Sharing All of The World

Previous research and first-hand reports suggest that humans have a harder time controlling physical movement and completing mental tasks in microgravity. Astronauts have experienced problems with balance and perceptual illusions -- feeling as if, for example, they are switching back and forth between right-side-up and upside down.
The Spaceflight Effects on Neurocognitive Performance: Extent, Longevity, and Neural Bases (NeuroMapping) study is examining changes in both brain structure and function and determining how long it takes to recover after returning from space.
Researchers are using both behavioral assessments and brain imaging. Astronauts complete timed obstacle courses and tests of their spatial memory, or the ability to mentally picture and manipulate a three-dimensional shape, before and after spaceflight. The spatial memory test also is performed aboard the station, along with sensory motor adaptation tests and computerized exercises requiring them to move and think simultaneously. Astronauts are tested shortly after arriving aboard the station, mid-way through and near the end of a six-month flight.
Structural and functional magnetic resonance imaging (MRI) scans of the brain are done pre-flight and post-flight.
"We are looking at the volume of different structures in the brain and whether they change in size or shape during spaceflight," said principal investigator Rachael D. Seidler, director of the University of Michigan's Neuromotor Behavior Laboratory.
Functional MRIs involve astronauts completing a task during the imaging, which will show researchers which parts of the brain they rely on to do so.
According to Seidler, both the behavioral assessment and brain imaging are important to help identify the relationship between physical changes in the brain and those in behavior.
"On Earth, your vestibular -- or balance -- system tells you how your head moves relative to gravity, but in space, the gravity reference is gone," Seidler said. "That causes these perceptual illusions, as well as difficulty coordinating movement of the eyes and head."
These difficulties could have serious consequences for astronauts, especially when changing between gravitational environments, such as landing on Mars. In those cases, astronauts will need to be able to perform tasks such as using tools and driving a rover, and they must be capable of escape in a landing emergency.
Identifying the physical mechanisms behind changes in behavior and how much time it takes to adapt will help researchers determine how best to help space explorers compensate. The study results could also reveal whether astronauts return to "normal" post-flight because the brain changes back, or if the brain instead learns to compensate for the changes that happened in space.
Scientists know that brain changes and adaptations happen here on Earth as well. As people age, for example, they use more brain networks than a younger person does to perform the same task. Chemotherapy, injury and illness also can trigger such adaptation. Co-investigator Patricia A. Reuter-Lorenz, chair of psychology at the University of Michigan, said a major benefit of this study is that the subjects are fit, healthy astronauts. That will make it possible to apply the findings across a range of causes.
Learning more about how the human brain changes in space will help scientists better understand the ways it can recover and adapt in space, and on Earth.
At least here on Earth, people can usually tell which way is up.

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The Spanish explorer Vicente Yáñez Pinzón first reported the existence of the Coalsack Nebula to Europe in 1499. The Coalsack later garnered the nickname of the Black Magellanic Cloud, a play on its dark appearance compared to the bright glow of the two Magellanic Clouds, which are in fact satellite galaxies of the Milky Way. These two bright galaxies are clearly visible in the southern sky and came to the attention of Europeans during Ferdinand Magellan's explorations in the 16th century. However, the Coalsack is not a galaxy. Like other dark nebulae, it is actually an interstellar cloud of dust so thick that it prevents most of the background starlight from reaching observers.
A significant number of the dust particles in dark nebulae have coats of frozen water, nitrogen, carbon monoxide and other simple organic molecules. The resulting grains largely prevent visible light from passing through the cosmic cloud. To get a sense of how truly dark the Coalsack is, back in 1970, the Finnish astronomer Kalevi Mattila published a study estimating that the Coalsack has only about 10 percent of the brightness of the encompassing Milky Way. A little bit of background starlight, however, still manages to get through the Coalsack, as is evident in the new ESO image and in other observations made by modern telescopes.
The little light that does make it through the nebula does not come out the other side unchanged. The light we see in this image looks redder than it ordinarily would. This is because the dust in dark nebulae absorbs and scatters blue light from stars more than red light, tinting the stars several shades more crimson than they would otherwise be.
Millions of years in the future the Coalsack's dark days will come to an end. Thick interstellar clouds like the Coalsack contain lots of dust and gas -- the fuel for new stars. As the stray material in the Coalsack coalesces under the mutual attraction of gravity, stars will eventually light up, and the coal "nuggets" in the Coalsack will "combust," almost as if touched by a flame.

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In this new image of Jupiter a broad range of features has been captured, including winds, clouds and storms. The scientists behind the new images took pictures of Jupiter using Hubble's Wide Field Camera 3 over a ten-hour period and have produced two maps of the entire planet from the observations. These maps make it possible to determine the speeds of Jupiter's winds, to identify different phenomena in its atmosphere and to track changes in its most famous features.
The new images confirm that the huge storm, which has raged on Jupiter's surface for at least three hundred years, continues to shrink, but that it may not go out without a fight. The storm, known as the Great Red Spot, is seen here swirling at the centre of the image of the planet. It has been decreasing in size at a noticeably faster rate from year to year for some time. But now, the rate of shrinkage seems to be slowing again, even though the spot is still about 240 kilometres smaller than it was in 2014.
The spot's size is not the only change that has been captured by Hubble. At the centre of the spot, which is less intense in colour than it once was, an unusual wispy filament can be seen spanning almost the entire width of the vortex. This filamentary streamer rotates and twists throughout the ten-hour span of the Great Red Spot image sequence, distorted by winds that are blowing at 540 kilometres per hour.
There is another feature of interest in this new view of our giant neighbour. Just north of the planet's equator, researchers have found a rare wave structure, of a type that has been spotted on the planet only once before, decades ago by the Voyager 2 mission, which was launched in 1977. In the Voyager 2 images the wave was barely visible and astronomers began to think its appearance was a fluke, as nothing like it has been seen since, until now.
The current wave was found in a region dotted with cyclones and anticyclones. Similar waves -- called baroclinic waves -- sometimes appear in Earth's atmosphere where cyclones are forming. The wave may originate in a clear layer beneath the clouds, only becoming visible when it propagates up into the cloud deck, according to the researchers.
The observations of Jupiter form part of the Outer Planet Atmospheres Legacy (OPAL) programme, which will allow Hubble to dedicate time each year to observing the outer planets. In addition to Jupiter,Neptune and Uranus have already been observed as part of the programme and maps of these planets will be placed in the public archive. Saturn will be added to the series later. The collection of maps that will be built up over time will help scientists not only to understand the atmospheres of giant planets in the Solar System, but also the atmospheres of our own planet and of the planets that are being discovered around other stars.

