Shocking behavior of a runaway star: High-speed encounter creates arc

Roguish runaway stars can have a big impact on their surroundings as they plunge through the Milky Way galaxy. Their high-speed encounters shock the galaxy, creating arcs, as seen in a newly released image from NASA’s Spitzer Space Telescope.In this case, the speedster star is known as Kappa Cassiopeiae, or HD 2905 to astronomers. It is a massive, hot supergiant moving at around 2.5 million mph relative to its neighbors (1,100 kilometers per second). But what really makes the star stand out in this image is the surrounding, streaky red glow of material in its path. Such structures are called bow shocks, and they can often be seen in front of the fastest, most massive stars in the galaxy.Bow shocks form where the magnetic fields and wind of particles flowing off a star collide with the diffuse, and usually invisible, gas and dust that fill the space between stars. How these shocks light up tells astronomers about the conditions around the star and in space. Slow-moving stars like our sun have bow shocks that are nearly invisible at all wavelengths of light, but fast stars like Kappa Cassiopeiae create shocks that can be seen by Spitzer’s infrared detectors.Incredibly, this shock is created about 4 light-years ahead of Kappa Cassiopeiae, showing what a sizable impact this star has on its surroundings. (This is about the same distance that we are from Proxima Centauri, the nearest star beyond the sun.)The Kappa Cassiopeiae bow shock shows up as a vividly red color. The faint green features in this image result from carbon molecules, called polycyclic aromatic hydrocarbons, in dust clouds along the line of sight that are illuminated by starlight.Delicate red filaments run through this infrared nebula, crossing the bow shock. Some astronomers have suggested these filaments may be tracing out features of the magnetic field that runs throughout our galaxy. …

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Massive neutrinos solve a cosmological conundrum

Scientists have solved a major problem with the current standard model of cosmology identified by combining results from the Planck spacecraft and measurements of gravitational lensing in order to deduce the mass of ghostly sub-atomic particles called neutrinos.The team, from the universities of Manchester and Nottingham, used observations of the Big Bang and the curvature of space-time to accurately measure the mass of these elementary particles for the first time.The recent Planck spacecraft observations of the Cosmic Microwave Background (CMB) — the fading glow of the Big Bang — highlighted a discrepancy between these cosmological results and the predictions from other types of observations.The CMB is the oldest light in the Universe, and its study has allowed scientists to accurately measure cosmological parameters, such as the amount of matter in the Universe and its age. But an inconsistency arises when large-scale structures of the Universe, such as the distribution of galaxies, are observed.Professor Richard Battye, from The University of Manchester School of Physics and Astronomy, said: “We observe fewer galaxy clusters than we would expect from the Planck results and there is a weaker signal from gravitational lensing of galaxies than the CMB would suggest.”A possible way of resolving this discrepancy is for neutrinos to have mass. The effect of these massive neutrinos would be to suppress the growth of dense structures that lead to the formation of clusters of galaxies.”Neutrinos interact very weakly with matter and so are extremely hard to study. They were originally thought to be massless but particle physics experiments have shown that neutrinos do indeed have mass and that there are several types, known as flavours by particle physicists. The sum of the masses of these different types has previously been suggested to lie above 0.06 eV (much less than a billionth of the mass of a proton).In this paper, Professor Battye and co-author Dr Adam Moss, from the University of Nottingham, have combined the data from Planck with gravitational lensing observations in which images of galaxies are warped by the curvature of space-time. They conclude that the current discrepancies can be resolved if massive neutrinos are included in the standard cosmological model. They estimate that the sum of masses of neutrinos is 0.320 +/- 0.081 eV (assuming active neutrinos with three flavours).Dr Moss said: “If this result is borne out by further analysis, it not only adds significantly to our understanding of the sub-atomic world studied by particle physicists, but it would also be an important extension to the standard model of cosmology which has been developed over the last decade.”The paper is published in Physical Review Letters and has been selected as an Editor’s choice.Story Source:The above story is based on materials provided by University of Manchester. Note: Materials may be edited for content and length.

