Astronomers discover a replica solar system

This image shows Kepler-444 and its five orbiting planets. (Courtesy of Peter Devine and Tiago Campante/University of Birmingham)

Scientists have located an ancient solar system, dating back to the dawn of the galaxy, which appears to be a miniature version of the inner planets in our own solar system.

An international research group, including Yale University professors of astronomy Sarbani Basu and Debra Fischer, announced the discovery Jan. 27 in The Astrophysical Journal. The findings are the result of observations made by the NASA Kepler spacecraft over a period of four years.

The old, Sun-like star, named Kepler-444, has five orbiting planets with sizes between those of Mercury and Venus. Kepler-444 formed 11.2 billion years ago, when the universe was less than 20% of its current age. This makes Kepler-444 the oldest known system of terrestrial-sized planets. The Kepler-444 system was already older than our own solar system is today when our Sun and planets were born.

“This system shows that planet formation could take place under very different conditions from the ones in which our solar system was formed and has implications for estimating the total number of planets in our galaxy, and other galaxies,” Basu said.

The five planets in the Kepler-444 system have orbits that are equivalent to less than one-tenth of Earth’s distance from the Sun. The Kepler-444 planets are rocky and Earth-like, but their exact compositions are uncertain.

The scientists carried out their research using asteroseismology — listening to the host star’s natural resonances, which are caused by sound trapped within it. These oscillations lead to miniscule changes or pulses in the star’s brightness, allowing researchers to measure the star’s diameter, mass, and age. The planets were then detected from the dimming that occurs when the planets transited, or passed across, the stellar disc. This fractional fading in the intensity of starlight enabled scientists to measure accurately the sizes of the planets relative to the size of the star.

“There are far-reaching implications for this discovery,” said lead author Tiago Campante of the University of Birmingham (U.K.). “We now know that Earth-sized planets have formed throughout most of the universe’s 13.8-billion-year history, which could provide scope for the existence of ancient life in the galaxy.”

The research collaboration involved nearly two-dozen institutions in the United States, England, Denmark, Portugal, Australia, Germany, and Italy.

Source: Yale university

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SOHO and Hinode Offer New Insight Into Solar Eruptions

Scientists are trying to understand the precise details of what creates giant explosions in the sun's atmosphere, such as this solar eruption from Oct. 14, 2012, as seen by NASA's Solar Dynamic Observatory. Image Credit: NASA/SDO/Amari

The sun is home to the largest explosions in the solar system. For example, it regularly produces huge eruptions known as coronal mass ejections – when billions of tons of solar material erupt off the sun, spewing into space and racing toward the very edges of the solar system. Scientists know that these ejections, called CMEs, are caused by magnetic energy building up on the sun, which suddenly releases. But the details of what causes the build up and triggers the release are not precisely understood.

A journal paper in Nature magazine on Oct. 23, 2014, used data from NASA missions to present an example of how something called a magnetic flux rope builds up over time until it is so unstable that even the slightest perturbation will send it flying. Understanding what triggers CMEs is crucial not only for better understanding of our sun, but also to lay the groundwork for predicting when such giant explosions might happen.

"We looked at a well-studied CME from 2006," said Tahar Amari first author on the Nature paper at Ecole Polytechnique in France. "We knew that there had been a great deal of data available for this CME and much analysis already done, but no one had created a comprehensive picture of what happened."

Amari and his colleagues used a traditional meteorology technique to examine the event: Gather observations from the days before the CME to track how the event grew over time. They used observations from the European Space Agency and NASA's Solar and Heliospheric Observatory, or SOHO, and the Japanese Aerospace Exploration Agency and NASA's Hinode, as well as from the Paris-Meudon Observatory.

Scientists created this model to examine the magnetic field before a giant solar eruption – a coronal mass ejection – which occurred on Dec. 13, 2006. The orange lines show magnetic field lines. The grey line represents what's called a flux rope, which built up the day before the event. Image Credit: Amari/Ecole Poytechnique

The team wanted to see if they could distinguish between two broad theories about how the magnetic energy develops. The first model describes a situation in which a series of loops of magnetic fields on the sun – known as an arcade – is the start of every active region CME. 

This arcade has a weak point at the top, a place where the energy from below can burst through once it's great enough. During the eruption a flux rope forms, which can be seen inside the CME as it surges away from the sun.

The second model assumes that the flux rope is there before the CME erupts. In this theory, no weak point is required. Instead, the flux rope gains more and more energy, and becomes increasingly unstable until a disturbance on the sun causes it to release the energy out into space.

Amari and his team used magnetic data from the surface obtained by Hinode, but they also needed magnetic data for the sun's atmosphere, the corona, which is strongly affected by its magnetic field.

"The corona is so hot that most of the techniques to measure the magnetic field don't work," said Amari. "So we developed an efficient and accurate model to compute the magnetic field there, based on the data we had from the surface, and the equations governing the physics of the low corona above active regions."

With these two data sets in hand, the team examined what happened in the four days before the 2006 CME erupted. They could see the magnetic energy building; it was clear something was emerging. Only, however, on the last day did a flux rope develop and only then did it have enough energy built up to power a CME eruption. At this point, some small disruption was enough of a nudge to make the flux rope erupt.

A model of the eruption of a giant magnetic rope that led to a coronal mass ejection on the sun in December 2006.

A model of the eruption of a giant magnetic rope that led to a coronal mass ejection on the sun in December 2006. The model showed that magnetic fields built up for several days before the eruption.

"In this case no weak point up in the atmosphere was needed to allow the energy to be released," said Amari. "There is, instead, a kind of critical value of energy, a value we can compute based on seeing an active magnetic region on the sun. Beneath that value the magnetic field will stay quiet. Above that, it is likely to erupt. There is also a critical height for rising flux rope, beyond which the magnetic loops above can no longer keep it confined."

