‘Death stars’ in Orion blast planets before they even form

The Orion Nebula is home to hundreds of young stars and even younger protostars known as proplyds. Many of these nascent systems will go on to develop planets, while others will have their planet-forming dust and gas blasted away by the fierce ultraviolet radiation emitted by massive O-type stars that lurk nearby.A team of astronomers from Canada and the United States has used the Atacama Large Millimeter/submillimeter Array (ALMA) to study the often deadly relationship between highly luminous O-type stars and nearby protostars in the Orion Nebula. Their data reveal that protostars within 0.1 light-years (about 600 billion miles) of an O-type star are doomed to have their cocoons of dust and gas stripped away in just a few millions years, much faster than planets are able to form.”O-type stars, which are really monsters compared to our Sun, emit tremendous amounts of ultraviolet radiation and this can play havoc during the development of young planetary systems,” remarked Rita Mann, an astronomer with the National Research Council of Canada in Victoria, and lead author on a paper in the Astrophysical Journal. “Using ALMA, we looked at dozens of embryonic stars with planet-forming potential and, for the first time, found clear indications where protoplanetary disks simply vanished under the intense glow of a neighboring massive star.”Many, if not all, Sun-like stars are born in crowded stellar nurseries similar to the Orion Nebula. Over the course of just a few million years, grains of dust and reservoirs of gas combine into larger, denser bodies. Left relatively undisturbed, these systems will eventually evolve into fully fledged star systems, with planets — large and small — and ultimately drift away to become part of the galactic stellar population.Astronomers believe that massive yet short-lived stars in and around large interstellar clouds are essential for this ongoing process of star formation. At the end of their lives, massive stars explode as supernovas, seeding the surrounding area with dust and heavy elements that will get taken up in the next generation of stars. These explosions also provide the kick necessary to initiate a new round of star and planet formation. But while they still shine bright, these larger stars can be downright deadly to planets if an embryonic solar systems strays too close.”Massive stars are hot and hundreds of times more luminous than our Sun,” said James Di Francesco, also with the National Research Council of Canada. “Their energetic photons can quickly deplete a nearby protoplanetary disk by heating up its gas, breaking it up, and sweeping it away.”Earlier observations with the Hubble Space Telescope revealed striking images of proplyds in Orion. …

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Astronomers get first peek into core of supernova, using NuSTAR telescope

Astronomers for the first time have peered into the heart of an exploding star in the final minutes of its existence.The feat is one of the primary goals of NASA’s NuSTAR mission, launched in June 2012 to measure high-energy X-ray emissions from exploding stars, or supernovae, and black holes, including the massive black hole at the center of our Milky Way Galaxy.The NuSTAR team reported in this week’s issue of the journal Nature the first map of titanium thrown out from the core of a star that exploded in 1671. That explosion produced the beautiful supernova remnant known as Cassiopeia A (Cas A).The well-known supernova remnant has been photographed by many optical, infrared and X-ray telescopes in the past, but these revealed only how the star’s debris collided in a shock wave with the surrounding gas and dust and heated it up. NuSTAR has produced the first map of high-energy X-ray emissions from material created in the actual core of the exploding star: the radioactive isotope titanium-44, which was produced in the star’s core as it collapsed to a neutron star or black hole. The energy released in the core collapse supernova blew off the star’s outer layers, and the debris from this explosion has been expanding outward ever since at 5,000 kilometers per second.”This has been a holy grail observation for high energy astrophysics for decades,” said coauthor and NuSTAR investigator Steven Boggs, UC Berkeley professor and chair of physics. “For the first time we are able to image the radioactive emission in a supernova remnant, which lets us probe the fundamental physics of the nuclear explosion at the heart of the supernova like we have never been able to do before.””Supernovae produce and eject into the cosmos most of the elements are important to life as we know it,” said UC Berkeley professor of astronomy Alex Filippenko, who was not part of the NuSTAR team. “These results are exciting because for the first time we are getting information about the innards of these explosions, where the elements are actually produced.”Boggs says that the information will help astronomers build three-dimensional computer models of exploding stars, and eventually understand some of the mysterious characteristics of supernovae, such as jets of material ejected by some. Previous observations of Cas A by the Chandra X-ray telescope, for example, showed jets of silicon emerging from the star.”Stars are spherical balls of gas, and so you might think that when they end their lives and explode, that explosion would look like a uniform ball expanding out with great power,” said Fiona Harrison, the principal investigator of NuSTAR at the California Institute of Technology. “Our new results show how the explosion’s heart, or engine, is distorted, possibly because the inner regions literally slosh around before detonating.”Expanding supernova remnantCas A is about 11,000 light years from Earth and the most studied nearby supernova remnant. In the 343 years since the star exploded, the debris from the explosion has expanded to about 10 light years across, essentially magnifying the pattern of the explosion so that it can be seen from Earth.Earlier observations of the shock-heated iron in the debris cloud led some astronomers to think that the explosion was symmetric, that is, equally powerful in all directions. Boggs noted, however, that the origins of the iron are so unclear that its distribution may not reflect the explosion pattern from the core.”We don’t know whether the iron was produced in the supernova explosion, whether it was part of the star when it originally formed, if it is just in the surrounding material, or even if the iron we see represents the actual distribution of iron itself, because we wouldn’t see it if it were not heated in the shock,” he said.The new map of titanium-44, which does not match the distribution of iron in the remnant, strongly suggests that there is cold iron in the interior that Chandra does not see. …

