Houdini-Like Vanishing Act in Space

Houdini-Like Vanishing Act in Space

  11:19:00 AM    Science Lover

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Astronomers report a baffling discovery never seen before: An extraordinary amount of dust around a nearby star has mysteriously disappeared.

Dust today, gone tomorrow. An artist's conceptualization 
of the dusty TYC 8241 2652 system as it may have appeared 
several years ago, when it was emitting large amounts of 
excess infrared radiation. (Credit: Gemini Observatory/
AURA artwork by Lynette Cook))

"It's like the classic magician's trick -- now you see it, now you don't," said Carl Melis, a postdoctoral scholar at UC San Diego and lead author of the research. "Only in this case, we're talking about enough dust to fill an inner solar system, and it really is gone!"

"It's as if the rings around Saturn had disappeared," said co-author Benjamin Zuckerman, a UCLA professor of physics and astronomy. "This is even more shocking because the dusty disc of rocky debris was bigger and much more massive than Saturn's rings. The disc around this star, if it were in our solar system, would have extended from the sun halfway out to Earth, near the orbit of Mercury."

The research on this cosmic vanishing act, which occurred around a star some 450 light years from Earth, in the direction of the constellation Centaurus, appears July 5 in the journal Nature.

"A perplexing thing about this discovery is that we don't have a satisfactory explanation to address what happened around this star," said Melis, a former UCLA astronomy graduate student. "The disappearing act appears to be independent of the star itself, as there is no evidence to suggest that the star zapped the dust with some sort of mega-flare or any other violent event."

Melis describes the star, designated TYC 8241 2652, as a "young analog of our sun" that only a few years ago displayed all of the characteristics of "hosting a solar system in the making," before transforming completely. Now, very little of the warm, dusty material thought to originate from collisions of rocky planets is apparent.

"Nothing like this has ever been seen in the many hundreds of stars that astronomers have studied for dust rings," Zuckerman said. "This disappearance is remarkably fast, even on a human time scale, much less an astronomical scale. The dust disappearance at TYC 8241 2652 was so bizarre and so quick, initially I figured that our observations must simply be wrong in some strange way."

Norm Murray, director of the Canadian Institute for Theoretical Astrophysics, who was not part of the research group, said, "The history of astronomy has shown that events that are not predicted and hard to explain can be game-changers."

The dust had been present around the star since at least 1983 (no one had observed the star in the infrared before then), and it continued to glow brightly in the infrared for 25 years. In 2009, it started to dim. By 2010, the dust emission was gone; the astronomers observed the star twice that year from the Gemini Observatory in Chile, six months apart. An infrared image obtained by the Gemini telescope as recently as May 1 of this year confirmed that the warm dust has now been gone for two-and-a-half years.

Like Earth, warm dust absorbs the energy of sunlight and re-radiates that heat energy as infrared radiation.

Because so much dust had been orbiting around the star, planets very likely are forming there, said Zuckerman, whose research is funded by NASA.

The lack of an existing model for what is going on around this star is forcing astronomers to rethink what happens within young solar systems in the making. The dust likely resulted from a violent collision -- but that would not explain where it went. Was it somehow swallowed by the star?

"Although we've identified a couple of mechanisms that are potentially viable, none are really compelling," Melis said. "In one case, gas produced in the impact that released the dust helps to quickly drag the dust particles into the star and thus to their doom. In another possibility, collisions of large rocks left over from an original major impact provide a fresh infusion of dust particles into the disc, which then instigate a runaway process where small grains chip into oblivion both themselves and also larger grains."

Major dusty regions are known to exist in our own solar system and include the asteroid belt between the orbits of Mars and Jupiter and another located beyond the orbit of Neptune. Nearly 30 years ago, NASA's Infrared Astronomical Satellite (IRAS) first discovered many similar regions orbiting other stars -- but no disappearing act like the one at TYC 8241 2652 has ever been seen during these three decades.

The research is based on multiple sets of observations of TYC 8241 2652 obtained with the Thermal-Region Camera Spectrograph on the Gemini South telescope in Chile, the IRAS, NASA's Wide-field Infrared Survey Explorer (WISE) satellite, NASA's Infrared Telescope on Mauna Kea in Hawaii, the Herschel Space Telescope of the European Space Agency (ESA), and AKARI (a Japanese/ESA infrared satellite).

"We were lucky to catch this disappearing act," Zuckerman said. "Such events could be relatively common, without our knowing it."

Co-authors of the Nature paper are Joseph Rhee, a former UCLA postdoctoral scholar in astronomy, who is now an astronomer at California State Polytechnic University in Pomona; Inseok Song, an assistant professor of physics and astronomy at the University of Georgia who also was a postdoctoral researcher at UCLA; and astronomers Simon Murphy and Michael Bessell at the Australian National University.

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NASA Web App Lets You Control Space & Time in 3D

NASA Web App Lets You Control Space & Time in 3D

  12:54:00 AM    Science Lover

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NASA has released its “Eyes on the Solar System” 3D environment, a free web browser-based application that lets you navigate a 3D version of the solar system. The app uses video game technology to let you control your point of view from anywhere in our solar system, speeding up time so you can see the motion of the planets, their satellites and NASA spacecraft.

We tried the Eyes on the Solar System app (download here), which first requires a download of the Unity Web Player for Mac and PC. Once you’ve done that, you can fly around beautifully produced models of all the planets, asteroids and the Sun. Or you can enter custom modules created by NASA that highlight missions such as Juno, the recently launched probe that’s currently on a five-year mission to Jupiter.

According to NASA:

“This is the first time the public has been able to see the entire solar system and our missions moving together in real time,” said Jim Green, director of NASA’s Planetary Science Division at the agency’s Headquarters in Washington. “It demonstrates NASA’s continued commitment to share our science with everyone.”

