Tracking a Solar Eruption Through the Solar System

Tracking a Solar Eruption Through the Solar System:

Ten spacecraft, from ESA’s Venus Express to NASA’s Voyager-2, felt the effect of a solar eruption as it washed through the solar system while three other satellites watched, providing a unique perspective on this space weather event. Scientists working on ESA’s Mars Express were looking forward to investigating the effects of the close encounter of Comet Siding Spring on the Red Planet’s atmosphere on October 19, 2014, but instead they found what turned out to be the imprint of a solar event.

While this made the analysis of any comet-related effects far more complex than anticipated, it triggered one of the largest collaborative efforts to trace the journey of an interplanetary coronal mass ejection – a CME – from the sun to the far reaches of the outer solar system.

Although Earth itself was not in the firing line, a number of sun-watching satellites near Earth – ESA’s Proba-2, the ESA/NASA SOHO and NASA’s Solar Dynamics Observatory – had witnessed a powerful solar eruption a few days earlier, on October 14, 2014.

NASA’s STEREO-A not only captured images of the other side of the sun with respect to Earth, but also collected in situ information as the CME rushed passed.

Thanks to the fortuitous locations of other satellites lying in the direction of the CME’s travel, unambiguous detections were made by three Mars orbiters – ESA’s Mars Express, NASA’s MAVEN and Mars Odyssey – and NASA’s Curiosity Rover operating on the Red Planet’s surface, ESA’s Rosetta at Comet 67P/Churyumov–Gerasimenko, and the international Cassini mission at Saturn.

Hints were even found as far out as NASA’s New Horizons, which was approaching Pluto at the time, and beyond to Voyager-2. However, at these large distances it is possible that evidence of this specific eruption may have merged with the background solar wind.

“CME speeds with distance from the sun is not well understood, in particular in the outer solar system,” said Olivier Witasse, a planetary scientist for the European Space Agency and lead author of the study published in Journal of Geophysical Research: Space Physics, a journal of the American Geophysical Union. “Thanks to the precise timings of numerous in situ measurements, we can better understand the process, and feed our results back into models.”

The measurements give an indication of the speed and direction of travel of the CME, which spread out over an angle of at least 116 degrees to reach Venus Express and STEREO-A on the eastern flank, and the spacecraft at Mars and Comet 67P Churyumov–Gerasimenko on the western flank.

From an initial maximum of about 1000 kilometers per second (621 miles per second) estimated at the sun, a strong drop to 647 kilometers per second (402 miles per second) was measured by Mars Express three days later, falling further to 550 kilometers per second (342 miles per second) at Rosetta after five days. This was followed by a more gradual decrease to 450–500 kilometers per second (280-311 miles per second) at the distance of Saturn a month since the event.

The data also revealed the evolution of the CME’s magnetic structure, with the effects felt by spacecraft for several days, providing useful insights on space weather effects at different planetary bodies. The signatures at the various spacecraft typically included an initial shock, a strengthening of the magnetic field, and increases in the solar wind speed.

In the case of ESA’s Venus Express, its science package was not switched on because Venus was “behind” the sun as seen from Earth, limiting communication capabilities. A faint indication was inferred from its star tracker being overwhelmed with radiation at the expected time of passage.

Furthermore, several craft carrying radiation monitors – Curiosity, Mars Odyssey, Rosetta and Cassini ­­– revealed an interesting and well-known effect: a sudden decrease in galactic cosmic rays. As a CME passes by, it acts like a protective bubble, temporarily sweeping aside the cosmic rays and partially shielding the planet or spacecraft.

A drop of about 20 percent in cosmic rays was observed at Mars – one of the deepest recorded at the Red Planet – and persisted for about 35 hours. At Rosetta, a reduction of 17 percent was seen that lasted for 60 hours, while at Saturn the reduction was slightly lower and lasted for about four days. The increase in the duration of the cosmic ray depression corresponds to a slowing of the CME and the wider region over which it was dispersed at greater distances.

“The comparison of the decrease in galactic cosmic ray influx at three widely separated locations due to the same CME is quite novel,” Witasse said. “While multispacecraft observations of CMEs have been done in the past, it is uncommon for the circumstances to be such to include so many spread across the inner and outer solar system like this.”

“Finally, coming back to our original intended observation of the passage of Comet Siding Spring at Mars, the results show the importance of having a space weather context for understanding how these solar events might influence or even mask the comet’s signature in a planet’s atmosphere,” he said.

Credit: agu.org

Tidally Locked Exoplanets May Be More Common than Previously Thought

Tidally Locked Exoplanets May Be More Common than Previously Thought:

Many exoplanets to be found by coming high-powered telescopes will probably be tidally locked — with one side permanently facing their host star — according to new research by astronomer Rory Barnes of the University of Washington.

Barnes, a UW assistant professor of astronomy and astrobiology, arrived at the finding by questioning the long-held assumption that only those stars that are much smaller and dimmer than the sun could host orbiting planets that were in synchronous orbit, or tidally locked, as the moon is with the Earth. His paper, “Tidal Locking of Habitable Exoplanets,” has been accepted for publication by the journal Celestial Mechanics and Dynamical Astronomy.

Tidal locking results when there is no side-to-side momentum between a body in space and its gravitational partner and they become fixed in their embrace. Tidally locked bodies such as the Earth and moon are in synchronous rotation, meaning that each takes exactly as long to rotate around its own axis as it does to revolve around its host star or gravitational partner. The moon takes 27 days to rotate once on its axis, and 27 days to orbit the Earth once.

