For the first time, a litter of four infant star siblings have been seen gestating in the belly of a gas cloud. Researchers say the finding supports the theory that most stars do not begin their lives alone.
In the Perseus star-forming region, four stars are emerging from a single parent filament, and have been observed moving together as a family. Three of the siblings are balls of gas (within the larger gas filament) that researchers say are on the cusp of collapsing into stars, while the fourth sibling has already become a star.
Scientists estimate that more than half of all stars like our sun live with a partner star, and yet scientists have little observational evidence to suggest whether these stars are born together, like twins, or come together later in life. Double-star systems impact many areas of astronomy, including the search for black holes and for habitable exoplanets. The new findings could give scientists a better idea of how multi-star systems emerge.
The newly discovered star babies appear to be less than 100,000 years old, and may be the “youngest multiple star system,” ever observed, according to Kaitlin M. Kratter, an assistant professor astronomy at the University of Arizona, who was not affiliated with the new research.
The new research shows that these four stars are forming from the same gas filament, and are linked together in a single system. But the stars (or soon-to-be-stars) are separated by 3 to 4 thousand astronomical units or AU (the distance from the Earth to the sun), which the authors of the new work say is a very large distance for star binaries. Normally, star twins are separated by only 10 to 1 hundred AU.
“These objects are so far apart that previously we all thought they were unrelated,” said Jaime Pineda, a researcher at the Max Planck Institute of Theoretical physics and lead author on the new research. “But with the new observations, we can measure that these systems are really part of a whole. In this case it’s the first time we can say it’s like a family.”
The researchers used three different telescopes to study the stellar babes. To show that the stars are part of the same family, the researchers had to measure their velocity, and show that they were moving as a unit.
“If you don’t know at what velocity the gas is moving you can’t make this kind of study about the level of bound-ness of the system,” said Pineda, who completed the research at the University of Zurich.
Star sibling rivalry
More than half of the stars in the universe are thought to exist in multi-star systems. It is through observing the motion of binary stars that scientists have identified black holes that have masses close to that of our sun. Binary stars can create Type Ia supernova, which scientists use to measure distances in the universe. Binary star collisions may create gravitational waves, or ripples in the fabric of space-time. Scientists have found potentially habitable planets around binary star suns.
“And yet the origins of the all-too-normal population are mysterious,” said Kratter, in an article in the journal Nature discussing the new research.
Binary systems are highly common, but full-grown quadruple star systems are much rarer.
“Given the relative rarity of quadruple star systems at older ages, one might think this discovery improbable, or lucky,” Kratter said. “On the contrary, it supports predictions that most stars begin their lives in a litter.”
It’s likely that after multi-star systems form, a kind of sibling rivalry sets in: the gravitational pull of all the bodies creates a highly unstable environment. While the researchers cannot say for sure what will happen to the four star siblings, Pineda said it’s likely at least one of them will be ejected later on.
Kratter also notes that young stars have more bound companions than older stars, indicating that while stars may be born in groups, they eventually move away from home, leaving behind a smaller pool of siblings. Some double-star systems may contain stars that were born together, while ejected stars may form binaries somewhere else.
The new result is a tantalizing piece of evidence that could help astronomers understand how star families form. Based on the new finding, Pineda said, researchers may want to re-examine other groups of stars that were previously assumed to be part of separate systems, to see if they are, in fact, part of the same family.
“I think it’s very likely that […] there are regions where we can repeat this experiment and try to determine […] in a more general way if this is a common result,” Pineda said, “Or if we’re looking at an odd ball.”
The exoplanet, called J1407b, could even harbor at least one Earth or Mars-sized moon, judging by a large gap in the rings, scientists have found. This discovery marks the first time researchers have found this kind of ring system outside of the solar system.
“This planet is much larger than Jupiter or Saturn, and its ring system is roughly 200 times larger than Saturn’s rings are today,” co-author of a new study about the rings Eric Mamajek, of the University of Rochester in New York, said in a statement. “You could think of it as kind of a super-Saturn.”
Exoplanets reveal themselves in their host star’s light. If a planet passes directly in front of its host star as observed from Earth, then the planet will block part of the star’s light and it will appear as though the star has momentarily dimmed. But in 2007, the young star 1SWASP J140747.93-394542.6 (located 433 light-years from Earth, toward the constellation Centaurus) showed a complex series of dimmings that lasted 56 days.
Mamajek and his colleagues first spotted the ring system in 2012, when they firs thought the dimming was caused by a ring system with at least four large rings. But further analysis by Matthew Kenworthy of the Leiden Observatory in the Netherlands and Mamajek estimate that the system is much more extensive with a total of 37 rings.
“The details that we see in the light curve are incredible,” Kenworthy said in the same statement. “The eclipse lasted for several weeks, but you see rapid changes on time scales of tens of minutes as a result of fine structures in the rings. The star is much too far away [for us] to observe the rings directly, but we could make a detailed model based on the rapid brightness variations in the starlight passing through the ring system.”
Typically, when an exoplanet crosses in front of its host star, the effect is tiny. A Jupiter-like planet, for example, might block 1 percent of a sun-like star’s light, producing an effect comparable to a mosquito flying in front of a flashlight a few thousand kilometers away from the observer. But in this case, the rings block as much as 95 percent of the star’s light.
Evidently, the rings are massive. By comparison, “if you were to grind up the four large Galilean moons of Jupiter into dust and ice and spread out the material over their orbits in a ring around Jupiter, the ring would be so opaque to light that a distant observer that saw the ring pass in front of the sun would see a very deep, multiday eclipse,” Mamajek said.
The data even show a clear gap that is 0.4 astronomical units (37 million miles) away from the super-Saturn. “One obvious explanation is that a satellite formed and carved out this gap,” said Kenworthy. “The mass of the satellite could be between that of Earth and Mars.”