You can even keep tabs on the current locations of NASA spacecraft, with the help of NASA’s actual mission data. Don’t forget to click the Full Screen button for the full effect. Fantastic stuff.



Get the app here.

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Solar wind samples give insight into birth of solar system

Solar wind samples give insight into birth of solar system

  9:33:00 AM    Science Lover

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Two papers in this week's issue of Science report the first oxygen and nitrogen isotopic measurements of the Sun, demonstrating that they are verydifferent from the same elements on Earth. These results were the top two priorities of NASA's Genesis mission, which was the first spacecraft to return from beyond the Moon, crashing in the Utah desert in 2004 after its parachute failed to deploy during re-entry.

The Solar Wind Concentrator is a special instrument built
by a team at Los Alamos National Laboratory to enhance
the flow of solar wind onto a small target to make possible
oxygen and nitrogen measurements. Shown here, the target
section of the concentrator, which produced essential
samples of nitrogen and oxygen.

Most of the Genesis payload consisted of fragile solar-wind collectors, which had been exposed to the solar particles over a period of two years. Nearly all of these collectors were decimated during the crash. But the capsule also contained a special instrument built by a team at Los Alamos National Laboratory to enhance the flow of solar wind onto a small target to make possible oxygen and nitrogen measurements. The targets of this Solar Wind Concentrator survived the crash and eventually yielded today's solar secrets.

"Genesis is the biggest comeback mission since Apollo 13," said Roger Wiens, a Los Alamos National Laboratory physicist and Genesis flight payload lead. "Everyone who saw the crash thought it was a terrible disaster, but instead the project has been fully successful, and the results are absolutely fascinating."

The results provide new clues to how the solar system was formed. Oxygen and nitrogen samples collected from various meteorites, as well as nitrogen sampled in lunar soil and in the Jupiter atmosphere by the Galileo probe, vary significantly from that on Earth by cosmochemical standards: 38 percent for nitrogen and up to 7 percent for oxygen. With the first solar wind samples in hand, showing the early Sun's composition, scientists can begin the game of determining where Earth's different O and N came from.



"For nitrogen, Jupiter and the Sun look the same," said Wiens. "It tells us that the original gaseous component of the inner and outer solar system was homogeneous for nitrogen, at least. So where did Earth gets its heavier nitrogen from? Maybe it came here in the material comets are made of. Perhaps it was bonded with organic materials."

For oxygen, the evidence points toward a different astrophysical mechanism called photochemical self-shielding, which the authors believe modified the composition of space dust before it coalesced to form the planets, including Earth. According to the article, the Sun shows an enrichment of pure 16O relative to Earth instead of differences in 16O, 17O, and 18O that are proportional to their atomic weight or some other mixture that doesn't show exclusive enrichment of a single isotope. This unique arrangement strongly favors the self-shielding theory, in which solar UV radiation was responsible for uniformly enhancing the two rarer isotopes, 17O and 18O, in the terrestrial planets.

The Science papers are titled "A 15N-poor isotopic composition for the solar system as shown by Genesis solar wind samples" and "The oxygen isotopic composition of the Sun inferred from captured solar wind." Wiens is among several collaborating authors on both papers, which together are cover stories for this issue. Other LANL coauthors, Beth Nordholt and Ron Moses, along with former LANL scientist Dan Reisenfeld, were all part of the team to develop and fly the Solar Wind Concentrator that provided the samples for the studies reported in Science.

And now that some of the particles flowing past Earth from the sun are in hand, "It's going to make a mission to a comet all the more interesting," Wiens said.

Provided by Los Alamos National Laboratory

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Dust Models Paint Alien's View of the Solar System

Dust Models Paint Alien's View of the Solar System

  6:11:00 PM    Science Lover

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New supercomputer simulations tracking the interactions of thousands of dust grains show what the solar system might look like to alien astronomers searching for planets. The models also provide a glimpse of how this view might have changed as our planetary system matured.

These images, produced by computer models that track the movement of icy grains, represent infrared snapshots of Kuiper Belt dust as seen by a distant observer. For the first time, the models include the effects of collisions among grains. By ramping up the collision rate, the simulations show how the distant view of the solar system might have changed over its history. (Credit: NASA/Goddard/Marc Kuchner and Christopher Stark)

"The planets may be too dim to detect directly, but aliens studying the solar system could easily determine the presence of Neptune -- its gravity carves a little gap in the dust," said Marc Kuchner, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Md. who led the study. "We're hoping our models will help us spot Neptune-sized worlds around other stars."

The dust originates in the Kuiper Belt, a cold-storage zone beyond Neptune where millions of icy bodies -- including Pluto -- orbit the sun. Scientists believe the region is an older, leaner version of the debris disks they've seen around stars like Vega and Fomalhaut.

"Our new simulations also allow us to see how dust from the Kuiper Belt might have looked when the solar system was much younger," said Christopher Stark, who worked with Kuchner at NASA Goddard and is now at the Carnegie Institution for Science in Washington, D.C. "In effect, we can go back in time and see how the distant view of the solar system may have changed."

Kuiper Belt objects occasionally crash into each other, and this relentless bump-and-grind produces a flurry of icy grains. But tracking how this dust travels through the solar system isn't easy because small particles are subject to a variety of forces in addition to the gravitational pull of the sun and planets.

The grains are affected by the solar wind, which works to bring dust closer to the sun, and sunlight, which can either pull dust inward or push it outward. Exactly what happens depends on the size of the grain.

The particles also run into each other, and these collisions can destroy the fragile grains. A paper on the new models, which are the first to include collisions among grains, appeared in the Sept. 7 edition of The Astronomical Journal.