The moon is thought to have been created by a Mars-sized celestial body slamming into the young Earth at an angle that set the world spinning initially with approximately 12-hour days.

“The possibility of tidal locking is an old idea, but nobody had ever gone through it systematically,” said Barnes, who is affiliated with the UW-based Virtual Planetary Laboratory.

In the past, he said, researchers tended to use that 12-hour estimation of Earth’s rotation period to model exoplanet behavior, asking, for example, how long an Earthlike exoplanet with a similar orbital spin might take to become tidally locked.

“What I did was say, maybe there are other possibilities — you could have slower or faster initial rotation periods,” Barnes said. “You could have planets larger than Earth, or planets with eccentric orbits — so by exploring that larger parameter space, you find that in fact the old ideas were very limited, there was just one outcome there.”

“Planetary formation models, however, suggest the initial rotation of a planet could be much larger than several hours, perhaps even several weeks,” Barnes said. “And so when you explore that range, what you find is that there’s a possibility for a lot more exoplanets to be tidally locked. For example, if Earth formed with no moon and with an initial ‘day’ that was four days long, one model predicts Earth would be tidally locked to the sun by now.”

Barnes writes: “These results suggest that the process of tidal locking is a major factor in the evolution of most of the potentially habitable exoplanets to be discovered in the near future.”

Being tidally locked was once thought to lead to such extremes of climate as to eliminate any possibility of life, but astronomers have since reasoned that the presence of an atmosphere with winds blowing across a planet’s surface could mitigate these effects and allow for moderate climates and life.

Barnes said he also considered the planets that will likely be discovered by NASA’s next planet-hunting satellite, the Transiting Exoplanet Survey Satellite or TESS, and found that every potentially habitable planet it will detect will likely be tidally locked.

Even if astronomers discover the long-sought Earth “twin” orbiting a virtual twin of the sun, that world may be tidally locked.

“I think the biggest implication going forward,” Barnes said, “is that as we search for life on any exoplanets we need to know if a planet is tidally locked or not.”

The research was funded by a NASA grant through the Virtual Planetary Laboratory.

Credit: washington.edu

Newly Detected House-Sized Asteroid to Pass by Earth on Wednesday

Newly Detected House-Sized Asteroid to Pass by Earth on Wednesday:

A newly discovered house-sized near-Earth object (NEO) is expected to fly by our planet on Wednesday, Aug. 16. The space rock, designated 2017 PD25, will miss the Earth at 3:45 UTC at a safe distance of about 9.6 lunar distances (LD), or 3.7 million kilometers with a relative velocity of 7.87 km/s.

2017 PD25 was discovered Aug. 12 by the Pan-STARRS 1 (PS1) telescope at the summit of Haleakala on the Hawaiian island of Maui. The Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) is an astronomical survey consisting of astronomical cameras, telescopes and a computing facility, surveying the sky for moving objects on a continual basis.

Astronomers reveal that 2017 PD25 has an absolute magnitude of 25.3 and a diameter between 16 and 52 meters. The asteroid has an orbital period of 3.26 years and a semimajor axis of 2.2 AU.

Besides the close approach on Wednesday, no other fly-bys of this asteroid are known at the moment.

There are 1,803 potentially hazardous asteroids (PHAs) discovered to date. PHAs are space rocks larger than approximately 100 meters that can come closer to Earth than 19.5 LD. However, none of the known PHAs is on a collision course with our planet.

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Gamma-ray Burst Captured in Unprecedented Detail

Gamma-ray Burst Captured in Unprecedented Detail:

Gamma-ray bursts are among the most energetic and explosive events in the universe. They are also short-lived, lasting from a few milliseconds to about a minute. This has made it tough for astronomers to observe a gamma-ray burst in detail. Using a wide array of ground- and space-based telescope observations, an international team led by University of Maryland astronomers constructed one of the most detailed descriptions of a gamma-ray burst to date.

The event, named GRB160625B, revealed key details about the initial “prompt” phase of gamma-ray bursts and the evolution of the large jets of matter and energy that form as a result of the burst. The group’s findings are published in the July 27, 2017 issue of the journal Nature.

“Gamma-ray bursts are catastrophic events, related to the explosion of massive stars 50 times the size of our sun. If you ranked all the explosions in the universe based on their power, gamma-ray bursts would be right behind the Big Bang,” said Eleonora Troja, an assistant research scientist in the UMD Department of Astronomy and lead author of the research paper. “In a matter of seconds, the process can emit as much energy as a star the size of our sun would in its entire lifetime. We are very interested to learn how this is possible.”

The group’s observations provide the first answers to some long-standing questions about how a gamma-ray burst evolves as the dying star collapses to become a black hole. First, the data suggest that the black hole produces a strong magnetic field that initially dominates the energy emission jets. Then, as the magnetic field breaks down, matter takes over and begins to dominate the jets. Most gamma-ray burst researchers thought that the jets were dominated by either matter or the magnetic field, but not both. The current results suggest that both factors play key roles.

“There has been a dichotomy in the community. We find evidence for both models, suggesting that gamma-ray burst jets have a dual, hybrid nature,” said Troja, who is also a visiting research scientist at NASA’s Goddard Space Flight Center. “The jets start off magnetic, but as the jets grow, the magnetic field degrades and loses dominance. Matter takes over and dominates the jets, although sometimes a weaker vestige of the magnetic field might survive.”

The data also suggest that synchrotron radiation—which results when electrons are accelerated in a curved or spiral pathway—powers the initial, extremely bright phase of the burst, known as the “prompt” phase. 