Earth-size exomoons might prove to be promising abodes for habitable life. Although astronomers have started digging through the wealth of data collected by NASA’s Kepler space telescope in search of their presence, none have shown up yet. But the case of J1407b looks promising and may shed light on both exomoons and “exorings.”
Still, the relationship between moons and rings remains a mystery. Despite the fact that half of the planets in the Earth’s solar system have rings, astronomers have yet to fully understand how these bands are created and maintained. Last year, astronomers even spotted a distant asteroid with rings, for the first time.
Rings might be ancient, having formed with the planet itself. Or they might be relatively new, created from the debris of objects that fell toward the planet. Or maybe they form and then quickly disintegrate into moons. [See amazing photos of Saturn's rings]
Exoring model for J1407b from Matthew Kenworthy on Vimeo.
The team thinks that the third scenario might be the most likely one in this case. Kenworthy and Mamajek expect that the rings will become thinner in the next several million years and eventually disappear as moons form from the material in the disks.
“The planetary science community has theorized for decades that planets like Jupiter and Saturn would have had, at an early stage, disks around them that then led to the formation of satellites,” said Mamajek. “However, until we discovered this object in 2012, no one had seen such a ring system. This is the first snapshot of satellite formation on million-kilometer scales around a substellar object.”
So maybe Saturn need not worry. In millions of years J1407b’s rings will be a thing of the past, and it will regain its crown.
The ring study has been accepted for publication in the Astrophysical Journal.
When astrobiologist contemplate life on nearby planets or moons, they often suggest such life would be simple. Instead of there being some kind of multicellular organism on, say, Jupiter’s moon Europa, scientists instead aim to find something more like a microbe.
But from such simple life, more complex lifeforms could eventually come to be. That’s what happened here on planet Earth, and that’s what could happen in other locations as well. How did the chemistry evolve to get life to where we are today? What transitions took place?
Frank Rosenzweig, an evolutionary geneticist at the University of Montana, is looking into such questions over the next five years with funding from the NASA Astrobiology Institute. His lab studies how life evolves “complex traits,” factors that influence everything from lifespan to biodiversity.
“Over my career, I’ve been interested in what are the genetic bases of adaptation and how do complex communities evolve from single clones,” Rosenzweig said. “Related to these questions are others such as how do the genetic ‘starting point’ and ecological setting influence the tempo and trajectory of evolutionary change.”
Shopping for life in the Solar System
Complex life is only known to exist on Earth, but scientists aren’t ruling out other locations in the Solar System. Our understanding of life’s evolution could be informed by studying the Saturnian moon Titan, whose hydrocarbon chemistry is considered a precursor to a living system. Researchers recently tried to replicate a substance in Titan’s atmosphere called tholins,which are organic aerosols created from solar radiation hitting the methane and nitrogen atmosphere.
Understanding how tholins and other substances are formed on Titan could give researchers a picture of how early Earth evolved life. Also, studying how Earthly life-forms and their biochemical precursors evolved from simple subunits to successively more complex and interdependent systems could give hints of how life might evolve on other moons or planets.
On Earth, examples of these transitions include collections of single proteins evolving into protein networks. For example, single-celled bacteria evolve into eukaryotic cells that contain two, or even three genomes. Also, competing microbes come together to form cooperative systems, such as microbial mats in hot springs and microbial biofilms lining the human gut. Each of these transitions results in increased bio-complexity, interdependence and a certain degree of autonomy for a new whole that is more than the sum of its parts.
Rosenzweig’s research developed out of previous NASA grants over the past six years, and from his being a panelist reviewing team-based proposals for the NASA Astrobiology Institute.
“There is, and still needs to be a lot of work done on chemical evolution, prebiotic (pre-life) evolution, extreme environments and bio-signatures,”Rosenzweig said. “It struck me that it might be worthwhile trying to convince NASA to add to its research portfolio a set of proposals focused on understanding the genetic basis underlying major evolutionary transitions that have led to higher-order complexity”
As such, Rosenzweig’s new research will focus on four areas where a complex system has arisen from simpler elements: metabolism, the eukaryotic cell, mutualism (co-operating species) and multicellularity. He will also look into a fifth area — mutations and gene interactions — that critically determines how quickly such complex systems can arise. He believes that lab experiments aimed at replicating key aspects of the evolution of life on Earth can better inform how we search in life-friendly locations on Mars, Europa, Saturn’s moon Titan, or elsewhere.
Rosenzweig plans to have eight different teams focusing on questions of evolution and changes from simple to more complex life. To integrate his teams’ experimental results into a broader framework he recruited theoreticians in the areas of population genetics and statistical physics. [6 Most Likely Place for Life in the Solar System]
Applications beyond Earth
Rosenzweig’s previous NASA funding came from the Exobiology and Evolutionary Biology Program. The first project, initiated in 2007, examined how genetic material (or genomes) evolve in yeast species that were cultured under limited resources. A second project, initiated in 2010, is investigating how founder cells in E. coli genotypes, and the environment in which they evolve, influence the diversity and stability of subsequent populations.
The first project led to an unexpected finding: stress may increase the frequency with which genome sequences are rearranged. Stress introduces new chromosomal variants into the species; population that could prove beneficial under challenging circumstances. Indeed, previous studies have indicated that new chromosomal variants are stress resistant. In 2013, Rosenzweig’s team, led by University of Montana research professor Eugene Kroll, began studying how yeast cultures respond to starvation.
This new line of inquiry has already led to one major publication entitled, “Starvation-associated genome restructuring can lead to reproductive isolation in yeast,” which was published in PLoS One in 2013. Therein, Kroll and Rosenzweig further show that yeast containing stress-adaptive genomic rearrangements become “reproductively isolated” from their ancestors, suggesting that, at least in lower fungi, geographic isolation may not be required to generate new species. A new project through NASA’s Exobiology and Evolutionary Biology Program, awarded Summer 2014, will enable the team to tease out the genetic mechanisms that underlie adaptation and reproductive isolation in starved yeast.
