NASA has announced the discovery of Kepler 186 f, an Earth-sized exoplanet in the habitable zone of its host star, Kepler 186.
This artistic concept is the result of scientists and artists collaborating to help imagine the appearance of the Kepler-186 star system and its planets. Credit: NASA.
The first Earth-sized exoplanet orbiting within the habitable zone of another star has been confirmed by observations with both the W. M. Keck Observatory and the Gemini Observatory. The initial discovery, made by NASA's Kepler Space Telescope, is one of a handful of smaller planets found by Kepler and verified using large ground-based telescopes. It also confirms that Earth-sized planets do exist in the habitable zone of other stars.
"What makes this finding particularly compelling is that this Earth-sized planet, one of five orbiting this star, which is cooler than the Sun, resides in a temperate region where water could exist in liquid form," says Elisa Quintana of the SETI Institute and NASA Ames Research Centre, who led the paper published in the current issue of the journal Science. The region in which this planet orbits its star is called the habitable zone, as it is thought that life would most likely form on planets with liquid water.
Steve Howell, Kepler's Project Scientist and a co-author on the paper, adds that neither Kepler (nor any telescope) is currently able to directly spot exoplanets of this size and proximity to their host star. "However, what we can do is eliminate essentially all other possibilities, so the validity of these planets is really the only viable option."
With such a small host star, the team employed a technique that eliminated the possibility that either a background star or a stellar companion could be mimicking what Kepler detected. To do this, they obtained extremely high spatial resolution observations from the eight-metre Gemini North telescope on Mauna Kea in Hawaii, using a technique called speckle imaging, as well as adaptive optics (AO) observations from the ten-metre Keck II telescope, Gemini's neighbour on Mauna Kea. Together, these data allowed the team to rule out sources close enough to the star's line-of-sight to confound the Kepler evidence, and conclude that Kepler's detected signal has to be from a small planet transiting its host star.
"The Keck and Gemini data are two key pieces of this puzzle," says Quintana. "Without these complementary observations, we wouldn't have been able to confirm this Earth-sized planet."
The Gemini "speckle" data directly imaged the system, zooming to within about 400 million miles (about 4 AU, approximately equal to the orbit of Jupiter in our Solar System) of the host star and confirming there were no other stellar-sized objects orbiting within this radius from the star. Augmenting this, Keck AO observations probed a larger region around the star but to fainter limits. According to Quintana, "These Earth-sized planets are extremely hard to detect and confirm, and now that we've found one, we want to search for more. Gemini and Keck will no doubt play a large role in these endeavours."
The host star, Kepler-186, is an M1-type dwarf star relatively close to our Solar System at 500 light years and in the constellation of Cygnus. The star is very dim, being over half a million times fainter than the faintest stars we can see with the naked eye. Five small planets have been found orbiting it – four of which are in very short-period orbits and are very hot. The planet designated Kepler-186f, however, is Earth-sized and orbits within the star's habitable zone. The Kepler evidence for this planetary system comes from the detection of planetary transits. These transits can be thought of as tiny eclipses of the host star by a planet (or planets) as seen from the Earth. When such planets block part of the star's light, its total brightness diminishes. Kepler detects that as a variation in the star's total light output and evidence for planets. So far, more than 3,800 candidate planets have been detected by this method with Kepler.
The Gemini data utilised the Differential Speckle Survey Instrument (DSSI) on the Gemini North telescope. DSSI is a visiting instrument developed by a team led by Howell who adds, "DSSI on Gemini rocks! With this combination, we can probe down into this star system to a distance of about 4 times that between the Earth and the Sun. It's simply remarkable that we can look inside other solar systems." DSSI works on a principle that utilises multiple short exposures of an object to capture and remove the noise introduced by atmospheric turbulence producing images with extreme detail.
Observations with the W.M. Keck Observatory used the Natural Guide Star Adaptive Optics system with the NIRC2 camera on the Keck II telescope. NIRC2 (the Near-Infrared Camera, second generation) works in combination with the Keck II adaptive optics system to obtain very sharp images at near-infrared wavelengths, achieving spatial resolutions comparable to or better than those achieved by the Hubble Space Telescope at optical wavelengths. NIRC2 is probably best known for helping to provide definitive proof of a central massive black hole at the centre of our galaxy. Astronomers also use NIRC2 to map surface features of Solar System bodies, detect planets orbiting other stars, and study detailed morphology of distant galaxies.
