heat is trapped on a planet.
Although the findings suggest that greenhouse gases can be as lethal for a planet as orbiting too close to a sun, this process would occur at carbon dioxide levels significantly higher than those experienced on Earth today, the researchers said.
Popp said it’s likely impossible for human activity to induce a similar moist greenhouse effect on Earth. To do so, human activity would have to raise the concentration of CO2 in the atmosphere considerably, even more than if all the available fossil fuel reserves were burned, the researchers said.
“This is an idealized study designed to give a comparison between solar [heating] and carbon dioxide,” Popp said. As such, Popp said a similar scenario wouldn’t happen on Earth anytime soon.
Some of the brightest objects in the known universe may abruptly go dark at the whims of the black holes that power them, new research shows.
A recent study reveals a dramatic example of this newly discovered type of object, called a “changing-look quasar,” which seems to have winked out in as little as a decade when its black hole no longer had gas to suck in.
“This is an intrinsic change in the gas that’s falling on the supermassive black hole,” Jessie Runnoe, a postdoctoral student at Pennsylvania State University and lead author of the new work, said at a news conference Jan. 8. Runnoe presented the results of the changing-look quasar at the American Astronomical Society meeting in “At least temporarily, the supermassive black hole has run out of fuel,” Runnoe said.
At the center of most galaxies lies a supermassive black hole weighing thousands to a billion times as much as the sun. As black holes swallow up nearby gas and dust, they can emit light and radio waves that shine brightly across the universe — a feature called a quasar.
However, if the material the black hole is sucking in runs out, the quasar’s powerful light appears to shut down quickly, the new research suggests. Astronomers are used to looking at objects that change over millions or billions of years, so the researchers were surprised to spot an object that changed over a decade or less.
“This is a brand-new phenomen[on],” John Ruan, a graduate student in astronomy at the University of Washington in Seattle, said at the same conference. Ruan is co-author of the new paper, and also led an archival search for more changing-look quasars in the Sloan Digital Sky Survey.
“We’ve never actually seen a quasar just turn off before,” he said.
In early 2015, after the discovery of the first changing-look quasar, Runnoe and her colleagues decided to visually search for the objects by eye rather than by computer in the Time Domain Spectroscopic Survey (TDSS), which incorporates data from Sloan and other sky surveys to identify objects that vary in brightness over time. And they uncovered a particularly striking example.
A strange object known as J1011+5422 lies approximately 3.4 billion light-years from Earth, and when it was first spotted by Sloan in 2003, it looked like a regular quasar. But when TDSS followed up in 2015, just 12 years later, the light from the bright quasar had faded away. Only the light from its parent galaxy shone through.
“The difference is pretty dramatic,” Runnoe said. “This is the most dramatic one we’ve found.”
Previous evidence suggested that quasars shut off over tens or hundreds of thousands of years, Ruan said.
“To observe a quasar shutting off in just a few years is very surprising,” he added.
The results were detailed Nov. 18 in the journal Monthly Notices of the Royal Astronomical Society.
Several phenomena could be responsible for the sudden cutoff in light streaming from the quasar, and Runnoe and her colleagues sought to determine which was responsible for J1011′s dramatic shutdown.
The most obvious cause would be a massive cloud of gas and dust moving between the quasar and the Earth. But after combing through more than a decade’s worth of observations made by Sloan, the astronomers concluded that the quasar slowly shut down over a period of at least 7 years, finally disappearing by 2015. In contrast, it should have taken a giant molecular cloud several decades to obscure the quasar. Furthermore, the team saw no signs of the cloud’s chemistry in the dimming light from the quasar — something they would have expected to see, especially as quasars are already used to study the chemistry of such clouds.
The researchers also considered that the original object was not a quasar at all but instead only an extremely bright flare caused by a star wandering too close to the black hole and being torn apart. However, such disruptions typically occur over months rather than years, making it an extremely unlikely scenario.
If aliens are out there, they may all be dead.
It might be relatively easy for life to evolve on hospitable planets throughout the universe, but very hard for it to get any kind of a foothold, a new study suggests.
This could be the answer, the study’s authors say, to the famous Fermi Paradox, which in its simplest form asks, “Where is everybody?”
Chopra and co-author Charley Lineweaver, also of ANU, posit that environmental conditions on young planets are unstable, and there is thus likely only a small window of time for life to get going, even on initially hospitable worlds.
