Astro Watch

ron Vapor Gives Clues to Formation of Earth and Moon Posted: 02 Mar 2015 03:30 PM PST Recreating the violent conditions of Earth's formation, scientists are learning more about how iron vaporizes and how this iron rain affected the formation of the Earth and Moon. Scientists from Lawrence Livermore National Laboratory, Sandia National Laboratory, Harvard University and UC Davis used one of the world's most powerful radiation sources, the Sandia National Laboratories Z-machine, to recreate conditions that led to Earth's formation. They subjected iron samples to high shock pressures in the machine, slamming aluminum plates into iron samples at extremely high speeds. They developed a new shock-wave technique to determine the critical impact conditions needed to vaporize the iron. "We care about when iron vaporizes because it is critical to learning how Earth's core grew," said co-author Sarah Stewart, UC Davis professor of Earth and Planetary Sciences. The study is published March 2 in Nature Geoscience. The researchers found that the shock pressure required to vaporize iron is much lower than expected, which means more iron was vaporized during Earth's formation than previously thought. Lead author Richard Kraus, formerly a graduate student under Stewart at Harvard, is now a research scientist at Lawrence Livermore National Laboratory. He said the results may shift how planetary scientists think about the processes and timing of Earth's core formation. "Rather than the iron in the colliding objects sinking down directly to the Earth's growing core, the iron is vaporized and spread over the surface within a vapor plume," said Kraus. "This means that the iron can mix much more easily with Earth's mantle." After cooling, the vapor would have condensed into an iron rain that mixed into the Earth's still-molten mantle. This process may also explain why the Moon, which is thought to have formed by this time, lacks iron-rich material despite being exposed to similarly violent collisions. The authors suggest the Moon's reduced gravity could have prevented it from retaining most of the vaporized iron. This artist’s illustration shows a planetary scale impact on the Moon. Illustration by W.K. Hartmann “One major problem is how we model iron during impact events, as it is a major component of planets and its behavior is critical to how we understand planet formation,” Kraus said. “In particular, it is the fraction of that iron that is vaporized on impact that is not well understood.” The work was conducted under the Sandia Z Fundamental Science Program and supported by the Department of Energy National Nuclear Security Administration. Credit: eurekalert.org, llnl.gov

ALMA and VLT Probe Surprisingly Dusty and Evolved Galaxy Posted: 02 Mar 2015 01:43 PM PST One of the most distant galaxies ever observed has provided astronomers with the first detection of dust in such a remote star-forming system and tantalising evidence for the rapid evolution of galaxies after the Big Bang. The new observations have used ALMA to pick up the faint glow from cold dust in the galaxy A1689-zD1 and used ESO’s Very Large Telescope to measure its distance. A team of astronomers, led by Darach Watson from the University of Copenhagen, used the Very Large Telescope’s X-shooter instrument along with the Atacama Large Millimeter/submillimeter Array (ALMA) to observe one of the youngest and most remote galaxies ever found. They were surprised to discover a far more evolved system than expected. It had a fraction of dust similar to a very mature galaxy, such as the Milky Way. Such dust is vital to life, because it helps form planets, complex molecules and normal stars. The target of their observations is called A1689-zD1. It is observable only by virtue of its brightness being amplified more than nine times by a gravitational lens in the form of the spectacular galaxy cluster, Abell 1689, which lies between the young galaxy and the Earth. Without the gravitational boost, the glow from this very faint galaxy would have been too weak to detect. We are seeing A1689-zD1 when the Universe was only about 700 million years old — five percent of its present age. It is a relatively modest system — much less massive and luminous than many other objects that have been studied before at this stage in the early Universe and hence a more typical example of a galaxy at that time. A1689-zD1 is being observed as it was during the period of reionisation, when the earliest stars brought with them a cosmic dawn, illuminating for the first time an immense and transparent Universe and ending the extended stagnation of the Dark Ages. Expected to look like a newly formed system, the galaxy surprised the observers with its rich chemical complexity and abundance of interstellar dust. “After confirming the galaxy’s distance using the VLT,” said Darach Watson, “we realised it had previously been observed with ALMA. We didn’t expect to find much, but I can tell you we were all quite excited when we realised that not only had ALMA observed it, but that there was a clear detection. One of the main goals of the ALMA Observatory was to find galaxies in the early