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Astronomers discover oldest star: Formed shortly after the Big Bang 13. 7 billion years ago

A team led by astronomers at The Australian National University has discovered the oldest known star in the Universe, which formed shortly after the Big Bang 13.7 billion years ago.The discovery has allowed astronomers for the first time to study the chemistry of the first stars, giving scientists a clearer idea of what the Universe was like in its infancy.”This is the first time that we’ve been able to unambiguously say that we’ve found the chemical fingerprint of a first star,” said lead researcher, Dr Stefan Keller of the ANU Research School of Astronomy and Astrophysics.”This is one of the first steps in understanding what those first stars were like. What this star has enabled us to do is record the fingerprint of those first stars.”The star was discovered using the ANU SkyMapper telescope at the Siding Spring Observatory, which is searching for ancient stars as it conducts a five-year project to produce the first digital map the southern sky.The ancient star is around 6,000 light years from Earth, which Dr Keller says is relatively close in astronomical terms. It is one of the 60 million stars photographed by SkyMapper in its first year.”The stars we are finding number one in a million,” says team member Professor Mike Bessell, who worked with Keller on the research.”Finding such needles in a haystack is possible thanks to the ANU SkyMapper telescope that is unique in its ability to find stars with low iron from their colour.”Dr Keller and Professor Bessell confirmed the discovery using the Magellan telescope in Chile.The composition of the newly discovered star shows it formed in the wake of a primordial star, which had a mass 60 times that of our Sun.”To make a star like our Sun, you take the basic ingredients of hydrogen and helium from the Big Bang and add an enormous amount of iron — the equivalent of about 1,000 times the Earth’s mass,” Dr Keller says.”To make this ancient star, you need no more than an Australia-sized asteroid of iron and lots of carbon. It’s a very different recipe that tells us a lot about the nature of the first stars and how they died.”Dr Keller says it was previously thought that primordial stars died in extremely violent explosions which polluted huge volumes of space with iron. But the ancient star shows signs of pollution with lighter elements such as carbon and magnesium, and no sign of pollution with iron.”This indicates the primordial star’s supernova explosion was of surprisingly low energy. Although sufficient to disintegrate the primordial star, almost all of the heavy elements such as iron, were consumed by a black hole that formed at the heart of the explosion,” he says.The result may resolve a long-standing discrepancy between observations and predictions of the Big Bang.The discovery was published in the latest edition of the journal Nature.Story Source:The above story is based on materials provided by The Australian National University. Note: Materials may be edited for content and length.

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Kepler finds a very wobbly planet: Rapid and erratic changes in seasons

Imagine living on a planet with seasons so erratic you would hardly know whether to wear Bermuda shorts or a heavy overcoat. That is the situation on a weird, wobbly world found by NASA’s planet-hunting Kepler space telescope.The planet, designated Kepler-413b, precesses, or wobbles, wildly on its spin axis, much like a child’s top. The tilt of the planet’s spin axis can vary by as much as 30 degrees over 11 years, leading to rapid and erratic changes in seasons. In contrast, Earth’s rotational precession is 23.5 degrees over 26,000 years. Researchers are amazed that this far-off planet is precessing on a human timescale.Kepler 413-b is located 2,300 light-years away in the constellation Cygnus. It circles a close pair of orange and red dwarf stars every 66 days. The planet’s orbit around the binary stars appears to wobble, too, because the plane of its orbit is tilted 2.5 degrees with respect to the plane of the star pair’s orbit. As seen from Earth, the wobbling orbit moves up and down continuously.Kepler finds planets by noticing the dimming of a star or stars when a planet transits, or travels in front of them. Normally, planets transit like clockwork. Astronomers using Kepler discovered the wobbling when they found an unusual pattern of transiting for Kepler-413b.”Looking at the Kepler data over the course of 1,500 days, we saw three transits in the first 180 days — one transit every 66 days — then we had 800 days with no transits at all. …

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One planet, two stars: New research shows how circumbinary planets form

Luke Skywalker’s home planet Tatooine would have formed far from its current location in the Star Wars universe, a new University of Bristol study into its real world counterparts, observed by the Kepler space telescope, suggests.Like the fictional Star Wars planet, Kepler-34(AB)b is a circumbinary planet, so-called because its orbit encompasses two stars. There are few environments more extreme than a binary star system in which planet formation can occur. Powerful gravitational perturbations from the two stars on the rocky building blocks of planets lead to destructive collisions that grind down the material. So, how can the presence of such planets be explained?In research published this week in Astrophysical Journal Letters, Dr Zoe Leinhardt and colleagues from Bristol’s School of Physics have completed computer simulations of the early stages of planet formation around the binary stars using a sophisticated model that calculates the effect of gravity and physical collisions on and between one million planetary building blocks.They found that the majority of these planets must have formed much further away from the central binary stars and then migrated to their current location.Dr Leinhardt said: “Our simulations show that the circumbinary disk is a hostile environment even for large, gravitationally strong objects. Taking into account data on collisions as well as the physical growth rate of planets, we found that Kepler 34(AB)b would have struggled to grow where we find it now.”Based on these conclusions for Kepler-34, it seems likely that all of the currently known circumbinary planets have also migrated significantly from their formation locations — with the possible exception of Kepler-47 (AB)c which is further away from the binary stars than any of the other circumbinary planets.Stefan Lines, lead author of the study, said: “Circumbinary planets have captured the imagination of many science-fiction writers and film-makers — our research shows just how remarkable such planets are. Understanding more about where they form will assist future exoplanet discovery missions in the hunt for earth-like planets in binary star systems.”Story Source:The above story is based on materials provided by University of Bristol. Note: Materials may be edited for content and length.