In the first 500 million years or so of a wet, rocky planet’s life, for example, it will be too hot and heavily bombarded to support life. Life could emerge over the next 500 million years, as the planet cools and the impact rates settle down a bit.
During that time, however, the planet will probably be losing its liquid water, perhaps as the result of a runaway greenhouse effect (as occurred on Venus), or perhaps because it got too cold. There’s a good chance that the planet will end up shifting from habitable to uninhabitable, as Venus and Mars apparently did, by roughly 1 billion to 1.5 billion years after its formation — unless life gets going fast enough to stabilize things, Chopra and Lineweaver say.
“Between the early heat pulses, freezing, volatile content variation, and runaway positive feedbacks, maintaining life on an initially wet rocky planet in the habitable zone may be like trying to ride a wild bull. Most life falls off,” they write in the study, which was published in the journal Astrobiology. “Life may be rare in the universe, not because it is difficult to get started, but because habitable environments are difficult to maintain during the first billion years.”
The researchers term this idea the “Gaian bottleneck” hypothesis. They contrast it with the “emergence bottleneck” concept, which postulates that it’s tough for life to get started at all.
It’s unclear, of course, which of these hypotheses better represents reality, or if either of them represents reality well at all. But there are possible (albeit difficult and time-consuming) ways to test such ideas out, the researchers said.
“One intriguing prediction of the Gaian bottleneck model is that the vast majority of fossils in the universe will be from extinct microbial life, not from multicellular species such as dinosaurs or humanoids that take billions of years to evolve,” Lineweaver said in the same statement.
Clusters of stars can harvest enough gas from their galaxies to give birth to a new generation of stars of their own, new research shows.
This finding could help shed light on how the building blocks of galaxies evolve, scientists added.
Globular clusters are densely packed, spherical collections of up to millions of stars orbiting the outskirts of galaxies. These clusters are up to 13 billion years old, making them among the oldest structures in the universe
“Star clusters are building blocks of galaxies — almost all stars formed in star clusters,” said study lead author Chengyuan Li, an astronomer at Peking University in Beijing.
Stars in globular clusters are thought to all form at the same time in a single burst from a common cloud of gas. After that point, star formation ends in those clusters.
“In a star cluster, the first stellar generation usually contains very massive stars, and those very massive stars will contribute very high-energy photons — that is, X-ray photons — into their environment,” Li told Space.com. “A cluster is initially gas-rich, but after that first batch of massive stars pours their energetic photons out, most of the gas will get accelerated and escape from the cluster. About 3 million to 10 million years later, the star cluster will be gas-free, hence quenching the star-forming process.”
However, about a decade ago, astronomers discovered signs that old globular clusters, ones more than 10 billion years old, often possess younger stars. Now, Li and his colleagues said they have strong evidence that the reason globular clusters may have younger stars is that they experienced more than one star-forming event, or “starburst.”
The researchers analyzed data from the Hubble Space Telescope regarding three globular clusters located in two dwarf galaxies orbiting the Milky Way. Two of the clusters, NGC 1783 and NGC 1696, are located about 160,000 light-years away from Earth in the Large Magellanic Cloud, and the third, NGC 411, is located about 190,000 light-years away in the Small Magellanic Cloud. NGC 1783 is about 180,000 times the mass of the sun, while NGC 1696 is about 50,000 solar masses and NGC 411 is about 32,000 solar masses.
The astronomers found that these globular clusters, which are each about 1.5 billion years old, are home to groups of stars a few hundred million years younger than other stars in the clusters. These younger stars make up about 0.2 to 2 percent the masses of those clusters.
Specifically, NGC 1783 is mostly about 1.4 billion years old, but some groups of its stars are 450 million and 890 million years old; NGC 1696 is mostly about 1.5 billion years old, but some of its stars are 500 million years old. And in 1.4-billion-year-old NGC 411, some stars are 320 million years old.
One potential explanation for these apparent differences in ages is that these stars only look relatively young, but are in fact “blue stragglers.” Such stars look younger due to an infusion of extra fuel they get after they either siphon gas from their neighbors or swallow other stars whole. However, the colors and locations of these younger stars are not what one would expect of blue stragglers from previous work, the researchers said.