"Observations from Keck and Gemini, combined with other data and numerical calculations, allowed us to be 99.98% confident that Kepler-186f is real," says Thomas Barclay, Kepler scientist and co-author on the paper. "Kepler started this story, and Gemini and Keck helped close it," he adds.
Observations at many sites in South America, including ESO's La Silla Observatory, have made the surprise discovery that the remote asteroid Chariklo is surrounded by two dense and narrow rings. This is the smallest object by far found to have rings and only the fifth body in the Solar System — after the much larger planets Jupiter, Saturn, Uranus and Neptune — to have this feature. The origin of these rings remains a mystery, but they may be the result of a collision that created a disc of debris.
The rings of Saturn are one of the most spectacular sights in the sky, and less prominent rings have also been found around the other giant planets. Despite many careful searches, no rings had been found around smaller objects orbiting the Sun in the Solar System. Now observations of the distant minor planet (10199) Chariklo as it passed in front of a star have shown that this object too is surrounded by two fine rings.
"We weren't looking for a ring and didn't think small bodies like Chariklo had them at all, so the discovery — and the amazing amount of detail we saw in the system — came as a complete surprise!" says Felipe Braga-Ribas (Observatório Nacional/MCTI, Rio de Janeiro, Brazil) who planned the observation campaign and is lead author on the new paper.
Chariklo is the largest member of a class known as the Centaurs and it orbits between Saturn and Uranus in the outer Solar System. Predictions had shown that it would pass in front of the star UCAC4 248-108672 on 3 June 2013, as seen from South America. Astronomers using telescopes at seven different locations, including the 1.54-metre Danish and TRAPPIST telescopes at ESO's La Silla Observatory in Chile, were able to watch the star apparently vanish for a few seconds as its light was blocked by Chariklo — an occultation.
But they found much more than they were expecting. A few seconds before, and again a few seconds after the main occultation there were two further very short dips in the star's apparent brightness. Something around Chariklo was blocking the light. By comparing what was seen from different sites the team could reconstruct not only the shape and size of the object itself but also the shape, width, orientation and other properties of the newly discovered rings.
The team found that the ring system consists of two sharply confined rings only seven and three kilometres wide, separated by a clear gap of nine kilometres — around a small 250-kilometre diameter object orbiting beyond Saturn.
"For me, it was quite amazing to realise that we were able not only to detect a ring system, but also pinpoint that it consists of two clearly distinct rings," adds Uffe Gråe Jørgensen (Niels Bohr Institute, University of Copenhagen, Denmark), one of the team. "I try to imagine how it would be to stand on the surface of this icy object — small enough that a fast sports car could reach escape velocity and drive off into space — and stare up at a 20-kilometre wide ring system 1000 times closer than the Moon."
Credit: ESO/L. Calçada/Nick Risinger
Although many questions remain unanswered, astronomers think that this sort of ring is likely to be formed from debris left over after a collision. It must be confined into the two narrow rings by the presence of small putative satellites.
"So, as well as the rings, it's likely that Chariklo has at least one small moon still waiting to be discovered," adds Felipe Braga Ribas.
The rings may prove to be a phenomenon that might in turn later lead to the formation of a small moon. Such a sequence of events, on a much larger scale, may explain the birth of our own Moon in the early days of the Solar System, as well as the origin of many other satellites around planets and asteroids.
The leaders of this project are provisionally calling the rings by the nicknames Oiapoque and Chuí, two rivers near the northern and southern extremes of Brazil.
By demonstrating rippling patterns (the effect of gravitational waves) in the cosmic microwave background, scientists have uncovered a major piece of evidence to support inflation and the Big Bang theory.
Astronomers are announcing today that they have acquired the first direct evidence that gravitational waves rippled through our infant universe during an explosive period of growth called inflation. This is the strongest confirmation yet of cosmic inflation theories, which say the universe expanded by 100 trillion trillion times, in less than the blink of an eye.
The findings were made with the help of NASA-developed detector technology on the BICEP2 telescope at the South Pole in collaboration with the National Science Foundation.
"Operating the latest detectors in ground-based and balloon-borne experiments allows us to mature these technologies for space missions and, in the process, make discoveries about the universe," said Paul Hertz, NASA's Astrophysics Division director in Washington.
Our universe burst into existence in an event known as the Big Bang, 13.8 billion years ago. Moments later, space itself ripped apart, expanding exponentially in an episode known as inflation. Tell-tale signs of this early chapter in our universe's history are imprinted in the skies, in a relic glow called the cosmic microwave background. Recently, this basic theory of the universe was again confirmed by the Planck satellite, a European Space Agency mission for which NASA provided detector and cooler technology.