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Bizarre alignment of planetary nebulae

Sep. 4, 2013 — The final stages of life for a star like our Sun result in the star blowing its outer layers out into the surrounding space, forming objects known as planetary nebulae in a wide range of beautiful and striking shapes. One type of such nebulae, known as bipolar planetary nebulae, create ghostly hourglass or butterfly shapes around their parent stars.All these nebulae formed in different places and have different characteristics. And neither the individual nebulae, nor the stars that formed them, would have interacted with other planetary nebulae. However, a new study by astronomers from the University of Manchester, UK, now shows surprising similarities between some of these nebulae: many of them line up in the sky in the same way [1].”This really is a surprising find and, if it holds true, a very important one,” explains Bryan Rees of the University of Manchester, one of the paper’s two authors. “Many of these ghostly butterflies appear to have their long axes aligned along the plane of our galaxy. By using images from both Hubble and the NTT we could get a really good view of these objects, so we could study them in great detail.”The astronomers looked at 130 planetary nebulae in the Milky Way’s central bulge. They identified three different types [2], and peered closely at their characteristics and appearance.”While two of these populations were completely randomly aligned in the sky, as expected, we found that the third — the bipolar nebulae — showed a surprising preference for a particular alignment,” says the paper’s second author Albert Zijlstra, also of the University of Manchester. “While any alignment at all is a surprise, to have it in the crowded central region of the galaxy is even more unexpected.”Planetary nebulae are thought to be sculpted by the rotation of the star system from which they form. This is dependent on the properties of this system — for example, whether it is a binary [3], or has a number of planets orbiting it, both of which may greatly influence the form of the blown bubble. …

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Oldest solar twin identified: New clues to help solve lithium mystery

Aug. 28, 2013 — A team led by astronomers in Brazil has used ESO’s Very Large Telescope to study the oldest solar twin known to date. Located 250 light-years away, the star HIP 102152 is more like the Sun than any other solar twin — except that it is nearly four billion years older. This older twin may be host to rocky planets and gives us an unprecedented chance to see how the Sun will look when it ages.Astronomers have only been observing the Sun with telescopes for 400 years — a tiny fraction of the Sun’s age of 4.6 billion years. It is very hard to study the history and future evolution of our star, but we can do this by hunting for rare stars that are almost exactly like our own, but at different stages of their lives. Now astronomers have identified a star that is essentially an identical twin to our Sun, but 4 billion years older — almost like seeing a real version of the twin paradox in action [1].Jorge Melendez (Universidade de São Paulo, Brazil), the leader of the team and co-author of the new paper explains: “For decades, astronomers have been searching for solar twins in order to know our own life-giving Sun better. But very few have been found since the first one was discovered in 1997. We have now obtained superb-quality spectra from the VLT and can scrutinise solar twins with extreme precision, to answer the question of whether the Sun is special.”The team studied two solar twins [2] — one that was thought to be younger than the Sun (18 Scorpii) and one that was expected to be older (HIP 102152). They used the UVES spectrograph on the Very Large Telescope (VLT) at ESO’s Paranal Observatory to split up the light into its component colours so that the chemical composition and other properties of these stars could be studied in great detail. They found that HIP 102152 in the constellation of Capricornus (The Sea Goat) is the oldest solar twin known to date. …

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A fluffy disk around a baby star

Aug. 23, 2013 — An international team of astronomers that are members of the Strategic Exploration of Exoplanets and Disks with Subaru Telescope (SEEDS) Project has used Subaru Telescope’s High Contrast Instrument for the Subaru Next Generation Adaptive Optics (HiCIAO) to observe a disk around the young star RY Tau (Tauri). The team’s analysis of the disk shows that a “fluffy” layer above it is responsible for the scattered light observed in the infrared image. Detailed comparisons with computer simulations of scattered light from the disk reveal that this layer appears to be a remnant of material from an earlier phase of stellar and disk development, when dust and gas were falling onto the disk.Since 2009, the five-year SEEDS Project (Note) has focused on direct imaging of exoplanets, i.e., planets orbiting stars outside of our Solar System, and disks around a targeted total of 500 stars. Planet formation, an exciting and active area for astronomical research, has long fascinated many scientists. Disks of dust and gas that rotate around young stars are of particular interest, because astronomers think that these are the sites where planets form–in these so-called “protoplanetary disks.” Since young stars and disks are born in molecular clouds, giant clouds of dust and gas, the role of dust becomes an important feature of understanding planet formation; it relates not only to the formation of rocky, Earth-like planets and the cores of giant Jupiter-like planets but also to that of moons, planetary rings, comets, and asteroids.As a part of the SEEDS Project, the current team of researchers used HiCIAO mounted on the Subaru Telescope to observe a possible planet-forming disk around the young star RY Tau. This star is about 460 light years away from Earth in the constellation Taurus and is around half a million years old. The disk has a radius of about 70 AU (10 billion kilometers), which is a few times larger than the orbit of Neptune in our own Solar System.Astronomers have developed powerful instruments to obtain images of protoplanetary disks, and Subaru Telescope’s HiCIAO is one of them. HiCIAO uses a mask to block out the light of the central star, which may be a million times brighter than its disk. They can then observe light from the star that has been reflected from the surface of the disk. …