Instead, Li and his colleagues calculated that as the orbits of these globular clusters took them through the gaseous disks of their galaxies, the clusters could have collected or accreted enough stray gas and dust to trigger new waves of star formation.
“Traditionally, scientists did not expect that a young star cluster can form additional stars after its initial formation,” Li said. “Our finding indicates that the evolution of a star cluster is much more complicated than what we thought — there must be frequent interactions between star clusters and their environment.”
Future research will aim to extend the findings to other globular clusters in the Magellanic Clouds and the Milky Way, the researchers said.
A huge alien world orbits 600 billion miles (1 trillion kilometers) from its host star, making its solar system the largest one known, a new study reports.
Astronomers have found the parent star for a gas-giant exoplanet named 2MASS J2126, which was previously thought to be a “rogue” world flying freely through space. The planet and its star are separated by about 7,000 astronomical units (AU), meaning the alien world completes one orbit every 900,000 years or so, researchers said. (One AU is the average distance from Earth to the sun — about 93 million miles, or 150 million km).
For comparison, Neptune lies about 30 AU from the sun, Pluto averages about 40 AU from Earth’s star and scientists think the newly hypothesized “Planet Nine” never gets more than 600 to 1,200 AU away from the sun.
“The planet is not quite as lonely as we first thought, but it’s certainly in a very long-distance relationship,” study lead author Niall Deacon, of the University of Hertfordshire in England, said in a statement.
The previous record for most widely separated planet and star was 2,500 AU, researchers said.
Deacon and his colleagues analyzed databases of rogue planets, young stars and brown dwarfs — strange objects bigger than planets, but too small to ignite the internal fusion reactions that power stars — to see if they could link any of them together.
The team found that 2MASS J2126, which was discovered eight years ago, and a red dwarf star called TYC 9486-927-1 are moving through space together about 104 light-years from Earth, strongly implying that they’re part of the same system.
The researchers were able to deduce a rough age for TYC 9486-927-1 and 2MASS J2126, based on the lithium signature in the star’s spectrum: between 10 million and 45 million years old. (Lithium is destroyed relatively early in a star’s life, so the more lithium a star has, the younger it is.)
2MASS J2126 has therefore completed a maximum of 50 orbits around the star so far.
Knowledge of the planet’s age allowed the researchers to calculate a mass for the planet: about 12 to 15 times that of Jupiter. Previous studies had estimated 2MASS J2126′s temperature to be about 2,730 degrees Fahrenheit (1,500 degrees Celsius). The planet appears to be broadly similar in these characteristics to the alien world Beta Pictoris b — but 2MASS J2126 orbits more than 700 times farther from its star than Beta Pictoris b does, team members said.
The odds that life could exist on 2MASS J2126 are very low, researchers said. But a hypothetical observer on the gas giant would see its sun as merely a bright star in the sky, and might not even realize that the planet and star were connected, they added. (It takes light from TYC 9486-927-1 a month to get to the planet; sunlight takes about 8 minutes to get to Earth.)
The exotic planetary system probably did not form from a large spinning disk of dust and gas, the way that Earth’s solar system did, study team members said. But exactly how it did take shape remains a mystery.
“How such a wide planetary system forms and survives remains an open question,” co-author Simon Murphy, of the Australian National University in Canberra, said in the same statement.
Some scientists have suggested that a big undiscovered body lying on the far outer reaches of the solar system could be responsible for many of the mass extinction events throughout Earth’s history, by shaking up the distant comet repository known as the Oort Cloud and sending some its denizens screaming toward our planet.
But Planet Nine — a newly proposed but not yet confirmed world perhaps 10 times more massive than Earth that’s thought to orbit far beyond Pluto — probably could not have triggered such “death from the skies” events, researchers said.
“I suspect it has something like zero effect on us,” said Mike Brown of the California Institute of Technology (Caltech) in Pasadena.
Brown and lead author Konstantin Batygin, also of Caltech, suggested the existence of Planet Nine in a paper that was published last week. They infer the planet’s presence based on indirect evidence: Computer models suggest that a distant, unseen world has shaped the strange orbits of a number of small objects in the Kuiper Belt, the ring of icy bodies beyond Neptune.
Planet Nine likely has an elliptical orbit, coming within 200 to 300 astronomical units (AU) of the sun at its closest approach and getting as far away as 600 to 1,200 AU, Brown said. (One AU is the distance from Earth to the sun — about 93 million miles, or 150 million kilometers).