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AU Microscopii, or AU Mic for short, is a young, nearby star surrounded by a large disc of dust [1]. Studies of such debris discs can provide valuable clues about how planets, which form from these discs, are created.
Astronomers have been searching AU Mic's disc for any signs of clumpy or warped features, as such signs might give away the location of possible planets. And in 2014 they used the powerful high-contrast imaging capabilities of ESO's newly installed SPHERE instrument, mounted on the Very Large Telescope for their search -- and discovered something very unusual.
"Our observations have shown something unexpected," explains Anthony Boccaletti of the Observatoire de Paris, France, lead author on the paper. "The images from SPHERE show a set of unexplained features in the disc which have an arch-like, or wave-like, structure, unlike anything that has ever been observed before."
Five wave-like arches at different distances from the star show up in the new images, reminiscent of ripples in water. After spotting the features in the SPHERE data the team turned to earlier images of the disc taken by the NASA/ESA Hubble Space Telescope in 2010 and 2011 to see whether the features were also visible in these [2]. They were not only able to identify the features on the earlier Hubble images -- but they also discovered that they had changed over time. It turns out that these ripples are moving -- and very fast!
"We reprocessed images from the Hubble data and ended up with enough information to track the movement of these strange features over a four-year period," explains team member Christian Thalmann (ETH Zürich, Switzerland). "By doing this, we found that the arches are racing away from the star at speeds of up to about 40,000 kilometres/hour!"
The features further away from the star seem to be moving faster than those closer to it. At least three of the features are moving so fast that they could well be escaping from the gravitational attraction of the star. Such high speeds rule out the possibility that these are conventional disc features caused by objects -- like planets -- disturbing material in the disc while orbiting the star. There must have been something else involved to speed up the ripples and make them move so quickly, meaning that they are a sign of something truly unusual [3].
"Everything about this find was pretty surprising!" comments co-author Carol Grady of Eureka Scientific, USA. "And because nothing like this has been observed or predicted in theory we can only hypothesise when it comes to what we are seeing and how it came about."
The team cannot say for sure what caused these mysterious ripples around the star. But they have considered and ruled out a series of phenomena as explanations, including the collision of two massive and rare asteroid-like objects releasing large quantities of dust, and spiral waves triggered by instabilities in the system's gravity.
But other ideas that they have considered look more promising.
"One explanation for the strange structure links them to the star's flares. AU Mic is a star with high flaring activity -- it often lets off huge and sudden bursts of energy from on or near its surface," explains co-author Glenn Schneider of Steward Observatory, USA. "One of these flares could perhaps have triggered something on one of the planets -- if there are planets -- like a violent stripping of material which could now be propagating through the disc, propelled by the flare's force."
"It is very satisfying that SPHERE has proved to be very capable at studying discs like this in its first year of operation," adds Jean-Luc Beuzit, who is both a co-author of the new study and also led the development of SPHERE itself.
The team plans to continue to observe the AU Mic system with SPHERE and other facilities, including ALMA, to try to understand what is happening. But, for now, these curious features remain an unsolved mystery.
Notes
[1] AU Microscopii lies just 32 light-years away from Earth. The disc essentially comprises asteroids that have collided with such vigour that they have been ground to dust.
[2] The data were gathered by Hubble's Space Telescope Imaging Spectrograph (STIS).
[3] The edge-on view of the disc complicates the interpretation of its three-dimensional structure.

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This artist's concept illustrates Kepler-16b, the first planet known to definitively orbit two stars - what's called a circumbinary planet. The planet, which can be seen in the foreground, was discovered by NASA's Kepler mission.
Credit: NASA/JPL-Caltech/T. Pyle

Astronomers could discover a plethora of planets around binary star systems ¬- stars that rotate around each other -- by measuring with high precision how stars move around each other, looking for disturbances exerted by possible exoplanets. So explains new research, "Survival of Planets Around Shrinking Stellar Binaries," published in the Proceedings of the National Academy Sciences, July 9, by Diego J. Munoz, Cornell postdoctoral researcher, and Dong Lai, professor of astronomy.
What once was fictional as young Skywalker saw the double suns from Tatooine is astronomical reality four decades later. Normal binary suns orbit each other every eight to 100 days, and the Kepler telescope easily can detect those exoplanets as they transit each sun.
Trouble starts in compact binary sun systems -- where sibling suns move closer together -- making it difficult for the most advanced telescopes to find them. Essentially, for Kepler and other telescopes, the planetary orbital plane of these double suns and their accompanying planets might be out of whack -- or misaligned -- rendering them invisible to us. "The current observational strategy inevitably misses a population of Tatooine planets, but future observations may reveal their existence," said Munoz.
NASA's Kepler telescope monitors star brightness in a Milky Way region near the constellation Cygnus, the swan. Measuring photons, Kepler detects lower light values -- and thus, a planetary transit.
Munoz explains that suns in the close binary system likely were once standard systems that have lost energy and shrunk, bringing the suns closer together. As the sibling sun's distance decreases, the orbits of that system's planets become misaligned, rendering it impossible for the Kepler telescope to detect planets -- which no longer cross in the front of the suns.
Munoz and Lai suggest scouting for exoplanet-caused disturbances for compact binary star systems, to determine a new population of circumbinary planets. Said Munoz: "Since this type of 'compact' binary is very common, it had been very puzzling that no planets had been detected."
This research was funded by the National Science Foundation and by NASA.

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Artist's impression of Gaia14aae.
Credit: Marisa Grove/Institute of Astronomy