But researchers had long sought more direct evidence for inflation in the form of gravitational waves, which squeeze and stretch space.
"Small, quantum fluctuations were amplified to enormous sizes by the inflationary expansion of the universe. We know this produces another type of waves called density waves – but we wanted to test if gravitational waves are also produced," said project co-leader Jamie Bock of NASA's Jet Propulsion Laboratory, which developed the BICEP2 detector technology.
The gravitational waves produced a characteristic swirly pattern in polarised light, called "B-mode" polarisation. Light can become polarised by scattering off surfaces. For example, polarised sunglasses reject polarised light to reduce glare. In the case of the cosmic microwave background, light has scattered off particles called electrons to become slightly polarised.
Gravitational waves from inflation create a distinctive "twist" pattern in the polarisation of the cosmic microwave background.
The BICEP2 team took on the challenge to detect B-mode polarisation by pulling together top experts in the field – developing revolutionary technology and traveling to the best observing site on Earth at the South Pole. The collaboration includes major contributions from Caltech; JPL; Stanford University, Stanford, Calif.; Harvard University, Cambridge, Mass.; and the University of Minnesota, Minneapolis.
As a result of experiments conducted since 2006, the team has been able to produce compelling evidence for the B-mode signal, and with it, the strongest support yet for cosmic inflation. The key to their success was the use of novel superconducting detectors. Superconductors are materials that, when chilled, allow electrical current to flow freely with zero resistance.
"Our technology combines properties of superconductivity with tiny structures that can only be seen with a microscope. These devices are manufactured using the same micro-machining process as the sensors in cellphones and Wii controllers," said Anthony Turner, who makes these devices using specialised fabrication equipment at JPL's Microdevices Laboratory.
The B-mode signal is extremely faint. In order to gain the necessary sensitivity to detect the polarisation signal, Bock and Turner developed a unique array of multiple detectors, akin to the pixels in modern digital cameras but with the added ability to detect polarisation. The whole detector system operates at a frosty 0.25 Kelvin, just 0.45 degrees Fahrenheit above the lowest temperature achievable, absolute zero.
"This extremely challenging measurement required an entirely new architecture," said Bock. "Our approach is like taking a camera and building it on a printed circuit board."
The BICEP2 experiment used 512 detectors, which sped up observations of the cosmic microwave background by 10 times over the team's previous measurements. Their new experiment, already making observations, uses 2,560 detectors.
These and future experiments not only help confirm that the Universe inflated dramatically, but are providing theorists with the first clues about the exotic forces that drove space and time apart. The results of this study have been submitted to the journal Nature. There is already talk of a Nobel Prize.
"This has been like looking for a needle in a haystack, but instead we found a crowbar," said co-leader Clem Pryke at the University of Minnesota.
When asked to comment on the implications of this discovery, Harvard theorist Avi Loeb said, "This work offers new insights into some of our most basic questions: Why do we exist? How did the universe begin? These results are not only a smoking gun for inflation, they also tell us when inflation took place and how powerful the process was."
A mixture of new and old observations going back 60 years has revealed an exotic binary system that includes the largest known yellow star.
The European Southern Observatory (ESO)'s Very Large Telescope Interferometer has found the largest yellow star – and one of the ten largest stars ever discovered. This hypergiant has been found to measure more than 1300 times the diameter of the Sun, and to be part of a double star system. The smaller companion is so close that it is actually in contact with the main star. Observations spanning over 60 years – some from amateur observers – also indicate that this rare and remarkable object is changing very rapidly and has been caught during a very brief phase of its life.
Olivier Chesneau (Observatoire de la Côte d'Azur, Nice, France) and an international team of astronomers found that this yellow hypergiant – HR 5171 A – was much bigger than they expected. It is so huge that, if placed in our Solar System, its radius would stretch beyond Jupiter. It is 50% larger than the famous red supergiant Betelgeuse and a million times brighter than our Sun.
"The new observations also showed that this star has a very close binary partner, which was a real surprise," says Chesneau. "The two stars are so close that they touch and the whole system resembles a gigantic peanut."
The astronomers made use of a technique called interferometry to combine the light collected from multiple individual telescopes, effectively creating a giant telescope up to 140 metres in size. The new results prompted the team to thoroughly investigate older observations of the star, to see how it had behaved in the past.