A distinguishing feature of this research, Rosenzweig notes, is that whereas most studies look at species’ performance in relatively benign environments, the yeast are studied under near-starvation conditions. This kind of severe stress may be a closer analog to what real species face in nature as populations genetically adapt to drastically altered circumstances. Inasmuch as starvation may serve as a cue to any kind of stress, from diminished resources to greatly altered temperature to an invasion by superior competitors, the results of this study should have implications for life on other planets.
Indeed, a major theme that runs through all of these investigations is that by studying evolutionary processes in the laboratory using simple unicellular species, we can expect to uncover rules that govern the tempo and trajectory of evolution in any population of self-replicating entities whose structure and function are programmed by information molecules.
“What I would like fellow astrobiology researchers to be alert to is evidence of differentiation, either at the level of different proteins in a metabolic network, different genotypes in a population of a given species, different genomes in a single cell, or different cells in a multicellular organism. In each case differentiation opens the door not only to competition but also to cooperation between variants, enabling a division of labor.” he said. “We should be mindful that, however they may be encoded, lifeforms are likely to have differentiated on other worlds. Therefore, we should be alert to the signatures left by these more complex forms of life.”
Five rocky alien worlds that are 80 percent as old as the universe itself have been discovered, suggesting that Earth-size planets have been a feature of the Milky Way galaxy almost since its beginning.
The newfound exoplanets circle Kepler-444, an 11.2-billion-year-old star about 25 percent smaller than the sun that lies 117 light-years from Earth. All of the worlds are Venus-size or smaller and are therefore rocky, though scientists know nothing else about their composition.
All five alien planets complete an orbit in less than 10 days, meaning they’re almost certainly too hot to support life as we know it. But Kepler-444 hints at the existence of other ancient planetary systems that may be more hospitable, researchers said.
“We now know that Earth-sized planets have formed throughout most of the universe’s 13.8-billion-year history, which could provide scope for the existence of ancient life in the galaxy,” lead study author Tiago Campante, of the University of Birmingham in England, said in a statement.
For perspective, Earth and everything else in our own solar system formed about 4.6 billion years ago.
Campante and his colleagues discovered Kepler-444 and its five known planets after analyzing data gathered by NASA’s Kepler space telescope. Kepler hunts for planets by noting the tiny brightness dips caused when they cross their host star’s face from the spacecraft’s perspective.
Kepler can also pick up brightness changes caused by sound waves within the star that affect its temperature and thus its luminosity. Studying these natural oscillations — a strategy known as asteroseismology — can help scientists determine a star’s size, mass and age.
“When asteroseismology emerged about two decades ago, we could only use it on the sun and a few bright stars, but thanks to Kepler, we can now apply the technique to literally thousands of stars,” said co-author Daniel Huber, of the University of Sydney in Australia.
“Asteroseismology allows us to precisely measure the radius of Kepler-444 and hence the sizes of its planets,” he added. “For the smallest planet in the Kepler-444 system, which is slightly larger than Mercury, we measured its size with an uncertainty of only 100 kilometers [62 miles].”
The $600 million Kepler mission launched in March 2009, tasked with helping scientists determine how commonly Earth-like planets occur throughout the Milky Way. The spacecraft has discovered more than 1,000 exoplanets to date, with more than 3,000 additional “candidates” awaiting confirmation by follow-up analysis or observations.
Kepler’s original planet hunt ended in May 2013, when the second of its four orientation-maintaining reaction wheels failed. But scientists are still combing through the instrument’s huge data set, as the new study shows. And Kepler has embarked upon a new mission called K2, which is continuing the exoplanet search but also includes observations of other cosmic objects and phenomena.
If they could see further ahead, they might be able totravel three times as far in a single Martian day, enabling them to better find sites to explore and gather more information, faster, than they can today.
To speed up the rovers’ work, NASA is considering sending a robotic helicopter to Mars that could act as a scout for their explorations.
“So why would we want to put a helicopter on Mars?” asks Mike Meacham, a mechanical engineer with NASA’s Jet Propulsion Laboratory (JPL), in a video presentation. “If I’m the rover right now, I can’t really see the terrain behind me. But if I had a helicopter with a camera on it, all of a sudden, I can see a whole lot more.”
Dubbed the Mars Helicopter, the robot could be an add-on to future Mars rovers. Weighing 2.2 pounds and measuring 3.6 feet from the tip of one blade to the other, the helicopter would be able to detach from the rover and fly on its own.
So far, JPL engineers have built a proof-of-concept prototype and have been testing it in a 25-foot vacuum chamber.
Because of the difference between the atmosphere on Earth and on Mars, the helicopter’s blades would have to spin at about 2,400 rpm to provide lift, NASA said.
“The system is designed to fly for two to three minutes every day,” said Bob Balaram, a chief engineer at JPL. “There’s a solar panel on the top and that provides us with enough energy for that short flight, as well as to keep us warm through the night. So in those two to three minutes, we expect to have daily flights of about half a kilometer or so.”
For now the JPL team is focused on relentlessly testing the helicopter.
The veteran tech pioneer, which long ago lost the mantle of the world’s most inventive company, is making a bold play to regain that title in the face of stiff competition from Google Inc and Apple Inc.
Virtual or enhanced reality is the next frontier in computing interaction, with Facebook Inc focusing on its Oculus virtual reality headset and Google working on its Glass project.
Microsoft said its wire-free Microsoft HoloLens device will be available around the same time as Windows 10 this autumn. Industry analysts were broadly excited at the prospect, but skeptical that it could produce a working model at a mass-market price that soon.
“That was kind of a ‘Oh wow!’ moment,” said Mike Silver, an analyst at Gartner who tried out the prototype on Wednesday. “You would expect to see a relatively high-priced model this year or next year, then maybe it’ll take another couple of years to bring it down to a more affordable level.”