An international team of researchers, with the assistance of amateur astronomers, have discovered a unique binary star system: the first known such system where one star completely eclipses the other. It is a type of two-star system known as a Cataclysmic Variable, where one super dense white dwarf star is stealing gas from its companion star, effectively 'cannibalising' it.
The system could also be an important laboratory for studying ultra-bright supernova explosions, which are a vital tool for measuring the expansion of the Universe. Details of the new research will be published in the journal Monthly Notices of the Royal Astronomical Society.
The system, named Gaia14aae, is located about 730 light years away in the Draco constellation. It was discovered by the European Space Agency's Gaia satellite in August 2014 when it suddenly became five times brighter over the course of a single day.
Astronomers led by the University of Cambridge analysed the information from Gaia and determined that the sudden outburst was due to the fact that the white dwarf -- which is so dense that a teaspoonful of material from it would weigh as much as an elephant -- is devouring its larger companion.
Additional observations of the system made by the Center for Backyard Astrophysics (CBA), a collaboration of amateur and professional astronomers, found that the system is a rare eclipsing binary, where one star passes directly in front of the other, completely blocking it out when viewed from Earth. The two stars are tightly orbiting each other, so a total eclipse occurs roughly every 50 minutes.
"It's rare to see a binary system so well-aligned" said Dr Heather Campbell of Cambridge's Institute of Astronomy, who led the follow-up campaign for Gaia14aae. "Because of this, we can measure the system with great precision in order to figure out what these systems are made of and how they evolved. It's a fascinating system -- there's a lot to be learned from it."
Using spectroscopy from the William Herschel Telescope in the Canary Islands, Campbell and her colleagues found that Gaia14aae contains large amounts of helium, but no hydrogen, which is highly unusual as hydrogen is the most common element in the Universe. The lack of hydrogen allowed them to classify Gaia14aae as a very rare type of system known as an AM Canum Venaticorum (AM CVn), a type of Cataclysmic Variable system where both stars have lost all of their hydrogen. This is the first known AM CVn system where one star totally eclipses the other.
"It's really cool that the first time that one of these systems was discovered to have one star completely eclipsing the other, that it was amateur astronomers who made the discovery and alerted us," said Campbell. "This really highlights the vital contribution that amateur astronomers make to cutting edge scientific research."
AM CVn systems consist of a small and hot white dwarf star which is devouring its larger companion. The gravitational effects from the hot and superdense white dwarf are so strong that it has forced the companion star to swell up like a massive balloon and move towards it.
The companion star is about 125 times the volume of our sun, and towers over the tiny white dwarf, which is about the size of the Earth -- this is similar to comparing a hot air balloon and a marble. However, the companion star is lightweight, weighing in at only one percent of the white dwarf's mass.
AM CVn systems are prized by astronomers, as they could hold the key to one of the greatest mysteries in modern astrophysics: what causes Ia supernova explosions? This type of supernova, which occurs in binary systems, is important in astrophysics as their extreme brightness makes them an important tool to measure the expansion of the Universe.
In the case of Gaia14aae, it's not known whether the two stars will collide and cause a supernova explosion, or whether the white dwarf will completely devour its companion first.
"Every now and then, these sorts of binary systems may explode as supernovae, so studying Gaia14aae helps us understand the brightest explosions in the Universe," said Dr Morgan Fraser of the Institute of Astronomy.
"This is an exquisite system: a very rare type of binary system in which the component stars complete orbits faster than the minute hand of a clock, oriented so that one eclipses the other," said Professor Tom Marsh of the University of Warwick. "We will be able to measure their sizes and masses to a higher accuracy than any similar system; it whets the appetite for the many new discoveries I expect from the Gaia satellite."
"This is an awesome first catch for Gaia, but we want it to be the first of many," said the Institute of Astronomy's Dr Simon Hodgkin, who is leading the search for more transients in Gaia data. "Gaia has already found hundreds of transients in its first few months of operation, and we know there are many more out there for us to find."
Gaia's mission, funded by the European Space Agency and involving scientists from across Europe, is to make the largest, most precise, three-dimensional map of the Milky Way ever attempted. During its five-year mission, which began in late 2013, Gaia's billion-pixel camera will detect and very accurately measure the motion of stars in their orbit around the centre of the galaxy. It will observe each of the billion stars about a hundred times, helping us to understand the origin and evolution of the Milky Way.
The research was supported by ESA Gaia, DPAC, and the DPAC Photometric Science Alerts Team. The DPAC is funded by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.
The follow-up campaign used several professional telescopes, including those located in the Canary Islands, where observing time was made available through the International Time Program.

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"This terrain is not easy to explain," said Jeff Moore, leader of the New Horizons Geology, Geophysics and Imaging Team (GGI) at NASA's Ames Research Center in Moffett Field, California. "The discovery of vast, craterless, very young plains on Pluto exceeds all pre-flyby expectations."
This fascinating icy plains region -- resembling frozen mud cracks on Earth -- has been informally named "Sputnik Planum" (Sputnik Plain) after the Earth's first artificial satellite. It has a broken surface of irregularly-shaped segments, roughly 12 miles (20 kilometers) across, bordered by what appear to be shallow troughs. Some of these troughs have darker material within them, while others are traced by clumps of hills that appear to rise above the surrounding terrain. Elsewhere, the surface appears to be etched by fields of small pits that may have formed by a process called sublimation, in which ice turns directly from solid to gas, just as dry ice does on Earth.
Scientists have two working theories as to how these segments were formed. The irregular shapes may be the result of the contraction of surface materials, similar to what happens when mud dries. Alternatively, they may be a product of convection, similar to wax rising in a lava lamp. On Pluto, convection would occur within a surface layer of frozen carbon monoxide, methane and nitrogen, driven by the scant warmth of Pluto's interior.
Pluto's icy plains also display dark streaks that are a few miles long. These streaks appear to be aligned in the same direction and may have been produced by winds blowing across the frozen surface.
The Tuesday "heart of the heart" image was taken when New Horizons was 48,000 miles (77,000 kilometers) from Pluto, and shows features as small as one-half mile (1 kilometer) across. Mission scientists will learn more about these mysterious terrains from higher-resolution and stereo images that New Horizons will pull from its digital recorders and send back to Earth during the next year.
The New Horizons Atmospheres team observed Pluto's atmosphere as far as 1,000 miles (1,600 kilometers) above the surface, demonstrating that Pluto's nitrogen-rich atmosphere is quite extended. This is the first observation of Pluto's atmosphere at altitudes higher than 170 miles above the surface (270 kilometers).
The New Horizons Particles and Plasma team has discovered a region of cold, dense ionized gas tens of thousands of miles beyond Pluto -- the planet's atmosphere being stripped away by the solar wind and lost to space.
"This is just a first tantalizing look at Pluto's plasma environment," said New Horizons co-investigator Fran Bagenal, University of Colorado, Boulder.
"With the flyby in the rearview mirror, a decade-long journey to Pluto is over --but, the science payoff is only beginning," said Jim Green, director of Planetary Science at NASA Headquarters in Washington. "Data from New Horizons will continue to fuel discovery for years to come."
Alan Stern, New Horizons principal investigator from the Southwest Research Institute (SwRI), Boulder, Colorado, added, "We've only scratched the surface of our Pluto exploration, but it already seems clear to me that in the initial reconnaissance of the solar system, the best was saved for last."
New Horizons is part of NASA's New Frontiers Program, managed by the agency's Marshall Space Flight Center in Huntsville, Alabama. The Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, designed, built and operates the New Horizons spacecraft and manages the mission for NASA's Science Mission Directorate. SwRI leads the mission, science team, payload operations and encounter science planning.
Follow the New Horizons mission on Twitter and use the hashtag #PlutoFlyby to join the conversation. Live updates are also available on the mission Facebook page.
For more information on the New Horizons mission, including fact sheets, schedules, video and new images, visit:
http://www.nasa.gov/newhorizons
and
http://solarsystem.nasa.gov/planets/plutotoolkit.cfm