Yellow hypergiants are very rare, with only a dozen or so known in our galaxy – the best-known example being Rho Cassiopeiae. They are among the biggest and brightest stars and have reached a stage of their lives when they are unstable and changing rapidly. Due to this instability, yellow hypergiants also expel material outwards, forming a large, extended atmosphere around the star.
HR 5171 A. Credit: ESO/Digitized Sky Survey 2
Despite its great distance of nearly 12,000 light-years from Earth, the object can just about be seen with the naked eye by the keen-sighted. HR 5171 A has been found to be getting bigger over the last 40 years, cooling as it grows, and its evolution has now been caught in action. Only a few stars are caught in this very brief phase, where they undergo a dramatic change in temperature as they rapidly evolve.
By analysing data on the star's varying brightness, using records from other observatories, the astronomers confirmed the object to be an eclipsing binary system where the smaller component passes in front and behind the larger one as it orbits. In this case, HR 5171 A is orbited by its companion star every 1,300 days. The smaller companion is only slightly hotter than HR 5171 A's surface temperature of 5000 degrees Celsius.
"The companion we have found is very significant, as it can have an influence on the fate of HR 5171 A," adds Chesneau. "For example, stripping off its outer layers and modifying its evolution."
This new discovery highlights the importance of studying these huge and short-lived yellow hypergiants, and could provide a means of understanding the evolutionary processes of massive stars in general.
We live in a galaxy known as the Milky Way – a vast collection of 300 billion stars, planets whizzing round them, and clouds of gas and dust floating in between. It has long been known that the Milky Way and its companion, Andromeda, are the dominant members of the "Local Group", a family of galaxies 3 million light years across. However, much less was known about our immediate neighbourhood slightly further out.
A new paper by Professor Marshall McCall of York University, Canada, maps out bright galaxies within 20-million light years – offering an expanded picture of what lies beyond our galactic doorstep. The work is published this week in the journal Monthly Notices of the Royal Astronomical Society.
"All bright galaxies within 20 million light years, including us, are organised in a 'Local Sheet' 34-million light years across and only 1.5-million light years thick", says McCall. "The Milky Way and Andromeda are encircled by 12 large galaxies arranged in a ring about 24-million light years across – this 'Council of Giants' stands in gravitational judgment of the Local Group by restricting its range of influence."
McCall says 12 of the 14 giants in the Local Sheet, including the Milky Way and Andromeda, are spiral galaxies that have highly flattened disks in which stars are forming. The remaining two are more puffy "elliptical" galaxies, whose stellar bulks were laid down long ago. Intriguingly, the two ellipticals sit on opposite sides of the Council. Winds expelled in the earliest phases of their development might have shepherded gas towards the Local Group, thereby helping to build the disks of the Milky Way and Andromeda.
McCall also examined how galaxies in the Council are spinning: "Thinking of a galaxy as a screw in a piece of wood, the direction of spin can be described as the direction the screw would move (in or out) if it were turned the same way as the galaxy rotates. Unexpectedly, the spin directions of Council giants are arranged around a small circle on the sky. This unusual alignment might have been set up by gravitational torques imposed by the Milky Way and Andromeda when the universe was smaller."
The boundary defined by the Council has led to insights about the conditions which led to the formation of the Milky Way. Most importantly, only a very small enhancement in the density of matter in the universe appears to have been required to produce the Local Group. To arrive at such an orderly arrangement as the Local Sheet and its Council, it seems that nearby galaxies must have developed within a pre-existing sheet-like foundation comprised primarily of dark matter.
"Recent surveys of the more distant universe have revealed that galaxies lie in sheets and filaments with large regions of empty space called voids in between" says McCall. "The geometry is like that of a sponge. What the new map reveals is that structure akin to that seen on large scales extends down to the smallest."
For the first time, astronomers have used the same imaging technology found in digital cameras to take a photo of a planet outside our Solar System with a ground-based telescope.
Credit: Jared Males/UA
University of Arizona researchers have taken images of a planet outside our Solar System with an Earth-based telescope using essentially the same type of imaging sensor found in digital cameras, instead of an infrared detector. Although it still has a long way to go, this new method brings astronomers a step closer to obtaining direct images of Earth-like planets from the visible part of the light spectrum.
"This is an important next step in the search for exoplanets, because imaging in visible light instead of infrared is what we likely have to do if we want to detect planets that might be suitable for harbouring life," said Jared Males, lead author on a report to be published in The Astrophysical Journal.