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Waking up to a new year: Exoplanet orbits its star in 8.5 hours

Aug. 19, 2013 — In the time it takes you to complete a single workday, or get a full night’s sleep, a small fireball of a planet 700 light-years away has already completed an entire year.Researchers at MIT have discovered an Earth-sized exoplanet named Kepler 78b that whips around its host star in a mere 8.5 hours — one of the shortest orbital periods ever detected. The planet is extremely close to its star — its orbital radius is only about three times the radius of the star — and the scientists have estimated that its surface temperatures may be as high as 3,000 degrees Kelvin, or more than 5,000 degrees Fahrenheit. In such a scorching environment, the top layer of the planet is likely completely melted, creating a massive, roiling ocean of lava.What’s most exciting to scientists is that they were able to detect light emitted by the planet — the first time that researchers have been able to do so for an exoplanet as small as Kepler 78b. This light, once analyzed with larger telescopes, may give scientists detailed information about the planet’s surface composition and reflective properties.Kepler 78b is so close to its star that scientists hope to measure its gravitational influence on the star. Such information may be used to measure the planet’s mass, which could make Kepler 78b the first Earth-sized planet outside our own solar system whose mass is known.The researchers reported their discovery of Kepler 78b in The Astrophysical Journal.In a separate paper, published in Astrophysical Journal Letters, members of that same group, along with others at MIT and elsewhere, observed KOI 1843.03, a previously discovered exoplanet with an even shorter orbital period: just 4 1/4 hours. The group, led by physics professor emeritus Saul Rappaport, determined that in order for the planet to maintain its extremely tight orbit around its star, it would have to be incredibly dense, made almost entirely of iron — otherwise, the immense tidal forces from the nearby star would rip the planet to pieces.”Just the fact that it’s able to survive there implies that it’s very dense,” says Josh Winn, an associate professor of physics at MIT, and co-author on both papers. “Whether nature actually makes planets that are dense enough to survive even closer in, that’s an open question, and would be even more amazing.”Dips in the dataIn their discovery of Kepler 78b, the team that wrote the Astrophysical Journal paper looked through more than 150,000 stars that were monitored by the Kepler Telescope, a NASA space observatory that surveys a slice of the galaxy. Scientists are analyzing data from Kepler in hopes of identifying habitable, Earth-sized planets.The goal for Winn and his colleagues was to look for Earth-sized planets with very short orbital periods.”We’ve gotten used to planets having orbits of a few days,” Winn says. “But we wondered, what about a few hours? …

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New strategy to disarm the dengue virus brings new hope for a universal dengue vaccine

Aug. 13, 2013 — A new strategy that cripples the ability of the dengue virus to escape the host immune system has been discovered by A*STAR’s Singapore Immunology Network (SIgN). This breakthrough strategy opens a door of hope to what may become the world’s first universal dengue vaccine candidate that can give full protection from all four serotypes of the dreadful virus.This research done in collaboration with Singapore’s Novartis Institute of Tropical Diseases (NITD) and Beijing Institute of Microbiology and Epidemiology is published in the Plos Pathogens journal, and is also supported by Singapore STOP Dengue Translational and Clinical Research (TCR) Programme grant.Early studies have shown that a sufficiently weakened virus that is still strong enough to generate protective immune response offers the best hope for an effective vaccine. However, over the years of vaccine development, scientists have learnt that the path to finding a virus of appropriate strength is fraught with challenges. This hurdle is compounded by the complexity of the dengue virus. Even though there are only four different serotypes, the fairly high rates of mutation means the virus evolve constantly, and this contributes to the great diversity of the dengue viruses circulating globally. Furthermore, in some cases, the immune response developed following infection by one of the four dengue viruses appears to increase the risk of severe dengue when the same individual is infected with any of the remaining three viruses. With nearly half the world’s population at risk of dengue infection and an estimated 400 million people getting infected each year[2], the need for a safe and long-lasting vaccine has never been greater.The new strategy uncovered in this study overcomes the prevailing challenges of vaccine development by tackling the virus’ ability to ‘hide’ from the host immune system. Dengue virus requires the enzyme called MTase (also known as 2′-O-methyltransferase) to chemically modify its genetic material to escape detection. In this study, the researchers discovered that by introducing a genetic mutation to deactivate the MTase enzyme of the virus, initial cells infected by the weakened MTase mutant virus is immediately recognised as foreign. …

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Astronomers image lowest-mass exoplanet around a sun-like star