Microsoft does not have a stellar record of bringing ground-breaking technology to life. Its Kinect motion-sensing game device caused an initial stir but never gripped the popular imagination.
The company showed off a crude test version of the visor – essentially jerry-rigged wires and cameras pulled over the head – to reporters and industry analysts at a gathering at its headquarters near Seattle.
It did not allow any photographs or video of the experience, but put some images on its website.
A new alien-planet–hunting telescope has just come online in Chile, and it could help scientists peer into the atmospheres of relatively small planets circling nearby stars.
The Next-Generation Transit Survey (NGTS for short) — located at the European Southern Observatory’s (ESO) Paranal Observatory — is designed to seek out planets two to eight times the diameter of Earth as they pass in front of their stars. Such a planet will cause the light of the star to dip ever so slightly when passing in front of it, allowing the telescope to detect the planet during its transit.
“We are excited to begin our search for small planets around nearby stars,” Peter Wheatley, an NGTS project lead from the University of Warwick, U.K., said in as statement. “The NGTS discoveries, and follow-up observations by telescopes on the ground and in space, will be important steps in our quest to study the atmospheres and composition of small planets such as the Earth.”
The instrument is designed to measure the brightness of stars more accurately than any other ground-based wide-field survey, ESO officials said. The NGTS is made up of 12 telescopes that will operate robotically, according to ESO. Astronomers using the survey hope to find small, bright planets in order to learn more about the densities of them.
By taking these measurements, scientists might be able to learn more about what makes up the planets — that is, whether the planets could be rocky, gaseous, watery or composed of other materials, ESO officials added.
“It may also be possible to probe the atmospheres of the exoplanets whilst they are in transit,” ESO officials said in the same statement. “During the transit, some of the star’s light passes through the planet’s atmosphere, if it has one, and leaves a tiny, but detectable, signature. So far, only a few such very delicate observations have been made, but NGTS should provide many more potential targets.”
NGTS’ work is only the beginning. Scientists will use other telescopes to conduct follow-up studies of planet candidates that the survey finds when looking at the sky.
A consortium from the United Kingdom, Sweden and Germany built the NGTS. ESO is an astronomy organization supported by 15 different countries. The organization operates three observing sites, including Paranal, around Chile.
“We needed a site where there were many clear nights and the air was clear and dry so that we could make very accurate measurements as often as possible — Paranal was the best choice by far,” Don Pollacco of the University of Warwick and an NGTS project lead, said in a statement.
“It takes one to know one,” as the old truism goes. When it comes to unraveling the mysteries of far-off exoplanets, the same holds true — one more reason why astronomers want to thoroughly understand the local planets right here in our Solar System.
A new scientific paper moves the ball forward in this regard by simulating how several rocky Solar System bodies would look if glimpsed at the light-years distance of alien worlds. Across such great spans, exoplanets are just dim specks. But what little light does get to us could, the study suggests, imply intriguing details about their surface features, provided we know what to look for.
Previous studies of Earth have demonstrated that oceans, continents and ice caps bounce back strikingly different amounts of light into space. Models demonstrate that even from considerable distances, an observer would be able to pick out the different types of surface materials of water, land and ice.
The new study extends this concept to solid worlds unlike Earth, such as Mars and the Galilean moons, to broaden our basis for comparison.
“We eventually want to investigate the surface environments of Earth-like exoplanets, and for this purpose the observable signatures of Earth have been widely studied,” said lead author Yuka Fujii, a postdoctoral research scientist at the Tokyo Institute of Technology’s Earth-Life Science Institute. “To interpret the data of unknown planets obtained in the future, we also need to know the possible variety of observable features of other, non-Earth-like planets.”
The study, titled “Geology and Photometric Variation of Solar System Bodies with Minor Atmospheres: Implications for Solid Exoplanets,” has been accepted for publication in the journal Astrobiology.
Staring right at you
Although astronomers have discovered nearly 2,000 exoplanets to date, we know very little about any of them. For the vast majority, we merely possess either a mass or a size measurement. Exoplanets are simply too remote and faint for our current suite of instruments to glean tangible, worldly properties like color, surface features and cloud cover.
Our most detailed exoplanetary information so far has it that a handful of these worlds harbor gases, such as water vapor and carbon dioxide, in their atmospheres. That knowledge comes from signatures imprinted by those gases onto light that has passed through the atmosphere. The measurement, though, is indirect. The light assumed to pertain to the exoplanet is separated out from the overwhelming glare of its star.
Fujii’s study goes a step further in considering worlds that we will “directly image.” The distinction: The light from a directly imaged world is just from the world itself, not inferred from within a star’s comparatively blinding glare. This happens to be how we study planets in the Solar System: We look right at them rather than teasing their presence out from a blaze of light.
Less than two dozen exoplanets have been directly imaged to date. The potential advantage of this technique is to be able to distinguish features on small, rocky exoplanets, the best places we think for life to arise.
Today’s top-notch telescopes, like the Hubble and Spitzer Space Telescopes, will not be up to this task, however. Instead, we must wait for next-generation telescopes and specialized instruments that can collect the planetary light more efficiently than today’s instruments, separately from the host star. Several of these instruments in the works may utilize the James Webb Space Telescope, slated for launch in 2018, and the “thirty meter” class of telescopes on the ground.
From here to there
To lay a foundation for this future work, Fujii’s study rendered Solar System worlds as far-off, dim exo-worlds. Fujii and colleagues collected existing data, as well as some fresh observations of Mercury, the Moon, Mars and the four Galilean moons of Jupiter (Io, Europa, Ganymede and Callisto).
Because these bodies are all relatively close, detailed maps have been made of their surfaces, consisting of thousands of pixels. Exoplanets, however, owing to their distance, can occupy only a single pixel — a so-called point source. To render Solar System bodies as point sources, Fujii averaged the total color, or brightness, of their numerous pixels down to a single pixel. (Ice, for instance, reflects more light than land, so it has a brighter color.)