Neptune orbits about 30 AU from the sun, and Pluto never gets farther than 49 AU from our star. So Planet Nine, if it exists, is very distant indeed — but not distant enough, Brown said, to stir up any of the trillions of comets in the Oort Cloud, which begins perhaps 5,000 AU from the sun.
The existence of such a “perturber” has been hypothesized as a way to explain the mysterious periodicity of big extinction events on Earth, which have recurred roughly every 27 million years over the last quarter-billion years or so.
“Really big planets really far away could do that,” Brown told Space.com. “Planet Nine is smaller than all these things that people have called ‘Planet X’ — that’s always been sort of Jupiter-sized, or even brown dwarf-sized, or something. This is a good bit smaller, and a good bit closer; it’s not in the realm of the comets.”
The putative Planet Nine also completes one orbit every 10,000 years or so, he added.
“That sounds like a long time, but it’s a pretty short orbit,” Brown said. “If it were doing this thing every time it went around the sun, it would’ve been doing a lot of it, and I don’t think there’s anything going on like that.”
Astronomer Scott Sheppard of the Carnegie Institution for Science in Washington, D.C., who is not part of the Batygin/Brown team, voiced similar sentiments. (Sheppard is conducting a hunt for undiscovered objects in the outer solar system; he co-discovered 2012 VP113 — one of the “trans-Neptunian objects,” or TNOs, whose orbital characteristics hint at the existence of Planet Nine.)
If Planet Nine exists, it could conceivably dislodge some TNOs (not Oort Cloud comets) and send them toward the inner solar system, Sheppard said.
“But most likely, the unknown massive object has been out there a very long time and thus cleared most objects near it long ago,” Sheppard told Space.com via email.
“I do think it could throw a few small objects into the inner solar system every so often, but I don’t think it would significantly increase the odds for a mass extinction event,” he added.
Densely packed groups of stars may make excellent cradles for complex space-traveling life to evolve. Despite studies that claim these environments, known as globular clusters, may be too harsh for life, a new study argues for a more optimistic view based on the evolving understanding of where planets lie outside the solar system.
“A globular cluster might be the first place in which intelligent life is identified in our galaxy,” lead study author Rosanne Di Stefano, of the Harvard-Smithsonian Center for Astrophysics, said in a statement. Di Stefano presented the new research today (Jan. 6) here at the 227th meeting of the American Astronomical Society.Globular clusters are massive groupings of millions of stars in a region only 100 light-years across. The clusters date back to the early life of the Milky Way — nearly 10 billion years ago. (For comparison, the universe is approximately 13.7 billion years old.) Although these clusters’ age raises some questions, it also provides ample time for civilizations that emerged to evolve and become complex
The advanced age of globular clusters means their stars are older, as well. The heavy elements found in younger stars, which are made up of previous generations, aren’t found within the hearts of globular cluster stars. This material, which would have been missing from the disks of dust and gas that built the star, is also required to build planets, so some scientists argue that worlds also would be missing from globular clusters.
But Di Stefano and her colleague Alak Ray, of Tata Institute of Fundamental Research in India, pointed out that stars have been found around noncluster stars that lack significant amounts of these elements. Although massive gas worlds tend to orbit stars with heavier elements, smaller rocky worlds that resemble Earth can be found around stars with varying amounts of the material.
“It’s premature to say there are no planets in globular clusters,” Ray said.
The dense population of the clusters also raises concerns about their habitability. The sun’s nearest stellar neighbor lies about four light-years (24 trillion miles, or 39 trillion kilometers) away. In a globular cluster, neighboring stars could be as much as 20 times closer. If a nearby star came too close, the effects of its gravity could fling a planet from its orbit.
In this case, the older age of the stars is an advantage. Di Stefano and Ray noted that bright stars like the sun would have been born, lived and died, leaving behind only faint, long-lived dwarf stars. These dimmer stars would require planets to orbit closer to their sun in order to maintain liquid water on their surface — a key requirement for the evolution of life as we know it. Their close orbits could help shield them from interactions with passing stars, according to a statement from the Harvard-Smithsonian Center for Astrophysics (CfA).