Aug. 5, 2013 — Using infrared data from the Subaru Telescope in Hawaii, an international team of astronomers has imaged a giant planet around the bright star GJ 504. Several times the mass of Jupiter and similar in size, the new world, dubbed GJ 504b, is the lowest-mass planet ever detected around a star like the sun using direct imaging techniques.”If we could travel to this giant planet, we would see a world still glowing from the heat of its formation with a color reminiscent of a dark cherry blossom, a dull magenta,” said Michael McElwain, a member of the discovery team at NASA’s Goddard Space Flight Center in Greenbelt, Md. “Our near-infrared camera reveals that its color is much more blue than other imaged planets, which may indicate that its atmosphere has fewer clouds.”GJ 504b orbits its star at nearly nine times the distance Jupiter orbits the sun, which poses a challenge to theoretical ideas of how giant planets form.According to the most widely accepted picture, called the core-accretion model, Jupiter-like planets get their start in the gas-rich debris disk that surrounds a young star. A core produced by collisions among asteroids and comets provides a seed, and when this core reaches sufficient mass, its gravitational pull rapidly attracts gas from the disk to form the planet.While this model works fine for planets out to where Neptune orbits, about 30 times Earth’s average distance from the sun (30 astronomical units, or AU), it’s more problematic for worlds located farther from their stars. GJ 504b lies at a projected distance of 43.5 AU from its star; the actual distance depends on how the system tips to our line of sight, which is not precisely known.”This is among the hardest planets to explain in a traditional planet-formation framework,” explained team member Markus Janson, a Hubble postdoctoral fellow at Princeton University in New Jersey. “Its discovery implies that we need to seriously consider alternative formation theories, or perhaps to reassess some of the basic assumptions in the core-accretion theory.”The research is part of the Strategic Explorations of Exoplanets and Disks with Subaru (SEEDS), a project to directly image extrasolar planets and protoplanetary disks around several hundred nearby stars using the Subaru Telescope on Mauna Kea, Hawaii. The five-year project began in 2009 and is led by Motohide Tamura at the National Astronomical Observatory of Japan (NAOJ).While direct imaging is arguably the most important technique for observing planets around other stars, it is also the most challenging.”Imaging provides information about the planet’s luminosity, temperature, atmosphere and orbit, but because planets are so faint and so close to their host stars, it’s like trying to take a picture of a firefly near a searchlight,” explained Masayuki Kuzuhara at the Tokyo Institute of Technology, who led the discovery team.The SEEDS project images at near-infrared wavelengths with the help of the telescope’s novel adaptive optics system, which compensates for the smearing effects of Earth’s atmosphere, and two instruments: the High Contrast Instrument for the Subaru Next Generation Adaptive Optics and the InfraRed Camera and Spectrograph. The combination allows the team to push the boundary of direct imaging toward fainter planets.A paper describing the results has been accepted for publication in The Astrophysical Journal and will appear in a future issue.The researchers find that GJ 504b is about four times more massive than Jupiter and has an effective temperature of about 460 degrees Fahrenheit (237 Celsius).It orbits the G0-type star GJ 504, which is slightly hotter than the sun and is faintly visible to the unaided eye in the constellation Virgo. The star lies 57 light-years away and the team estimates the systems is about 160 million years, based on methods that link the star’s color and rotation period to it age.Young star systems are the most attractive targets for direct exoplanet imaging because their planets have not existed long enough to lose much of the heat from their formation, which enhances their infrared brightness.”Our sun is about halfway through its energy-producing life, but GJ504 is only one-thirtieth its age,” added McElwain. …

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Under leaden skies: Where heavy metal clouds the stars

Aug. 1, 2013 — In a paper shortly to be published in the Oxford University Press journal Monthly Notices of the Royal Astronomical Society, a team of astronomers from the Armagh Observatory in Northern Ireland report the discovery of two unusual stars with extremely high concentrations of lead in their atmospheres.Naslim Neelamkodan, Simon Jeffery, Natalie Behara and Alan Hibbert are studying the surfaces of small hot stars, known as helium-rich subdwarfs. They are already known to be peculiar because they contain much less hydrogen and much more helium than normal.Three years ago they discovered one with a very high surface concentration of zirconium — better known for making false diamonds. Now studying a group of similar stars, they have discovered two which have surfaces containing ten thousand (10,000) times more lead than is present on the surface of the Sun.The discoveries were made in two stars, known as HE 2359-2844, 800 light years distant in the direction of the constellation of Sculptor and HE 1256-2738, located 1000 light years away in the constellation of Hydra. The astronomers studied the stars using observations from the archives of the European Southern Observatory’s Very Large Telescope in Chile. The light signatures, or spectra, of both stars showed a few features which did not match any atoms expected to be present. After some detective work, the team realised that the features were due to lead.With atomic number 82, lead is one of the heaviest naturally occurring elements; in the Sun there is less than one lead atom for every ten billion hydrogen atoms. At around 38000 degrees Celsius, the surfaces of HE 2359-2844 and HE 1256-2738 are so hot that three electrons are removed from every lead atom. The resulting ions produce distinctive lines in the star’s spectrum, from which the concentration of lead in the atmosphere can be measured. Using the same technique, HE 2359-2844 was also found to show ten thousand times more yttrium and zirconium than on the Sun. …