As a world rotates, the brightness of this single pixel varies over time if the world’s surface is not all the same. For example, when Earth rotates such that the vast Pacific Ocean faces toward an observer, the planet’s overall brightness changes compared to when, say, the giant landmass of Asia swings into view.
“Due to the spin rotation, we see different slices of the surface at different times,” said Fujii. “So if the brightness varies as the planet rotates, it indicates non-uniform surface material.”
Telltale light changes
The various worlds considered in the study did demonstrate average color variations over time that could be explicitly tied to factors affecting their surface compositions.
For a waterless body like the Moon, regions with potentially large contrasts to elsewhere on the lunar surface are “maria,” the dark lava fields that form the pareidolic “Man in the Moon” patterns. And sure enough, the Moon stood out as a Solar System object with discernibly dissimilar light-reflecting regions.
Mercury, though it has a fairly uniformly gray color, has smooth plains covering 40 percent of its otherwise heavily cratered surface. The effect on its light reflectance patterns was similar in some ways, but not as dramatic as that of the two-tone Moon.
Io, meanwhile, jumped out thanks to its raging volcanoes, which have slathered the surface in yellows and reds, famously looking like pizza. The brightnesses of the other three Galilean moons, Europa, Ganymede and Callisto, fluctuated because of patches of darker material deposited on lighter, water ice. Ganymede’s light patterns also hinted at its rumpled surface, with grooves and ridges owing to past internal heating events.
Mars, interestingly, had a lot of light variability at longer wavelengths, because fine-grained particles on the Red Planet’s surface scatter these forms of light. The iron oxides, or rust, that covers a significant portion of Mars, however, are efficient at absorbing shorter wavelength light. So the notable presences and absences of certain wavelength of light told a convincing tale of what large expanses of the Mars’ surface are like.
Overall, over the course of a single rotation of a planet or moon, these geological characteristics caused changes in brightness ranging from five percent to a quote noticeable 50 percent.
“Other Solar System bodies are also distinct, exhibiting various interesting surface features, some of which affect their characteristic surface colors, highlighting the amazing diversity that awaits future reconnaissance, and thus the need for continued study,” said Fujii.
Getting the basics down
The results point to how we might, with direct imaging, begin to pick out exoplanets with distinct, yet familiar geologic histories and perhaps even habitable conditions.
One major aspect that the study sidesteps is the lack of atmospheres in the chosen worlds. Intervening gases, and especially clouds, can make surface characterization difficult or impossible using direct imaging. For example, the thick, cloudy atmospheres of Venus or Saturn’s moon, Titan, completely hide their faces.
But in the case of Earth, although clouded here and there, the primary surface entities of continents, oceans and ice caps, can clearly be identified even at tremendous distance, the evidence suggests.
Although indirect atmospheric characterization of habitable exo-worlds will surely precede direct surface imaging, both of these techniques will need to be brought to bear to figure out if, and what sort of, alien life has developed.
“We think this kind of survey is useful,” said Fujii, “because in terms of astrobiology, we will be interested in the details of the planetary surfaces after we know the atmospheric profiles.”
Along with setting aside atmospheres for now, another caveat of Fujii’s study is that the first solid, potentially life-friendly exo-worlds we will likely directly image will be significantly heftier than Earth. These “super-Earths” are on the order of up to twice Earth’s width and several times its mass. Per their bigness, super-Earths will be easier to find and examine.
“We wish we had super-Earth counterparts in the Solar System, because then we would definitely study their properties first,” said Fujii.
Even so, building upon Fujii’s results, astronomers should be well-placed to get a bead on super-Earth surfaces — at least compared to familiar Solar System objects.
“Now that we have a handful of planets and satellites in the Solar System whose properties we know in some detail,” said Fujii, “we want to make the most of that knowledge, which we consider as necessary target practice.”
NASA has a far-fetched plan for a mission that will require a robotic tag-team effort, a rocket lifting off from the surface of Mars and a spacecraft that will scoop up Martian rocks orbiting the Red Planet.
Ashwin Vasavada, the new project scientist for NASA’s Mars Rover Curiosity project, said scientists are working on a plan to not just send a rover to study rocks on Mars. Vasavada and his team are working to bring some of those rocks back to Earth so geologists can study them here.
Getting those rocks from Mars to Earth won’t be an easy task. Vasavada has a plan for that.
Vasavada, a planetary scientist, has been the deputy project scientist for NASA’s Curiosity rover since 2004. He took over as the project head, succeeding John Grotzinger, who had held the post for seven years. Grotzinger recently became chairman of Caltech’s Division of Geological and Planetary Sciences but will remain a member of Curiosity’s science team.
“In the future, we’ll work to bring [Martian] rocks back to Earth,” Vasavada said ”I’m looking forward to that. Curiosity is about the most you can do sending tools to Mars. The next step will be to send rocks back to Earth.”
To ferry Martian rocks back to Earth will take a multi-pronged plan that might play out over the better part of 10 years.
The next robotic rover is expected to be sent to Mars in 2020, Vasavada said. It is being designed to hunt for signs of past life, as well as to make oxygen and rocket fuel on the Red Planet.
However, it also is being designed to collect rocks and soil samples and store them in a cache. The rover will leave that cache behind as it moves on to conduct other scientific studies on Mars. After that, another NASA mission will send a rocket and a smaller rover to the surface of Mars. That rover will pick up the cache of samples and put them on the rocket, which will launch itself and place those samples in orbit around Mars.
To wrap up the effort, another spacecraft will be launched for Mars that will grab the samples in orbit and bring them back to Earth, where scientists can study them firsthand.
Vasavada said the project is intended to be completed before NASA is expected to send humans to Mars in the 2030s.
All eight newfound alien planets appear to orbit in their parent stars’ habitable zone — that just-right range of distances that may allow liquid water to exist on a world’s surface — and all of them are relatively small, researchers said.