The presence of an old star could also indicate an older planet. On Earth, life is thought to have evolved after about 3.5 billion years. According to the CfA statement, a 10-billion-year-old planet would give life time to not only bloom, but evolve into intelligent and technologically advanced beings. Life on these ancient worlds would have had ample time to become a spacefaring species.
“Once planets form, they can survive for long periods of time — even longer than the age of the universe,” said Di Stefano.
While nearby stars may cause planets to be less stable, they can be a boon for interstellar travel. With nearby stars in galactic clusters as much as 20 times closer than the sun’s nearest neighbors, the opportunities for potential exploration, settlement and communication could be enhanced, the new study suggests.
“We call it the ‘globular cluster opportunity,’” Di Stefano said. “Sending a broadcast between the stars wouldn’t take any longer than a letter from the U.S. to Europe in the 18th century.”
Communication directed from one star in a globular cluster to the next could help scientists to spot advanced civilizations, CfA’s statement added. Targeting globular clusters with SETI search methods could reveal radio or laser broadcasts sent from one stellar system to the next.
Messages wouldn’t be the only things that could pass between the stars — spaceships could travel more easily from one system to the next, Di Stefano noted.
“The [NASA] Voyager probes are 100 billion miles [160 billion km] from Earth, or one-tenth as far as it would take to reach the closest star if we lived in a globular cluster,” Di Stefano said.
Launched in 1977, Voyager 1 and 2 were sent to the outer solar system. After passing the gas giants, the two probes continued on to the edge of the solar system and into interstellar space.
“That means sending an interstellar probe is something a civilization at our technological level could do in a globular cluster,” Di Stefano said.
A new technique could allow scientists to photograph potentially life-supporting planets in nearby multistar systems, its developers say.
The most straightforward way to learn about alien planets is to look at them directly with a telescope, rather than relying on indirect methods such as noticing their effects on the stars they circle.
Direct imaging of exoplanets requires a way to blot out the overwhelming glare of a star. This task is challenging enough when a one-star system is the target, and it’s even tougher with multistar systems. This latter fact is a problem, because binary stars are common throughout the Milky Way galaxy. Indeed, the nearest stellar system to Earth, Alpha Centauri, consists of two stars, known as Alpha Centauri A and B. (A third star, called Proxima Centauri, also lies nearby; it is considered by some astronomers to be part of this system as well.)
Most systems featuring sunlike stars “are actually multi[-star systems],” Ruslan Belikov, an astronomer at NASA’s Ames Research Center in California, said during a session at the 227th meeting of the American Astronomical Society here Wednesday (Jan. 7). “A telescope that is only imaging single-star systems will generally miss these.”
“Alpha Centauri, which is the closest star to us, would be by far the best target [for direct imaging] … if it wasn’t binary,” he added. Because of Alpha Centauri’s proximity to Earth (about 4.3 light-years), researchers could use a relatively small space telescope to get a close look.
But Belikov and his colleagues have come up with a possible solution for this problem.
Scientists hoping to directly image an exoplanet use special tools on or in front of a telescope to block out a star’s light, and they can also use optical techniques through a telescope’s mirrors or processing after the image is collected to cancel out extra noise and interference.
Belikov’s group figured out how to deform mirrors enough to blot out the disruptive effects of two stars at once, beyond the usual limit of how much interference a mirror can correct for. This and other modifications could theoretically allow astronomers to image planets in binary systems such as Alpha Centauri, Belikov said.
Going beyond the deformable mirror’s usual limit relies on a faint grating pattern introduced on many mirrors as a byproduct of the manufacturing process — something that can lead to tiny distortions often seen as a bug of such mirrors rather than a feature.
“We as scientists delight in disproving conventional wisdom in such things, but in this case it’s especially so,” Belikov said. “The reason we can do this impossible thing is because of something that is generally considered to be a deficiency.”
The newly proposed set of techniques can be applied to telescopes without complex hardware modifications, Belikov said. Finding a way to look at multiple-star systems like Alpha Centauri using a similar process could lead to glimpses of interesting alien planets — in Alpha Centauri’s case, with a much smaller telescope than previously thought possible. But Belikov’s AAS talk had another takeaway message as well.
“The most important conclusion of all is to have zero respect for authority telling you that something is impossible,” he said. “Unless it’s a law of physics.”
Get ready for your close-up, black holes: The Event Horizon Telescope (EHT), which will take some of the best images of black holes ever captured by humans, is ramping up its worldwide network of telescopes.