"People felt that the collision calculation couldn't be done because there are just too many of these tiny grains too keep track of," Kuchner said. "We found a way to do it, and that has opened up a whole new landscape."

With the help of NASA's Discover supercomputer, the researchers kept tabs on 75,000 dust particles as they interacted with the outer planets, sunlight, the solar wind -- and each other.

The size of the model dust ranged from about the width of a needle's eye (0.05 inch or 1.2 millimeters) to more than a thousand times smaller, similar in size to the particles in smoke. During the simulation, the grains were placed into one of three types of orbits found in today's Kuiper Belt at a rate based on current ideas of how quickly dust is produced.

From the resulting data, the researchers created synthetic images representing infrared views of the solar system seen from afar.

Through gravitational effects called resonances, Neptune wrangles nearby particles into preferred orbits. This is what creates the clear zone near the planet as well as dust enhancements that precede and follow it around the sun.

"One thing we've learned is that, even in the present-day solar system, collisions play an important role in the Kuiper Belt's structure," Stark explained. That's because collisions tend to destroy large particles before they can drift too far from where they're made. This results in a relatively dense dust ring that straddles Neptune's orbit.

To get a sense of what younger, heftier versions of the Kuiper Belt might have looked like, the team sped up the dust production rate. In the past, the Kuiper Belt contained many more objects that crashed together more frequently, generating dust at a faster pace. With more dust particles came more frequent grain collisions.

Using separate models that employed progressively higher collision rates, the team produced images roughly corresponding to dust generation that was 10, 100 and 1,000 times more intense than in the original model. The scientists estimate the increased dust reflects conditions when the Kuiper Belt was, respectively, 700 million, 100 million and 15 million years old.

"We were just astounded by what we saw," Kuchner said.

As collisions become increasingly important, the likelihood that large dust grains will survive to drift out of the Kuiper Belt drops sharply. Stepping back through time, today's broad dusty disk collapses into a dense, bright ring that bears more than a passing resemblance to rings seen around other stars, especially Fomalhaut.

"The amazing thing is that we've already seen these narrow rings around other stars," Stark said. "One of our next steps will be to simulate the debris disks around Fomalhaut and other stars to see what the dust distribution tells us about the presence of planets."

The researchers also plan to develop a more complete picture of the solar system's dusty disk by modeling additional sources closer to the sun, including the main asteroid belt and the thousands of so-called Trojan asteroids corralled by Jupiter's gravity.

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Colorful Mix of Asteroids Discovered, May Aid Future Space Travel

Colorful Mix of Asteroids Discovered, May Aid Future Space Travel

  12:27:00 AM    Science Lover

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New research from NASA's Spitzer Space Telescope reveals that asteroids somewhat near Earth, termed near-Earth objects, are a mixed bunch, with a surprisingly wide array of compositions.

This image, taken by NASA's Near Earth Asteroid 
Rendezvous mission in 2000, shows a close-up view 
of Eros, an asteroid with an orbit that takes it somew
hat close to Earth. NASA's Spitzer Space Telescope 
observed Eros and dozens of other near-Earth 
asteroids as part of an ongoing survey to study 
their sizes and compositions using 
infrared light. (Credit: NASA/JHUAPL)

Like the chocolates and fruity candies inside a piñata, these asteroids come in assorted colors and compositions. Some are dark and dull; others are shiny and bright. The Spitzer observations of 100 known near-Earth asteroids demonstrate that their diversity is greater than previously thought.

The findings are helping astronomers better understand near-Earth objects as a whole -- a population whose physical properties are not well known.

"These rocks are teaching us about the places they come from," said David Trilling, assistant professor of physics and astronomy at Northern Arizona University, and lead author of a new paper on the research appearing in the September issue of Astronomical Journal. "It's like studying pebbles in a streambed to learn about the mountains they tumbled down."

One of the mission's programs is to survey about 700 near-Earth objects, cataloguing their individual traits. By observing in infrared, Spitzer is helping to gather more accurate estimates of asteroids' compositions and sizes than what is possible with visible-light alone.

Trilling and his team have analyzed preliminary data on 100 near-Earth asteroids so far. They plan to observe 600 more over the next year. There are roughly 7,000 known near-Earth objects out of a population expected to number in the tens to hundreds of thousands.

"Very little is known about the physical characteristics of the near-Earth population," Trilling said. "Our data will tell us more about the population, and how it changes from one object to the next. This information could be used to help plan possible future space missions to study a near-Earth object."

The data show that some of the smaller objects have surprisingly high albedos (a measurement of how much sunlight an object reflects). Since asteroid surfaces become darker with time due to exposure to solar radiation, the presence of lighter, shinier surfaces for some asteroids may indicate that they are relatively young. This is evidence for the continuing evolution of the near-Earth object population.

In addition, the asteroids observed so far have a greater degree of diversity than expected, indicating that they might have different origins. Some might come from the main belt between Mars and Jupiter, and others could come from farther out in the solar system. This diversity also suggests that the materials that went into creating the asteroids -- the same materials that make up our planets -- were probably mixed together like a big solar-system soup very early on in its history.

The research complements that of NASA's Wide-field Infrared Survey Explorer, or WISE, an all-sky infrared survey mission up in space now. WISE has already observed more than 430 near-Earth objects. Of these, more than 110 are newly discovered.

In the future, both Spitzer and WISE will reveal even more about the "flavors" of near-Earth objects. This could reveal new clues about how the cosmic objects might have dotted our young planet with water and organics -- ingredients needed to jump-start life.

Other authors include Cristina Thomas, a post-doctoral scholar of physics and astronomy at NAU, and researchers from around the world.