“Synchrotron radiation is the only emission mechanism that can create the same degree of polarization and the same spectrum we observed early in the burst,” Troja said. “Our study provides convincing evidence that the prompt gamma-ray burst emission is driven by synchrotron radiation. This is an important achievement because, despite decades of investigation, the physical mechanism that drives gamma-ray bursts had not yet been unambiguously identified.”

Comprehensive coverage of GRB160625B from a wide variety of telescopes that gathered data in multiple spectra made these conclusions possible, the researchers said.

“Gamma-ray bursts occur at cosmological distances, with some dating back to the birth of the universe,” said Alexander Kutyrev, an associate research scientist in the UMD Department of Astronomy and a co-author of the research paper. “The events are unpredictable and once the burst occurs, it’s gone. We are very fortunate to have observations from a wide variety of sources, especially during the prompt phase, which is very difficult to capture.” 

NASA’s Fermi Gamma-ray Space Telescope first detected the gamma-ray emission from GRB160625B. Soon afterward, the ground-based MASTER-IAC telescope, a part of Russia’s MASTER robotic telescope network located at the Teide Observatory in Spain’s Canary Islands, followed up with optical light observations while the prompt phase was still active. 

MASTER-IAC gathered critical data on the proportion of polarized optical light relative to the total light produced by the prompt phase,, providing the crucial link between synchrotron radiation and the prompt phase of this gamma-ray burst. 

A magnetic field can also influence how much polarized light is emitted as time passes and the burst evolves. Because the researchers were able to analyze polarization data that spanned nearly the entire timeframe of the burst—a rare achievement—they were able to discern the presence of a magnetic field and track how it changed as GRB160625B progressed.

“There is very little data on polarized emission from gamma-ray bursts,” said Kutyrev, who is also an associate scientist at NASA’s Goddard Space Flight Center. “This burst was unique because we caught the polarization state at an early stage. This is hard to do because it requires a very fast reaction time and there are relatively few telescopes with this capability. This paper shows how much can be done, but to get results like this consistently, we will need new rapid-response facilities for observing gamma-ray bursts.”

In addition to the gamma-ray and optical light observations, NASA’s Swift Gamma-ray Burst Mission spacecraft captured X-ray and ultraviolet data. The Reionization and Transient InfraRed/Optical Project camera—a collaboration between NASA, the University of California system and the National Autonomous University of Mexico installed at Mexico’s Observatorio Astrónomico Nacional in Baja California—captured infrared data. 

The group also gathered radio observations from Commonwealth Scientific and Industrial Research Organisation’s Australia Telescope Compact Array, located north of Sydney in rural New South Wales, and the National Radio Astronomy Observatory’s Very Large Array outside of Socorro, New Mexico.

In addition to Troja and Kutyrev, UMD co-authors of this paper include Adjunct Assistant Professor Brad Cenko and Astronomy Graduate Student Vicki Toy.

Credit: umdrightnow.umd.edu

Galactic David and Goliath

Galactic David and Goliath:

The gravitational dance between two galaxies in our local neighborhood has led to intriguing visual features in both as witnessed in this new NASA/ESA Hubble Space Telescope image. The tiny NGC 1510 and its colossal neighbor NGC 1512 are at the beginning of a lengthy merger, a crucial process in galaxy evolution. Despite its diminutive size, NGC 1510 has had a significant effect on NGC 1512’s structure and amount of star formation.

Galaxies come in a range of shapes and sizes, and astronomers use this fact to classify them based on their appearance. NGC 1512, the large galaxy to the left in this image, is classified as a barred spiral, named after the bar composed of stars, gas and dust slicing through its center. The tiny NGC 1510 to the right, on the other hand, is a dwarf galaxy. Despite their very different sizes, each galaxy affects the other through gravity, causing slow changes in their appearances.

The bar in NGC 1512 acts as a cosmic funnel, channeling the raw materials required for star formation from the outer ring into the heart of the galaxy. This pipeline of gas and dust in NGC 1512 fuels intense star birth in the bright, blue, shimmering inner disc known as a circumnuclear starburst ring, which spans 2400 light-years.

Both the bar and the starburst ring are thought to be at least in part the result of the cosmic scuffle between the two galaxies — a merger that has been going on for 400 million years.

NGC 1512, which has been observed by Hubble in the past, is also home to a second, more serene, star-forming region in its outer ring. This ring is dotted with dozens of HII regions, where large swathes of hydrogen gas are subject to intense radiation from nearby, newly formed stars. This radiation causes the gas to glow and creates the bright knots of light seen throughout the ring.

Remarkably, NGC 1512 extends even further than we can see in this image — beyond the outer ring — displaying malformed, tendril-like spiral arms enveloping NGC 1510. These huge arms are thought to be warped by strong gravitational interactions with NGC 1510 and the accretion of material from it. But these interactions are not just affecting NGC 1512; they have also taken their toll on the smaller of the pair.

The constant tidal tugging from its neighbor has swirled up the gas and dust in NGC 1510 and kick-started star formation that is even more intense than in NGC 1512. This causes the galaxy to glow with the blue hue that is indicative of hot new stars.

NGC 1510 is not the only galaxy to have experienced the massive gravitational tidal forces of NGC 1512. Observations made in 2015 showed that the outer regions of the spiral arms of NGC 1512 were indeed once part of a separate, older galaxy. This galaxy was ripped apart and absorbed by NGC 1512, just as it is doing now to NGC 1510.

Together, the pair demonstrate how interactions between galaxies, even if they are of very different sizes, can have a significant influence on their structures, changing the dynamics of their constituent gas and dust and even triggering starbursts. Such interactions between galaxies, and galaxy mergers in particular, play a key role in galactic evolution.