By 2018, the EHT will be an observatory that harnesses the power of nine telescopes around the world, including ones in Chile, Arizona, Hawaii, Antarctica and Greenland. These instruments will work together to get higher-resolution images than any of these scopes can achieve alone. The target of their observations will be black holes — scientists hope to see the material moving around these dark monsters, as well as the shadow of the black hole itself.
“One thing that could excite the public almost as much as a Pluto flyby would be a picture of a black hole, up close and personal,” Feryal Ӧzel, a professor of astronomy and astrophysics at the University of Arizona, said during a talk here at the 227th meeting of the American Astronomical Society, where a few thousand astronomers and astrophysicists have gathered to discuss the latest news in the field. (Ӧzel’s comment was made in reference to the massive public interest in the images captured by NASA’s New Horizons probe, which flew by the dwarf planet last July.) [The Strangest Black Holes in the Universe]
Other telescopes have studied black holes in the past, but the goal of the EHT is to take images that surpass the resolution of any previous black-hole snapshots. With that information, scientists would be able to see the area around a black hole — a place where the pull of gravity is so extreme that very strange things happen.
For example, the black hole at the center of the galaxy known as Messier 87 has a massive, narrow jet of material, roughly 5,000 light-years long, spewing away from it. In contrast, the black hole at the center of the Milky Way — Sagittarius A* — has very little matter around it and no jets. In galaxies known as active galactic nuclei (AGNs), black holes accelerate huge clouds of material around them, and radiate more light than the entire Milky Way galaxy. What leads to such a drastic difference between these objects? With EHT, Ӧzel said, scientists may finally be able to answer that question.
“Is it the magnetic field structure that is different? Is it the spin that is different? Or is it something else about the accretion flow that is different?” Ӧzel said. “This will open a brand-new window into studying accretion physics.”
And then there’s Einstein. His theory of general relativity has been tested using observations in Earth’s solar system — for example, the way light bends around the sun — and beyond. But there are few cosmic environments as extreme as the one around a black hole, where the gravity can be millions of times stronger than it is around a star. As a result, the EHT will reveal the effects of gravity (which are described by the theory of relativity) “on scales that have never been probed before,” said Ӧzel, who is a scientist on the EHT project team and is leading some of the theoretical work that will be combined with the observations. “Get to the edge of a black hole, and the general relativity tests you can perform are qualitatively and quantitatively different,” Ӧzel said.
Understandably, Ӧzel and other black-hole scientists are eager to start getting data from EHT. One of the major requirements of imaging black holes in such high resolution is to have a very large telescope. In fact, Ӧzel said that achieving the resolution of EHT effectively requires a telescope the size of the Earth.
“Of course nobody would fund an Earth-sized telescope,” Ӧzel said. But the “next-best thing” is to combine observations from multiple telescopes on the surface of the Earth that are separated by very large distances, Ӧzel said. With this technique, scientists can observe an object in significantly higher resolution than the telescopes could achieve alone — effectively giving scientists an “Earth-size” telescope.
The first data from the EHT project were collected in the mid-2000s, by three telescopes — one each in Hawaii, Arizona and California. The group collaborated to look at the black hole at the center of the Milky Way galaxy, called Sagittarius A*. In 2014, the collaboration added the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to its array, and doubled its resolution, according to the EHT website.
Six telescopes in the EHT array are already taking data, and a total of nine are expected to be contributing to the project by 2018, according to Shep Doeleman, principal investigator for EHT.
Early in 2015, the collaboration added the South Pole Telescope to its array, which connected the other telescopes such that the EHT effectively spanned the entire Earth. In 2017, the EHT will be able to make observations with ALMA that will boost its sensitivity by a factor of 10, Doeleman told Space.com in an email. In 2018, an additional telescope will join the group from Greenland.
“One of the innovative aspects of the EHT is that we use existing telescopes at the highest altitudes (where they are above most of the atmosphere) and outfit them with specialized instrumentation that enables us to link them together,” Doeleman said. “So we don’t build new dishes, and we leverage over a [billion dollars] of existing telescopes.”
However, there are still obstacles, he noted. “Last year, one of the facilities participating in the EHT had to close due to lack of funding,” Doeleman said. “We can still do all the EHT [work] planned because new sites are coming online, but we remain ‘en guard’ for threats against EHT sites.”