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NASA’s Chandra Observatory catches giant black hole rejecting material

Aug. 29, 2013 — Astronomers using NASA’s Chandra X-ray Observatory have taken a major step in explaining why material around the giant black hole at the center of the Milky Way Galaxy is extraordinarily faint in X-rays. This discovery holds important implications for understanding black holes.New Chandra images of Sagittarius A* (Sgr A*), which is located about 26,000 light-years from Earth, indicate that less than 1 percent of the gas initially within Sgr A*’s gravitational grasp ever reaches the point of no return, also called the event horizon. Instead, much of the gas is ejected before it gets near the event horizon and has a chance to brighten, leading to feeble X-ray emissions.These new findings are the result of one of the longest observation campaigns ever performed with Chandra. The spacecraft collected five weeks’ worth of data on Sgr A* in 2012. The researchers used this observation period to capture unusually detailed and sensitive X-ray images and energy signatures of super-heated gas swirling around Sgr A*, whose mass is about 4 million times that of the sun.”We think most large galaxies have a supermassive black hole at their center, but they are too far away for us to study how matter flows near it,” said Q. Daniel Wang of the University of Massachusetts in Amherst, who led of a study published Thursday in the journal Science. “Sgr A* is one of very few black holes close enough for us to actually witness this process.”The researchers found that the Chandra data from Sgr A* did not support theoretical models in which the X-rays are emitted from a concentration of smaller stars around the black hole. Instead, the X-ray data show the gas near the black hole likely originates from winds produced by a disk-shaped distribution of young massive stars.”This new Chandra image is one of the coolest I’ve ever seen,” said co-author Sera Markoff of the University of Amsterdam in the Netherlands. “We’re watching Sgr A* capture hot gas ejected by nearby stars, and funnel it in towards its event horizon.”To plunge over the event horizon, material captured by a black hole must lose heat and momentum. …

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NASA releases images of Earth by two interplanetary spacecraft

July 22, 2013 — Color and black-and-white images of Earth taken by two NASA interplanetary spacecraft on July 19 show our planet and its moon as bright beacons from millions of miles away in space.NASA’s Cassini spacecraft captured the color images of Earth and the moon from its perch in the Saturn system nearly 900 million miles (1.5 billion kilometers) away. MESSENGER, the first probe to orbit Mercury, took a black-and-white image from a distance of 61 million miles (98 million kilometers) as part of a campaign to search for natural satellites of the planet.In the Cassini images Earth and the moon appear as mere dots — Earth a pale blue and the moon a stark white, visible between Saturn’s rings. It was the first time Cassini’s highest-resolution camera captured Earth and its moon as two distinct objects.It also marked the first time people on Earth had advance notice their planet’s portrait was being taken from interplanetary distances. NASA invited the public to celebrate by finding Saturn in their part of the sky, waving at the ringed planet and sharing pictures over the Internet. More than 20,000 people around the world participated.”We can’t see individual continents or people in this portrait of Earth, but this pale blue dot is a succinct summary of who we were on July 19,” said Linda Spilker, Cassini project scientist, at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “Cassini’s picture reminds us how tiny our home planet is in the vastness of space, and also testifies to the ingenuity of the citizens of this tiny planet to send a robotic spacecraft so far away from home to study Saturn and take a look-back photo of Earth.”Pictures of Earth from the outer solar system are rare because from that distance, Earth appears very close to our sun. A camera’s sensitive detectors can be damaged by looking directly at the sun, just as a human being can damage his or her retina by doing the same. Cassini was able to take this image because the sun had temporarily moved behind Saturn from the spacecraft’s point of view and most of the light was blocked.A wide-angle image of Earth will become part of a multi-image picture, or mosaic, of Saturn’s rings, which scientists are assembling. This image is not expected to be available for several weeks because of the time-consuming challenges involved in blending images taken in changing geometry and at vastly different light levels, with faint and extraordinarily bright targets side by side.”It thrills me to no end that people all over the world took a break from their normal activities to go outside and celebrate the interplanetary salute between robot and maker that these images represent,” said Carolyn Porco, Cassini imaging team lead at the Space Science Institute in Boulder, Colo. “The whole event underscores for me our ‘coming of age’ as planetary explorers.”In the MESSENGER image, Earth and the moon are less than a pixel, but appear very large because they are overexposed. …

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Cluster spacecraft detects elusive space wind