Credit: spacetelescope.org

A Tale of Three Stellar Cities

A Tale of Three Stellar Cities:

Using new observations from ESO’s VLT Survey Telescope, astronomers have discovered three different populations of young stars within the Orion Nebula Cluster. This unexpected discovery adds very valuable new insights for the understanding of how such clusters form. It suggests that star formation might proceed in bursts, where each burst occurs on a much faster time-scale than previously thought.

OmegaCAM — the wide-field optical camera on ESO’s VLT Survey Telescope (VST) — has captured the spectacular Orion Nebula and its associated cluster of young stars in great detail, producing a beautiful new image. This object is one of the closest stellar nurseries for both low and high-mass stars, at a distance of about 1350 light-years.

But this is more than just a pretty picture. A team led by ESO astronomer Giacomo Beccari has used these data of unparallelled quality to precisely measure the brightness and colors of all the stars in the Orion Nebula Cluster. These measurements allowed the astronomers to determine the mass and ages of the stars. To their surprise, the data revealed three different sequences of potentially different ages.

“Looking at the data for the first time was one of those ‘Wow!’ moments that happen only once or twice in an astronomer's lifetime,” says Beccari, lead ­author of the paper presenting the results. “The incredible quality of the OmegaCAM images revealed without any doubt that we were seeing three distinct populations of stars in the central parts of Orion.”

Monika Petr-Gotzens, co-author and also based at ESO Garching, continues, “This is an important result. What we are witnessing is that the stars of a cluster at the beginning of their lives didn’t form altogether simultaneously. This may mean that our understanding of how stars form in clusters needs to be modified.”

The astronomers looked carefully at the possibility that instead of indicating different ages, the different brightnesses and colors of some of the stars were due to hidden companion stars, which would make the stars appear brighter and redder than they really were. But this idea would imply quite unusual properties of the pairs, which have never before been observed. Other measurements of the stars, such as their rotation speeds and spectra, also indicated that they must have different ages.

“Although we cannot yet formally disprove the possibility that these stars are binaries, it seems much more natural to accept that what we see are three generations of stars that formed in succession, within less than three million years,” concludes Beccari.

The new results strongly suggest that star formation in the Orion Nebula Cluster is proceeding in bursts, and more quickly than had been previously thought.

Credit: ESO

Upcoming Asteroid Flyby Will Help NASA Planetary Defense Network

Upcoming Asteroid Flyby Will Help NASA Planetary Defense Network:

For the first time, NASA will use an actual space rock for an observational campaign to test NASA's network of observatories and scientists who work with planetary defense. The asteroid, named 2012 TC4, does not pose a threat to the Earth, but NASA is using it as a test object for an observational campaign because of its close flyby on Oct. 12, 2017.

NASA has conducted such preparedness drills rehearsing various aspects of an asteroid impact, such as deflection, evacuation and disaster relief, with other entities in the past. Traditionally, however, these exercises involved hypothetical impactors, prompting Vishnu Reddy of the University of Arizona's Lunar and Planetary Laboratory to propose a slightly more realistic scenario, one that revolves around an actual close approach of a near-Earth asteroid, or NEA. 

"The question is: How prepared are we for the next cosmic threat?" said Reddy, an assistant professor of planetary science at the Lunar and Planetary Laboratory. "So we proposed an observational campaign to exercise the network and test how ready we are for a potential impact by a hazardous asteroid."

NASA's Planetary Defense Coordination Office, or PDCO, the federal entity in charge of coordinating efforts to protect Earth from hazardous asteroids, accepted Reddy's idea to conduct an observational campaign as part of assessing its Earth-based defense network and identified the upcoming close approach of 2012 TC4 as a good opportunity to conduct the exercise. Reddy will assist Michael Kelley, who serves as a program scientist with NASA PDCO and as the lead on the exercise. 

The goal of the TC4 exercise is to recover, track and characterize 2012 TC4 as a potential impactor in order to exercise the entire system from observations, modeling, prediction and communication. 

Measuring between 30 and 100 feet, roughly the same size as the asteroid that exploded over Chelyabinsk, Russia, on Feb. 15, 2013, TC4 was discovered by the Pan-STARRS 1 telescope on Oct. 5, 2012, at Haleakala Observatory on Maui, Hawaii. Given its orbital uncertainty, the asteroid will pass as close as 6,800 kilometers (4,200 miles) above the Earth’s surface.

"This is a team effort that involves more than a dozen observatories, universities and labs across the globe so we can collectively learn the strengths and limitations of our planetary defense capabilities," said Reddy, who is coordinating the campaign for NASA PDCO. 

Since its discovery in 2012, the uncertainty in the asteroid's orbit has slowly increased, as it would for any asteroid as time passes. Therefore, the first order of business will be to "recover" the object — in other words, nail down its exact path. Reddy and his collaborators hope that depending on its predicted brightness, the asteroid would be visible again to large ground-based telescopes in early August. 

"One of the strengths of UA research is partnering with federal agencies or industry to work together in solving some of the grand challenges we face," said Kimberly Andrews Espy, the UA's senior vice president for research. "This project is a perfect example of matching UA capabilities — from our world-class imaging to our expertise in space sciences — with an external need."

The UA is home to the Catalina Sky Survey, one of the most prolific asteroid discoverers, and the Spacewatch project that recovers and tracks faint NEAs. Both teams will take part in the planetary defense exercise.