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Richest Planetary System Discovered

Richest Planetary System Discovered

  2:16:00 AM    Science Lover

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Astronomers using ESO's world-leading HARPS instrument have discovered a planetary system containing at least five planets, orbiting the Sun-like star HD 10180. The researchers also have tantalising evidence that two other planets may be present, one of which would have the lowest mass ever found. This would make the system similar to our Solar System in terms of the number of planets (seven as compared to the Solar System's eight planets). Furthermore, the team also found evidence that the distances of the planets from their star follow a regular pattern, as also seen in our Solar System.

The planetary system around the Sun-like star HD 
10180 (artist’s impression). (Credit: ESO/L. Calçada)

"We have found what is most likely the system with the most planets yet discovered," says Christophe Lovis, lead author of the paper reporting the result. "This remarkable discovery also highlights the fact that we are now entering a new era in exoplanet research: the study of complex planetary systems and not just of individual planets. Studies of planetary motions in the new system reveal complex gravitational interactions between the planets and give us insights into the long-term evolution of the system."

The team of astronomers used the HARPS spectrograph, attached to ESO's 3.6-metre telescope at La Silla, Chile, for a six-year-long study of the Sun-like star HD 10180, located 127 light-years away in the southern constellation of Hydrus (the Male Water Snake). HARPS is an instrument with unrivalled measurement stability and great precision and is the world's most successful exoplanet hunter.

Thanks to the 190 individual HARPS measurements, the astronomers detected the tiny back and forth motions of the star caused by the complex gravitational attractions from five or more planets. The five strongest signals correspond to planets with Neptune-like masses -- between 13 and 25 Earth masses [1] -- which orbit the star with periods ranging from about 6 to 600 days. These planets are located between 0.06 and 1.4 times the Earth-Sun distance from their central star.

"We also have good reasons to believe that two other planets are present," says Lovis. One would be a Saturn-like planet (with a minimum mass of 65 Earth masses) orbiting in 2200 days. The other would be the least massive exoplanet ever discovered, with a mass of about 1.4 times that of the Earth. It is very close to its host star, at just 2 percent of the Earth-Sun distance. One "year" on this planet would last only 1.18 Earth-days.

"This object causes a wobble of its star of only about 3 km/hour -- slower than walking speed -- and this motion is very hard to measure," says team member Damien Ségransan. If confirmed, this object would be another example of a hot rocky planet, similar to Corot-7b (eso0933).

The newly discovered system of planets around HD 10180 is unique in several respects. First of all, with at least five Neptune-like planets lying within a distance equivalent to the orbit of Mars, this system is more populated than our Solar System in its inner region, and has many more massive planets there [2]. Furthermore, the system probably has no Jupiter-like gas giant. In addition, all the planets seem to have almost circular orbits.

So far, astronomers know of fifteen systems with at least three planets. The last record-holder was 55 Cancri, which contains five planets, two of them being giant planets. "Systems of low-mass planets like the one around HD 10180 appear to be quite common, but their formation history remains a puzzle," says Lovis.

Using the new discovery as well as data for other planetary systems, the astronomers found an equivalent of the Titius-Bode law that exists in our Solar System: the distances of the planets from their star seem to follow a regular pattern [3]. "This could be a signature of the formation process of these planetary systems," says team member Michel Mayor.

Another important result found by the astronomers while studying these systems is that there is a relationship between the mass of a planetary system and the mass and chemical content of its host star. All very massive planetary systems are found around massive and metal-rich stars, while the four lowest-mass systems are found around lower-mass and metal-poor stars [4]. Such properties confirm current theoretical models.

The discovery was announced Aug. 24 at the international colloquium "Detection and dynamics of transiting exoplanets," at the Observatoire de Haute-Provence, France.

Notes

[1] Using the radial velocity method, astronomers can only estimate a minimum mass for a planet as the mass estimate also depends on the tilt of the orbital plane relative to the line of sight, which is unknown. From a statistical point of view, this minimum mass is however often close to the real mass of the planet.

[2] On average the planets in the inner region of the HD 10180 system have 20 times the mass of the Earth, whereas the inner planets in our own Solar System (Mercury, Venus, Earth and Mars) have an average mass of half that of the Earth.

[3] The Titius-Bode law states that the distances of the planets from the Sun follow a simple pattern. For the outer planets, each planet is predicted to be roughly twice as far away from the Sun as the previous object. The hypothesis correctly predicted the orbits of Ceres and Uranus, but failed as a predictor of Neptune's orbit.

[4] According to the definition used in astronomy, "metals" are all the elements other than hydrogen and helium. Such metals, except for a very few minor light chemical elements, have all been created by the various generations of stars. Rocky planets are made of "metals."

More information

This research was presented in a paper submitted to Astronomy and Astrophysics ("The HARPS search for southern extra-solar planets. XXVII. Up to seven planets orbiting HD 10180: probing the architecture of low-mass planetary systems" by C. Lovis et al.).

The team is composed of C. Lovis, D. Ségransan, M. Mayor, S. Udry, F. Pepe, and D. Queloz (Observatoire de Genève, Université de Genève, Switzerland), W. Benz (Universität Bern, Switzerland), F. Bouchy (Institut d'Astrophysique de Paris, France), C. Mordasini (Max-Planck-Institut für Astronomie, Heidelberg, Germany), N. C. Santos (Universidade do Porto, Portugal), J. Laskar (Observatoire de Paris, France), A. Correia (Universidade de Aveiro, Portugal), and J.-L. Bertaux (Université Versailles Saint-Quentin, France) and G. Lo Curto (ESO).