“Most of these planets have a good chance of being rocky, like Earth,” study lead author Guillermo Torres, of the Harvard-Smithsonian Center for Astrophysics (CfA), said in a statement.
The haul doubles the number of known habitable-zone planets that are potentially rocky, study team members said.
The newly discovered worlds were all detected by NASA’s prolific Kepler space telescope, then confirmed using observations by other telescopes and a computer program that assessed the statistical probability that they are bona fide planets (as opposed to false positives).
While none of the eight is a true “alien Earth,” two of them — known as
and Kepler-442b — stand out for their similarities to our home planet (though both worlds orbit red dwarfs, stars that are smaller and dimmer than Earth’s sun).
Kepler-438b, which lies 470 light-years from our solar system, is just 12 percent wider than Earth and has a 70 percent chance of being rocky, study team members said. The planet completes one orbit every 35 days and receives about 40 percent more energy from its star than Earth does from the sun.
Kepler-442b is about one-third larger than Earth, and has a 60 percent chance of being rocky. The exoplanet’s orbital period is 112 days, and it gets about two-thirds as much energy as Earth, scientists said. Kepler-442b is about 1,100 light-years from Earth.
As intriguing as these two worlds are, there’s no guarantee that either of them could actually host life, team members stressed.
“We don’t know for sure whether any of the planets in our sample are truly habitable,” co-author David Kipping, also of the CfA, said in the same statement. “All we can say is that they’re promising candidates.” [The Search For Another Earth (Video)]
Such hedging is unavoidable at this point, because researchers just don’t have enough information. For starters, there’s the uncertainty about the planets’ composition, as evidenced by the estimated rockiness probabilities. (Nobody knows for sure where the dividing line lies between rocky and gaseous worlds, in terms of planet size.)
Furthermore, a planet’s surface temperature is highly dependent on the composition and thickness of its atmosphere, and nothing is known about the air surrounding Kepler-438b, Kepler-442b or any of the other newfound worlds.
And some scientists employ a more restrictive definition of “habitable zone” than others. Indeed, study team member Douglas Caldwell, who presented the results today (Jan. 6) at the annual winter meeting of the American Astronomical Society (AAS) in Seattle, said that only three of the newly confirmed planets are “securely” in the habitable zone.
But he’s not discounting the life-hosting chances of the other five.
“All of these planets are small, all of them are potentially habitable — and, in fact, have a more than a 50 percent chance of being in the slightly extended habitable zone — and all are interesting,” Caldwell, who’s based at the SETI (Search for Extraterrestrial Intelligence) Institute in Mountain View, California, said during a AAS press briefing today.
Other big exoplanet news was announced today at the AAS meeting as well — namely, that scientists have identified 554 new planet candidates in the Kepler mission’s database, bringing the number of total Kepler candidates to 4,175.
Just over 1,000 alien planets identified as potential worlds by Kepler have been officially confirmed to date, but it’s likely that around 90 percent will eventually be validated, mission team members say.
Among the newly announced 554 candidates are eight that are small (between 1 and 2 times as wide as Earth) and orbit in their stars’ habitable zones. Six of these eight potential planets circle a sunlike star.
“These candidates represent the closest analogues to the Earth-sun system found to date,” Fergal Mullally of the Kepler Science Office said during today’s AAS news conference. “This is what Kepler has been looking for. We are now closer than we have ever been to finding a twin for the Earth around another star.”
The $600 million Kepler mission launched in March 2009 to determine how common Earthlike planets are throughout the Milky Way galaxy. A glitch ended the spacecraft’s original planet hunt in May 2013, but researchers are still combing through Kepler’s huge database. (The 554 new candidates were pulled from observations made between May 2009 and April 2013.)
And last year, Kepler embarked upon a new, two-year mission called K2, during which the observatory is searching for planets in a more limited fashion and is also studying supernova explosions, star clusters and other cosmic objects and phenomena.
Kepler has discovered more than half of all known exoplanets. The total alien-planet tally currently hovers around 1,800; the number differs slightly depending on which database is consulted.
The Gemini Planet Imager (GPI), which is installed on the Gemini South telescope in Chile, first started observing the heavens in November 2013 and didn’t begin full science operations until this past November. But the instrument has already detected unexpected differences between two sister exoplanets and helped characterize the ring of dust and rocky bodies surrounding a young star, researchers announced Tuesday (Jan. 6).
Astronomers trained GPI on HR 8799, a star found about 130 light-years from Earth that’s known to host four planets. One stunning GPI image captured three of those planets, as well as the star, in the same frame. And GPI’s measurements revealed significant differences in the light coming from two of the worlds, HR 8799c and HR 8799d — a surprise, since both planets are about the same size (roughly 20 percent larger than Jupiter) and appear to be the same color.
“This was not expected at all based on the prior photometry,” Marshall Perrin, of the Space Telescope Science Institute in Baltimore, said Tuesday during a news conference at the annual winter meeting of the American Astronomical Society in Seattle.
Perrin and his colleagues aren’t yet sure what the divergent spectra mean, but they have a theory.
“We believe that, most likely, what we’re seeing is more uniform cloud cover on one of these planets versus more patchy cloud cover on the other, where you can see deeper into the atmospheric layers,” Perrin said.
The Gemini Planet Imager has also studied the circumstellar disc surrouding HR 4796A, a young star that lies about 240 light-years from Earth. This ring of dust and planetary building blocks — which Perrin likened to a scaled-up version of our own solar system’s Kuiper Belt — has been observed by other instruments, but GPI’s keen eyes have revealed new insights.
For example, GPI’s measurements show that HR 4796A’s disc is partially opaque, suggesting that its dust is packed much more tightly than the dust at the outer reaches of Earth’s solar system, Perrin said.
“In some ways, it’s analogous to one of Saturn’s rings — very narrow, slightly optically thick to get the brightness ratio right on the two sides of the disc,” he said. “We’re still thinking about the dynamics of this.”