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Scientists want to understand the details of what happens at those boundaries because various events there can disturb our space environment. When strong enough, this space weather can interrupt our communications systems or electronics on board satellites. While scientists have occasionally spotted Kelvin-Helmholtz waves at this boundary before -- giving scientists reason to wonder if they could enhance or enable such space weather -- the new papers show the waves are much more common than expected. The second paper presents a case study describing a previously unobserved way in which the waves can be initiated. Together, the two sets of research suggest the waves may have more of an effect on our space environment than previously realized.
"We have known before that Kelvin-Helmholtz waves exist at the boundaries of Earth's magnetic environment -- but they were considered relatively rare and thought to only appear under specialized conditions," said Shiva Kavosi, a space scientist at the University of New Hampshire in Durham, and first author on one of the papers, which appeared in Nature Communications on May 11, 2015. "It turns out they can appear under any conditions and are much more prevalent than we thought. They're present 20% of the time."
The waves are a direct result of the way our planet fits into the larger solar system. Planet Earth is a gigantic magnet and its magnetic influence extends outward in a large bubble called a magnetosphere. A constant flow of particles from the sun, called the solar wind, blows by the magnetosphere -- not unlike a wind blowing over the surface of the ocean. During certain situations, particles and energy from the sun can breach the magnetosphere, crossing into near-Earth space. It is this influx that lies at the heart of the space weather events that can affect our technology closer to home.
To spot the frequency of the Kelvin-Helmholtz waves, the team relied on instrument data from two NASA spacecraft: the Advanced Composition Explorer, or ACE, and the Time History of Events and Macroscale Interactions during Substorms, or THEMIS. ACE sits between Earth and the sun, measuring the solar wind about 30-60 minutes before it makes contact with Earth's magnetosphere. THEMIS orbits Earth, regularly moving in and out of the magnetosphere boundaries. The researchers first established what the Kelvin-Helmholtz waves looked like with numerical simulations. They then used THEMIS observations to see when and where they occur. Next, they correlated what they saw at the magnetopause boundaries with what ACE measured in the solar wind. Previous theories suggested that the Kelvin-Helmholtz waves would only occur under very specific situations, such as when the solar wind's magnetic fields pointed in the same direction as Earth's. Unexpectedly, the team found that the Kelvin-Helmholtz waves appeared under a wide variety of conditions. Fast and slow winds and winds with magnetic fields pointed in any direction were all equally capable of producing these classic waves.
While the first paper compared Kelvin-Helmholtz waves to what was seen in the solar wind, the second team compared it to what was happening closer to Earth and provides a possible explanation as to why they may be observed so frequently. The second paper was released online in the Journal of Geophysical Research on June 26, 2015, and was conducted by Brian Walsh at Boston University and Evan Thomas, a student at Virginia Tech in Blacksburg, Virginia, who is collocated at NASA's Goddard Space Flight Center in Greenbelt, Maryland. Thomas works with data from a network of ground observatories known as SuperDARN, short for Super Dual Auroral Radar Network. These measure electric fields in near-Earth space. Walsh focuses on THEMIS data. Using the combined space- and ground-based observations, the team detected Kelvin-Helmholtz waves propagating down the side of the magnetosphere's boundary. THEMIS also spotted something else: Just before the waves began, a reservoir of charged gas around Earth -- known as the plasmasphere -- sent out a thin plume of plasma that traveled over 20,000 miles to contact the edges of the magnetosphere, depositing additional atoms into that crucial sun-Earth boundary.
Such plumes are fairly regular occurrences, but this is the first time they've been correlated with Kelvin-Helmholtz waves. This case study suggests that the plume itself may trigger the waves, perhaps because it increases the density at the magnetosphere boundary, thus creating a fluid that is substantially more sluggish than the faster solar wind blowing past -- the necessary conditions for a Kelvin-Helmholtz wave.
"The theory of Kelvin-Helmholtz waves is well-developed, but we don't have many observations," said Thomas. "These new observations show that the waves are happening more often than expected and are probably more important than we thought -- but we still don't know all the details."
Understanding that crucial magnetospheric boundary and how it can let in solar material requires an understanding of the variety of processes that can affect and disrupt it.
"There are a lot of processes proposed for how material enters into the magnetosphere," said Raeder. "And Kelvin-Helmholtz waves are one of them. Previously we thought the waves weren't happening often enough to have a strong effect, but if Kelvin-Helmholtz waves perturb the boundary and mix the solar material with near-Earth space, then that would be a way for the plasma from the solar wind to get into the magnetosphere."
Whether or not Kelvin-Helmholtz waves are a strong trigger for space weather events near Earth, these crucial details help paint a more complete picture of our magnetosphere, ultimately helping us to protect our home planet.

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In the early morning hours of July 8, mission scientists received this new view of Pluto -- the most detailed yet returned by the Long Range Reconnaissance Imager (LORRI) aboard New Horizons. The image was taken on July 7, when the spacecraft was just under 5 million miles (8 million kilometers) from Pluto, and is the first to be received since the July 4 anomaly that sent the spacecraft into safe mode.
This view is centered roughly on the area that will be seen close-up during New Horizons' July 14 closest approach. This side of Pluto is dominated by three broad regions of varying brightness. Most prominent are an elongated dark feature at the equator, informally known as "the whale," and a large heart-shaped bright area measuring some 1,200 miles (2,000 kilometers) across on the right. Above those features is a polar region that is intermediate in brightness.
"The next time we see this part of Pluto at closest approach, a portion of this region will be imaged at about 500 times better resolution than we see today," said Jeff Moore, Geology, Geophysics and Imaging Team Leader of NASA's Ames Research Center. "It will be incredible!"

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This map gives mission scientists an important tool to decipher the complex and intriguing pattern of bright and dark markings on Pluto's surface. Features from all sides of Pluto can now be seen at a glance and from a consistent perspective, making it much easier to compare their shapes and sizes.
The elongated dark area informally known as "the whale," along the equator on the left side of the map, is one of the darkest regions visible to New Horizons. It measures some 1,860 miles (3,000 kilometers) in length.
Directly to the right of the whale's "head" is the brightest region visible on the planet, which is roughly 990 miles (1,600 kilometers) across. This may be a region where relatively fresh deposits of frost -- perhaps including frozen methane, nitrogen and/or carbon monoxide -- form a bright coating.
Continuing to the right, along the equator, we see the four mysterious dark spots that have so intrigued the world, each of which is hundreds of miles across. Meanwhile, the whale's "tail," at the left end of the dark feature, cradles a bright donut-shaped feature about 200 miles (350 kilometers) across. At first glance it resembles circular features seen elsewhere in the solar system, from impact craters to volcanoes. But scientists are holding off on making any interpretation of this and other features on Pluto until more detailed images are in hand.
Of course, higher-resolution images in the days to come will allow mission scientists to make more accurate maps, but this map is a tantalizing preview.
"We're at the 'man in the moon' stage of viewing Pluto," said John Spencer of the Southwest Research Institute, Boulder, Colorado, deputy leader of the Geology, Geophysics and Imaging team. "It's easy to imagine you're seeing familiar shapes in this bizarre collection of light and dark features. However, it's too early to know what these features really are."

