Posted on by Fraser Cain

Claritas Fossae on Mars

The region Claritas Fossae. Image credit: ESA Click to enlarge
This image, taken by the High Resolution Stereo Camera (HRSC) on board ESA’s Mars Express spacecraft, shows the ancient tectonic region of Claritas Fossae on Mars.

This region, west of Solis Planum, is a tectonic and volcanic area located south-east of the Tharsis volcano group (the Tharsis Montes) on the Tharsis rise. It extends roughly north to south for approximately 1800 kilometres.

The scene shows an area covering roughly 200 km by 1150 km and centred approximately at 258? East and 32? South. This is a high-resolution image of Claritas Fossae further to the one which was published on 31 March 2004.

Original Source: ESA Mars Express

Posted on by Fraser Cain

Astrophoto: M-81 by Tom Davis

Image credit: M-81 by Tom Davis.
Draw a line from the left bottom star through the top right star of the Big Dipper’s bowl then extend it roughly the same distance upward and you’ll see the location of this magnificent winter galaxy, the eighty first entry in Charles Messier’s catalog, known as M-81. It was first identified in the late 1700’s by German astronomer Johann Bode, so it’s also sometimes knownn as Bode’s Nebula.

Located only 12 million light years from Earth, a relative stone’s throw by intergalactic distances, M-81 is one of the brightest galaxies visible from in the night sky and can be spotted from a dark site, far from any city lights, without need for any optical assistance.

This picture was photographed by astrophotographer Tom Davis, from his Inkom, Idaho home in late January 2006 during a clear-sky break in an otherwise cloudy winter season. Tom photographed through a six inch, f/7 Astro-Physics refractor with a SBIG ST-10XME three mega-pixel camera.

M-81 exhibits beautifully symmetrical spiral arms and numerous dark lanes of dust in this 2.5 hour exposure. Some of these dusty ribbons may be evidence of interaction with its companion galaxy, M-82, which also shows signs of disturbance that is thought to be caused by M-81.

Do you have photos you’d like to share? Post them to the Universe Today astrophotography forum or email them, and we might feature one in Universe Today.

Written by R. Jay GaBany

Posted on by Fraser Cain

System Maps Microfossils in 3-D

A 650-million-year-old fossil. Image credit: Dr. J. William Schopf/UCLA. Click to enlarge
UCLA paleobiologist J. William Schopf and colleagues have produced 3-D images of ancient fossils – 650 million to 850 million years old – preserved in rocks, an achievement that has never been done before.

If a future space mission to Mars brings rocks back to Earth, Schopf said the techniques he has used, called confocal laser scanning microscopy and Raman spectroscopy, could enable scientists to look at microscopic fossils inside the rocks to search for signs of life, such as organic cell walls. These techniques would not destroy the rocks.

“It’s astounding to see an organically preserved, microscopic fossil inside a rock and see these microscopic fossils in three dimensions,” said Schopf, who is also a geologist, microbiologist and organic geochemist. “It’s very difficult to get any insight about the biochemistry of organisms that lived nearly a billion years ago, and this (confocal microscopy and Raman spectroscopy) gives it to you. You see the cells in the confocal microscopy, and the Raman spectroscopy gives you the chemistry.

“We can look underneath the fossil, see it from the top, from the sides, and rotate it around; we couldn’t do that with any other technique, but now we can, because of confocal laser scanning microscopy. In addition, even though the fossils are exceedingly tiny, the images are sharp and crisp. So, we can see how the fossils have degraded over millions of years, and learn what are real biological features and what has been changed over time.”

His research is published in the January issue of the journal Astrobiology, in which he reports confocal microscopy results of the ancient fossils. (He published ancient Raman spectroscopy 3-D images of ancient fossils in 2005 in the journal Geobiology.)

Since his first year as a Harvard graduate student in the 1960s, Schopf had the goal of conducting chemical analysis of an individual microscopic fossil inside a rock, but had no technique to do so, until now.

“I have wanted to do this for 40 years, but there wasn’t any way to do so before,” said Schopf, the first scientist to use confocal microscopy to study fossils embedded in such ancient rocks. He is director of UCLA’s Institute of Geophysics and Planetary Physics Center for the Study of Evolution and the Origin of Life.

Raman spectroscopy, a technique used primarily by chemists, allows you to see the molecular and chemical structure of ancient microorganisms in three dimensions, revealing what the fossils are made of without destroying the samples. Raman spectroscopy can help prove whether fossils are biological, Schopf said. This technique involves a laser from a microscope focused on a sample; most of the laser light is scattered, but a small part gets absorbed by the fossil.

Schopf is the first scientist to use this technique to analyze ancient microscopic fossils. He discovered that the composition of the fossils changed; nitrogen, oxygen and sulfur were removed, leaving carbon and hydrogen.