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Incredible Shrinking Moon : NASA's Lunar Reconnaissance Orbiter Reveals

Incredible Shrinking Moon : NASA's Lunar Reconnaissance Orbiter Reveals

  10:37:00 AM    Science Lover

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Newly discovered cliffs in the lunar crust indicate the moon shrank globally in the geologically recent past and might still be shrinking today, according to a team analyzing new images from NASA's Lunar Reconnaissance Orbiter (LRO) spacecraft. The results provide important clues to the moon's recent geologic and tectonic evolution.

Another fault cut across and deformed several 
small diameter (~40-m diameter) impact craters 
(arrows) on the flanks of Mandel'shtam crater 
(6.5°N, 161°E). The fault carried near-surface 
crustal materials up and over the craters, burying
parts of their floors and rims. About half of the rim
and floor of a 20 m-in-diameter crater shown in 
the box has been lost. Since small craters only 
have a limited lifetime before they are destroyed 
by newer impacts, their deformation by the fault 
shows the fault to be relatively young. (Credit: NASA
/Goddard/Arizona State University/Smithsonian)

The moon formed in a chaotic environment of intense bombardment by asteroids and meteors. These collisions, along with the decay of radioactive elements, made the moon hot. The moon cooled off as it aged, and scientists have long thought the moon shrank over time as it cooled, especially in its early history. The new research reveals relatively recent tectonic activity connected to the long-lived cooling and associated contraction of the lunar interior.

"We estimate these cliffs, called lobate scarps, formed less than a billion years ago, and they could be as young as a hundred million years," said Dr. Thomas Watters of the Center for Earth and Planetary Studies at the Smithsonian's National Air and Space Museum, Washington. While ancient in human terms, it is less than 25 percent of the moon's current age of more than four billion years. "Based on the size of the scarps, we estimate the distance between the moon's center and its surface shrank by about 300 feet," said Watters, lead author of a paper on this research appearing in Science August 20.

"These exciting results highlight the importance of global observations for understanding global processes," said Dr. John Keller, Deputy Project Scientist for LRO at NASA's Goddard Space Flight Center, Greenbelt, Md. "As the LRO mission continues in to a new phase, with emphasis on science measurements, our ability to create inventories of lunar geologic features will be a powerful tool for understanding the history of the moon and the solar system."

The scarps are relatively small; the largest is about 300 feet high and extends for several miles or so, but typical lengths are shorter and heights are more in the tens of yards (meters) range. The team believes they are among the freshest features on the moon, in part because they cut across small craters. Since the moon is constantly bombarded by meteors, features like small craters (those less than about 1,200 feet across) are likely to be young because they are quickly destroyed by other impacts and don't last long. So, if a small crater has been disrupted by a scarp, the scarp formed after the crater and is even younger. Even more compelling evidence is that large craters, which are likely to be old, don't appear on top any of the scarps, and the scarps look crisp and relatively undegraded.

Lobate scarps on the moon were discovered during the Apollo missions with analysis of pictures from the high-resolution Panoramic Camera installed on Apollo 15, 16, and 17. However, these missions orbited over regions near the lunar equator, and were only able to photograph some 20 percent of the lunar surface, so researchers couldn't be sure the scarps were not just the result of local activity around the equator. The team found 14 previously undetected scarps in the LRO images, seven of which are at high latitudes (more than 60 degrees). This confirms that the scarps are a global phenomenon, making a shrinking moon the most likely explanation for their wide distribution, according to the team.

As the moon contracted, the mantle and surface crust were forced to respond, forming thrust faults where a section of the crust cracks and juts out over another. Many of the resulting cliffs, or scarps, have a semi-circular or lobe-shaped appearance, giving rise to the term "lobate scarps." Scientists aren't sure why they look this way; perhaps it's the way the lunar soil (regolith) expresses thrust faults, according to Watters.

Lobate scarps are found on other worlds in our solar system, including Mercury, where they are much larger. "Lobate scarps on Mercury can be over a mile high and run for hundreds of miles," said Watters. Massive scarps like these lead scientists to believe that Mercury was completely molten as it formed. If so, Mercury would be expected to shrink more as it cooled, and thus form larger scarps, than a world that may have been only partially molten with a relatively small core. Our moon has more than a third of the volume of Mercury, but since the moon's scarps are typically much smaller, the team believes the moon shrank less.

Because the scarps are so young, the moon could have been cooling and shrinking very recently, according to the team. Seismometers emplaced by the Apollo missions have recorded moonquakes. While most can be attributed to things like meteorite strikes, the Earth's gravitational tides, and day/night temperature changes, it's remotely possible that some moonquakes might be associated with ongoing scarp formation, according to Watters. The team plans to compare photographs of scarps by the Apollo Panoramic Cameras to new images from LRO to see if any have changed over the decades, possibly indicating recent activity.

While Earth's tides are most likely not strong enough to create the scarps, they could contribute to their appearance, perhaps influencing their orientation, according to Watters. During the next few years, the team hopes to use LRO's high-resolution Narrow Angle Cameras (NACs) to build up a global, highly detailed map of the moon. This could identify additional scarps and allow the team to see if some have a preferred orientation or other features that might be associated with Earth's gravitational pull.

"The ultrahigh resolution images from the NACs are changing our view of the moon," said Dr. Mark Robinson of the School of Earth and Space Exploration at Arizona State University, Tempe, Ariz., a coauthor and Principal Investigator of the Lunar Reconnaissance Orbiter Camera. "We've not only detected many previously unknown lunar scarps; we're also seeing much greater detail on the scarps identified in the Apollo photographs."

The research was funded by NASA's Exploration Systems Mission Directorate at NASA Headquarters, Washington. The team includes researchers from the Smithsonian, Arizona State, the SETI Institute, Mountain View, Calif., NASA Ames Research Center, Moffett Field, Calif., Cornell University, Ithaca, N.Y., Institut für Planetologie, Westfälische Wilhelms-Universität, Münster, Germany, Brown University, Providence, R.I., and the Johns Hopkins University Applied Physics Laboratory, Laurel, Md.