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Pulsating star sheds light on exoplanet

July 29, 2013 — A team of researchers has devised a way to measure the internal properties of stars — a method that offers more accurate assessments of their orbiting planets.The research, which appears in Proceedings of the National Academy of Sciences, was conducted by a multi-national team of scientists, including physicists at New York University, Princeton University, and the Max Planck Institute for Solar System Research.The researchers examined HD 52265 — a star approximately 92 light years away and nearly 20 percent more massive than our Sun. More than a decade ago, scientists identified an exopanet — a planet outside our Solar System — in the star’s orbit. HD 52265, then, served as an ideal model for both measuring stars’ properties and how such properties can shed light on planetary systems.Previously, scientists inferred stars’ properties, such as radius, mass, and age, by considering observations of their brightness and color. Often these stars’ properties were not known to sufficient accuracy to further characterize the nearby planets.In the PNAS study, the scientists adopted a new approach to characterize star-planet systems: asteroseismology, which identifies the internal properties of stars by measuring their surface oscillations. Some have compared this approach to seismologists’ use of earthquake oscillations to examine Earth’s interior.Here, they were able to make several assessments of the star’s traits, including its mass, radius, age, and — for the first time — internal rotation. They used the COROT space telescope, part of a space mission led by the French Space Agency (CNES) in conjunction with the European Space Agency (ESA), to detect tiny fluctuations in the intensity of starlight caused by starquakes. The researchers confirmed the validity of the seismic results by comparing them with independent measurements of related phenomena. These included the motion of dark spots on the star’s surface and the star’s spectroscopic rotational velocity.Unlike other methods, the technique of asteroseismology returns both the rotation period of the star and the inclination of the rotation axis to the line of sight.The scientists could then use these findings to make a more definitive determination of an orbiting exoplanet. While it had previously been identified as an exoplanet by other scientists, some raised doubts about this conclusion, positing that it could actually be a brown dwarf — an object too small to be a star and too large to be a planet.But, armed with the precise calculations yielded by asteroseismology, the researchers on the PNAS study were able to enhance the certainty of the earlier conclusion. Specifically, given the inclination of the rotation axis of HD 52265 and the minimum mass of the nearby exoplanet, the researchers could infer the true mass of the latter — which was calculated to be roughly twice that of our planet Jupiter and therefore too small to be a brown dwarf.The study’s authors included: Katepalli Sreenivasan, president of Polytechnic Institute of NYU and dean of engineering at NYU; Shravan Hanasoge, an associate research scholar in geosciences at Princeton University and a visiting scholar at NYU’s Courant Institute of Mathematical Sciences; and Laurent Gizon, director of the Max Planck Institute for Solar System Research and a professor at the University of Goettingen in Germany.

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Discovery of a new class of white blood cells uncovers target for better vaccine design

July 17, 2013 — Scientists at A*STAR’s Singapore Immunology Network (SIgN) have discovered a new class of white blood cells in human lung and gut tissues that play a critical role as the first line of defence against harmful fungal and bacterial infections. This research will have significant impact on the design of vaccines and targeted immunotherapies for diseases caused by infectious microbes such as the hospital-acquired pneumonia.The scientists also showed for the first time that key immune functions of this new class of white blood cells are similar to those found in mice. This means that findings in the mouse studies can be applied to develop advanced clinical therapies for the human immune system. The study done in collaboration with Newcastle University was published in the journal Immunity.New Class of White Blood CellsAll immune responses against infectious agents are activated and regulated by dendritic cells (DCs), a specialised group of white blood cells which present tiny fragments from micro-organisms, vaccines or tumours to the T cells. T cells are immune cells that circulate around our bodies to scan for cellular abnormalities and infections. Of the different T cells, T helper 17 (Th17) cells specialise in activating a protective response crucial for our body to eliminate harmful bacteria or fungi.In this study, the scientists identified a new subset of DCs (named CD11b+ DCs), which are capable of activating such protective Th17 response. They also showed that mice lacking the CD11b+ DCs were unable to induce the protective Th17 response against the Aspergillus fumigatus, one of the most common fungal species in hospital-acquired infections.The team leader, Dr Florent Ginhoux from SIgN said, “As dendritic cells have the unique ability to ‘sense’ the type of pathogen present in order to activate the appropriate immune response, they are attractive targets to explore for vaccine development. This discovery revealed fresh inroads to better exploit dendritic cells for improved vaccine design against life-threatening fungal infections.”Acting Executive Director of SIgN, Associate Professor Laurent Rénia said, “Life-threatening fungal infections have increased over the years yet treatment options remain limited. This study demonstrates how fundamental research that deepens our understanding of the body’s immune system can translate into potential clinical applications that could save lives and impact healthcare.”