Even though the image was taken at a wavelength just beyond human eye visibility, the use of a digital camera-type imaging sensor – known as a charge-coupled device (CCD) – opens up the possibility of imaging exoplanets in visible light, which has not been possible with Earth-based telescopes until now. So far, all Earth-based images taken of exoplanets close to their stars have been infrared images, which detect the planets' heat. This limits the technology to gas giants – massive, hot planets, still young enough to shed heat. In contrast, older and possibly habitable planets that have cooled since their formation don't show up in infrared images as readily, and to image them, astronomers will have to rely on cameras capable of detecting visible light.
"Our ultimate goal is to image what we call pale blue dots," said Laird Close, a professor in the Department of Astronomy, who co-authored the paper. "After all, the Earth is blue. And that's where you want to look for other planets: in reflected blue light."
Pale blue dot: Earth-like planets like this imaginary world may one day be photographed in visible light.
The photographed planet, Beta Pictoris b, is located approximately 63 light-years away in the constellation of Pictor, orbiting the 4th magnitude debris disk star Beta Pictoris. It orbits the star at only nine times the Earth-Sun distance, making its orbit smaller than Saturn's. In the team's CCD images, Beta Pictoris b appears about 100,000 times fainter than its host star, making it the faintest object imaged so far at such high contrast and at such relative proximity to its star. New images of this planet helped to confirm that its atmosphere is at a temperature of roughly 2600 degrees Fahrenheit (1700 Kelvin). It is estimated that Beta Pictoris b has a radius about 65% larger than Jupiter's.
"Because the Beta Pictoris system is 63.4 light years from Earth, the scenario is equivalent to imaging a dime right next to a lighthouse beam from more than four miles away," Males said. "Our image has the highest contrast ever achieved on an exoplanet that is so close to its star."
As well as the host star's overwhelming brightness, the astronomers had to overcome turbulence in Earth's atmosphere, which causes stars to twinkle and images to blur. The success reported here is mostly due to an adaptive optics system developed by Close and his team that eliminates much of the atmosphere's effect.
The Magellan Adaptive Optics technology is very good at removing this turbulence, or blurring, by means of a deformable mirror changing shape 1,000 times each second in real time. Adaptive optics have been used for more than 20 years at observatories in Arizona – most recently at the Large Binocular Telescope – and the latest version has now been deployed in the high desert of Chile at the Magellan 6.5-metre telescope.
The team also imaged the planet with both of MagAO's cameras, giving the scientists two completely independent simultaneous images of the same object in infrared, as well as bluer light, to compare and contrast.
"An important part of signal processing is proving that the tiny dot of light is really a planet and not a speckle of noise," said Katie Morzinski, a member of the MagAO team. "I obtained the second image in the infrared spectrum – at which the hot planet shines brightly – to serve as an unequivocal control that we are indeed looking at the planet. Taking the two images simultaneously helps to prove the planet image on the CCD is real and not just noise."
NASA has announced the discovery of 715 exoplanets by its Kepler mission, increasing the total number of confirmed planets outside our Solar System to nearly 1,700.
The newly-verified worlds orbit 305 stars, revealing multiple-planet systems much like our own Solar System. Nearly 95% of these planets are smaller than Neptune, which is almost four times the size of Earth. This discovery marks a significant increase in the number of known small-sized planets more akin to Earth than previously identified exoplanets.
"The Kepler team continues to amaze and excite us with their planet hunting results," said John Grunsfeld, associate administrator for NASA's Science Mission Directorate in Washington. "The fact that these new planets and solar systems look somewhat like our own, portends a great future when we have the James Webb Space Telescope in space to characterise the new worlds."
Since the discovery of the first planets outside our solar system in the mid-late 1990s, verification has been a laborious planet-by-planet process. Now, scientists have a statistical technique that can be applied to many planets at once when they are found in systems that harbour more than one planet around the same star.
"Four years ago, Kepler began a string of announcements of first hundreds, then thousands, of planet candidates – but they were only candidate worlds," said Jack Lissauer, a planetary scientist at NASA's Ames Research Centre. "We've now developed a process to verify multiple planet candidates in bulk, to deliver planets wholesale, and have used it to unveil a veritable bonanza of new worlds."
Four of these new planets are less than 2.5 times the size of Earth and orbit in their sun's habitable zone, defined as the range of distance from a star where the surface temperature may be suitable for life-giving liquid water. One of these habitable zone planets, Kepler-296f, orbits a star roughly half the size and 5% the brightness of our sun. Kepler-296f is twice the size of Earth – but scientists do not yet know whether it is a gas world, with a thick hydrogen-helium envelope, or a water world surrounded by a deep ocean.