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Almost every galaxy, including our own, appears to have a black hole at its core. Most of the time these are quiet, with just their invisible gravitational pull shaping their surroundings. But in about 10 per cent of galaxies the central black hole is much more active, swallowing material and spitting out giant jets.
The new study, which is being presented at the National Astronomy Meeting in Llandudno, Wales, shows, for the first time, convincing evidence of the onset, the 'switching on' of this active phase, in a black hole at the centre of the galaxy NGC 660 -- 42 million light years away in the constellation of Pisces.
In 2012, astronomers noticed that NGC 660 had suddenly become hundreds of times brighter over just a few months. Normal galaxies do not change their brightness very quickly as they are very large systems made of many (relatively) small individual components in the form of stars, gas and dust.
Over the last three years, a team of scientists led by Dr Megan Argo of the Jodrell Bank Centre for Astrophysics, has been trawling through archived results from ground- and space-based telescopes. They then used data from three radio observatories: the UK's e-MERLIN telescope operated from Jodrell Bank, the Westerbork array in the Netherlands and the European VLBI network (EVN), which also includes telescopes in Russia, China and South Africa, that was combined to simulate a much larger instrument -- a technique known as interferometry.
Sam's contribution was to use x-ray astronomy to check the brightness of the source before and after the radio brightening, which helped to rule out potential reasons for the brightening and come to the conclusion that it is most likely to be a newly-awoken supermassive black hole.
Sam says: "As supermassive black holes are so huge, they evolve very slowly, remaining dormant for thousands of years at a time, so to catch one waking up is really incredible."
The new images reveal a new, very bright radio source in the very centre of NGC 660, right where the researchers expect to find the central supermassive black hole.
Inactive black holes do not emit large amounts of radiation, so they can only be detected by their gravitational effect on the orbits of stars around them. However, the black hole in NGC 660 is now very obvious, and is many hundreds of times brighter than anything seen in the centre of NGC 660 in the archive of radio images before 2010.
The parallel results from e-MERLIN show that the object is slowly fading, and is similar to other galaxies with more mature systems, and the highest resolution images from the EVN show evidence of a high-speed jet of material leaving the vicinity of the black hole.
Material (gas, dust and stars) near a black hole can sit in stable orbits around the central massive object for a long time, but eventually it loses energy, spirals in, and falls onto the black hole. At the same time, some material is ejected and this seems to have created the outburst and jet now seen in NGC 660.
Studying the jet will give astronomers a clue about the initial eruption of the jet, and how much material fell onto the black hole to cause the outburst in the first place.

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Around 85% of the matter in the Universe is dark [1], and of a type not understood by physicists. Although it doesn't shine or absorb light, astronomers can detect this dark matter through its effect on stars and galaxies, specifically from its gravitational pull. A major project using ESO's powerful survey telescopes is now showing more clearly than ever before the relationships between this mysterious dark matter and the shining galaxies that we can observe directly [2].
The project, known as the Kilo-Degree Survey (KiDS), uses imaging from the VLT Survey Telescope and its huge camera, OmegaCAM. Sited at ESO's Paranal Observatory in Chile, this telescope is dedicated to surveying the night sky in visible light -- and it is complemented by the infrared survey telescope VISTA. One of the major goals of the VST is to map out dark matter and to use these maps to understand the mysterious dark energy that is causing our Universe's expansion to accelerate.
The best way to work out where the dark matter lies is through gravitational lensing -- the distortion of the Universe's fabric by gravity, which deflects the light coming from distant galaxies far beyond the dark matter. By studying this effect it is possible to map out the places where gravity is strongest, and hence where the matter, including dark matter, resides.
As part of the first cache of papers, the international KiDS team of researchers, led by Koen Kuijken at the Leiden Observatory in the Netherlands [3], has used this approach to analyse images of over two million galaxies, typically 5.5 billion light-years away [4]. They studied the distortion of light emitted from these galaxies, which bends as it passes massive clumps of dark matter during its journey to Earth.
The first results come from only 7% of the final survey area and concentrate on mapping the distribution of dark matter in groups of galaxies. Most galaxies live in groups -- including our own Milky Way, which is part of the Local Group -- and understanding how much dark matter they contain is a key test of the whole theory of how galaxies form in the cosmic web. From the gravitational lensing effect, these groups turn out to contain around 30 times more dark than visible matter.
"Interestingly, the brightest galaxy nearly always sits in the middle of the dark matter clump," says Massimo Viola (Leiden Observatory, the Netherlands) lead author of one of the first KiDS papers.
"This prediction of galaxy formation theory, in which galaxies continue to be sucked into groups and pile up in the centre, has never been demonstrated so clearly before by observations," adds Koen Kuijken.
The findings are just the start of a major programme to exploit the immense datasets coming from the survey telescopes and the data are now being made available to scientists worldwide through the ESO archive.
The KiDS survey will help to further expand our understanding of dark matter. Being able to explain dark matter and its effects would represent a major breakthrough in physics.
Notes
[1] Astronomers have found that the total mass/energy content of the Universe is split in the proportions 68% dark energy, 27% dark matter and 5% "normal" matter. So the 85% figure relates to the fraction of "matter" that is dark.
[2] Supercomputer calculations show how a Universe filled with dark matter will evolve: over time dark matter will clump into a huge cosmic web structure, and galaxies and stars form where gas is sucked into the densest concentrations of dark matter.
[3] The international KiDS team of researchers includes scientists from the Netherlands, the UK, Germany, Italy and Canada.
[4] This work made use of the 3D map of galaxy groups, provided by the Galaxy And Mass Assembly project (GAMA), following extensive observations on the Anglo-Australian Telescope.
Further information: http://kids.strw.leidenuniv.nl/papers.php