Credit: arizona.edu

Possible First Exomoon Detected

Possible First Exomoon Detected:

A signal has been spotted that might be the first moon detected outside our solar system, and researchers are gearing up to use the Hubble Space Telescope to confirm it. David Kipping at Columbia University in New York and his colleagues have been using the Kepler Space Telescope to search for moons around other worlds for years, but they haven’t found any yet. “We’ve had candidates in the past and investigated them, and most of them have evaporated,” said Kipping.

The candidate moon is known as Kepler-1625 b I and is observed around a star that lies some 4,000 light-years from Earth. On account of its large size, team members have dubbed it a "Nept-moon".

Kepler-1625 b is a candidate planet that Kepler, NASA’s flagship exoplanet mission, had previously observed. Periodic dips in the host star’s brightness indicated that a massive object was crossing the line of sight from the star to Earth; but the dips were lopsided, suggesting that perhaps instead of one object there were two: a Jupiter-sized planet with a Neptune-sized moon in tow. If this were indeed an ‘exomoon’, it would have been a long-awaited discovery. But it was still a big if.

“It wasn’t something we were planning on announcing, because at this point it’s only a candidate,” said Kipping, who would have preferred to be more cautious with the news. “It really only takes the slightest misstep in our language to miscommunicate the reality of what we have.”

If Kipping and his team are able to verify this detection, as well as being the first exomoon we’ve ever seen, it would be a much larger moon than we’ve ever seen before. This indicates that there may be even more types of moon than the many we’ve already observed.

“It would be analogous to the first exoplanet detections, which defied our prejudices from the solar system as well,” says Duncan Forgan at the University of St Andrews in the UK.

A paper about the candidate moon is published on the arXiv pre-print site.

Credit: newscientist.com, nature.com

Astrophysicists Map Out the Light Energy Contained Within the Milky Way

Astrophysicists Map Out the Light Energy Contained Within the Milky Way:

For the first time, a team of scientists have calculated the distribution of all light energy contained within the Milky Way, which will provide new insight into the make-up of our galaxy and how stars in spiral galaxies such as ours form. The study is published in the journal Monthly Notices of the Royal Astronomical Society.

This research, conducted by astrophysicists at the University of Central Lancashire (UCLan), in collaboration with colleagues from the Max Planck Institute for Nuclear Physics in Heidelberg, Germany and from the Astronomical Institute of the Romanian Academy, also shows how the stellar photons, or stellar light, within the Milky Way control the production of the highest energy photons in the Universe, the gamma-rays. This was made possible using a novel method involving computer calculations that track the destiny of all photons in the galaxy, including the photons that are emitted by interstellar dust, as heat radiation.

Previous attempts to derive the distribution of all light in the Milky Way based on star counts have failed to account for the all-sky images of the Milky Way, including recent images provided by the European Space Agency's Planck Space Observatory, which map out heat radiation or infrared light.

Lead author Prof Cristina Popescu from the University of Central Lancashire, said: "We have not only determined the distribution of light energy in the Milky Way, but also made predictions for the stellar and interstellar dust content of the Milky Way.”

By tracking all stellar photons and making predictions for how the Milky Way should appear in ultraviolet, visual and heat radiation, scientists have been able to calculate a complete picture of how stellar light is distributed throughout our Galaxy. An understanding of these processes is a crucial step towards gaining a complete picture of our Galaxy and its history.

The modelling of the distribution of light in the Milky Way follows on from previous research that Prof Popescu and Dr Richard Tuffs from the Max Planck Institute for Nuclear Physics conducted on modelling the stellar light from other galaxies, where the observer has an outside view.

Commenting on the research, Dr Tuffs, one of the co-authors of the paper, said: “It has to be noted that looking at galaxies from outside is a much easier task than looking from inside, as in the case of our Galaxy.”

Scientists have also been able to show how the stellar light within our Galaxy affects the production of gamma-ray photons through interactions with cosmic rays. Cosmic rays are high-energy electrons and protons that control star and planet formation and the processes governing galactic evolution. They promote chemical reactions in interstellar space, leading to the formation of complex and ultimately life-critical molecules.

Dr Tuffs added: "Working backwards through the chain of interactions and propagations, one can work out the original source of the cosmic rays."

The research, funded by the Leverhulme Trust, was strongly interdisciplinary, bringing together optical and infrared astrophysics and astro-particle physics. Prof Popescu notes: “We had developed some of our computational programs before this research started, in the context of modelling spiral galaxies, and we need to thank the UK's Science and Technology Facility Council (STFC) for their support in the development of these codes. This research would also not have been possible without the support of the Leverhulme Trust, which is greatly acknowledged.”

Credit: ras.org.uk

Asteroid 2017 NB7 to Fly By Earth on August 6

Asteroid 2017 NB7 to Fly By Earth on August 6:

A newly discovered Amor-type asteroid, designated 2017 NB7 is slated to pass by Earth on Sunday, Aug. 6 at a safe distance of 6.8 lunar distances (LD), or 2.6 million kilometers. The near-Earth object (NEO) will fly by our planet at approximately 10:43 UTC with a relative velocity of 5.98 km/s.

2017 NB7 was detected on July 1, 2017 by the Mount Lemmon Survey (MLS), which uses a 1.52 m cassegrain reflector telescope at Mount Lemmon Observatory in Arizona. MLS is one of the most prolific surveys when it comes to discovering new NEOs. It has detected more than 50,000 minor planets to date.

Astronomers reveal that 2017 NB7 has a diameter between 36 and 110 meters, and an absolute magnitude of 23.6. The asteroid has a semimajor axis of approximately 1.6 AU and orbits the sun every two years.