This latest find brings the confirmed count of planets outside our solar system to nearly 1,700. As we continue to reach toward the stars, each discovery brings us one step closer to a more accurate understanding of our place in the Galaxy. Launched in 2009, Kepler is the first NASA mission to find potentially habitable Earth-size planets. So far, it has discovered more than 3,600 planet candidates, of which 961 have been verified as bona-fide worlds. Details of the 750 planets announced this week are published in The Astrophysical Journal on 10th March.
The first global, detailed geologic map of Ganymede – the largest moon in our Solar System – has been produced by researchers in the U.S.
Using images from NASA's Voyager flyby (1979) and the orbital Galileo probe (1995-2003), researchers have created the first global geological map of Jupiter's largest moon, Ganymede. With its varied terrain and possible underground ocean, Ganymede is considered a prime target in the search for habitable environments in our Solar System, and the researchers hope this new map will aid in future exploration.
The work – led by Professor Geoffrey Collins of Wheaton College in Massachusetts – took years to complete. It was published this week by the U.S. Geological Survey and is available as a PDF download along with a geospatial database.
"This map illustrates the incredible variety of geological features on Ganymede and helps to make order from the apparent chaos of its complex surface," said Robert Pappalardo of NASA's Jet Propulsion Laboratory in California. "It is helping planetary scientists to decipher the evolution of this icy world and will aid in upcoming spacecraft observations."
Jupiter Icy Moons Explorer (JUICE) is scheduled to reach the gas giant in 2030. This hi-tech orbiter will study Ganymede in extreme detail, identifying possible locations for a surface landing. Rovers might then follow later in the 2030s. NASA is contributing a U.S.-led instrument and hardware for two European-led instruments on JUICE.
Size comparison of Earth, the Moon, and Ganymede.
Since its discovery in 1610, Ganymede has been the focus of repeated observation – first by ground-based telescopes, then later flyby missions and spacecraft orbiting Jupiter. These studies depict a complex, icy world, whose surface is characterised by a striking contrast between its two major terrain types: the dark, very old, highly cratered regions, and the lighter, relatively younger regions marked with an extensive array of grooves and ridges.
According to researchers, three major geologic periods have been identified for Ganymede that involve the dominance of impact cratering, then tectonic upheaval, followed by a decline in geologic activity. This map illustrates surface features, such as furrows, grooves and impact craters, allowing scientists to decipher distinct geologic time periods for an object in the outer Solar System for the first time. It will enable researchers to compare the geology of other gas giant moons, because almost any type of feature that is found on other icy satellites has a similar feature somewhere on Ganymede.
"The surface of Ganymede is more than half as large as all the land area on Earth, so there is a wide diversity of locations to choose from," Collins said. "Ganymede also shows features that are ancient alongside more recently formed features, adding historical diversity in addition to geographic diversity."
Human colonisation of Ganymede is a possibility in the future – but will face major technical challenges. Although it possesses a magnetosphere (the only known moon with such a feature), it is overshadowed by Jupiter's magnetic field. Ganymede receives about 8 rem of radiation per day. It is more likely that Callisto (0.01 rem a day) would be settled first.
With new satellite technology, it is becoming possible to count individual whales and to automatically estimate their population size. Using Very High Resolution (VHR) satellite imagery, alongside image processing software, researchers were able to detect and count the number of whales breeding off the coast of Argentina.
Satellite images compared with aerial photograph (top right)
The new method, published this week in the journal PLoS ONE, could revolutionise how whale populations are estimated. Marine mammals are extremely difficult to count on a large scale and traditional methods – such as counting from platforms or land – can be costly and inefficient.
Lead author Peter Fretwell from the British Antarctic Survey (BAS): “This is a proof of concept study that proves whales can be identified and counted by satellite. Whale populations have always been difficult to assess; traditional means of counting them are localized, expensive and lack accuracy. The ability to count whales automatically, over large areas in a cost effective way will be of great benefit to conservation efforts for this and potentially other whale species.”
Previously, satellites have provided limited success in counting whales – but their accuracy has improved in recent years. The BAS team began by taking a single WorldView2 satellite image of a bay where southern right whales gather to calve and mate. Driven to near extinction, these whales have made a limited recovery following a whaling ban. In recent years, however, many deaths have been seen on their nursery grounds at Peninsula Valdes. Their population size is now unknown but with this sharp increase in calf mortality, estimates are needed.