Confocal microscopy uses a focused laser beam to make the organic walls of the fossils fluoresce, allowing them to be viewed in three dimensions. The technique, first used by biologists to study the inner workings of living cells, is new to geology.

The ancient microorganisms are “pond scum,” among the earliest life, much too small to be seen with the naked eye.

Schopf’s UCLA co-authors include geology graduate students Abhishek Tripathi and Andrew Czaja, and senior scientist Anatoliy Kudryavtsev. The research is funded by NASA.

Schopf is editor of “Earth’s Earliest Biosphere” and “The Proterozoic Biosphere: A Multidisciplinary Study,” companion books that provide the most comprehensive knowledge of more than 4 billion years of the earth’s history, from the formation of the solar system 4.6 billion years ago to events half‑a‑billion years ago.

Original Source: UCLA News Release

Posted on by Fraser Cain

The New 10th Planet Is Larger than Pluto

The size of UB313 compared with Pluto, Charoon, Moon and Earth. Image credit: Max Planck Institute. Click to enlarge
Claims that the Solar System has a 10th planet are bolstered by the finding by a group lead by Bonn astrophysicists that this alleged planet, announced last summer and tentatively named 2003 UB313, is bigger than Pluto. By measuring its thermal emission, the scientists were able to determine a diameter of about 3000 km, which makes it 700 km larger than Pluto and thereby marks it as the largest solar system object found since the discovery of Neptune in 1846 (Nature, 2 February 2006).

Like Pluto, 2003 ub313 is one of the icy bodies in the so-called Kuiper belt that exists beyond Neptune. It is the most distant object ever seen in the Solar System. Its very elongated orbit takes it up to 97 times farther from the Sun than is the Earth – almost twice as far as the most distant point of Pluto’s orbit – so that it takes twice as long as Pluto to orbit the Sun. When it was first seen, UB313 appeared to be at least as big as Pluto. But an accurate estimate of its size was not possible without knowing how reflective it is. A team lead by Prof. Frank Bertoldi from the University of Bonn and the Max Planck Institute for Radio Astronomy (MPIfR) and the MPIfR’s Dr. Wilhelm Altenhoff has now resolved this problem by using measurements of the amount of heat UB313 radiates to determine its size, which when combined with the optical observations also allowed them to determine its reflectivity. “Since UB313 is decidedly larger than Pluto,” Frank Bertoldi remarks, “it is now increasingly hard to justify calling Pluto a planet if UB313 is not also given this status.”

UB313 was discovered in January 2005 by Prof. Mike Brown and his colleagues from the Californian Institute of Technology in a sky survey using a wide field digital camera that searches for distant minor planets at visible wavelengths. They discovered a slowly moving, spatially unresolved source, the apparent speed of which allowed them to determine its distance and orbital shape. However, they were not able to determine the size of the object, although from its optical brightness it was believed to be larger than Pluto.

Astronomers have found small planetary objects beyond the orbits of Neptune and Pluto since 1992, confirming a then 40-year old prediction by astronomers Kenneth Edgeworth (1880-1972) and Gerard P. Kuiper (1905-1973) that a belt of smaller planetary objects beyond Neptune exists. The so-called Kuiper Belt contains objects left from the formation of our planetary system some 4.5 billion years ago. In their distant orbits they were able to survive the gravitational clean-up of similar objects by the large planets in the inner solar system. Some Kuiper Belt objects are still occasionally deflected to then enter the inner solar system and may appear as short period comets.

In optically visible light, the solar system objects are visible through the light they reflect from the Sun. Thus, the apparent brightness depends on their size as well as on the surface reflectivity. Latter is known to vary between 4% for most comets to over 50% for Pluto, which makes any accurate size determination from the optical light alone impossible.

The Bonn group therefore used the IRAM 30-meter telescope in Spain, equipped with the sensitive Max-Planck Millimeter Bolometer (MAMBO) detector developed and built at the MPIfR, to measure the heat radiation of 2003 qq47 at a wavelength of 1.2 mm, where reflected sunlight is negligible and the object brightness only depends on the surface temperature and the object size. The temperature can be well estimated from the distance to the sun, and thus the observed 1.2 mm brightness allows a good size measurement. One can further conclude that the UB313 surface is such that it reflects about 60% of the incident solar light, which is very similar to the reflectivity of Pluto.

“The discovery of a solar system object larger than Pluto is very exciting,” Dr. Altenhoff exclaims, who has researched minor planets and comets for decades. “It tells us that Pluto, which should properly also be counted to the Kuiper Belt, is not such an unusual object. Maybe we can find even other small planets out there, which could teach us more about how the solar system formed and evolved. The Kuiper Belt objects are the debris from its formation, an archeological site containing pristine remnants of the solar nebula from which the sun and the planets formed.” Dr. Altenhoff made the pioneering discovery of heat radiation from Pluto in 1988 with a predecessor of the current detector at the IRAM 30-meter telescope.