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Asteroid Might Hit Earth in 2182

Asteroid Might Hit Earth in 2182

  8:59:00 PM    Science Lover

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The potentially hazardous asteroid '(101955) 1999 RQ36' has a one-in-a-thousand chance of impacting the Earth, and more than half of this probability indicates that this could happen in the year 2182, based on a global study in which Spanish researchers have been involved. Knowing this fact may help design in advance mechanisms aimed at deviating the asteroid's path.

Asteroids and comets visited by spacecraft. (Credit: ESA, NASA, JAXA, RAS, JHUAPL, UMD, OSIRIS)

"The total impact probability of asteroid '(101955) 1999 RQ36' can be estimated in 0.00092 -- approximately one-in-a-thousand chance -- but what is most surprising is that over half of this chance (0.00054) corresponds to 2182," explains María Eugenia Sansaturio, co-author of the study and researcher of Universidad de Valladolid (UVA). The research also involved scientists from the University of Pisa (Italy), the Jet Propulsion Laboratory (USA) and INAF-IASF-Rome (Italy).

Scientists have estimated and monitored the potential impacts for this asteroid through 2200 by means of two mathematical models (Monte Carlo Method and line of variations sampling). Thus, the so called Virtual Impactors (VIs) have been searched. VIs are sets of statistical uncertainty leading to collisions with the Earth on different dates of the XXII century. Two VIs appear in 2182 with more than half the chance of impact.

Asteroid '(101955) 1999 RQ36' is part of the Potentially Hazardous Asteroids (PHA), which have the possibility of hitting the Earth due to the closeness of their orbits, and they may cause damages. This PHA was discovered in 1999 and has around 560 meters in diameter.

The Yarkovsky effect

In practice, its orbit is well determined thanks to 290 optical observations and 13 radar measurements, but there is a significant "orbital uncertainty" because, besides gravity, its path is influenced by the Yarkovsky effect. Such disturbance slightly modifies the orbits of the Solar System's small objects because, when rotating, they radiate from one side the radiation they take from the sun through the other side.

The research, which has been published in the journal Icarus, predicts what could happen in the upcoming years considering this effect. Up to 2060, divergence of the impacting orbits is moderate; between 2060 and 2080 it increases 4 orders of magnitude because the asteroid will approach the Earth in those years; then, it increases again on a slight basis until another approach in 2162, it then decreases, and 2182 is the most likely year for the collision.

"The consequence of this complex dynamic is not just the likelihood of a comparatively large impact, but also that a realistic deflection procedure (path deviation) could only be made before the impact in 2080, and more easily, before 2060," stands out Sansaturio.

The scientist concludes: "If this object had been discovered after 2080, the deflection would require a technology that is not currently available. Therefore, this example suggests that impact monitoring, which up to date does not cover more than 80 or 100 years, may need to encompass more than one century. Thus, the efforts to deviate this type of objects could be conducted with moderate resources, from a technological and financial point of view."

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Prospects for Finding New Earths Boosted

Prospects for Finding New Earths Boosted

  10:33:00 AM    Science Lover

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A team of astronomers from Germany, Bulgaria and Poland have used a completely new technique to find an exotic extrasolar planet. The same approach is sensitive enough to find planets as small as the Earth in orbit around other stars. The group, led by Dr Gracjan Maciejewski of Jena University in Germany, used Transit Timing Variation to detect a planet with 15 times the mass of the Earth in the system WASP-3, 700 light years from the Sun in the constellation of Lyra.

This image shows the faint star WASP-3 
(magnitude 10.5 or about 60 times fainter than can 
be seen with the unaided eye) in the centre of the 
image, made using the 90-cm telescope of the 
University Observatory Jena. The star is enlarged with 
better sensitivity and resolution in the inlay in the 
lower left. WASP-3 is at a distance of 700 light years and 
is located in the constellation Lyra. North is up, east to 
the left. The large image is a composite of three images 
taken using different filters (blue, visual and red) and 
the small inlay only uses a red filter. (Credit: Gracan 
Maciejewski, Dinko Dimitrov, Ralph 
Neuhäuser, Andrzej Niedzielski et al.)

They publish their work in the journal Monthly Notices of the Royal Astronomical Society.

Transit Timing Variation (TTV) was suggested as a new technique for discovering planets a few years ago. Transits take place where a planet moves in front of the star it orbits, temporarily blocking some of the light from the star. So far this method has been used to detect a number of planets and is being deployed by the Kepler and Corot space missions in its search for planets similar to the Earth.

If a (typically large) planet is found, then the gravity of additional smaller planets will tug on the larger object, causing deviations in the regular cycle of transits. The TTV technique compares the deviations with predictions made by extensive computer-based calculations, allowing astronomers to deduce the makeup of the planetary system.

For this search, the team used the 90-cm telescopes of the University Observatory Jena and the 60-cm telescope of the Rohzen National Astronomical Observatory in Bulgaria to study transits of WASP-3b, a large planet with 630 times the mass of the Earth.

"We detected periodic variations in the transit timing of WASP-3b. These variations can be explained by an additional planet in the system, with a mass of 15 Earth-mass (i.e. one Uranus mass) and a period of 3.75 days," said Dr Maciejewski.

"In line with international rules, we called this new planet WASP-3c." This newly discovered planet is among the least massive planets known to date and also the least massive planet known orbiting a star which is more massive than our Sun.

This is the first time that a new extra-solar planet has been discovered using this method. The new TTV approach is an indirect detection technique, like the previously successful transit method.