The team explored the initial conditions from this event and put the information into another dynamical model the team had developed. The simulation mirrored what was actually seen, with an eruption occurring only when the critical energy and height were reached on the last day.

Amari points out that just because this CME contained a flux rope prior to eruption, it doesn't mean that other CMEs can’t erupt based on other physical catalysts. But it clearly describes one mechanism that is at work on the sun.

By measuring and calculating the magnetic fields on the sun, coupled with determining how to measure the critical tipping point where a CME can erupt, the paper offers new ways to determine the possibility of eruption from any given active area on the sun.

Source: Nasa

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'Iron Sun' is not a rock band, but a key to how stars transmit energy

Physicist Jim Bailey of Sandia National Laboratories observes a wire array that will heat foam to roughly 4 million degrees until it emits a burst of X-rays that heats a foil target to the interior conditions of the sun. Credit: Photo by Randy Montoya, Sandia National Laboratories

Working at temperatures matching the interior of the sun, researchers at Sandia National Laboratories' Z machine have been able to determine experimentally, for the first time in history, iron's role in inhibiting energy transmission from the center of the sun to near the edge of its radiative band -- the section of the solar interior between the sun's core and outer convection zone.

Because that role is much greater than formerly surmised, the new, experimentally derived amount of iron's opacity -- essentially, its capacity for hindering the transport of radiative energy originating in nuclear fusion reactions deep in the sun's interior -- helps close a theoretical gap in the Standard Solar Model, widely used by astrophysicists as a foundation to model the behavior of stars.

"Our data, when inserted into the theoretical model, bring its predictions more closely into alignment with physical observations," said Sandia lead investigator Jim Bailey. His team's work appeared Jan. 1 in the journal Nature.

The gap between the model and observations appeared in 2000 when analysis of spectra emerging from the sun forced scientists to lower their estimates of energy-absorbing elements such as oxygen, nitrogen and carbon by 30 to 50 percent.

The decreased abundances meant that the model then predicted that energy would arrive at the sun's radiative edge more readily than before. This created a discrepancy between the star's theoretical structure and its measured structure, which is based on variations in temperatures and densities at different locations.

To make the model once again agree with observations, scientists needed a way to balance the decreased resistance to radiation transport caused by the lowered amounts of the elements.

Bailey's experimental group, including Taisuke Nagayama, Guillaume Loisel and Greg Rochau, in painstaking experiments spanning a 10-year period, discovered that the widely used astrophysical estimate of the wavelength-dependent opacity of iron should be increased between 30 to 400 percent. That difference does not represent a large uncertainty but rather how much iron's opacity varies with the wavelength of the radiation.

"This represents roughly half the change in the mean opacity needed to resolve the solar problem, even though iron is only one of many elements that contribute," the authors write in their paper.

Getting accurate data has been difficult, as "the inside of a star is one of the most mysterious places in the universe," Bailey said. "It's too opaque for distant instruments to see inside and analyze reactions within it, and too hot to send a probe into it. It has also been too difficult to run tests under appropriate conditions in a laboratory. So the physics that describes how atoms, embedded in solar plasma, absorb radiation, has never been experimentally tested. Yet that process dominates the way energy generated by nuclear reactions in the sun's interior is transported to the outside.

"Fortunately, in our Z experiments, we can create temperature and density conditions nearly the same as the region inside the sun that affects the discrepancy the most -- the edge of the zone where radiative energy transport dominates -- in a sample that's big enough, lasts long enough, and is uniform enough to test. We used that new capability to measure the opacity of iron, one of a few elements that plays the most important part in radiative energy transfer."

Iron is important because, of all the elements abundant in the sun, it maintains the highest number of bound electrons essential in radiative energy transfer, and thus has a large effect on the outcome of solar models.

Still, the upward revision of opacities as a solution is bound to be controversial.

"No matter what we do, we can't make measurements at all the different conditions we need to know," said Nagayama. "There are 20 elements present, and a large range of temperatures and densities. We study iron because its complex electronic structure is a challenge to represent in opacity theories. And it is important in solar physics. The sun is a test bed to model other stars. Without experimental tests, we don't know if these models are accurate. To the extent we fail to understand the sun, then the workings of other stars are subject to some uncertainty."

Sandia's Z machine creates the temperature of the sun's interior -- about 2.1 million degrees -- in a target about the size of a grain of sand. From that small sample, Bailey could do what theorists cannot: hold in his hand tangible evidence for the way iron atoms behave inside stars.

The target design for recent experiments involved intermingled iron and magnesium, tamped by plastic and beryllium layers on both sides. Radiation streaming through the sample heats up the iron and magnesium, which expand. The plastic restrains the expansion to keep it more uniform for opacity measurements. Magnesium provides information about corresponding density and temperature.

The work was sponsored by the National Nuclear Security Administration and the DOE Office of Science.

Source: DOE/Sandia National Laboratories

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Record-breaking black hole outburst detected

An image of a simulation of the gas cloud’s encounter with Sgr A*. The blue lines mark the orbits of the so-called “S” stars that are in close orbits around the supermassive black hole.
Credit: Image by ESO/MPE/Marc Schartmann

Last September, after years of watching, a team of scientists led by Amherst College astronomy professor Daryl Haggard observed and recorded the largest-ever flare in X-rays from a supermassive black hole at the center of the Milky Way. The astronomical event, which was detected by NASA's Chandra X-ray Observatory, puts the scientific community one step closer to understanding the nature and behavior of supermassive black holes.

Haggard and her colleagues discussed the flare today during this year's meeting of the American Astronomical Society in Seattle.

Supermassive black holes are the largest of black holes, and all large galaxies have one. The one at the center of our galaxy, the Milky Way, is called Sagittarius A* (or, Sgr A*, as it is called), and scientists estimate that it contains about four and a half million times the mass of our Sun.