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In the zone: How scientists search for habitable planets

July 17, 2013 — There is only one planet we know of, so far, that is drenched with life. That planet is Earth, as you may have guessed, and it has all the right conditions for critters to thrive on its surface. Do other planets beyond our solar system, called exoplanets, also host life forms?Astronomers still don’t know the answer, but they search for potentially habitable planets using a handful of criteria. Ideally, they want to find planets just like Earth, since we know without a doubt that life took root here. The hunt is on for planets about the size of Earth that orbit at just the right distance from their star — in a region termed the habitable zone.NASA’s Kepler mission is helping scientists in the quest to find these worlds, sometimes called Goldilocks planets after the fairy tale because they orbit where conditions are “just right” for life. Kepler and other telescopes have confirmed a handful so far, all of which are a bit larger than Earth — the Super Earths. The search for Earth’s twin, a habitable-zone planet as small as Earth, is ongoing.An important part of this research is the continuing investigation into exactly where a star’s habitable zone starts and stops.The habitable zone is the belt around a star where temperatures are ideal for liquid water — an essential ingredient for life as we know it — to pool on a planet’s surface. Earth lies within the habitable zone of our star, the sun. Beyond this zone, a planet would probably be too cold and frozen for life (though it’s possible life could be buried underneath a moon’s surface). A planet lying between a star and the habitable zone would likely be too hot and steamy.That perfect Goldilocks planet within the zone wouldn’t necessarily be home to any furry creatures. …

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Disks don’t need planets to make patterns, NASA study shows

July 13, 2013 — Many young stars known to host planets also possess disks containing dust and icy grains, particles produced by collisions among asteroids and comets also orbiting the star. These debris disks often show sharply defined rings or spiral patterns, features that could signal the presence of orbiting planets. Astronomers study the disk features as a way to better understand the physical properties of known planets and possibly uncover new ones.But a new study by NASA scientists sounds a cautionary note in interpreting rings and spiral arms as signposts for new planets. Thanks to interactions between gas and dust, a debris disk may, under the right conditions, produce narrow rings on its own, no planets needed.Watch the changing dust density and the growth of structure in this simulated debris disk, which extends about 100 times farther from its star than Earth’s orbit around the sun. At left, the disk is seen from a 24-degree angle; at right, it’s face-on. Lighter colors show higher dust density.”When the mass of gas is roughly equal to the mass of dust, the two interact in a way that leads to clumping in the dust and the formation of patterns,” said lead researcher Wladimir Lyra, a Sagan Fellow at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “In essence, the gas shepherds the dust into the kinds of structures we would expect to be see if a planet were present.”A paper describing the findings was published in the July 11 issue of Nature.The warm dust in debris disks is easy to detect at infrared wavelengths, but estimating the gas content of disks is a much greater challenge. As a result, theoretical studies tend to focus on the role of dust and ice particles, paying relatively little attention to the gas component. Yet icy grains evaporate and collisions produce both gas and dust, so at some level all debris disks must contain some amount of gas.”All we need to produce narrow rings and other structures in our models of debris disks is a bit of gas, too little for us to detect today in most actual systems,” said co-author Marc Kuchner, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Md.Here’s how it works. When high-energy ultraviolet light from the central star strikes a clump of dust and ice grains, it drives electrons off the particles. …

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Hubble finds a true blue planet: Giant Jupiter-sized planet located 63 light-years away

July 11, 2013 — Astronomers using NASA’s Hubble Space Telescope have deduced the actual visible-light color of a planet orbiting another star 63 light-years away.If seen directly it would look like a “deep blue dot,” reminiscent of Earth’s color as seen from space. But that’s where all comparison ends. The planet’s daytime atmosphere is nearly 2,000 degrees Fahrenheit, and it possibly rains glass — sideways — in howling 4,500-mile-per-hour winds.The cobalt blue color doesn’t come from the reflection of a tropical ocean, but rather from a hazy blow-torched atmosphere and perhaps from high clouds laced with silicate particles. The condensation temperature of silicates could form very small drops of glass that would scatter blue light more than red light.The turbulent alien world, cataloged HD 189733b, is one of the nearest exoplanets to Earth that can be seen crossing the face of its star. It has been intensively studied by Hubble and other observatories, and its atmosphere is dramatically changeable and exotic.The observations yield new insights into the chemical composition and cloud structure of a bizarre “hot Jupiter” class planet, which orbits precariously close to its parent star.Clouds often play key roles in planetary atmospheres, and detecting the presence and importance of clouds in hot Jupiters is crucial, say researchers. “We obviously don’t know much on the physics and climatology of silicate clouds, so we are exploring a new domain of atmospheric physics,” said team member Frederic Pont of the University of Exeter, South West England, the United Kingdom.The team used Hubble’s Space Telescope Imaging Spectrograph to measure changes in the color of light from the planet before, during, and after the passage of the planet behind the parent star. This technique is possible because the planet’s orbit is tilted edge-on as viewed from Earth; therefore, it routinely passes in front of and then behind the star.Hubble measured a small drop in light — about one part in 10,000 — when the planet went behind the star, and a slight change in the color of the light, too. “We saw the light becoming less bright in the blue, but not in the green or the red. This means that the object that disappeared is blue because light was missing in the blue, but not in the red when it was hidden,” said Pont.The team’s study will be published online July 11 and will appear in the August 1 issue of the Astrophysical Journal Letters.Earlier observations have reported evidence for the scattering of blue light on the planet. But this most recent Hubble observation gives confirming evidence, said the researchers.The planet HD 189733b was discovered in 2005. …

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Feeding galaxy caught in distant searchlight