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Located roughly 270 million light-years from Earth in the constellation of Centaurus (The Centaur), a bright constellation in the southern sky, ESO 381-12, also known as PGC 42871, is categorised as a lenticular galaxy -- a hybrid galaxy type that shares properties with both spiral galaxies and elliptical galaxies.
The delicate shells that bloom outwards from ESO 381-12 are very rarely found around this type of galaxy and their cause is a bit of a cosmic mystery. It is thought that PGC 42871 may have recently interacted with another galaxy, sending shock waves through its structure much like ripples in a pond. These galactic mergers are violent processes, smashing together material within the clashing galaxies and completely changing how they look and how they will evolve in the future. This violent event likely triggered a wave of star formation throughout the galaxy, leading to the creation of many hot young stars.
Astronomers have studied ESO 381-12 in detail because of its very unusual structure. It was one of a sample of galaxies explored by Hubble's Advanced Camera for Surveys during a recent study of the properties of shell galaxies created in merger events a billion or so years ago.
The prominent galaxy at the right of the frame, known as ESO 381-13 or PGC 42877, is a different beast altogether and both active star formation and dust can be seen within it. However, ESO 381-13 and the shell galaxy are at very similar distances from Earth and, despite their differences, may well be interacting.

On June 30, a team led by Andrew Beardmore at the University of Leicester, U.K., imaged the system using the X-ray Telescope aboard Swift, revealing a series concentric rings extending about one-third the apparent size of a full moon. A movie made by combining additional observations acquired on July 2 and 4 shows the expansion and gradual fading of the rings.
Astronomers say the rings result from an "echo" of X-ray light. The black hole's flares emit X-rays in all directions. Dust layers reflect some of these X-rays back to us, but the light travels a longer distance and reaches us slightly later than light traveling a more direct path. The time delay creates the light echo, forming rings that expand with time.
Detailed analysis of the expanding rings shows that they all originate from a large flare that occurred on June 26 at 1:40 p.m. EDT. There are multiple rings because there are multiple reflecting dust layers between 4,000 and 7,000 light-years away from us. Regular monitoring of the rings and how they change as the eruption continues will allow astronomers to better understand their nature.
"The flexible planning of Swift observations has given us the best dust-scattered X-ray ring images ever seen," Beardmore said. "With these observations we can make a detailed study of the normally invisible interstellar dust in the direction of this black hole."
V404 Cygni is located about 8,000 light-years away. Every couple of decades the black hole fires up in an outburst of high-energy light. Its previous eruption ended in 1989.
The investigating team includes scientists from the Universities of Leicester, Southampton, and Oxford in the U.K., the University of Alberta in Canada, and the European Space Agency in Spain.
Swift was launched in November 2004 and is managed by NASA's Goddard Space Flight Center in Greenbelt, Maryland. Goddard operates the spacecraft in collaboration with Penn State University in University Park, Pennsylvania, the Los Alamos National Laboratory in New Mexico and Orbital Sciences Corp. in Dulles, Virginia. International collaborators are located in the United Kingdom and Italy. The mission includes contributions from Germany and Japan.

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Transits of Venus are so rare that they only happen twice in a lifetime. About every 115 years, Venus will appear to cross over the face of our home star twice, with eight years passing between the pair of transits. This stunning phenomenon is not only incredible to watch, but it provides a unique opportunity for scientific observations of one of our nearest neighboring planets.
NASA'S Solar Dynamics Observatory, or SDO, and the joint Japanese Aerospace Exploration Agency and NASA's Hinode mission took pictures of the entire event in several wavelengths of light. A team of scientists led by Fabio Reale of the University of Palermo used these pictures to watch the backlit planet as it crossed in front of the sun. By observing the planet's atmosphere in different wavelengths of light during its journey, they learned more about what kinds of atoms and molecules are actually in its atmosphere. This work was published in Nature Communications on June 23, 2015.
Just as on Earth, each of the layers of Venus' atmosphere absorb light differently from one another. Some layers may completely absorb a certain wavelength of light, while that same wavelength can pass right through another layer. As Venus passes across the face of the sun -- which emits light in almost every wavelength of the electromagnetic spectrum -- scientists get a rare chance to see how all different types of light filter through Venus's atmosphere.
A layer in the upper atmosphere around Venus--called the thermosphere--absorbs certain high-energy wavelengths of light. When looking at the planet against the sun in one of these high-energy wavelengths, the thermosphere will appear opaque, rather than transparent as it does in visible light.
"Radiation goes into the atmosphere and is absorbed, creating ions and a layer of the atmosphere called the ionosphere," said Dean Pesnell, SDO project scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. Because the energy in this light is captured by the ions, it is not re-emitted on the other side. In certain wavelengths, Venus's atmosphere is as solid as a wall, blocking light from traveling to our eyes. To our telescopes, the atmosphere is as dark as the planet itself -- so, Venus will appear to have a different size, depending on the wavelength of the telescope's pictures.
Reale and his team chose images of the Venus transit taken in several X-ray and ultraviolet wavelengths and measured the apparent size of the planet to within several miles. For each set of pictures, the team calculated just how large the atmospheric blocking was--a measure of how high in Venus' atmosphere that particular wavelength of light is completely absorbed.
Because the various types of atoms absorb light slightly differently, the height of this light absorption lets scientists know how many and what types of molecules make up Venus's atmosphere. This information is important for planning missions to Venus, as those ions and molecules can change the amount of course-altering drag a spacecraft feels.
"Learning more about the composition of the atmosphere is very important for understanding the braking process for spacecraft when they enter the upper atmosphere of the planet, a process called aerobraking," said Reale.
The shape of Venus' atmosphere also gave scientists important clues to how the sun impacts the atmosphere. "If the atmosphere observed were asymmetric, that could tell us more about how the star is impacting the planet," said Sabrina Savage, NASA project scientist for Hinode.
During the transit, only the sides of the atmosphere could be seen, but they were particularly interesting areas. From the perspective of Venus, these were the areas where day turns into night and night turns into day--on Earth, these transition areas can host interesting effects in the ionosphere. The data from the Venus transit showed that these two transition areas are virtually the same.
"The planet appeared very round in all wavelengths," said Pesnell. "If the transition from day to night were different from the transition from night to day, you would expect a bulge in the atmosphere on one side of the planet."
Studying the Venus transit can also help improve studies of planets around other stars. Such exoplanets are often discovered by transits just like this, as we can detect the very small amount of light the planets block as they pass across their home star. The more we can observe transiting planets close to home the more it will teach us about how to study distant exoplanets that we can't currently see in as much detail. When instrument technology advances, we may be able to gather better information about the atmospheres of such exoplanets as well.
"In the future, there might be missions that have enough sensitivity to detect the difference in radius in different wavelengths," said Reale. "In particular, if there are exoplanets with an extremely thick thermosphere, the size difference in different wavelengths will be larger and there will be a better chance of detecting the change."