While GPI has been characterizing alien worlds and systems, it has not discovered any exoplanets yet. But that could change over the next few years, as astronomers plan to use the instrument to search 600 nearby stars for Jupiter-like planets.
GPI is designed to find and characterize such large gas giants. The instrument isn’t sensitive enough to study small, rocky worlds — but its operations may help researchers develop future gear that can do just that, Perrin said.
“We’re going to be opening up a lot of new discoveries, hopefully, over the next few years in terms of exoplanet imaging and, in the long run, taking these technologies and scaling them to future 30-meter telescopes, and perhaps large telescopes in space, to continue direct imaging and push down towards the Earth-like planet regime,” he said.
Scientists have used computer modeling to show that so-called “super-Earth” planets — worlds that are up to five times more massive than Earth — can play host to long-lived oceans. The modeling shows that the oceans can potentially remain on the planet for billions of years, possibly allowing life to develop on the alien planet. Researchers presented the new super-Earth findings during a news conference at the 225th meeting of the American Astronomical Society here in Seattle.
“When people consider whether a planet is in the habitable zone, they think about its distance from the star and its temperature,” lead author of the super-Earth study Laura Schaefer of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts said in a statement. “However, they should also think about oceans, and look at super-Earths to find a good sailing or surfing destination.”
Scientists think that Earth’s oceans have existed for almost the entire history of the planet, and water is key to life as humanity understands it. Therefore, finding other worlds with long-lived oceans could help scientists narrow down planets that might have a good chance of hosting life.
Earth’s oceans are recycled. Water from the planet’s oceans is pulled into the mantle from the crust due to geological activity, but water is also released from the mantle and back into the surface oceans through volcanic activity. The new computer model produced by Schaefer and her team was designed to test if this water recycling can occur on super-Earths with plate tectonics as well, according to the CfA.
In fact, some planets larger than Earth could be even better at maintaining oceans than this planet. Schaefer’s model shows that a planet two to four times the mass of Earth could host oceans continuously for 10 billion years. The largest planet in the study, which was about five times more massive than Earth, didn’t develop an ocean in the computer model for about 1 billion years, but those planets’ oceans, once formed, continue to persist on the surface for a long amount of time. .
Schaefer and her team suggest that it might be better to hunt for life on older super-Earths. Researchers might have a better chance of finding complex life on planets that are 1 billion years older than Earth, the team said.
“It takes time to develop the chemical processes for life on a global scale, and time for life to change a planet’s atmosphere,” the CfA’s Dimitar Sasselov, a co-author on the study, said in a statement. “So, it takes time for life to become detectable.”
A recent Search for Extraterrestrial Intelligence (SETI) effort studied 86 candidates in the Kepler space observatory’s field for radio signals that could potentially indicate the presence of an intelligent civilization.
Of course, no radio signals were found, but the search did identify the most promising Kepler objects for wide-band observations using the Green Bank Telescope in West Virginia.
“The 86 target stars were selected because they hosted planets discovered by [the year] 2011 with properties that could be conducive to the development of life,” said Abhimat Gautam, of the University of California, Berkeley.
Gautam, who recently completed his senior undergratuate year at the University of California, Berkeley and was part of the Berkeley SETI Research Center, presented the results at the 224th summer meeting of the American Astronomical Society in Boston, Massachusetts in June.
Widening the search
By 2011, Kepler had revealed 1,235 planetary candidates (as of Dec. 31, 2014, that number stands at 4,183, with 996 of them confirmed as planets). Gautam worked with Andrew Siemion and other scientists of the Berkeley SETI Research Center to select 86 planetary candidates that had surface temperatures between minus 50 and 100 degrees Celsius (minus 58 to 212 degrees Fahrenheit), a radius smaller than three times that of Earth, and an orbital period of more than 50 days. Such conditions placed the objects within the habitable zone around their stars, the region where liquid water can exist on the surface and where life might best be able to develop on a planet.
The Green Bank Telescope (the world’s largest fully steerable radio telescope, located in Green Bank, West Virginia) targeted the parent stars using a wide-band signal. Scientists had performed previous searches of the Kepler field in the narrow band with no success. Only 5 Hertz (Hz) wide on the radio spectrum, narrow-band signals are only known to arise from artificial sources on Earth, Gautam said. The narrow-band range is commonly used in SETI searches.
By switching to wide-band, Gautam hoped for a number of benefits. Wide-band signals cover 2.5 Megahertz (MHz), which is half a billion times wider than previous searches. Increasing the region of the radio spectrum observed means that listening scientists can search for broader signals than those previously observed. [13 Ways to Hunt Intelligent Aliens]
The interstellar medium — the gas and dust between stars — can spread the signal out as it travels through the material, causing a delay that could provide a rough estimate of the distance to any detectable source and allowing SETI astronomers to track potential communications back to their origins.
In addition, a wide-band signal may be more commonly used for intentional signaling, Gautam said.
“An advanced alien civilization may even use a pulsar for signaling, which can be more easily and effectively detected in a wide-band search.”
Gautam, who is now pursuing a doctorate in astronomy at the University of California, Los Angeles, first took interest in SETI through the SETI@Home project while still in high school. He contacted Dan Werthimer, chief scientist for SETI@Home, in search of available research projects.
“When UC Berkeley undergraduate students majoring in the physical sciences express an interest in continuing on for a graduate degree in their field, one of the first suggestions they receive is to seek out research opportunities,” SETI’s Andrew Siemion told Astrobiology Magazine in an email.
Gautam presented the results while he was still an undergraduate student because “it was all his work,” Siemion said. “Abhimat was a fantastic member of our research group.”
Scanning the skies
The SETI search focused both on active signals deliberately broadcast by a potential civilization, as well as passive signals such as those created by Earth’s television shows and airport radars.