Universe from their cold gas and dust emissions — and here we had it!” This view includes infrared light images from the WFC3 instrument on the NASA/ESA Hubble Space Telescope as well as visible light views. It shows a close up look at part of the rich galaxy cluster Abell 1689. The huge concentration of mass bends light coming from more distant objects and can increase their total apparent brightness and make them visible. One such object, A1689-zD1, appears on this picture as the elongated reddish object in the box. New observations with ALMA and ESO’s VLT have revealed that A1689-zD1 is a dusty galaxy seen when the Universe was just 700 million years old. Its light has been magnified by a factor of more than nine by the massive gravitational lensing effect of the cluster. Credit: ESO/J. Richard This galaxy was a cosmic infant — but it proved to be precocious. At this age it would be expected to display a lack of heavier chemical elements — anything heavier than hydrogen and helium, defined in astronomy as metals. These are produced in the bellies of stars and scattered far and wide once the stars explode or otherwise perish. This process needs to be repeated for many stellar generations to produce a significant abundance of the heavier elements such as carbon, oxygen and nitrogen. Surprisingly, the galaxy A1689-zD1 seemed to be emitting a lot of radiation in the far infrared, indicating that it had already produced many of its stars and significant quantities of metals, and revealed that it not only contained dust, but had a dust-to-gas ratio that was similar to that of much more mature galaxies. “Although the exact origin of galactic dust remains obscure,” explains Darach Watson, “our findings indicate that its production occurs very rapidly, within only 500 million years of the beginning of star formation in the Universe — a very short cosmological time frame, given that most stars live for billions of years.” The findings suggest A1689-zD1 to have been consistently forming stars at a moderate rate since 560 million years after the Big Bang, or else to have passed through its period of extreme starburst very rapidly before entering a declining state of star formation. Prior to this result, there had been concerns among astronomers that such distant galaxies would not be detectable in this way, but A1689-zD1 was detected using only brief observations with ALMA. Kirsten Knudsen (Chalmers University of Technology, Sweden), co-author of the paper, added, “This amazingly dusty galaxy seems to have been in a rush to make its first generations of stars. In the future, ALMA will be able to help us to find more galaxies like this, and learn just what makes them so keen to grow up.” This research was presented in a paper entitled “A dusty, normal galaxy in the epoch of reionization” by D. Watson et al., to appear online in the journal Nature on 2 March 2015. The team is composed of D. Watson (Niels Bohr Institute, University of Copenhagen, Denmark), L. Christensen (University of Copenhagen), K. K. Knudsen (Chalmers University of Technology, Sweden), J. Richard (CRAL, Observatoire de Lyon, Saint Genis Laval, France), A. Gallazzi (INAF-Osservatorio Astrofisico di Arcetri, Firenze, Italy) and M. J. Michalowski (SUPA, Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh, UK). Credit: ESO

New Method Makes Space Weather Easier to Predict Posted: 02 Mar 2015 12:52 PM PST Scientists can now gain a better understanding of space weather – the dreaded solar winds and flares – thanks to the development of high spatial resolution observation and computing methods. For the first time, it will thus be possible to study the interrelated events that occur on the sun and trigger solar activity. To this effect, a current project funded by the Austrian Science Fund (FWF) is in the process of developing new methods that can generate three-dimensional images and will allow scientists to study the chronological sequence and evolution of processes taking place in the sun’s interior. These new methods will make it possible to link detailed observational data about the sun with complex computer simulations of solar activity. The sun’s surface is turbulent and constantly in motion: Dynamo effects create magnetic fields which, together with currents, travel outward towards the sun’s surface, thereby determining the sun’s activity. The solar activity in turn influences how much radiation reaches the earth. Long-term variations of this activity can also affect the earth’s climate. A Flood of Data About Solar Wind The team headed by project leader Prof. Arnold Hanslmeier is particularly interested in what are known as solar magnetic flux tubes. These flux tubes were discovered only a few years ago and are a precursor of solar flares. Prof. Hanslmeier explains: "It is believed that flux tubes form underneath the sun’s surface a few days before a solar flare erupts. Yet the forces that generate these flux tubes remain largely unknown." The team is also interested in the heating mechanisms that occur on the sun’s surface and directly affect the sun’s lower atmosphere. The methods being developed by Prof. Hanslmeier will make it possible to