Besides 2017 NB7, one more space rock is expected to give fly by Earth on Aug. 6. The asteroid 2017 OJ7, which is 41-130 meters in diameter, will miss our planet at a much larger distance of nearly 30 LD (11.5 million kilometers).

Currently, there are 1,803 Potentially Hazardous Asteroids (PHAs) detected, however none of them is on a collision course with our planet. PHAs are asteroids larger than 100 meters that can come closer to Earth than 19.5 LD.

Astronomers Discover ‘Heavy Metal’ Supernova Rocking Out

Astronomers Discover ‘Heavy Metal’ Supernova Rocking Out:

Many rock stars don’t like to play by the rules, and a cosmic one is no exception. A team of astronomers has discovered that an extraordinarily bright supernova occurred in a surprising location. This “heavy metal” supernova discovery challenges current ideas of how and where such super-charged supernovas occur.

Supernovas are some of the most energetic events in the Universe. When a massive star runs out of fuel, it can collapse onto itself and create a spectacular explosion that briefly outshines an entire galaxy, dispersing vital elements into space.

In the past decade, astronomers have discovered about fifty supernovas, out of the thousands known, that are particularly powerful. These explosions are up to 100 times brighter than other supernovas caused by the collapse of a massive star.

Following the recent discovery of one of these “superluminous supernovas”, a team of astronomers led by Matt Nicholl from the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., has uncovered vital clues about where some of these extraordinary objects come from.

Cambridge University’s Gaia Science Alerts team discovered this supernova, dubbed SN 2017egm, on May 23, 2017 with the European Space Agency’s Gaia satellite. A team led by Subo Dong of the Kavli Institute for Astronomy and Astrophysics at Peking University used the Nordic Optical Telescope to identify it as a superluminous supernova.

SN 2017egm is located in a spiral galaxy about 420 million light years from Earth, making it about three times closer than any other superluminous supernova previously seen. Dong realized that the galaxy was very surprising, as virtually all known superluminous supernovas have been found in dwarf galaxies that are much smaller than spiral galaxies like the Milky Way.

Building on this discovery, the CfA team found that SN 2017egm’s host galaxy has a high concentration of elements heavier than hydrogen and helium, which astronomers call “metals”. This is the first clear evidence for a metal-rich birthplace for a superluminous supernova. The dwarf galaxies that usually host superluminous supernovas are known to have a low metal content, which was thought to be an essential ingredient for making these explosions.

“Superluminous supernovas were already the rock stars of the supernova world,” said Nicholl. “We now know that some of them like heavy metal, so to speak, and explode in galaxies like our own Milky Way.”

“If one of these went off in our own Galaxy, it would be much brighter than any supernova in recorded human history and would be as bright as the full Moon,” said co-author Edo Berger, also of the CfA. “However, they’re so rare that we probably have to wait several million years to see one.”

The CfA researchers also found more clues about the nature of SN 2017egm. In particular, their new study supports the idea that a rapidly spinning, highly magnetized neutron star, called a magnetar, is likely the engine that drives the incredible amount of light generated by these supernovas.

While the brightness of SN 2017egm and the properties of the magnetar that powers it overlap with those of other superluminous supernovas, the amount of mass ejected by SN 2017egm may be lower than the average event. This difference may indicate that the massive star that led to SN 2017egm lost more mass than most superluminous supernova progenitors before exploding. The spin rate of the magnetar may also be slower than average.

These results show that the amount of metals has at most only a small effect on the properties of a superluminous supernova and the engine driving it. However, the metal-rich variety occurs at only about 10% of the rate of the metal-poor ones. Similar results have been found for bursts of gamma rays associated with the explosion of massive stars. This suggests a close association between these two types of objects.

From July 4th, 2017 until September 16th, 2017 the supernova is not observable because it is too close to the Sun. After that, detailed studies should be possible for at least a few more years.

“This should break all records for how long a superluminous supernova can be followed”, said co-author Raffaella Margutti of Northwestern University in Evanston, Illinois. “I’m excited to see what other surprises this object has in store for us.”

The CfA team observed SN 2017egm on June 18th with the 60-inch telescope at the Smithsonian Astrophysical Observatory’s Fred Lawrence Whipple Observatory in Arizona.

A paper by Matt Nicholl describing these results was recently accepted for publication in The Astrophysical Journal Letters, and is available online. In addition to Berger and Margutti, the co-authors of the paper are Peter Blanchard, James Guillochon, and Joel Leja, all of the CfA, and Ryan Chornock of Ohio University in Athens, Ohio.

A copy of the paper is available online.

Credit: cfa.harvard.edu

Gravity Waves Detected in Sun's Interior Reveal Rapidly Rotating Core

Gravity Waves Detected in Sun's Interior Reveal Rapidly Rotating Core:

Scientists using the ESA/NASA SOHO solar observatory have found long-sought gravity modes of seismic vibration that imply the Sun’s core is rotating four times faster than its surface. Just as seismology reveals Earth’s interior structure by the way in which waves generated by earthquakes travel through it, solar physicists use ‘helioseismology’ to probe the solar interior by studying sound waves reverberating through it. On Earth, it is usually one event that is responsible for generating the seismic waves at a given time, but the Sun is continuously ‘ringing’ owing to the convective motions inside the giant gaseous body.

Higher frequency waves, known as pressure waves (or p-waves), are easily detected as surface oscillations owing to sound waves rumbling through the upper layers of the Sun. They pass very quickly through deeper layers and are therefore not sensitive to the Sun’s core rotation.

Conversely, lower frequency gravity waves (g-waves) that represent oscillations of the deep solar interior have no clear signature at the surface, and thus present a challenge to detect directly.