The enclosed bays in this region contain shallow, calm waters – increasing the chance of spotting the whales from space. Three main criteria were used to identify whales: objects visible in the image should be the right size and shape; they should be in the right place (where whales would be expected to be) and there should be no (or few) other types of objects that could be mistaken as whales.
Whales in the image were manually counted, finding 55 probable whales, 23 possible whales and 13 sub-surface features. Several automated methods where then tested against these numbers. A ‘thresholding’ of the Coastal Band of the WorldView2 image gave the greatest accuracy. This part of the image uses light from the far blue end of the spectrum, which penetrates the water column deeper and reveals more whales. This technique found 89% of probable whales identified in the manual count.
This semi-automated technique needs some user input to identify the best threshold. Future satellite platforms, however, will provide much higher quality imagery and Worldview3 is planned to be launched later this year. This will allow for greater confidence in identifying whales and differentiating mother and calf pairs. Such technological advancements may also allow scientists to apply this method to other species.
NASA plans to send humans to Mars by 2033, but SpaceX CEO and billionaire entrepreneur Elon Musk wants to go there much sooner. In this interview, he outlines his thoughts on the current state of manned space exploration and his hopes for the not-too-distant future, including a "Mars Colonial Transporter".
Would you want to live on Mars? Let us know in the comments below...
Scientists using the far-infrared abilities of the Herschel space observatory have made the first definitive detection of water vapour on the largest and roundest object in the asteroid belt, Ceres. A space probe is due to arrive there in 2015.
Plumes of water vapour are thought to shoot up periodically from Ceres when portions of its icy surface warm slightly. Ceres is classified as a dwarf planet – a Solar System body larger than an asteroid, but smaller than a planet.
Herschel is a European Space Agency (ESA) mission with important NASA contributions.
"This is the first time water vapour has been unequivocally detected on Ceres or any other object in the asteroid belt and provides proof that Ceres has an icy surface and an atmosphere," said Michael Küppers of ESA in Spain, lead author of a paper in the journal Nature.
The results come at just the right time for NASA's Dawn mission, which is on its way to Ceres now after spending more than a year orbiting the large asteroid Vesta. Dawn is scheduled to arrive at Ceres in the spring of 2015, where it will take the closest ever look at its surface.
"We've got a spacecraft on the way to Ceres, so we don't have to wait long before getting more context on this intriguing result, right from the source itself," said Carol Raymond, deputy principal investigator at NASA's Jet Propulsion Laboratory in California. "Dawn will map the geology and chemistry of the surface in high resolution, revealing the processes that drive the outgassing activity."
For the last century, Ceres was known as the largest asteroid in our Solar System. But in 2006, the International Astronomical Union, a governing organisation responsible for naming planetary objects, reclassified Ceres as a dwarf planet because of its large size. It is roughly 590 miles (950 kilometres) in diameter. When it first was spotted in 1801, astronomers thought it was a planet orbiting between Mars and Jupiter. Later, other bodies with similar orbits were found, marking the discovery of our Solar System's main belt of asteroids.
Scientists believe Ceres contains rock in its interior with a thick mantle of ice that – if melted – would amount to more fresh water than is present on all of Earth. The materials making up Ceres likely date from the first few million years of our Solar System's existence and accumulated before the planets formed.
Scale image of Earth, the Moon and Ceres.
Until now, ice had been theorised to exist on Ceres but had not been detected conclusively. It took Herschel's far-infrared vision to see, finally, a clear spectral signature of the water vapour. But Herschel did not see water vapour every time it looked. While the telescope spied water vapour four different times, on one occasion there was no signature.
Here is what scientists think is happening: when Ceres swings through the part of its orbit that is closer to the Sun, a portion of its icy surface becomes warm enough to cause water vapour to escape in plumes at a rate of about 6 kilograms (13 pounds) per second. When Ceres is in the colder part of its orbit, no water escapes.
The strength of the signal also varied over hours, weeks and months, because of the water vapour plumes rotating in and out of Herschel's views as the object spun on its axis. This enabled the scientists to localise the source of water to two darker spots on the surface of Ceres, previously seen by NASA's Hubble Space Telescope and ground-based telescopes. These dark spots might be more likely to outgas because dark material warms faster than light material. When the Dawn spacecraft arrives at Ceres, it will investigate these features.