link data gained from high-resolution telescopic images with data generated by complex computer simulations. The conventional computation methods that are currently available are actually lagging behind the rapid development of solar telescopes and computer power, as the project leader explains: "New high-resolution solar telescopes generate such vast amounts of data that it is impossible to analyse all of the data individually. That requires automated processes – which is exactly what we are now developing. These processes will allow us to achieve unimaginable temporal and spatial resolution when computing solar dynamics. We are particularly excited about the upcoming opportunity to work with Europe’s largest solar telescope on the Canary Islands." Segmented & Computed More specifically, the aim of the project is to develop 2D and 3D algorithms that can calculate extremely small segments of solar magnetic flux tubes using imaging- and simulation data. This research is complemented by comparable segmentations of convective upward and downward flows of the sun’s hot plasma. Prof. Hanslmeier explains the purpose of these calculations: "Segmentation allows us to represent the solar magnetic flux tubes and convection currents as three-dimensional images. At the same time, we can observe how this three-dimensional representation evolves over time. This gives us an essential link between actual observations and theoretical simulations." For the team headed by Prof. Hanslmeier, this link is the key to gaining a better understanding of the mechanisms that lead to the formation of flux tubes and subsequently cause these flux tubes to develop into solar flares. The findings of this FWF-funded project will therefore be a vital tool for scientists to not only better understand the intensity of solar flares and solar winds, but to also detect this solar activity sooner and take the necessary precautions. In light of the threat that strong solar winds can pose for essential electric infrastructure in space and here on earth, the significance of these findings will go far beyond fundamental scientific insight. Credit: fwf.ac.at

Dawn Spacecraft Nears Historic Dwarf Planet Arrival Posted: 02 Mar 2015 12:22 PM PST NASA’s Dawn spacecraft has returned new images captured on approach to its historic orbit insertion at the dwarf planet Ceres. Dawn will be the first mission to successfully visit a dwarf planet when it enters orbit around Ceres on Friday, March 6. "Dawn is about to make history," said Robert Mase, project manager for the Dawn mission at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California. "Our team is ready and eager to find out what Ceres has in store for us." Recent images show numerous craters and unusual bright spots that scientists believe tell how Ceres, the first object discovered in our solar system’s asteroid belt, formed and whether its surface is changing. As the spacecraft spirals into closer and closer orbits around the dwarf planet, researchers will be looking for signs that these strange features are changing, which would suggest current geological activity. “Studying Ceres allows us to do historical research in space, opening a window into the earliest chapter in the history of our solar system,” said Jim Green, director of NASA’s Planetary Science Division at the agency’s Headquarters in Washington. “Data returned from Dawn could contribute significant breakthroughs in our understanding of how the solar system formed.” Dawn began its final approach phase toward Ceres in December. The spacecraft has taken several optical navigation images and made two rotation characterizations, allowing Ceres to be observed through its full nine-hour rotation. Since Jan. 25, Dawn has been delivering the highest-resolution images of Ceres ever captured, and they will continue to improve in quality as the spacecraft approaches. Sicilian astronomer Father Giuseppe Piazzi spotted Ceres in 1801. As more such objects were found in the same region, they became known as asteroids, or minor planets. Ceres was initially classified as a planet and later called an asteroid. In recognition of its planet-like qualities, Ceres was designated a dwarf planet in 2006, along with Pluto and Eris. Ceres is named for the Roman goddess of agriculture and harvests. Craters on Ceres will similarly be named for gods and goddesses of agriculture and vegetation from world mythology. Other features will be named for agricultural festivals. Launched in September 2007, Dawn explored the giant asteroid Vesta for 14 months in 2011 and 2012, capturing detailed images and data about that body. Both Vesta and Ceres orbit the sun between Mars and Jupiter, in the main asteroid belt. This two-stop tour of our solar system is made possible by Dawn’s ion propulsion system, its three ion engines being much more efficient than chemical propulsion. Ceres rotates in this sped-up movie comprised of images taken by NASA's Dawn mission during its approach to the dwarf planet. The images were taken on Feb. 19, 2015, from a distance of nearly 29,000 miles (46,000 kilometers). Dawn observed Ceres for a full rotation of the dwarf planet, which lasts about nine hours. The images have a resolution of 2.5 miles (4 kilometers) per pixel. Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA "Both Vesta and Ceres were on their way to becoming planets, but their development was interrupted by the gravity of Jupiter,” said Carol Raymond, deputy project scientist at JPL. “These two bodies are like fossils from the dawn of the solar system, and they shed light on its origins." Ceres and Vesta have several important differences. Ceres is the most massive body in the asteroid belt, with an average diameter of 590 miles (950 kilometers). Ceres' surface covers about 38 percent of the area of the continental United States. Vesta has an average diameter of 326 miles (525 kilometers), and is the second most massive body in the belt. The asteroid formed earlier than Ceres and is a very dry body. Ceres, in contrast, is estimated to be 25 percent water by mass. "By studying Vesta and Ceres, we will gain a better understanding of the formation of our solar system, especially the terrestrial planets and most importantly the Earth," said Raymond. "These bodies are samples of the building blocks that have formed Venus, Earth and Mars. Vesta-like bodies are believed to have contributed heavily to the core of our planet, and Ceres-like bodies may have provided our water." "We would not be able to orbit and explore these two worlds without ion propulsion,” Mase said. “Dawn capitalizes on this innovative technology to deliver big science on a small budget.” In addition to the Dawn mission, NASA will launch in 2016 its Origins-Spectral Interpretation-Resource Identification-Security-Regolith Explorer (OSIRIS-REx) spacecraft. This mission will study a large asteroid in unprecedented detail and return samples to Earth. NASA also places a high priority on tracking and protecting Earth from asteroids. NASA's Near-Earth Object (NEO) Program at the agency’s headquarters manages and funds the search, study and monitoring of asteroids and comets whose orbits periodically bring them close to Earth. NASA is pursuing an Asteroid Redirect Mission (ARM), which will identify, redirect and send astronauts to explore an asteroid. Among its many exploration goals, the mission could demonstrate basic planetary defense techniques for asteroid deflection. Dawn's mission is managed by JPL for NASA's Science Mission Directorate in Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK, Inc., in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, Max Planck Institute for Solar System Research, Italian Space Agency and Italian National Astrophysical Institute are international partners on the mission team. Credit: NASA

Simulating Space for JWST's Four Infrared Instruments Posted: 02 Mar 2015 11:56 AM PST Building a space telescope is no mean feat. Conditions here on Earth are drastically different from those experienced in orbit around our planet. How do we know that any telescope built in our controlled laboratories can withstand the harsh environment of space? Luckily, we can recreate space-like conditions using simulators such as this thermal–vacuum chamber at NASA’s Goddard Space Flight Center in Maryland, USA. In this image, the chamber is not in action, as shown by the presence of a photographer wielding a torch on the sidelines. When switched on, multiple pumps suck all the air out to create a space-like vacuum, and the temperature can drop to a toe-curlingly low –253°C. However, the real star of this image is the futuristic gold-coloured frame and its contents. This frame holds the Integrated Science Instrument Module, a structure containing the science instruments for 2018’s James Webb Space Telescope, or JWST, successor to the Hubble Space Telescope. Along with the frame, this module weighs about as much as an elephant and houses four instruments to observe in the infrared, a part of the spectrum that is key for exploring the origins of the Universe and the properties of very distant cosmic objects. This capability is the reason for the chamber’s extremely low temperature: infrared light is emitted by warm objects. To avoid infrared emissions from the telescope itself interfering with JWST’s observations, the entire telescope must be cooled to very low temperatures. In space, JWST will make use of a giant sunshield to keep it completely in the shadows. This will keep the telescope at –233°C. The JWST team hit a milestone last summer as all four science instruments passed their cryogenic testing in this chamber. The three near-infrared units were cooled to around –233°C, while the mid-infrared instrument reached an even lower –266°C, for a total of 116 days. For more information, read here. After these tests, one of the units – the Near InfraRed Spectrograph – was removed and fitted with new detectorsand ‘microshutters’, a new technology to study hundreds of celestial objects simultaneously using minuscule windows the width of a human hair. When this upgraded instrument is returned, the entire module will continue with further environmental tests to reproduce the conditions endured during launch and in space.  JWST is a joint project of NASA, ESA and the Canadian Space Agency. Credit: ESA