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.
It turns out that sailing through interstellar space isn’t so peaceful.
NASA’s Voyager 1 spacecraft — the only object made by humans to reach interstellar space — might still be caught what scientists have described as a cosmic “tsunami wave,” a shock wave that first hit the probe in February, according to new research. You can hear the eerie interstellar vibrations in a video, courtesy of NASA.
“Most people would have thought the interstellar medium would have been smooth and quiet,” study researcher Don Gurnett, professor of physics at the University of Iowa, and the principal investigator of Voyager 1′s plasma wave instrument, said in a statement from NASA. “But these shock waves seem to be more common than we thought.” [Photo Timeline: Voyager 1 in Interstellar Space]
Such a shock wave was what helped scientists determine that Voyager 1, which launched in 1977 on a “grand tour” of the outer planets, had officially left the solar system.
Last year, researchers keeping tabs on the car-sized spacecraft (12 billion miles away) analyzed measurements the Voyager 1 made in the aftermath of a powerful eruption from the sun known as a coronal mass ejection, or CME. This solar blast occurred in March 2012 and hit Voyager 1 from April to May 2013. The shock wave caused the particles around the spacecraft to vibrate substantially. Based on the frequency of these vibrations, scientists could measure the density of the probe’s surroundings.
The density of the particles around Voyager 1 was 40 times higher than scientists had previously observed when the space probe was still in the outer layers of the heliosphere, the giant bubble of charged particles and magnetic fields that surrounds the sun and the planets in our solar system. Voyager 1 team members concluded that the spacecraft had exited the heliosphere and entered a new cosmic realm. After researchers went back and looked at old data, they concluded that Voyager 1 crossed into interstellar space on August 25, 2012.
Voyager 1 detected its third and most recent interstellar shock wave in February. The vibrations were still going on as of November data, according to NASA. That’s remarkable considering that over the course of this event, the spacecraft has traveled 250 million miles (400 million kilometers).
The researchers say they are not sure how fast the wave is moving or how big a region it covers. And they’re still trying to understand what they can learn from these waves.
“The density of the plasma is higher the farther Voyager goes,” Ed Stone, project scientist for the Voyager mission from the California Institute of Technology, said in a statement from NASA. “Is that because the interstellar medium is denser as Voyager moves away from the heliosphere, or is it from the shock wave itself? We don’t know yet.”
The Nordic Optical Telescope on La Palma — one of the Canary Islands off the west coast of Africa — observed 55 Cancri e, a planet twice the size of Earth, as it passed in front of its parent star and caused a dip in the star’s brightness, according to a new study. This is the first time a planet in this “super-Earth” size category orbiting a sunlike star has been observed by a ground-based telescope using this detection method, the researchers say.
First identified in 2004 by a space-based telescope, 55 Cancri e has a diameter of about 16,000 miles (26,000 kilometers) — about twice that of Earth. The alien world is eight times as massive as Earth, making it a so-called super-Earth, a planet more massive than Earth but significantly smaller than gas giants like Neptune and Uranus. While not habitable, the planet’s size and position around a sunlike star make it similar to planets that might support life, researchers say.
The planet’s detection with the Nordic telescope shows that observatories on the ground could use what’s called the transit method — watching for dips in the brightness of a star to indicate a planet passing in front of it — to assist space-based telescopes in follow-up studies of super-Earths or Earthlike exoplanets, scientists say.
Nearly 2,000 exoplanets have now been confirmed, and upcoming exoplanet searches promise to expand that catalog.
“We expect these surveys to find so many nearby terrestrial worlds that space telescopes simply won’t be able to follow up on all of them. Future ground-based instrumentation will be key, and this study shows it can be done,” Mercedes Lopez-Morales, co-author of the new research and a researcher at the Harvard-Smithsonian Center for Astrophysics (CfA), said in a statement.
Five exoplanets orbit the star 55 Cancri, which is located 40 light-years from Earth and is visible to the naked eye. The closest-orbiting of those five is 55 Cancri e, which completes one lap around the star every 18 hours. When the planet passes between Earth and the parent star, 55 Cancri appears to dim by 1/2000th (or 0.05 percent) for almost 2 hours, researchers said.
Detecting such subtle changes is difficult for telescopes on the ground because of the blurring effect of Earth’s atmosphere. Space-based telescopes escape this problem completely, but technologies exist to help ground-based telescopes adapt to this challenge.
Daytime temperatures on 55 Cancri e likely reach higher than 3,100 degrees Fahrenheit (1,700 degrees Celsius) — hot enough to melt metal and much too hot to support life. But scientists involved with the study say this approach could help characterize the atmosphere of more hospitable Earthlike or super-Earth planets.