A team of astronomers from Germany, Bulgaria and Poland have used a completely new technique to find an exotic extrasolar planet. The same approach is sensitive enough to find planets as small as the Earth in orbit around other stars. The group, led by Dr Gracjan Maciejewski of Jena University in Germany, used Transit Timing Variation to detect a planet with 15 times the mass of the Earth in the system WASP-3, 700 light years from the Sun in the constellation of Lyra. They publish their work in the journal Monthly Notices of the Royal Astronomical Society.

The discovery of the second, 15 Earth-mass planet makes the WASP-3 system very intriguing. The new planet appears to be trapped in an external orbit, twice as long as the orbit of the more massive planet. Such a configuration is probably a result of the early evolution of the system.

The TTV method is very attractive, because it is particularly sensitive to small perturbing planets, even down to the mass of the Earth. For example, an Earth-mass planet will pull on a typical gas giant planet orbiting close to its star and cause deviations in the timing of the larger objects' transits of up to 1 minute.

This is a big enough effect to be detected with relatively small 1-m diameter telescopes and discoveries can be followed up with larger instruments. The team are now using the 10-m Hobby-Eberly Telescope in Texas to study WASP-3c in more detail.

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Coolest Stars Come out of the Dark: Spitzer Spies Frigid Brown Dwarfs

Coolest Stars Come out of the Dark: Spitzer Spies Frigid Brown Dwarfs

  1:21:00 AM    Science Lover

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Astronomers have uncovered what appear to be 14 of the coldest stars known in our universe. These failed stars, called brown dwarfs, are so cold and faint that they'd be impossible to see with current visible-light telescopes. Spitzer's infrared vision was able to pick out their feeble glow, much as a firefighter uses infrared goggles to find hot spots buried underneath a dark forest floor.

This artist's concept shows simulated data predicting the hundreds of failed stars, or brown dwarfs, that NASA's Wide-field Infrared Survey Explorer (WISE) is expected to add to the population of known stars in our solar neighborhood. (Credit: AMNH/UCB/NASA/JPL-Caltech)

The brown dwarfs join only a handful of similar objects previously discovered. The new objects are between the temperatures of about 450 Kelvin to 600 Kelvin (350 to 620 degrees Fahrenheit). As far as stars go, this is bitter cold -- as cold, in some cases, as planets around other stars.

These cool orbs have remained elusive for years, but will soon start coming out of the dark in droves. NASA's Wide-field Infrared Survey Explorer (WISE) mission, which is up scanning the entire sky now in infrared wavelengths, is expected to find hundreds of objects of a similarly chilly disposition, if not even colder. WISE is searching a volume of space 40 times larger than that sampled in the recent Spitzer study, which concentrated on a region in the constellation Boötes. The Spitzer mission is designed to look at targeted patches of sky in detail, while WISE is combing the whole sky.

"WISE is looking everywhere, so the coolest brown dwarfs are going to pop up all around us," said Peter Eisenhardt, the WISE project scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif., and lead author of a recent paper in the Astronomical Journal on the Spitzer discoveries. "We might even find a cool brown dwarf that is closer to us than Proxima Centauri, the closest known star."

Brown dwarfs form like stars out of collapsing balls of gas and dust, but they are puny in comparison, never collecting enough mass to ignite nuclear fusion and shine with starlight. The smallest known brown dwarfs are about 5 to 10 times the mass of our planet Jupiter -- that's as massive as some known gas-giant planets around other stars. Brown dwarfs start out with a bit of internal heat left over from their formation, but with age, they cool down. The first confirmed brown dwarf was announced in 1995.

"Brown dwarfs are like planets in some ways, but they are in isolation," said astronomer Daniel Stern, co-author of the Spitzer paper at JPL. "This makes them exciting for astronomers -- they are the perfect laboratories to study bodies with planetary masses."

Most of the new brown dwarfs found by Spitzer are thought to belong to the coolest known class of brown dwarfs, called T dwarfs, which are defined as being less than about 1,500 Kelvin (2,240 degrees Fahrenheit). One of the objects appears to be so cold that it may even be a long-sought Y dwarf -- a proposed class of even colder stars. The T and Y classes are part of a larger system categorizing all stars; for example, the hottest, most massive stars are O stars; our sun is a G star.

"Models indicate there may be an entirely new class of stars out there, the Y dwarfs, that we haven't found yet," said co-author Davy Kirkpatrick, a co-author of the study and a member of the WISE science team at the California Institute of Technology, Pasadena, Calif. "If these elusive objects do exist, WISE will find them." Kirkpatrick is a world expert in brown dwarfs -- he came up with L, T and Y classifications for the cooler stars.

Kirkpatrick says that it's possible that WISE could find an icy, Neptune-sized or bigger object in the far reaches of our solar system -- thousands of times farther from the sun than Earth. There is some speculation amongst scientists that such a cool body, if it exists, could be a brown dwarf companion to our sun. This hypothetical object has been nicknamed "Nemesis."

"We are now calling the hypothetical brown dwarf Tyche instead, after the benevolent counterpart to Nemesis," said Kirkpatrick. "Although there is only limited evidence to suggest a large body in a wide, stable orbit around the sun, WISE should be able to find it, or rule it out altogether."

The 14 objects found by Spitzer are hundreds of light-years away -- too far away and faint for ground-based telescopes to see and confirm with a method called spectroscopy. But their presence implies that there are a hundred or more within only 25 light-years of our sun. Because WISE is looking everywhere, it will find these missing orbs, which will be close enough to confirm with spectroscopy. It's possible that WISE will even find more brown dwarfs within 25-light years of the sun than the number of stars known to exist in this space.

"WISE is going to transform our view of the solar neighborhood," said Eisenhardt. We'll be studying these new neighbors in minute detail -- they may contain the nearest planetary system to our own."