Scientists working with Chandra have observed Sgr A* repeatedly since the telescope was launched into space in 1999. Haggard and fellow astronomers were originally using Chandra to see if Sgr A* would consume parts of a cloud of gas, known as G2.

"Unfortunately, the G2 gas cloud didn't produce the fireworks we were hoping for when it got close to Sgr A*," she said. "However, nature often surprises us and we saw something else that was really exciting."

Haggard and her team detected an X-ray outburst last September that was 400 times brighter than the usual X-ray output from Sgr A*. This "megaflare" was nearly three times brighter than the previous record holder that was seen in early 2012. A second enormous X-ray flare, 200 times brighter than Sgr A* in its quiet state, was observed with Chandra on October 20, 2014.

Haggard and her team have two main ideas about what could be causing Sgr A* to erupt in this extreme way. One hypothesis is that the gravity of the supermassive black hole has torn apart a couple of asteroids that wandered too close. The debris from such a "tidal disruption" would become very hot and produce X-rays before disappearing forever across the black hole's point of no return (called the "event horizon").

"If an asteroid was torn apart, it would go around the black hole for a couple of hours -- like water circling an open drain -- before falling in," said colleague and co-principal investigator Fred Baganoff of the Massachusetts Institute of Technology in Cambridge, MA. "That's just how long we saw the brightest X-ray flare last, so that is an intriguing clue for us to consider."

If that theory holds up, it means astronomers have found evidence for the largest asteroid ever to be torn apart by the Milky Way's black hole.

Another, different idea is that the magnetic field lines within the material flowing towards Sgr A* are packed incredibly tightly. If this were the case, these field lines would occasionally interconnect and reconfigure themselves. When this happens, their magnetic energy is converted into the energy of motion, heat and the acceleration of particles -- which could produce a bright X-ray flare. Such magnetic flares are seen on the Sun, and the Sgr A* flares have a similar pattern of brightness levels to the solar events.

"At the moment, we can't distinguish between these two very different ideas," said Haggard. "It's exciting to identify tensions between models and to have a chance to resolve them with present and future observations."

In addition to the giant flares, Haggard and her team also collected more data on a magnetar -- a neutron star with a strong magnetic field -- located close to Sgr A*. This magnetar is undergoing a long X-ray outburst, and the Chandra data are allowing astronomers to better understand this unusual object.

As for the G2: Astronomers estimate that the gas cloud made its closest approach -- still about 15 billion miles away from the edge of the black hole -- in the spring of 2014. The researchers estimate the record breaking X-ray flares were produced about a hundred times closer to the black hole, making it very unlikely that the Chandra flares were associated with G2.

Source: Amherst College

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Gravity may have saved the universe after the Big Bang, say researchers

Center of the Milky Way galaxy (stock image). Credit: © DR / Fotolia

New research by a team of European physicists could explain why the universe did not collapse immediately after the Big Bang.

Studies of the Higgs particle -- discovered at CERN in 2012 and responsible for giving mass to all particles -- have suggested that the production of Higgs particles during the accelerating expansion of the very early universe (inflation) should have led to instability and collapse.

Scientists have been trying to find out why this didn't happen, leading to theories that there must be some new physics that will help explain the origins of the universe that has not yet been discovered. Physicists from Imperial College London, and the Universities of Copenhagen and Helsinki, however, believe there is a simpler explanation.

In a new study in Physical Review Letters, the team describe how the spacetime curvature -- in effect, gravity -- provided the stability needed for the universe to survive expansion in that early period. The team investigated the interaction between the Higgs particles and gravity, taking into account how it would vary with energy.

They show that even a small interaction would have been enough to stabilise the universe against decay.

"The Standard Model of particle physics, which scientists use to explain elementary particles and their interactions, has so far not provided an answer to why the universe did not collapse following the Big Bang," explains Professor Arttu Rajantie, from the Department of Physics at Imperial College London.

"Our research investigates the last unknown parameter in the Standard Model -- the interaction between the Higgs particle and gravity. This parameter cannot be measured in particle accelerator experiments, but it has a big effect on the Higgs instability during inflation. Even a relatively small value is enough to explain the survival of the universe without any new physics!"

The team plan to continue their research using cosmological observations to look at this interaction in more detail and explain what effect it would have had on the development of the early universe. In particular, they will use data from current and future European Space Agency missions measuring cosmic microwave background radiation and gravitational waves.

"Our aim is to measure the interaction between gravity and the Higgs field using cosmological data," says Professor Rajantie. "If we are able to do that, we will have supplied the last unknown number in the Standard Model of particle physics and be closer to answering fundamental questions about how we are all here."

The research is funded by the Science and Technology Facilities Council, along with the Villum Foundation, in Denmark, and the Academy of Finland.

Source: Imperial College London

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NASA-funded FOXSI to observe X-rays from Sun

The Focusing Optics X-ray Solar Imager, or FOXSI, mission launched for the first time in November 2012, as shown here. It will fly again on a sounding rocket for a 15-minute flight in December 2014 to observe hard X-rays from the sun. Credit: NASA/FOXSI

An enormous spectrum of light streams from the sun. We're most familiar with the conventional visible white light we see with our eyes from Earth, but that's just a fraction of what our closest star emits. NASA regularly watches the sun in numerous wavelengths because different wavelengths provide information about different temperatures and processes in space. Looking at all the wavelengths together helps to provide a complete picture of what's occurring on the sun over 92 million miles away -- but no one has been able to focus on high energy X-rays from the sun until recently.

In early December 2014, the Focusing Optics X-ray Solar Imager, or FOXSI, mission will launch aboard a sounding rocket for a 15-minute flight with very sensitive hard X-ray optics to observe the sun. This is FOXSI's second flight -- now with new and improved optics and detectors. FOXSI launched previously in November 2012. The mission is led by Säm Krucker of the University of California in Berkeley.