“With this result, we are also closing in on the detection of the atmospheres of small planets with ground-based telescopes,” Lopez-Morales said. “We are slowly paving the way toward the detection of biosignatures in Earthlike planets around nearby stars.”
Another super-Earth called , located 42 light-years from Earth, was previously detected by ground-based telescopes using the same transit method, researchers said. GJ 1214b is larger than 55 Cancri e, with a diameter about 2.7 times that of Earth and a mass seven times greater than Earth’s. GJ 1214b orbits a red dwarf, a class of stars that are significantly smaller and dimmer than Earth’s sun. 55 Cancri e was the first super-Earth detected around a main sequence star, similar to our sun.
After its initial detection, 55 Cancri e also became the first super-Earth seen by NASA’s Spitzer Space Telescope, using light directly from the planet. Thus, it has now served twice as a litmus test for super-Earth detection methods.
In addition to the wealth of planets identified by NASA’s Kepler Space Telescope, the space agency’s Transiting Exoplanet Survey Satellite (TESS) mission, scheduled for launch in 2017, is expected to “discover thousands of exoplanets in orbit around the brightest stars in the sky,” according to the TESS website. The European Space Agency’s Planetary Transits and Oscillations of stars (PLATO) mission, planned for launch in 2024, will also search for a large number of exoplanets.
“Our observations show that we can detect the transits of small planets around sunlike stars using ground-based telescopes,” Ernst de Mooij of Queen’s University Belfast in the United Kingdom and lead author of the study, said in the statement from CfA. “This is especially important because upcoming space missions, such as TESS and PLATO, should find many small planets around bright stars, and we will want to follow up the discoveries with ground-based instruments.”
The solar system has many examples of moons orbiting planets; Jupiter and Saturn both possess more than 60 satellites. However, these moons are usually much smaller than their planets — Earth is nearly four times wider than its moon and more than 80 times its mass.
Still, some moons are as large as planets. For instance, Ganymede, Jupiter’s largest moon, is larger than Mercury, and three-quarters the diameter of Mars. Also, moons at times are nearly as large as their worlds; Pluto’s largest moon, Charon, is about half the diameter of the dwarf planet itself. This raises the intriguing possibility that planets of equal size could orbit each other. [The Strangest Alien Planets]
Binary stars, or two stars orbiting each other, are very common throughout the Milky Way galaxy. Some of these two-star systems are even known to host exoplanets — worlds with two suns, like Luke Skywalker’s home planet of Tatooine in “Star Wars.” Binary asteroids also exist in the solar system. However, binary or double planets involving Earth-size worlds are currently only science fiction.
One possible way that binary planets might form is when two worlds orbiting a star get close enough to one another to interact gravitationally. To see if these systems are possible, researchers simulated two rocky Earth-sized planets veering toward each other. They modeled each world as made up of 10,000 particles and varied the speed of the planets and the angles of their approaches. The scientists managed to simplify their models so that each simulation took as little as a day to run instead of up to a week as they did at the beginning of their work.
The scientists ran about two dozen simulations. However, these simulations often resulted in the planets colliding, typically merging or accreting together into a larger planet and sometimes leaving behind a disk of debris from which a moon could form. Also, in some simulations, the planets collided in a grazing manner at high speeds, resulting in “hit and run” interactions in which the worlds escaped from one another.
Still, about one-third of the simulations resulted in binary planets forming. These involved relatively slow, grazing collisions.
“Previously, the only expected outcomes of large-body impacts of this sort were escape or accretion — that is, either the two bodies do not stay together or they merge into one, occasionally with a disk of debris,” study co-author Keegan Ryan, an undergraduate student at the California Institute of Technology in Pasadena, told Space.com. “Our findings suggest the possibility of another outcome — binary planets. The bodies stay mostly intact, but end in a bound orbit with one another.”
These binary planets would loom extraordinarily close to one another, separated by a distance of about half the diameter of each of the worlds. Over time, the rate at which both planets spin would fall into lockstep, with each world only turning one face toward its partner.
Such binaries can persist for billions of years, researchers say, provided they form at least half an astronomical unit or more away from their parent stars — far enough away for the star’s gravitational pull to not disrupt the binary planet system. (One astronomical unit, or AU, is the average distance between the sun and Earth, about 93 million miles, or 150 million kilometers.)
The research team’s goal from here “is to run more simulations, increase the parameters of the simulations, and work to get a better picture of the probability that a binary planet might form,” Ryan said.