July 5, 2013 — Astronomers have always suspected that galaxies grow by pulling in material from their surroundings, but this process has proved very difficult to observe directly. Now ESO’s Very Large Telescope has been used to study a very rare alignment between a distant galaxy [1] and an even more distant quasar — the extremely bright centre of a galaxy powered by a supermassive black hole. The light from the quasar passes through the material around the foreground galaxy before reaching Earth, making it possible to explore in detail the properties of the gas around the galaxy [2]. These new results give the best view so far of a galaxy in the act of feeding.”This kind of alignment is very rare and it has allowed us to make unique observations,” explains Nicolas Bouché of the Research Institute in Astrophysics and Planetology (IRAP) in Toulouse, France, lead author of the new paper. “We were able to use ESO’s Very Large Telescope to peer at both the galaxy itself and its surrounding gas. This meant we could attack an important problem in galaxy formation: how do galaxies grow and feed star formation?”Galaxies quickly deplete their reservoirs of gas as they create new stars, and so must somehow be continuously replenished with fresh gas to keep going. Astronomers suspected that the answer to this problem lay in the collection of cool gas from the surroundings by the gravitational pull of the galaxy. In this scenario, a galaxy drags gas inwards, which then circles around the galaxy, rotating with it before falling in. Although some evidence of such accretion had been observed in galaxies before [3], the motion of the gas and its other properties had not been fully explored up to now.The astronomers used two instruments known as SINFONI and UVES [4], both of which are mounted on ESO’s VLT at the Paranal Observatory in northern Chile. The new observations showed both how the galaxy itself was rotating, and revealed the composition and motion of the gas outside the galaxy.”The properties of this vast volume of surrounding gas were exactly what we would expect to find if the cold gas was being pulled in by the galaxy,” says co-author Michael Murphy (Swinburne University of Technology, Melbourne, Australia). …

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White dwarf star throws light on possible variability of a constant of Nature

July 4, 2013 — An international team led by the University of New South Wales has studied a distant star where gravity is more than 30,000 times greater than on Earth to test its controversial theory that one of the constants of Nature is not a constant.Dr Julian Berengut and his colleagues used the Hubble Space Telescope to measure the strength of the electromagnetic force — known as alpha — on a white dwarf star.Their results, which do not contradict the variable constant theory, are to be published in the journal Physical Review Letters. Dr Berengut, of the UNSW School of Physics, said the team’s previous research on light from distant quasars suggests that alpha — known as the fine-structure constant — may vary across the universe.”This idea that the laws of physics are different in different places in the cosmos is a huge claim, and needs to be backed up with solid evidence,” he says.”A white dwarf star was chosen for our study because it has been predicted that exotic, scalar energy fields could significant alter alpha in places where gravity is very strong.””Scalar fields are forms of energy that often appear in theories of physics that seek to combine the Standard Model of particle physics with Einstein’s general theory of relativity.””By measuring the value of alpha near the white dwarf and comparing it with its value here and now in the laboratory we can indirectly probe whether these alpha-changing scalar fields actually exist.”White dwarfs are very dense stars near the ends of their lives. The researchers studied the light absorbed by nickel and iron ions in the atmosphere of a white dwarf called G191-B2B. The ions are kept above the surface by the star’s strong radiation, despite the pull of its extremely strong gravitational field.”This absorption spectrum allows us to determine the value of alpha with high accuracy. We found that any difference between the value of alpha in the strong gravitational field of the white dwarf and its value on Earth must be smaller than one part in ten thousand,” Dr Berengut says.”This means any scalar fields present in the star’s atmosphere must only weakly affect the electromagnetic force.” Dr Berengut said that more precise measurements of the iron and nickel ions on earth are needed to complement the high-precision astronomical data.”Then we should be able to measure any change in alpha down to one part per million. That would help determine whether alpha is a true constant of Nature, or not.”

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Astronomer uncovers the hidden identity of an exoplanet

July 1, 2013 — Hovering about 70 light-years from Earth — that’s “next door” by astronomical standards — is a star astronomers call HD 97658, which is almost bright enough to see with the naked eye. But the real “star” is the planet HD 97658b, not much more than twice Earth’s diameter and a little less than eight times its mass. HD 97658b is a super-Earth, a class of planet for which there is no example in our home solar system.While the discovery of this particular exoplanet is not new, determining its true size and mass is, thanks to Diana Dragomir, a postdoctoral astronomer with UC Santa Barbara’s Las Cumbres Observatory Global Telescope (LCOGT). As part of her research, Dragomir looked for transits of this exoplanet with Canada’s Microvariability & Oscillations of Stars (MOST) space telescope. The telescope was launched in 2003 to a pole-over-pole orbit about 510 miles high. Dragomir analyzed the data using code written by LCOGT postdoctoral fellow Jason Eastman. The results were published online today in the Astrophysical Journal Letters.A super-Earth is an exoplanet with a mass and radius between those of Earth and Neptune. Don’t be fooled by the moniker though. Super-Earth refers to the planet’s mass and does not imply similar temperature, composition, or environment to Earth. The brightness of HD 97658 means astronomers can study this star and planet in ways not possible for most of the exoplanet systems that have been discovered around fainter stars.HD 97658b was discovered in 2011 by a team of astronomers using the Keck Observatory and a technique sometimes called Doppler wobble. …

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