Due to launch from White Sands Missile Range in New Mexico, on Dec. 9, 2014, FOXSI will be able to collect six minutes worth of data during the 15-minute flight. Sounding rockets provide a short trip for a relatively low price -- yet allow scientists to gather robust data on various things, such as X-ray emission, which cannot be seen from the ground as they are blocked by Earth's atmosphere.

"Hard X-rays are a signature of particles accelerating on the sun," said Steven Christe, the project scientist for FOXSI at NASA's Goddard Space Flight Center in Greenbelt, Maryland. 

"The sun accelerates particles when it releases magnetic energy. The biggest events like solar flares release giant bursts of energy and send particles flying, sometimes directed towards Earth. But the sun is actually releasing energy all the time and that process is not well-understood."

Scientists want to understand these energy releases both because they contribute to immense explosions on the sun that can send particles and energy toward Earth, but also because that energy helps heat up the sun's atmosphere to temperatures of millions of degrees -- 1,000 times hotter than the surface of the sun itself. Observing many wavelengths of light allows us to probe different temperatures within the sun's atmosphere. Looking for hard X-rays, is not only one of the best ways to measure the highest temperatures, up to tens of millions of degrees, but it also helps track accelerated particles.

The sensitivity of the FOXSI instrument means the team can investigate very faint events on the sun, including tiny energy releases commonly known as nanoflares. Nanoflares are thought to occur constantly, but are so small that we can't see them with current telescopes. Spotting hard X-rays with FOXSI would be a confirmation that these small flares do exist. Moreover, it would suggest that nanoflares behave in a similar fashion as larger flares, accelerating particles in much the same way that big flares do.

"It's not necessarily true that these small flares accelerate particles. Perhaps they are just small heating events and the physics is different," said Christe. "That's one of the things we're trying to figure out."

Viewing such faint events requires extra sensitive optics. FOXSI carries something called grazing-incidence optics -- built by NASA's Marshall Space Flight Center in Huntsville, Alabama -- that are unlike any previous ones launched into space for solar observations. 

Techniques to collect and observe high energy X-rays streaming from the sun have been hampered by the fact that these wavelengths cannot be focused with conventional lenses the way visible light can be. When X-rays encounter most materials, including a standard glass lens, they usually pass right through or are absorbed. Such lenses can't, therefore, be used to adjust the X-ray's path and focus the incoming beams. So X-ray telescopes have previously relied on imaging techniques that don't use focusing. This is effective when looking at a single bright event on the sun, such as the large burst of X-rays from a solar flare, but it doesn't work as well when searching for many faint events simultaneously.

The FOXSI instrument makes use of mirrors that can successfully cause x-rays to reflect -- as long as the x-ray mirrors are nearly parallel to the incoming X-rays. Several of these mirrors in combination help collect the X-ray light before funneling it to the detector. This focusing makes faint events appear brighter and crisper.

The FOXSI launch is scheduled for Dec. 9 between 2 and 3 pm EST. The shutter door on the optics system opens up after the payload reaches an altitude of 90 miles, one minute after launch. FOXSI then begins six minutes of observing the sun. After the observations, the door on the optics system closes. The rocket deploys a parachute and the instruments float down to the ground in the hopes of being used again.

The FOXSI mission made it through this process successfully once before, when it flew in 2012. On its first flight, the telescope successfully viewed a flare in progress. On this second flight, the team has updated some of the optics to be more sensitive and has removed insulation blankets that blocked some of the X-rays during the last flight. They also upgraded some of the detectors with new detectors built by the Japanese Aerospace Exploration Agency using a new detector material. Last time they used silicon and this time they are using cadmium telluride.

Such refurbishing illustrates a key value of sounding rockets: Making adjustments to the instruments on relatively low-cost flights has great benefit for future missions. By testing FOXSI on a sounding rocket, it can be perfected to use on a larger satellite with even larger, more sensitive optics.

In addition to developing technology, these low-cost missions help train students and young scientists.

"Sounding rockets are a great way for students to be heavily involved in every aspect of a space mission, from electronics testing to observational planning," said Lindsay Glesener, FOXSI's project manager at the University of California in Berkeley, who was also a graduate student during FOXSI's first flight. "Development on low-cost missions is the way that,scientists, engineers, and even the telescopes get prepared to work on an eventual satellite mission."

FOXSI is a collaboration between the United States and the Japanese Aerospace Exploration Agency. FOXSI is supported through NASA's Sounding Rocket Program at the Goddard Space Flight Center's Wallops Flight Facility in Virginia. NASA's Heliophysics Division manages the sounding rocket program.

Source: NASA/Goddard Space Flight Center

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Large coronal hole near the sun's north pole

The European Space Agency/NASA Solar and Heliospheric Observatory, or SOHO, captured this image of a gigantic coronal hole hovering over the sun’s north pole on July 18, 2013, at 9:06 a.m. EDT.
Credit: ESA & NASA/SOHO

The European Space Agency/NASA Solar and Heliospheric Observatory, or SOHO, captured this image of a gigantic coronal hole hovering over the sun's north pole on July 18, 2013, at 9:06 a.m. EDT. Coronal holes are dark, low density regions of the sun's outermost atmosphere, the corona. They contain little solar material, have lower temperatures, and therefore, appear much darker than their surroundings.

Coronal holes are a typical feature on the sun, though they appear at different places and with more frequency at different times of the sun's activity cycle. The activity cycle is currently ramping up toward what is known as solar maximum, currently predicted for late 2013. During this portion of the cycle, the number of coronal holes decreases. During solar max, the magnetic fields on the sun reverse and new coronal holes appear near the poles with the opposite magnetic alignment. The coronal holes then increase in size and number, extending further from the poles as the sun moves toward solar minimum again. At such times, coronal holes have appeared that are even larger than this one.