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The discovery runs counter to most observations about black holes, which are massive areas of space with extraordinarily strong gravity that can pull in anything -- even light. In most cases, black holes and their host galaxies expand at the same rate.
This particular black hole formed in the early universe, roughly two billion years after the Big Bang. An international research group made the discovery during a project to map the growth of supermassive black holes across cosmic time. The team included astronomers from Yale University, ETH Zurich, the Max-Planck Institute in Germany, Harvard University, the University of Hawaii, INAF-Osservatorio Astronomico di Roma, and Oxford University.
"Our survey was designed to observe the average objects, not the exotic ones," said C. Megan Urry, Yale's Israel Munson Professor of Astrophysics and co-author of a study about the phenomenon in the journal Science. "This project specifically targeted moderate black holes that inhabit typical galaxies today. It was quite a shock to see such a ginormous black hole in such a deep field."
Deep-field surveys are intended to look at faint galaxies; they point at small areas of the sky for a longer period of time, meaning the total volume of space being sampled is relatively small.
This particular black hole, located in the galaxy CID-947, is among the most massive black holes ever found. It measures nearly 7 billion solar masses (a solar mass is equivalent to the mass of our Sun).
However, it was the mass of the surrounding galaxy that most surprised the research team. "The measurements correspond to the mass of a typical galaxy," said lead author Benny Trakhtenbrot, a researcher at ETH Zurich's Institute for Astronomy. "We therefore have a gigantic black hole within a normal-size galaxy."
Most galaxies, including our own Milky Way, have a black hole at their center, holding millions to billions of solar masses. Not only does the new study challenge previous notions about the way host galaxies grow in relation to black holes, it also challenges earlier suggestions that the radiation emitted by expanding black holes curtails the creation of stars.
Stars were still forming in CID-947, the researchers said, and the galaxy could continue to grow. They said CID-947 could be a precursor of the most extreme, massive systems observed in today's local universe, such as the galaxy NGC 1277 in the Perseus constellation, 220 million light years from the Milky Way. But if so, they said, the growth of the black hole still greatly anticipated the growth of the surrounding galaxy, contrary to what astronomers thought previously.
Urry and her colleagues credited the W.M. Keck Observatory in Hawaii and the Chandra COSMOS legacy survey in aiding the team's work. "The sensitivity and versatility of Keck's new infrared spectrometer, MOSFIRE, was critical to this discovery," Urry said.
Other co-authors of the paper include Francesca Civano, an associate research scientist at Yale; David Rosario, of the Max-Planck Institute; Martin Elvis, of Harvard; Kevin Schawinski, of ETH Zurich and a former Einstein Fellow at Yale; Hyewon Suh, of Harvard; Angela Bongiorno, of INAF-Osservatorio Astronomico di Roma; and Brooke Simmons, of Oxford and a former graduate student at Yale.

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Results will be presented today by Prof Valentina Zharkova at the National Astronomy Meeting in Llandudno.
It is 172 years since a scientist first spotted that the Sun's activity varies over a cycle lasting around 10 to 12 years. But every cycle is a little different and none of the models of causes to date have fully explained fluctuations. Many solar physicists have put the cause of the solar cycle down to a dynamo caused by convecting fluid deep within the Sun. Now, Zharkova and her colleagues have found that adding a second dynamo, close to the surface, completes the picture with surprising accuracy.
"We found magnetic wave components appearing in pairs, originating in two different layers in the Sun's interior. They both have a frequency of approximately 11 years, although this frequency is slightly different, and they are offset in time. Over the cycle, the waves fluctuate between the northern and southern hemispheres of the Sun. Combining both waves together and comparing to real data for the current solar cycle, we found that our predictions showed an accuracy of 97%," said Zharkova.
Zharkova and her colleagues derived their model using a technique called 'principal component analysis' of the magnetic field observations from the Wilcox Solar Observatory in California. They examined three solar cycles-worth of magnetic field activity, covering the period from 1976-2008. In addition, they compared their predictions to average sunspot numbers, another strong marker of solar activity. All the predictions and observations were closely matched.
Looking ahead to the next solar cycles, the model predicts that the pair of waves become increasingly offset during Cycle 25, which peaks in 2022. During Cycle 26, which covers the decade from 2030-2040, the two waves will become exactly out of synch and this will cause a significant reduction in solar activity.
"In cycle 26, the two waves exactly mirror each other -- peaking at the same time but in opposite hemispheres of the Sun. Their interaction will be disruptive, or they will nearly cancel each other. We predict that this will lead to the properties of a 'Maunder minimum'," said Zharkova. "Effectively, when the waves are approximately in phase, they can show strong interaction, or resonance, and we have strong solar activity. When they are out of phase, we have solar minimums. When there is full phase separation, we have the conditions last seen during the Maunder minimum, 370 years ago."

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"I have always loved showing the stars to people" said astronomer Alastair Bruce, the leader of the project, provisionally named StarSightVR, "but now I can guarantee perfect cloudless skies, and show the universe to people all round the world, while they stay in the comfort of their own homes."
'Some people are also simply unable to come to places like the Royal Observatory or to travel to dark skies, so this technology could help them enjoy astronomy in a way that until now wasn't possible."
The Oculus Rift virtual reality headset has created a huge stir. Thousands of people are testing out the prototype, Facebook have already bought the company, and the headsets should go on sale early in 2016. The buzz so far has mostly been about what it will do for three dimensional immersive gaming, but Alastair Bruce, a PhD student at the University of Edinburgh, and a keen gamer himself, saw the potential for public interest in astronomy. "I decided the way ahead was to combine the headset with Stellarium, because that software is very popular as well as really good, and what's more it's open source, which means we could get the benefit to the maximum number of people."
Alastair got together with his supervisor, Prof Andy Lawrence, and they applied for a small grant from the Science and Technology Facilities Council (STFC), which allowed them to buy test equipment, and pay for a software engineer (Guillaume Chereau) to make the necessary changes to the Stellarium software.
"It worked beautifully" said Andy Lawrence. "We showed off an early version to people at the Edinburgh International Science Festival in April, and it just knocked their socks off. You feel like you are really outside looking at the starry sky, but it's even better. You can see fainter stars, speed up the rotation of Earth, look at deep sky objects, and even take the ground away so you feel like you are seeing the stars from space."
The team will very soon release their new best test open source variety of Stellarium. This means that anybody with an Oculus Rift headset will be able to download the new software and try it out for themselves. But the team see this as just the start. "We have a clear idea of the next steps in development -- the things we want to add or make better before an official release -- but unfortunately we have now run out of money," said Lawrence.
As well as releasing the new software, and adding features to the code, what Bruce and Lawrence want to do next is to use the system to run presenter-led group stargazing sessions live over the Internet. "We love showing people the stars and explaining what they are looking at, here on the rooftop at the Royal Observatory," said Bruce, "so we thought, why not use the Oculus Rift to do that remotely?"
The team built changes into Stellarium so that their central version could act as a master, sending information to remote versions. The idea is that each user switches their copy of Stellarium to 'join show' mode, and listens to the astronomer-presenter over an audio link, while the presenter points where they need to look, adjusts day/night settings, switches constellation guiding lines on and off, and so on.
"Ideally we would run a StarSightVR show perhaps once a month," said Lawrence, "but we don't know yet how popular it would be, or how well it will scale up. Our plan is to run a trial event or two and see how we go."
Tania Johnston, STFC Public Engagement manager at the observatory, added: "The new StarSightVR system has enormous potential. STFC is committed to diversity and inclusion, but I often deal with people who have conditions that limit their involvement with our work. So giving them access to such an incredible virtual reality astronomy experience -- over the internet -- could overcome some of those most fundamental barriers.
The trial shows will be run through the Royal Observatory Edinburgh Trust, a charitable organisation that supports heritage and public interest in astronomy.