In contrast to p-waves, for which pressure is the restoring force, buoyancy (gravity) acts as the restoring force of the gravity waves.

“The solar oscillations studied so far are all sound waves, but there should also be gravity waves in the Sun, with up-and-down, as well as horizontal motions like waves in the sea,” says Eric Fossat, lead author of the paper describing the result, published in Astronomy & Astrophysics.

“We’ve been searching for these elusive g-waves in our Sun for over 40 years, and although earlier attempts have hinted at detections, none were definitive. Finally, we have discovered how to unambiguously extract their signature.”

Eric and his colleagues used 16.5 years of data collected by SOHO’s dedicated ‘Global Oscillations at Low Frequencies’ (GOLF) instrument. By applying various analytical and statistical techniques, a regular imprint of the g-modes on the p-modes was revealed.

In particular, they looked at a p-mode parameter that measures how long it takes for an acoustic wave to travel through the Sun and back to the surface again, which is known to be 4 hours 7 minutes. A series of modulations was detected in this p-mode parameter that could be interpreted as being due to the g-waves shaking the structure of the core.

The signature of the imprinted g-waves suggests the core is rotating once every week, nearly four times faster than the observed surface and intermediate layers, which vary from 25 days at the equator to 35 days at the poles.

“G-modes have been detected in other stars, and now thanks to SOHO we have finally found convincing proof of them in our own star,” adds Eric. “It is really special to see into the core of our own Sun to get a first indirect measurement of its rotation speed. But, even though this decades long search is over, a new window of solar physics now begins.”

The rapid rotation has various implications, for example: is there any evidence for a shear zone between the differently rotating layers? What do the periods of the g-waves tell us about the chemical composition of the core? What implication does this have on stellar evolution and the thermonuclear processes in the core?

“Although the result raises many new questions, making an unambiguous detection of gravity waves in the solar core was the key aim of GOLF. It is certainly the biggest result of SOHO in the last decade, and one of SOHO’s all-time top discoveries,” says Bernhard Fleck, ESA’s SOHO project scientist.

ESA’s upcoming solar mission, Solar Orbiter will also ‘look’ into the solar interior but its main focus is to provide detailed insights into the Sun’s polar regions, and solar activity. Meanwhile ESA’s future planet-hunting mission, Plato, will investigate seismic activity in stars in the exoplanet systems it discovers, adding to our knowledge of relevant processes in Sun-like stars.

Credit: ESA

NASA Continues to Study Pulsars, 50 Years After Their Chance Discovery

NASA Continues to Study Pulsars, 50 Years After Their Chance Discovery:

A little bit of “scruff” in scientific data 50 years ago led to the discovery of pulsars – rapidly spinning dense stellar corpses that appear to pulse at Earth. Astronomer Jocelyn Bell made the chance discovery using a vast radio telescope in Cambridge, England. Although it was built to measure the random brightness flickers of a different category of celestial objects called quasars, the 4.5-acre telescope produced unexpected markings on Bell’s paper data recorder every 1.33730 seconds. The pen traces representing radio brightness revealed an unusual phenomenon.

“The pulses were so regular, so much like a ticking clock, that Bell and her supervisor Anthony Hewish couldn’t believe it was a natural phenomenon,” said Zaven Arzoumanian of NASA's Goddard Space Flight Center in Greenbelt, Maryland. “Once they found a second, third and fourth they started to think differently.”

The unusual stellar objects had been previously predicted but never observed. Today, scientists know of over 2,000 pulsars. These rotating “lighthouse” neutron stars begin their lives as stars between about seven and 20 times the mass of our sun. Some are found to spin hundreds of times per second, faster than the blades of a household blender, and they possess enormously strong magnetic fields.

Technology advances in the past half-century allowed scientists to study these compact stellar objects from space using different wavelengths of light, especially those much more energetic than the radio waves received by the Cambridge telescope. Several current NASA missions continue to study these natural beacons.

The Neutron star Interior Composition Explorer, or NICER, is the first NASA mission dedicated to studying pulsars. In a nod to the anniversary of Bell’s discovery, NICER observed the famous first pulsar, known today as PSR B1919+21.

NICER launched to the International Space Station in early June and started science operations last month. Its X-ray observations – the part of the electromagnetic spectrum in which these stars radiate both from their million-degree solid surfaces and from their strong magnetic fields – will reveal how nature’s fundamental forces behave within the cores of these objects, an environment that doesn’t exist and can’t be reproduced anywhere else. "What's inside a pulsar?" is one of many long-standing astrophysics questions about these ultra-dense, fast-spinning, powerfully magnetic objects.

The “stuff” of pulsars is a collection of particles familiar to scientists from over a century of laboratory studies on Earth – neutrons, protons, electrons, and perhaps even their own constituents, called quarks. However, under such extreme conditions of pressure and density, their behavior and interactions aren’t well understood. New, precise measurements, especially of the sizes and masses of pulsars are needed to pin down theories.

“Many nuclear-physics models have been developed to explain how the make-up of neutron stars, based on available data and the constraints they provide,” said Goddard’s Keith Gendreau, the principal investigator for NICER. “NICER’s sensitivity, X-ray energy resolution and time resolution will improve these by more precisely measuring their radii, to an order of magnitude improvement over the state of the art today.”

The mission will also pave the way for future space exploration by helping to develop a Global Positioning System-like capability for the galaxy. The embedded Station Explorer for X-ray Timing and Navigation Technology, or SEXTANT, demonstration will use NICER’s X-ray observations of pulsar signals to determine NICER's exact position in orbit.