The holes are important to our understanding of space weather, as they are the source of a high-speed wind of solar particles that streams off the sun some three times faster than the slower wind elsewhere. While it's unclear what causes coronal holes, they correlate to areas on the sun where magnetic fields soar up and away, failing to loop back down to the surface, as they do elsewhere.

Source: NASA/Goddard Space Flight Center

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NASA's SDO sees massive filament erupt on sun

Eruptive events on the sun can be wildly different. Some come just with a solar flare, some with an additional ejection of solar material called a coronal mass ejection (CME), and some with complex moving structures in association with changes in magnetic field lines that loop up into the sun's atmosphere, the corona. Credit: Image courtesy of NASA/Goddard Space Flight Center

Eruptive events on the sun can be wildly different. Some come just with a solar flare, some with an additional ejection of solar material called a coronal mass ejection (CME), and some with complex moving structures in association with changes in magnetic field lines that loop up into the sun's atmosphere, the corona.

On July 19, 2012, an eruption occurred on the sun that produced all three. A moderately powerful solar flare exploded on the sun's lower right limb, sending out light and radiation. Next came a CME, which shot off to the right out into space. And then, the sun treated viewers to one of its dazzling magnetic displays -- a phenomenon known as coronal rain.

Over the course of the next day, hot plasma in the corona cooled and condensed along strong magnetic fields in the region. Magnetic fields, themselves, are invisible, but the charged plasma is forced to move along the lines, showing up brightly in the extreme ultraviolet wavelength of 304 Angstroms, which highlights material at a temperature of about 50,000 Kelvin. This plasma acts as a tracer, helping scientists watch the dance of magnetic fields on the sun, outlining the fields as it slowly falls back to the solar surface.

Source: NASA/Goddard Space Flight Center

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Because you can't eat just one: Star will swallow two planets

In this artist's conception, the doomed world Kepler-56b is being tidally shredded and consumed by its aging host star. New research shows that Kepler-56b will be engulfed by its star in about 130 million years, while its sibling Kepler-56c will be swallowed in 155 million years. This is the first time that two known exoplanets in a single system have a predicted "time of death." Credit: David A. Aguilar (CfA)

Two worlds orbiting a distant star are about to become a snack of cosmic proportions. Astronomers announced today that the planets Kepler-56b and Kepler-56c will be swallowed by their star in a short time by astronomical standards. Their ends will come in 130 million and 155 million years, respectively.

"As far as we know, this is the first time two known exoplanets in a single system have a predicted 'time of death,'" says lead author Gongjie Li of the Harvard-Smithsonian Center for Astrophysics (CfA).

She presented her research today at a meeting of the American Astronomical Society.

The Kepler-56 system provides a glimpse into the future of our solar system. In about five billion years our Sun will become a red giant star, swelling to immense proportions and engulfing Mercury and Venus.

The star Kepler-56 is becoming a red giant star as well. It already has ballooned out to four times the Sun's size. As it ages, it will continue to expand outward. Not only will the star grow larger, but its tides will get stronger, dragging its planets inward to their eventual doom.

Kepler-56b orbits its host star once every 10.5 days, while Kepler-56c orbits every 21.4 days. Both of them are much closer to their star than Mercury is to the Sun. As a result, they will meet their fate much faster. Li and her collaborators calculated the evolution of both the star's size (using the publicly available MESA code) and the planets' orbits to predict when the planets will be destroyed.

Even before they vanish, the two planets will be subjected to immense heating from the steadily growing star. Their atmospheres will begin to boil off, and the planets themselves will be stretched into egg shapes by stellar tides.

The only survivor in the system will be Kepler-56d, a gas giant planet circling in a 3.3-Earth-year orbit. It will watch from a safe distance as its two sibling worlds meet their demise.

The Kepler-56 planetary system also is notable for being the first "tilted" multiplanet system to be discovered. The orbits of the inner two planets are tipped significantly from the star's equator. This was unexpected since planets form from the same disk of gas and dust as the star, so they should orbit in nearly the same plane as the star's equator (as do the planets in our solar system).

The team was able to better constrain the tilt of these planets, compared to earlier work. 

They found that the most probable tilt was either 37 or 131 degrees.

Li and her colleagues also investigated the inclination of the outer planet and determined that its orbit is likely to be tilted relative to the star as well. Future observations should help astronomers to characterize this system, and to explain how it became so skewed.

Source: Harvard-Smithsonian Center for Astrophysics

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Jupiter's moons remain slightly illuminated, even in eclipse

A schematic image of the model to show that the Galilean satellites eclipsed in Jovian shadow are illuminated by scattered sunlight by the haze in the Jovian upper atmosphere. The size and the distance of the satellites are not to the scale. This process is similar to one that causes red color of the Earth’s Moon during its total eclipse. Credit: NASA, JAXA, Tohoku University

Astronomers using the Subaru Telescope and Hubble Space Telescope have found that Jupiter's Galilean satellites (Io, Europa, Ganymede, and Callisto) remain slightly bright (up to one millionth of their normal state) even when in the Jovian shadow and not directly illuminated by the Sun. The effect is particularly pronounced for Ganymede and Callisto. The finding was made by researchers at Tohoku University, Institute of Space and Astronautical Science/Japan Aerospace Exploration Agency (ISAS/JAXA), National Astronomical Observatory of Japan (NAOJ), and elsewhere.

The mechanism of this phenomenon is still under investigation, but the researchers suggest that indirect forward scattering of sunlight by hazes in the upper Jovian atmosphere could be the reason for the illumination. This effect is similar to the one that causes Earth's moon to look red during a total lunar eclipse.