Other authors of the Spitzer paper are Roger Griffith and Amy Mainzer of JPL; Ned Wright, A.M. Ghez and Quinn Konopacky of UCLA; Matthew Ashby and Mark Brodwin of the Harvard-Smithsonian Center for Astrophysics, Cambridge; Mass., Michael Brown of Monash University, Australia; R.S. Bussmann of the University of Arizona, Tucson; Arjun Dey of National Optical Astronomy Observatory, Tucson, Ariz.; Eilat Glikman of Caltech; Anthony Gonzalez and David Vollbach of the University of Florida, Gainesville; and Shelley Wright of the University of California, Berkeley.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.

JPL manages the Wide-field Infrared Survey Explorer for NASA's Science Mission Directorate, Washington. The principal investigator, Edward Wright, is at UCLA. The mission was competitively selected under NASA's Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md. The science instrument was built by the Space Dynamics Laboratory, Logan, Utah, and the spacecraft was built by Ball Aerospace & Technologies Corp., Boulder, Colo. Science operations and data processing take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.

For more information about Spitzer, visit http://spitzer.caltech.edu/ and http://www.nasa.gov/spitzer. More information about WISE is online at http://wise.astro.ucla.edu and http://www.nasa.gov/wise.

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Scientists Explain Puzzling Lake Asymmetry on Saturn's Moon Titan

Scientists Explain Puzzling Lake Asymmetry on Saturn's Moon Titan

  11:42:00 PM    Science Lover

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Researchers at the California Institute of Technology (Caltech) suggest that the eccentricity of Saturn's orbit around the sun may be responsible for the unusually uneven distribution of methane and ethane lakes over the northern and southern polar regions of the planet's largest moon, Titan. On Earth, similar "astronomical forcing" of climate drives ice-age cycles.

This image shows the northern and southern hemispheres of Titan, showing the disparity between the abundance of lakes in the north and their paucity in the South. The hypothesis presented favors long-term flux of volatile hydrocarbons, predominantly methane, from hemisphere to hemisphere. Recently the direction of transport has been from south to north, but the effect would have reversed tens of thousands of years ago. (Credit: The mosaic includes Cassini SAR, ISS, and VIS images (NASA/JPL/Caltech/University of Arizona/Cassini Imaging Team).)

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How The Moon Produces Its Own Water

How The Moon Produces Its Own Water

  6:48:00 PM    Science Lover

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The Moon is a big sponge that absorbs electrically charged particles given out by the Sun. These particles interact with the oxygen present in some dust grains on the lunar surface, producing water. This discovery, made by the ESA-ISRO instrument SARA onboard the Indian Chandrayaan-1 lunar orbiter, confirms how water is likely being created on the lunar surface.

Chandrayaan-1 SARA measurements of hydrogen flux recorded on the Moon on 6 February 2009. (Credit: Elsevier 2009 (Wieser et al.), ESA-ISRO SARA data)

It also gives scientists an ingenious new way to take images of the Moon and any other airless body in the Solar System.

The lunar surface is a loose collection of irregular dust grains, known as regolith. Incoming particles should be trapped in the spaces between the grains and absorbed. When this happens to protons they are expected to interact with the oxygen in the lunar regolith to produce hydroxyl and water. The signature for these molecules was recently found and reported by Chandrayaan-1’s Moon Mineralogy Mapper (M3) instrument team.

The SARA results confirm that solar hydrogen nuclei are indeed being absorbed by the lunar regolith but also highlight a mystery: not every proton is absorbed. One out of every five rebounds into space. In the process, the proton joins with an electron to become an atom of hydrogen. “We didn’t expect to see this at all,” says Stas Barabash, Swedish Institute of Space Physics, who is the European Principal Investigator for the Sub-keV Atom Reflecting Analyzer (SARA) instrument, which made the discovery.

Although Barabash and his colleagues do not know what is causing the reflections, the discovery paves the way for a new type of image to be made. The hydrogen shoots off with speeds of around 200 km/s and escapes without being deflected by the Moon’s weak gravity. Hydrogen is also electrically neutral, and is not diverted by the magnetic fields in space. So the atoms fly in straight lines, just like photons of light. In principle, each atom can be traced back to its origin and an image of the surface can be made. The areas that emit most hydrogen will show up the brightest.

Whilst the Moon does not generate a global magnetic field, some lunar rocks are magnetised. Barabash and his team are currently making images, to look for such ‘magnetic anomalies’ in lunar rocks. These generate magnetic bubbles that deflect incoming protons away into surrounding regions making magnetic rocks appear dark in a hydrogen image.

The incoming protons are part of the solar wind, a constant stream of particles given off by the Sun. They collide with every celestial object in the Solar System but are usually stopped by the body’s atmosphere. On bodies without such a natural shield, for example asteroids or the planet Mercury, the solar wind reaches the ground. The SARA team expects that these objects too will reflect many of the incoming protons back into space as hydrogen atoms.

This knowledge provides timely advice for the scientists and engineers who are readying ESA’s BepiColombo mission to Mercury. The spacecraft will be carrying two similar instruments to SARA and may find that the inner-most planet is reflecting more hydrogen than the Moon because the solar wind is more concentrated closer to the Sun.

SARA was one of three instruments that ESA contributed to Chandrayaan-1, the lunar orbiter that finished its mission in August 2009. The instrument was built jointly by scientific groups from Sweden, India, Japan, and Switzerland: Swedish Institute of Space Physics, Kiruna, Sweden; Vikram Sarabhai Space Centre, Trivandrum, India; University of Bern, Switzerland; and Institute of Space and Astronautical Science, Sagamihara, Japan. The instrument is led by Principal Investigators Stanislav Barabash, IRF, Sweden, and Anil Bhardwaj, VSSC, India.
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