July 2, 2013 — A new study provides the first conclusive proof of the existence of a space wind first proposed theoretically over 20 years ago. By analysing data from the European Space Agency’s Cluster spacecraft, researcher Iannis Dandouras detected this plasmaspheric wind, so-called because it contributes to the loss of material from the plasmasphere, a donut-shaped region extending above Earth’s atmosphere. The results are published today in Annales Geophysicae, a journal of the European Geosciences Union (EGU).”After long scrutiny of the data, there it was, a slow but steady wind, releasing about 1 kg of plasma every second into the outer magnetosphere: this corresponds to almost 90 tonnes every day. It was definitely one of the nicest surprises I’ve ever had!” said Dandouras of the Research Institute in Astrophysics and Planetology in Toulouse, France.The plasmasphere is a region filled with charged particles that takes up the inner part of Earth’s magnetosphere, which is dominated by the planet’s magnetic field.To detect the wind, Dandouras analysed the properties of these charged particles, using information collected in the plasmasphere by ESA’s Cluster spacecraft. Further, he developed a filtering technique to eliminate noise sources and to look for plasma motion along the radial direction, either directed at Earth or outer space.As detailed in the new Annales Geophysicae study, the data showed a steady and persistent wind carrying about a kilo of the plasmasphere’s material outwards each second at a speed of over 5,000 km/h. This plasma motion was present at all times, even when Earth’s magnetic field was not being disturbed by energetic particles coming from the Sun.Researchers predicted a space wind with these properties over 20 years ago: it is the result of an imbalance between the various forces that govern plasma motion. But direct detection eluded observation until now.”The plasmaspheric wind is a weak phenomenon, requiring for its detection sensitive instrumentation and detailed measurements of the particles in the plasmasphere and the way they move,” explains Dandouras, who is also the vice-president of the EGU Planetary and Solar System Sciences Division.The wind contributes to the loss of material from Earth’s top atmospheric layer and, at the same time, is a source of plasma for the outer magnetosphere above it. Dandouras explains: “The plasmaspheric wind is an important element in the mass budget of the plasmasphere, and has implications on how long it takes to refill this region after it is eroded following a disturbance of the planet’s magnetic field. Due to the plasmaspheric wind, supplying plasma — from the upper atmosphere below it — to refill the plasmasphere is like pouring matter into a leaky container.”The plasmasphere, the most important plasma reservoir inside the magnetosphere, plays a crucial role in governing the dynamics of Earth’s radiation belts. These present a radiation hazard to satellites and to astronauts travelling through them. …

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NASA’s Voyager 1 explores final frontier of our ‘solar bubble’

June 27, 2013 — Data from Voyager 1, now more than 11 billion miles (18 billion kilometers) from the sun, suggest the spacecraft is closer to becoming the first human-made object to reach interstellar space.Research using Voyager 1 data and published in the journal Science today provides new detail on the last region the spacecraft will cross before it leaves the heliosphere, or the bubble around our sun, and enters interstellar space. Three papers describe how Voyager 1’s entry into a region called the magnetic highway resulted in simultaneous observations of the highest rate so far of charged particles from outside heliosphere and the disappearance of charged particles from inside the heliosphere.Scientists have seen two of the three signs of interstellar arrival they expected to see: charged particles disappearing as they zoom out along the solar magnetic field, and cosmic rays from far outside zooming in. Scientists have not yet seen the third sign, an abrupt change in the direction of the magnetic field, which would indicate the presence of the interstellar magnetic field.”This strange, last region before interstellar space is coming into focus, thanks to Voyager 1, humankind’s most distant scout,” said Ed Stone, Voyager project scientist at the California Institute of Technology in Pasadena. “If you looked at the cosmic ray and energetic particle data in isolation, you might think Voyager had reached interstellar space, but the team feels Voyager 1 has not yet gotten there because we are still within the domain of the sun’s magnetic field.”Scientists do not know exactly how far Voyager 1 has to go to reach interstellar space. They estimate it could take several more months, or even years, to get there. The heliosphere extends at least 8 billion miles (13 billion kilometers) beyond all the planets in our solar system. It is dominated by the sun’s magnetic field and an ionized wind expanding outward from the sun. Outside the heliosphere, interstellar space is filled with matter from other stars and the magnetic field present in the nearby region of the Milky Way.Voyager 1 and its twin spacecraft, Voyager 2, were launched in 1977. They toured Jupiter, Saturn, Uranus and Neptune before embarking on their interstellar mission in 1990. They now aim to leave the heliosphere. …

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