“You can time the pulsations of pulsars distributed in many directions around a spacecraft to figure out where the vehicle is and navigate it anywhere,” said Arzoumanian, who is also the NICER science lead. “That’s exactly how the GPS system on Earth works, with precise clocks flown on satellites in orbit.”

Scientists have tested this method using computer and lab simulations. SEXTANT will demonstrate pulsar-based navigation for the first time in space.

NICER-SEXTANT is the first astrophysics mission dedicated to studying pulsars, 50 years after their discovery. “I think it is going to yield many more scientific discoveries than we can anticipate now,” said Gendreau.

NICER-SEXTANT is a two-in-one mission. NICER is an Astrophysics Mission of Opportunity within NASA's Explorer program, which provides frequent flight opportunities for world-class scientific investigations from space utilizing innovative, streamlined, and efficient management approaches within the heliophysics and astrophysics science areas. NASA's Space Technology Mission Directorate supports the SEXTANT component of the mission, demonstrating pulsar-based spacecraft navigation.

Credit: NASA

Cutting-edge Adaptive Optics Facility Sees First Light

Cutting-edge Adaptive Optics Facility Sees First Light:

The Unit Telescope 4 (Yepun) of ESO’s Very Large Telescope (VLT) has now been transformed into a fully adaptive telescope. After more than a decade of planning, construction and testing, the new Adaptive Optics Facility (AOF) has seen first light with the instrument MUSE, capturing amazingly sharp views of planetary nebulae and galaxies. The coupling of the AOF and MUSE forms one of the most advanced and powerful technological systems ever built for ground-based astronomy.

The Adaptive Optics Facility (AOF) is a long-term project on ESO’s Very Large Telescope (VLT) to provide an adaptive optics system for the instruments on Unit Telescope 4 (UT4), the first of which is MUSE (the Multi Unit Spectroscopic Explorer). Adaptive optics works to compensate for the blurring effect of the Earth’s atmosphere, enabling MUSE to obtain much sharper images and resulting in twice the contrast previously achievable. MUSE can now study even fainter objects in the Universe.

“Now, even when the weather conditions are not perfect, astronomers can still get superb image quality thanks to the AOF,” explains Harald Kuntschner, AOF Project Scientist at ESO.

Following a battery of tests on the new system, the team of astronomers and engineers were rewarded with a series of spectacular images. Astronomers were able to observe the planetary nebulae IC 4406, located in the constellation Lupus (The Wolf), and NGC 6369, located in the constellation Ophiuchus (The Serpent Bearer). The MUSE observations using the AOF showed dramatic improvements in the sharpness of the images, revealing never before seen shell structures in IC 4406.

The AOF, which made these observations possible, is composed of many parts working together. They include the Four Laser Guide Star Facility (4LGSF) and the very thin deformable secondary mirror of UT4. The 4LGSF shines four 22-watt laser beams into the sky to make sodium atoms in the upper atmosphere glow, producing spots of light on the sky that mimic stars. Sensors in the adaptive optics module GALACSI (Ground Atmospheric Layer Adaptive Corrector for Spectroscopic Imaging) use these artificial guide stars to determine the atmospheric conditions.

One thousand times per second, the AOF system calculates the correction that must be applied to change the shape of the telescope’s deformable secondary mirror to compensate for atmospheric disturbances. In particular, GALACSI corrects for the turbulence in the layer of atmosphere up to one kilometer above the telescope. Depending on the conditions, atmospheric turbulence can vary with altitude, but studies have shown that the majority of atmospheric disturbance occurs in this “ground layer” of the atmosphere.

“The AOF system is essentially equivalent to raising the VLT about 900 meters higher in the air, above the most turbulent layer of atmosphere,” explains Robin Arsenault, AOF Project Manager. “In the past, if we wanted sharper images, we would have had to find a better site or use a space telescope — but now with the AOF, we can create much better conditions right where we are, for a fraction of the cost!”

The corrections applied by the AOF rapidly and continuously improve the image quality by concentrating the light to form sharper images, allowing MUSE to resolve finer details and detect fainter stars than previously possible. GALACSI currently provides a correction over a wide field of view, but this is only the first step in bringing adaptive optics to MUSE. A second mode of GALACSI is in preparation and is expected to see first light early 2018. This narrow-field mode will correct for turbulence at any altitude, allowing observations of smaller fields of view to be made with even higher resolution.

“Sixteen years ago, when we proposed building the revolutionary MUSE instrument, our vision was to couple it with another very advanced system, the AOF,” says Roland Bacon, project lead for MUSE. “The discovery potential of MUSE, already large, is now enhanced still further. Our dream is becoming true.”

One of the main science goals of the system is to observe faint objects in the distant Universe with the best possible image quality, which will require exposures of many hours. Joël Vernet, ESO MUSE and GALACSI Project Scientist, comments: “In particular, we are interested in observing the smallest, faintest galaxies at the largest distances. These are galaxies in the making — still in their infancy — and are key to understanding how galaxies form.”

Furthermore, MUSE is not the only instrument that will benefit from the AOF. In the near future, another adaptive optics system called GRAAL will come online with the existing infrared instrument HAWK-I, sharpening its view of the Universe. That will be followed later by the powerful new instrument ERIS.

“ESO is driving the development of these adaptive optics systems, and the AOF is also a pathfinder for ESO’s Extremely Large Telescope,” adds Arsenault. “Working on the AOF has equipped us — scientists, engineers and industry alike — with invaluable experience and expertise that we will now use to overcome the challenges of building the ELT.”

Credit: ESO