The type of continuous observations of the Galilean satellites in eclipse made by the Japanese team also provides a much better basis for studying the hazes in Jupiter's atmosphere, which are difficult to study otherwise (Note 1). In addition, this detailed study method for a planetary atmosphere will provide new insights about the atmospheres of exoplanets, which are only beginning to be studied.

Dr. Tsumura Kohji (FRIS, Tohoku University), the PI on the project, explained that this unexpected finding is really the outcome of attempts to measure diffuse light from the distant universe. "It is a serendipitous discovery made as a by-product of a cosmological study," he said. "It is very interesting that it provides us a new method to investigate the atmosphere of Jupiter and of exoplanets. I will keep studying from nearby space (the solar system and exoplanets) out to the farthest universe through this project."

The research team started its observations with the Subaru Telescope in February of 2012. 
The idea was to detect the diffuse light from the most distant parts of the universe. To do this, team members planned to use the Galilean satellites in eclipse as "occulters" to block distant background emissions. This would allow an extremely accurate separation of the background light from the very bright foreground radiation from our solar system (known as the zodiacal light).

The team assumed that the Galilean satellites would be "dark" while in Jupiter's shadow, and the difference in brightness[??] between the dark satellite as an occulter and its surrounding sky would allow the team to determine the still-unknown level of background emission from the distant universe. Instead, they found an unexpected surprise: Ganymede and Callisto were still somewhat "bright" (illuminated) even when eclipsed (relative to the expected level of near-zero). Their eclipsed luminosity was one millionth of their un-eclipsed brightness, which is low enough that this phenomenon has been undetected until now.

To understand why the Galileans remain ever-so-slightly bright even when they're in eclipse, the project team of astronomers and planetary scientists considered several theories based on their multi-band observational data, including data from Spitzer Space Telescope. The most plausible is that the Galilean satellites are still illuminated during eclipse by sunlight that is scattered by hazes in the Jovian upper atmosphere. By comparison, the sunlight refracted in the atmosphere does not contribute to the illumination during the eclipse.

Although Jupiter is a familiar planet, there are many unresolved issues about its atmosphere. One example is the origin of the cloud particles composing Jupiter's banded appearance. The cloud particles are assumed to grow from tiny particles called aerosols or hazes. Researchers expect that those hazes form somewhere in the upper part of Jupiter's atmosphere, which is very difficult to observe. The unexpected discovery of haze-induced brightening of the Galileans provides a new way to study the mysterious part of Jupiter's atmosphere. In addition, since astronomers usually observe the planets in our solar system by reflected sunlight, one of the unique aspects of these new observations at Jupiter is that observers can precisely measure the transmitted sunlight through the planetary atmosphere (Note 2).

This new method of studying the upper atmosphere of Jupiter via transmitted sunlight provides a basis for the study of other planetary systems. Exoplanet discoveries now occur quite regularly and atmospheres around some of them have been investigated using "transit observations" (when the exoplanet passes between us and the host star, resulting in the star becoming slightly dimmer). In such observations, some characteristics of the exoplanet's atmosphere are revealed as host starlight passes through it. This is the same situation seen with Jupiter and its Galilean satellites, and makes studies of transmitted sunlight of the planets in our solar system essential for comparison.

The observations for this project were very challenging because the Galilean satellites (while eclipsed) are extremely faint and they are located next to the incredibly bright disk of Jupiter. In addition, the eclipses only happen at very specific times, and Jupiter and the satellites are continuously in motion during the observations. The complexity of the situation requires the observation procedure to be much more sophisticated. This new discovery required thorough preparations by the project team and conscientious support by the operations staff.

Source: National Astronomical Observatory of Japan

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NASA-funded FOXSI to observe X-rays from Sun

The Focusing Optics X-ray Solar Imager, or FOXSI, mission launched for the first time in November 2012, as shown here. It will fly again on a sounding rocket for a 15-minute flight in December 2014 to observe hard X-rays from the sun. Credit: NASA/FOXSI

An enormous spectrum of light streams from the sun. We're most familiar with the conventional visible white light we see with our eyes from Earth, but that's just a fraction of what our closest star emits. NASA regularly watches the sun in numerous wavelengths because different wavelengths provide information about different temperatures and processes in space. Looking at all the wavelengths together helps to provide a complete picture of what's occurring on the sun over 92 million miles away -- but no one has been able to focus on high energy X-rays from the sun until recently.

In early December 2014, the Focusing Optics X-ray Solar Imager, or FOXSI, mission will launch aboard a sounding rocket for a 15-minute flight with very sensitive hard X-ray optics to observe the sun. This is FOXSI's second flight -- now with new and improved optics and detectors. FOXSI launched previously in November 2012. The mission is led by Säm Krucker of the University of California in Berkeley.

Due to launch from White Sands Missile Range in New Mexico, on Dec. 9, 2014, FOXSI will be able to collect six minutes worth of data during the 15-minute flight. Sounding rockets provide a short trip for a relatively low price -- yet allow scientists to gather robust data on various things, such as X-ray emission, which cannot be seen from the ground as they are blocked by Earth's atmosphere.

"Hard X-rays are a signature of particles accelerating on the sun," said Steven Christe, the project scientist for FOXSI at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "The sun accelerates particles when it releases magnetic energy. The biggest events like solar flares release giant bursts of energy and send particles flying, sometimes directed towards Earth. But the sun is actually releasing energy all the time and that process is not well-understood."

Scientists want to understand these energy releases both because they contribute to immense explosions on the sun that can send particles and energy toward Earth, but also because that energy helps heat up the sun's atmosphere to temperatures of millions of degrees -- 1,000 times hotter than the surface of the sun itself. Observing many wavelengths of light allows us to probe different temperatures within the sun's atmosphere. Looking for hard X-rays, is not only one of the best ways to measure the highest temperatures, up to tens of millions of degrees, but it also helps track accelerated particles.