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"A planet's atmosphere provides a good guide to likely conditions on the surface," said Barstow, of the University of Oxford. "The Earth's atmosphere contains significant amounts of nitrogen, oxygen, ozone and water. By contrast, its inhospitable 'evil twin', Venus, has an atmosphere made mostly of carbon dioxide, which drives its surface temperature to a blistering 450 degrees Celsius."
A successor to the Hubble Space Telescope, JWST is due for launch in 2018 and will study the Universe in infrared wavelengths. Barstow's study shows that JWST may be able to differentiate between a planet with a clement, Earth-like atmosphere, and one with more hostile conditions such as are found on our neighbouring planet Venus. JWST will have the capability to detect key markers that could indicate the presence of a climate like our own when looking at Earth-sized planets around stars that are smaller and redder than our Sun.
Different gases have already been identified successfully in the atmospheres of several large, hot, Jupiter-sized planets by studying tiny variations in the starlight that passes through their atmospheres when they cross in front of their parent stars. However, these variations are miniscule: the light filtered through the exoplanet's atmosphere is one ten-thousandth of the total starlight detected. Studying planets the size of the Earth is an even greater challenge. Although JWST would struggle with analysing a Solar System exactly like our own, it would be capable of studying Earth-like planets around cooler stars -- if such a system were to be found.
"If we took the Earth and Venus, and placed them in orbit around a cool, red star that's not too far away, our study shows that JWST could tell them apart. Earth's ozone layer, 10 kilometres above the surface, is produced when light from the Sun interacts with molecules of oxygen in our atmosphere, and it produces an unmistakable signal that could be detected by JWST. Venus, without a substantial ozone layer, would look very different," said Barstow. "That's assuming that planets starting out like Earth and Venus would evolve in the same way around a cool star!"
However, JWST will be used for a wide range of astronomical applications, not just detecting exoplanets, and securing time on the telescope will be highly competitive. To make these detections, astronomers would need to observe the exoplanets at least 30 times, taking valuable telescope time.
"Future telescopes that are dedicated to observing the atmospheres of many rocky planets around different stars will be required to fully resolve the question of habitability on exoplanets. In the meantime, JWST will observe many other weird and wonderful planets in unprecedented detail," said Barstow.

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Astronomers are aware of many active galaxies which emanate such jets from their centre. These gas jets can be seen in the radio region, and occasionally in visible light and in the X-ray and gamma radiation regions as well. There is still a great deal of uncertainty about the mechanism of their formation. What is clear is that hot gas in the form of a disk orbits the central black hole. It is probable that strong magnetic fields, which accelerate the particles at right angles to the disk and into the jets, occur here as well.
This central machinery cannot, however, be observed directly from Earth due to the large distances involved. A stroke of luck helped Ievgen Vovk from the Max Planck Institute of Physics and his colleagues in Geneva here. The researchers looked at an active galaxy known as PKS 1830-211. This is a blazar -- a rare case in which one of the two jets happens to be directed towards Earth so that the astronomers look directly into the jet along the longitudinal axis.
It so happens that there is a galaxy roughly half way between Earth and the blazar, which is billions of light years away. Its strong gravitation causes the space around it to curve. The light of the blazar behind it passes through this space well and takes a detour -- as if it were passing through a lens. PKS 1830-211 thus appears in the sky as two images; and these images are brighter than the blazar would be without this lens effect.
Astronomers had already recorded intensity flare ups in the radio region which originated from events in the blazar. Since the light propagation paths of the two images are different in length, they do not light up simultaneously after a flare up, but around 26 days apart. Vovk and his colleagues have now scoured the data from the Large Area Telescope on board the Fermi space telescope looking for such flare ups in the gamma ray region.
The resolution of the telescope here is not sufficient to be able to image the two pictures separately, but the astronomers also found flare ups which occurred periodically with an almost constant delay. "The period was approximately as long as that in the radio region, but the amplification factors of the intensity were much larger and more variable," says Ievgen Vovk.
This behaviour and further findings from observations can be best explained with an interesting assumption: Although the brightness variations in the gamma ray region also originate from the flare ups in the blazar, they are amplified to different degrees by the gravitational lens effect of individual stars in the foreground galaxy. This always occurs when a star happens to pass in front of the gamma ray emitting part of the blazar as seen from Earth.
The splitting of the images produced here is so small as to be unobservable. "It would correspond to the size of an ant on the Moon," says Vovk. Astrophysicists call this a micro-gravitational lens effect. However, the intensity amplification of the images by factors of two to seven is much greater than in the radio region. The stars thus briefly highlight the gamma ray region, as it were, as if through a magnifying glass.
All findings can be best explained in the context of the micro-gravitational lens effect with a very compact gamma ray region which extends over several ten billion kilometres. This corresponds roughly to the diameter of our solar system or to that of a black hole with a mass of one billion solar masses.
"According to our findings, the gamma ray region is only slightly larger than the black hole itself," says Andrii Neronov from the University of Geneva. Since the jet originating from the centre widens with increasing distance, the gamma radiation is probably being generated very close to the black hole, i.e. quasi at the foot of the jet.
How this radiation is generated is still not known. According to the most prevalent theory, the black hole and the gas disk are surrounded by a strong magnetic field in which particles such as electrons are accelerated to almost the speed of light. These can collide with light particles (photons), transferring so much energy to the particles in the process that they become gamma or X-ray photons.

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