The results are somewhat unexpected because comets, the icier cousins of asteroids, are known typically to sprout jets and plumes, while objects in the asteroid belt are not.
"The lines are becoming more and more blurred between comets and asteroids," said Seungwon Lee of JPL, who helped with the water vapour models along with Paul von Allmen, also of JPL. "We knew before about main belt asteroids that show comet-like activity, but this is the first detection of water vapour in an asteroid-like object."
This evening – at 18:17 GMT – the European Space Agency's Rosetta spacecraft awoke from hibernation mode in preparation for its encounter with a comet, 67P/Churyumov–Gerasimenko.
The probe was launched in March 2004 and performed several flybys – of Earth, Mars and two asteroids – before entering a low power state in June 2011, in order to conserve energy. It has now reawakened and successfully communicated with ESA teams back on Earth.
The spacecraft consists of two main elements: the orbiter, which features 12 instruments, and the "Philae" robotic lander with an additional nine instruments. The first images of 67P are expected in May, from 2 million km (1.25 million mi) away. Rendezvous with the comet occurs in August this year, with deployment of the lander in November. Because of the comet's extremely low gravity, a harpoon system will lock the probe and drag it towards the surface, with legs dampening its eventual impact. Additional drills are used to further secure the lander on the comet.
Once on the surface, Philae will conduct the most detailed study of a comet ever attempted. Measurements of the ice, nucleus and chemical compounds present could reveal new details about the Solar System's history; perhaps even the origin of life itself. Among its many instruments are a drill that will bore 23 cm below the surface. A camera will also take high-resolution images (2048 × 2048 pixels) of the descent and a panorama of the landing site.
Rosetta will be the first spacecraft to fly alongside a comet as it heads towards the inner Solar System and the first to examine at close range how a frozen comet is transformed by the Sun's warmth. The mission runs until December 2015.
President Barack Obama has signed a budget that provides NASA with $17.6 billion for this year – fully funding both the heavy-lift Space Launch System and Orion capsule that will eventually take humans to Mars.
The Space Launch System (left) and Orion capsule (right).
NASA's budget for 2014 was passed by Congress earlier this week and officially signed by the President on Friday. A total of $17.65 billion has been allocated to the space agency, which is slightly less than the $17.7 billion it had requested. However, some analysts had expected a figure as low as $16.1 billion, due to recent budget cuts and spending concerns arising from the sequester of 2013. For space enthusiasts, the final approved figure is therefore a welcome surprise.
Some highlights from the budget include:
• $1,918 million for the Space Launch System (SLS).
The SLS is a heavy launch vehicle intended to replace the Space Shuttle. It is designed to be upgraded over time with more powerful versions. Initially carrying payloads of 70 metric tons into orbit, the SLS will eventually be fitted with an upper "Earth Departure Stage" capable of lifting at least 130 metric tons. This will be 12 metric tons greater than the Apollo-era Saturn V, making it the largest and most powerful rocket ever built. It will take astronauts and hardware to asteroids, the Moon, Mars, and most of the Earth's Lagrangian points. A first unmanned test launch is planned for 2017, with NASA being allocated an extra $200 million to ensure this deadline is met. A manned flight around the Moon and possibly to an asteroid is expected to occur in 2021, with manned missions to Mars in the 2030s. The additional funding in this year's budget will "maintain critical forward momentum" on the program, according to legislators.
• $1,197 million for the Orion Multi-Purpose Crew Vehicle (MPCV).
Orion is a small capsule designed to transport up to six astronauts and cargo beyond Earth orbit. It will be integrated with and carried by the SLS rockets. A first unmanned test flight is scheduled for later this year, during which its altitude will reach higher than any spacecraft intended for human use since 1973. Manned flights will commence in the 2020s.
• $5,151 million for science.
This includes $80 million for planning and development of a Europa mission. The next Discovery-class mission will be announced by May 2014, with selection of the mission(s) in September 2015. Meanwhile, NASA's flagship project and Hubble successor – the James Webb Space Telescope – remains funded and on track for delivery in 2018. Among its primary objectives will be capturing images of reionization and "first light" from stars after the Big Bang.
The remaining budget will go towards operational maintenance, space technology, aeronautics, grants, education and other services provided by NASA. Despite this week's good news, however, the longer term picture is less clear for NASA. As shown in the graph below, its budget as a percentage of the federal budget has been gradually declining and is now a mere fraction of its peak in the 1960s. It will be interesting to see how the private sector can influence the agency's strategy in the coming decades.