The sensitivity of the FOXSI instrument means the team can investigate very faint events on the sun, including tiny energy releases commonly known as nanoflares. Nanoflares are thought to occur constantly, but are so small that we can't see them with current telescopes. Spotting hard X-rays with FOXSI would be a confirmation that these small flares do exist. Moreover, it would suggest that nanoflares behave in a similar fashion as larger flares, accelerating particles in much the same way that big flares do.

"It's not necessarily true that these small flares accelerate particles. Perhaps they are just small heating events and the physics is different," said Christe. "That's one of the things we're trying to figure out."

Viewing such faint events requires extra sensitive optics. FOXSI carries something called grazing-incidence optics -- built by NASA's Marshall Space Flight Center in Huntsville, Alabama -- that are unlike any previous ones launched into space for solar observations. 

Techniques to collect and observe high energy X-rays streaming from the sun have been hampered by the fact that these wavelengths cannot be focused with conventional lenses the way visible light can be. When X-rays encounter most materials, including a standard glass lens, they usually pass right through or are absorbed. Such lenses can't, therefore, be used to adjust the X-ray's path and focus the incoming beams. So X-ray telescopes have previously relied on imaging techniques that don't use focusing. This is effective when looking at a single bright event on the sun, such as the large burst of X-rays from a solar flare, but it doesn't work as well when searching for many faint events simultaneously.

The FOXSI instrument makes use of mirrors that can successfully cause x-rays to reflect -- as long as the x-ray mirrors are nearly parallel to the incoming X-rays. Several of these mirrors in combination help collect the X-ray light before funneling it to the detector. This focusing makes faint events appear brighter and crisper.

The FOXSI launch is scheduled for Dec. 9 between 2 and 3 pm EST. The shutter door on the optics system opens up after the payload reaches an altitude of 90 miles, one minute after launch. FOXSI then begins six minutes of observing the sun. After the observations, the door on the optics system closes. The rocket deploys a parachute and the instruments float down to the ground in the hopes of being used again.

The FOXSI mission made it through this process successfully once before, when it flew in 2012. On its first flight, the telescope successfully viewed a flare in progress. On this second flight, the team has updated some of the optics to be more sensitive and has removed insulation blankets that blocked some of the X-rays during the last flight. They also upgraded some of the detectors with new detectors built by the Japanese Aerospace 

Exploration Agency using a new detector material. Last time they used silicon and this time they are using cadmium telluride.

Such refurbishing illustrates a key value of sounding rockets: Making adjustments to the instruments on relatively low-cost flights has great benefit for future missions. By testing FOXSI on a sounding rocket, it can be perfected to use on a larger satellite with even larger, more sensitive optics.

In addition to developing technology, these low-cost missions help train students and young scientists.

"Sounding rockets are a great way for students to be heavily involved in every aspect of a space mission, from electronics testing to observational planning," said Lindsay Glesener, 

FOXSI's project manager at the University of California in Berkeley, who was also a graduate student during FOXSI's first flight. "Development on low-cost missions is the way that,scientists, engineers, and even the telescopes get prepared to work on an eventual satellite mission."

FOXSI is a collaboration between the United States and the Japanese Aerospace Exploration Agency. FOXSI is supported through NASA's Sounding Rocket Program at the Goddard Space Flight Center's Wallops Flight Facility in Virginia. NASA's Heliophysics Division manages the sounding rocket program.

Source:  NASA/Goddard Space Flight Center

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Sun sizzles in high-energy X-rays

X-rays stream off the sun in this image showing observations from by NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, overlaid on a picture taken by NASA's Solar Dynamics Observatory (SDO).
Credit: NASA/JPL-Caltech/GSFC

For the first time, a mission designed to set its eyes on black holes and other objects far from our solar system has turned its gaze back closer to home, capturing images of our sun. NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, has taken its first picture of the sun, producing the most sensitive solar portrait ever taken in high-energy X-rays.

NuSTAR will give us a unique look at the sun, from the deepest to the highest parts of its atmosphere," said David Smith, a solar physicist and member of the NuSTAR team at University of California, Santa Cruz.

Solar scientists first thought of using NuSTAR to study the sun about seven years ago, after the space telescope's design and construction was already underway (the telescope launched into space in 2012). Smith had contacted the principal investigator, Fiona Harrison of the California Institute of Technology in Pasadena, who mulled it over and became excited by the idea.

"At first I thought the whole idea was crazy," says Harrison. "Why would we have the most sensitive high energy X-ray telescope ever built, designed to peer deep into the universe, look at something in our own back yard?" Smith eventually convinced Harrison, explaining that faint X-ray flashes predicted by theorists could only be seen by NuSTAR.

While the sun is too bright for other telescopes such as NASA's Chandra X-ray Observatory, NuSTAR can safely look at it without the risk of damaging its detectors. The sun is not as bright in the higher-energy X-rays detected by NuSTAR, a factor that depends on the temperature of the sun's atmosphere.
This first solar image from NuSTAR demonstrates that the telescope can in fact gather data about sun. And it gives insight into questions about the remarkably high temperatures that are found above sunspots -- cool, dark patches on the sun. Future images will provide even better data as the sun winds down in its solar cycle.

"We will come into our own when the sun gets quiet," said Smith, explaining that the sun's activity will dwindle over the next few years.

With NuSTAR's high-energy views, it has the potential to capture hypothesized nanoflares -- smaller versions of the sun's giant flares that erupt with charged particles and high-energy radiation. Nanoflares, should they exist, may explain why the sun's outer atmosphere, called the corona, is sizzling hot, a mystery called the "coronal heating problem." The corona is, on average, 1.8 million degrees Fahrenheit (1 million degrees Celsius), while the surface of the sun is relatively cooler at 10,800 Fahrenheit (6,000 degrees Celsius). It is like a flame coming out of an ice cube. Nanoflares, in combination with flares, may be sources of the intense heat.