“We expect intentional, active signals to be brighter and easier to detect than non-intentional, passive signals,” Gautam said.
With the Green Bank Telescope pointed at each target star, the radio beam would span approximately 4.2 light-years, wide enough to engulf the planetary system, including unknown bodies.
According to Siemion’s SETI blog, the search also covered a region of the radio spectrum known as the “terrestrial microwave window,” which can travel through both interstellar space and Earth’s atmosphere with little distortion. Within that window, the SETI search covered the “water hole,” a region of the radio spectrum bounded by the two products of water — hydrogen and hydroxyl.
“Some scientists have suggested that if an extraterrestrial intelligence were to deliberately signal other intelligent beings, they might chose this band,” Siemion wrote.
The team found no sign of an intelligent civilization. They concluded that less than 1 percent of the stars in the region produce a radio signal greater than 60 times that of the Arecibo radio telescope in Puerto Rico.
“The Arecibo Planetary Radar is the most powerful radio transmitter on Earth,” Gautam said. “This provides a good estimate for calculating estimates of the detect-ability of Earth-like technology in our search.”
As scientists ramp up the search for Earth-size planets outside our solar system, one team says it’s possible that “stretched-out” rocky exoplanets could be found orbiting close to their parent stars.
These exoplanets would be extremely hot, bent out of shape by the gravitational pull of their parent stars and likely inhospitable to life. But studying these worlds could shed light on the internal structure of rocky planets, researchers said.
“Imagine taking a planet like the Earth or Mars, placing it near a cool red star and stretching it out,” study lead author Prabal Saxena, an astrophysicist at George Mason University, said in a statement. “Analyzing the new shape alone will tell us a lot about the otherwise impossible to see internal structure of the planet and how it changes over time.”
Scientists are already familiar with gas giants that orbit close to their parent stars; many such “hot Jupiters” have been discovered to date. Such worlds tend to have high temperatures (more than 1,832 degrees Fahrenheit, or 1,000 degrees Celsius) and experience extreme tidal forces from the star’s gravity.
Prabal’s team created a model in which rocky planets are similarly close to red dwarf stars, the most common type of star in the galaxy. Because red dwarfs are dimmer than the sun, it can be easier to find planets crossing across their faces and blocking their light — a search strategy known as the transit method.
The model revealed that close-orbiting rocky planets should be tidally locked to their star so that one side always faces its stellar companion, just as the near side of the moon always faces Earth. The star’s gravity should also stretch out the core of the planet, making it easier to spot a transit because of the world’s unusual shape.
Signals could be detectable by currently operating telescopes, the team added, with a higher probability of success coming from newer telescopes in production. These include NASA’s $8.8 billion James Webb Space Telescope, set to launch in 2018, and the ground-based European Extremely Large Telescope (E-ELT), which is expected to start observing the heavens in the mid-2020s.
The study was published online this month in the journal Monthly Notices of the Royal Astronomical Society.
NASA’s Kepler space telescope is discovering alien planets again.
The prolific spacecraft has spotted its first new alien planet since being hobbled by a malfunction in May 2013, researchers announced today (Dec. 18). The newly discovered world, called HIP 116454b, is a “super Earth” about 2.5 times larger than our home planet. It lies 180 light-years from Earth, in the constellation Pisces — close enough to be studied by other instruments, scientists said.
“Like a phoenix rising from the ashes, Kepler has been reborn and is continuing to make discoveries,” study lead author Andrew Vanderburg, of the Harvard-Smithsonian Center for Astrophysics (CfA), said in a statement. “Even better, the planet it found is ripe for follow-up studies.”
Kepler launched in March 2009, on a 3.5-year mission to determine how frequently Earth-like planets occur around the Milky Way galaxy. The spacecraft has been incredibly successful to date, finding nearly 1,000 confirmed planets — more than half of all known alien worlds — along with about 3,200 other “candidates,” the vast majority of which should turn out to be the real deal.
The spacecraft finds planets by the “transit method,” watching for the telltale dimming caused when a world cross the face of, or transits, its parent star from Kepler’s perspective. Such work requires incredibly precise pointing — an ability the spacecraft lost in May 2013, when the second of its four orientation-maintaining reaction wheels failed.
But the Kepler team didn’t give up on the spacecraft. They devised a way to increase Kepler’s stability by using the subtle pressure of sunlight, then proposed a new mission called K2, which would continue Kepler’s exoplanet hunt in a limited fashion and also study other cosmic objects and phenomena, such as active galaxies and supernova explosions.
\NASA greenlit K2 for two years in May of this year, but Kepler first detected HIP 116454b even earlier. Vanderburg and his colleagues — who developed special software to analyze data gathered by the spacecraft in its compromised state — noticed a single transit of the planet in Kepler observations from a nine-day test run in February.
The astronomers then confirmed the discovery using the HARPS-North spectrograph on the Telescopio Nazionale Galileo in the Canary Islands, off the west coast of Africa.
HIP 116454b is about 20,000 miles (32,000 kilometers) wide and is 12 times more massive than Earth, scientists said. The planet’s density suggests that it is either primarily covered by water or is a “mini Neptune” with a large, thick atmosphere.
HIP 116454b lies just 8.4 million miles (13.5 million km) from its host star, an “orange dwarf” slightly smaller and cooler than the sun, and completes one orbit every 9.1 days. The close-orbiting planet is too hot to host life as we know it, researchers said.
The planet’s relative proximity to Earth means it will likely attract further attention in the future.
“HIP 116454b will be a top target for telescopes on the ground and in space,” said study co-author John Johnson, of Harvard University and the CfA.
The new study has been accepted for publication in The Astrophysical Journal.
While HIP 116454b is the first planet spotted by Kepler in its current state, it isn’t the first world to be confirmed in the wake of the May 2013 glitch. Many other discoveries have rolled in since then, as researchers work to validate the trove of planet candidates Kepler detected during its prime mission.