Ryan and his colleagues Miki Nakajima and David Stevenson detailed their findings Nov. 11 at the American Astronomical Society’s Division for Planetary Sciences meeting in Tucson, Arizona.
Starshade” technology that could help astronomers find and characterize rocky, Earthlike alien worlds was put to the test earlier this year in the Nevada desert.
A starshade, also dubbed an external occulter, is a precisely shaped screen that flies in far-away formation with a space telescope. The device blocks a star’s light to create a high-contrast shadow, so that only light from an orbiting exoplanet enters the telescope for detailed study.
While a starshade to hunt alien planets has not been flown before, researchers studying the technique are drawing upon a track record of success in fielding large, deployable antennas in space. Some designs foresee a fully deployed starshade measuring some 110 feet (34 meters) in diameter, with a 65-foot (20 m) inner disk and 28 outstretched flowerlike petals, each over 22 feet (7 m) in length.
The starshade idea has moved beyond the drawing board.
Subscale versions of starshades have undergone nighttime desert testing, most recently at central Nevada’s Smith Creek dry lake bed over five nights in late May and early June of this year. Previously, a California test locale was used. [How the Planet-Hunting Starshade Unfolds in Space (Video)]
Desert appraisals of hardware have focused on how computational optical predictions stack up against in-the-field performance of two different starshade shapes, said Steve Warwick, program manager for starshade field testing at Northrop Grumman Aerospace Systems.
The recent Nevada test took advantage of the thin air and very dark skies at high-altitude Smith Creek, Warwick said. A six-person team made use of a modified Celestron telescope and ultrabright, light-emitting diodes (LEDs) placed about 1 mile (1.6 kilometers) away. The LEDs were all finely aligned with an automated stand topped by a starshade model sitting in the middle of the test range.
Data and images were gathered at the telescope stand.
“As you can imagine, we take a lot of data while we’re sitting out there in tents at night,” Warwick told Space.com. “There is a lot of post-processing that we have to do … and that’s underway at the moment.”
A lot will be asked of a starshade on a planet-hunting space mission.
“What we’re trying to do here is look at a lighthouse from a mile away and spot a firefly that’s just a half inch away from that lighthouse,” he said. “We’re trying to block the light from the lighthouse.”
In the simplest terms, a starshade is a specially shaped finger placed in front of a bright source to dim the light, said Ron Polidan, manager of science systems at Northrop Grumman Aerospace Systems.
“So in essence you can consider it a traveling dark spot,” Polidan said.
Deployment in space
Polidan said that company technologists are looking at several options on how best to unfold a large starshade in space. For example, there’s heritage to be found in Northrop’s lead work on NASA’s Tracking and Data Relay Satellite System, he said, as well as in building the space agency’s $8.8 billion James Webb Space Telescope (JWST).
“So part of the assessment going on with the desert tests is to understand simple and reliable deployment systems,” Polidan told Space.com.
Northrop Grumman’s starshade is “telescope agnostic,” said Warwick. That is, it could be used with JWST, which is scheduled to blast off in 2018, or with other space scopes being considered. In the end, it’s up to NASA, he said.
Starshades aid in direct imaging, helping telescopes gather photons arriving from a target planet. They can help deliver spectroscopic looks of the atmosphere of an exoplanet, “and that’s where it feeds into the search for life,” Warwick said.
Additional starshade testing in the desert is in the offing for next year, Warwick said. All the ground work, he said, is confidence-building in order to move forward on a future space-size starshade mission.
“We can never do an ‘end-to-end test’ of the starshade concept. So instead, we break the testing into two parts,” said Sara Seager, professor of planetary science and physics at the Massachusetts Institute of Technology in Cambridge, Massachusetts.
Seager is chair of a current 18-month NASA-sponsored Starshade Probe-Class mission Science and Technology Definition Team.
Seager told Space.com via email that one test phase involves fabrication and deployment to show that the required tolerances and construction of the starshade petals can be met. The other is subscale environmental testing in a lab or outdoors to demonstrate that starshade experts “understand the math and that diffraction behaves as we expect,” she said.
“This two-step process is our best option,” Seager said.
Seeing is believing
There’s one simple bottom line for Seager: Seeing is believing. The desert testing offers one way to make that happen.
“What we would absolutely love to see is an actual astronomical discovery using the starshade,” Seager said. “People have conceived putting the starshade on one mountain top and a telescope on a lower mountain peak.”
When an object of interest passes over the starshade — say a star with a debris disk — perhaps an interesting observation can be made, she said.
“We have to show the world that the starshade is a part of the astronomer’s tool kit,” Seager said.