If NuSTAR can catch nanoflares in action, it may help solve this decades-old puzzle.

"NuSTAR will be exquisitely sensitive to the faintest X-ray activity happening in the solar atmosphere, and that includes possible nanoflares," said Smith.
What's more, the X-ray observatory can search for hypothesized dark matter particles called axions. Dark matter is five times more abundant than regular matter in the universe. Everyday matter familiar to us, for example in tables and chairs, planets and stars, is only a sliver of what's out there. While dark matter has been indirectly detected through its gravitational pull, its composition remains unknown.

It's a long shot, say scientists, but NuSTAR may be able spot axions, one of the leading candidates for dark matter, should they exist. The axions would appear as a spot of X-rays in the center of the sun.

Meanwhile, as the sun awaits future NuSTAR observations, the telescope is continuing with its galactic pursuits, probing black holes, supernova remnants and other extreme objects beyond our solar system.

NuSTAR is a Small Explorer mission led by Caltech and managed by NASA's Jet Propulsion Laboratory, also in Pasadena, for NASA's Science Mission Directorate in Washington. The spacecraft was built by Orbital Sciences Corporation, Dulles, Virginia. Its instrument was built by a consortium including Caltech; JPL; the University of California, Berkeley; Columbia University, New York; NASA's Goddard Space Flight Center, Greenbelt, Maryland; the Danish Technical University in Denmark; Lawrence Livermore National Laboratory, Livermore, California; ATK Aerospace Systems, Goleta, California; and with support from the Italian Space Agency (ASI) Science Data Center.

NuSTAR's mission operations center is at UC Berkeley, with the ASI providing its equatorial ground station located at Malindi, Kenya. The mission's outreach program is based at Sonoma State University, Rohnert Park, California. NASA's Explorer Program is managed by Goddard. JPL is managed by Caltech for NASA.

Source: NASA

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Magnetic fields frozen into meteorite grains tell a shocking tale of solar system birth

Magnetic field lines (green) weave through the cloud of dusty gas surrounding the newborn Sun. In the foreground are asteroids and chondrules, the building blocks of chondritic meteorites. While solar magnetic fields dominate the region near the Sun, out where the asteroids orbit, chondrules preserve a record of varying local magnetic fields. Credit: Science

The most accurate laboratory measurements yet made of magnetic fields trapped in grains within a primitive meteorite are providing important clues to how the early solar system evolved. The measurements point to shock waves traveling through the cloud of dusty gas around the newborn Sun as a major factor in solar system formation.

The results appear in a paper published Nov. 13 in the journal Science. The lead author is graduate student Roger Fu of MIT, working under Benjamin Weiss; Steve Desch of Arizona State University's School of Earth and Space Exploration is a co-author of the paper.

"The measurements made by Fu and Weiss are astounding and unprecedented," says Desch. 
"Not only have they measured tiny magnetic fields thousands of times weaker than a compass feels, they have mapped the magnetic fields' variation recorded by the meteorite, millimeter by millimeter."

Construction debris
It may seem all but impossible to determine how the solar system formed, given it happened about 4.5 billion years ago. But making the solar system was a messy process, leaving lots of construction debris behind for scientists to study.

Among the most useful pieces of debris are the oldest, most primitive and least altered type of meteorites, called the chondrites (KON-drites). Chondrite meteorites are pieces of asteroids, broken off by collisions, that have remained relatively unmodified since they formed at the birth of the solar system. They are built mostly of small stony grains, called chondrules, barely a millimeter in diameter.

Chondrules themselves formed through quick melting events in the dusty gas cloud -- the solar nebula -- that surrounded the young sun. Patches of the solar nebula must have been heated above the melting point of rock for hours to days. Dustballs caught in these events made droplets of molten rock, which then cooled and crystallized into chondrules.

Tiny magnets
As chondrules cooled, iron-bearing minerals within them became magnetized like bits on a hard drive by the local magnetic field in the gas. These magnetic fields are preserved in the chondrules even down to the present day.

The chondrule grains whose magnetic fields were mapped in the new study came from a meteorite named Semarkona, after the place in India where it fell in 1940. It weighed 691 grams, or about a pound and a half.

The scientists focused specifically on the embedded magnetic fields captured by "dusty" olivine grains that contain abundant iron-bearing minerals. These had a magnetic field of about 54 microtesla, similar to the magnetic field at Earth's surface, which ranges from 25 to 65 microtesla.

Coincidentally, many previous measurements of meteorites also implied similar field strengths. But it is now understood that those measurements detected magnetic minerals contaminated by Earth's magnetic field, or even from hand magnets used by meteorite collectors.

"The new experiments," Desch says, "probe magnetic minerals in chondrules never measured before. They also show that each chondrule is magnetized like a little bar magnet, but with 'north' pointing in random directions."

This shows, he says, they became magnetized before they were built into the meteorite, and not while sitting on Earth's surface.

Shocks and more shocks
"My modeling for the heating events shows that shock waves passing through the solar nebula is what melted most chondrules," Desch explains. Depending on the strength and size of the shock wave, the background magnetic field could be amplified by up to 30 times.
He says, "Given the measured magnetic field strength of about 54 microtesla, this shows the background field in the nebula was probably in the range of 5 to 50 microtesla."

There are other ideas for how chondrules might have formed, some involving magnetic flares above the solar nebula, or passage through the sun's magnetic field. But those mechanisms require stronger magnetic fields than what is measured in the Semarkona samples.

This reinforces the idea that shocks melted the chondrules in the solar nebula at about the location of today's asteroid belt, which lies some two to four times farther from the sun than Earth now orbits.

Desch says, "This is the first really accurate and reliable measurement of the magnetic field in the gas from which our planets formed."

Source: Arizona State University

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