The size measurement of 2003 UB313 is published in the 2 February 2006 issue of Nature. The research team includes Prof. Dr. Frank Bertoldi (Bonn University and MPIfR), Dr. Wilhelm Altenhoff (MPIfR), Dr. Axel Weiss (MPIfR), Prof. Dr. Karl M. Menten (MPIfR), and Dr. Clemens Thum (IRAM).

UB313 is a members of a ring of some 100,000 objects on the outskirts of the solar system, beyond Neptune at distances over 4 billion km from the sun, over 30 times the distance between Earth and Sun. The objects in this “Kuiper belt” circle the sun in stable orbits with periods of about 300 years. In the middle of the last century, the existence of a ring of small planetary objects was first suggested by the astronomers Kenneth Edgeworth (1880-1972) and Gerard P. Kuiper (1905-1973), but the first discovery of a “Kuiper belt object” was not until 1992. By now, over 700 such objects are known. UB313 is somewhat different from the normal Kuiper belt in that its orbit is highly excentric and 45 degrees inclined to the ecliptic plane of the planets and Kuiper Belt. It is likely that is originated in the Kuiper Belt and was deflected to its inclined orbit by Neptune.

Original Source: Max Planck Society

Update: Pluto is demoted

Posted on by Fraser Cain

Binary Icy Asteroid in Jupiter’s Orbit

An artist’s illustration of the binary asteroids Patroclus (center) and Menoetius. Image credit: W.M. Keck Observatory. Click to enlarge
A bound pair of icy comets similar to the dirty snowballs circling outside the orbit of Neptune has been found lurking in the shadow of Jupiter.

Astronomers at the University of California, Berkeley, working with colleagues in France and at the Keck Telescope in Hawaii, have calculated the density of a known binary asteroid system that shares Jupiter’s orbit, and concluded that Patroclus and its companion probably are composed mostly of water ice covered by a patina of dirt.

Because dirty snowballs are thought to have formed in the outer reaches of the solar system, from which they are occasionally dislodged and end up looping closer to the sun as comets, the team suggests that the asteroid probably formed far from the sun. It most likely was captured in one of Jupiter’s Trojan points – two eddies where debris collects in Jupiter’s orbit – during a period when the inner solar system was intensely bombarded by comets, around 650 million years after the formation of the solar system.

If confirmed, this could mean that many or most of the probably thousands of Jupiter’s Trojan asteroids are dirty snowballs that originated much farther from the sun and at the same time as the objects now occupying the Kuiper Belt.

“It’s our suspicion that the Trojans are small Kuiper Belt objects,” said study leader Franck Marchis, a research astronomer at UC Berkeley.

Marchis and colleagues from the Institut de M??bf?canique C??bf?leste et Calculs d’??bf?ph??bf?m??bf?rides (IMCCE) at the Observatoire de Paris and from the W. M. Keck Observatory report their findings in the Feb. 2 issue of Nature.

The team’s conclusion adds support to a recent hypothesis about the evolution of the orbits of our solar system’s largest planets, Jupiter, Saturn, Uranus and Neptune, put forth by a group of researchers headed by Alessandro Morbidelli, a theoretical astronomer with the Conseil National de la Recherche Scientifique laboratory of the Observatoire de la Cote d’Azur, Nice, France.
Diagram of the asteroid 617 Patroclus and its companion in the solar system

In a Nature paper last year, Morbidelli and colleagues proposed that icy comets would have been captured in Jupiter’s Trojan points during the early history of the solar system. According to their scenario, during the first few hundred million years after the birth of the solar system, the large gas planets orbited closer to the sun, enveloped in a cloud of billions of large asteroids called planetesimals, perhaps 100 kilometers (62 miles) in diameter or less. Interactions with these planetesimals caused the large gaseous planets to migrate outward until about 3.9 billion years ago, when Jupiter and Saturn entered resonant orbits and began tossing the planetesimals around like confetti, some of them leaving the solar system for good.

The bulk of the remaining planetesimals settled into orbits beyond Neptune – today’s Kuiper Belt and the source of short-period comets – but a small number were captured in the Trojan eddies of the giant planets, in particular Jupiter.

“This is the first time anyone has determined directly the density of a Trojan asteroid, and it supports the new scenario proposed by Morbidelli,” said coauthor Daniel Hestroffer, an astronomer at the IMCEE. “These asteroids would have been captured in the Trojan points at a time when the rocky planets were still forming, and this perturbation of the planetesimals about 650 million years after the birth of the solar system could have created the late bombardment of the moon and Mars.”

Though Marchis refers to the scenario as “a nice story,” he admits that more work needs to be done to provide support for it.

“We need to discover more binary Trojans and observe them to see if low density is a characteristic of all Trojans,” he said.

Trojan asteroids are those caught in the so-called Lagrange points of Jupiter’s orbit, located the same distance from Jupiter as Jupiter is from the sun – 5 astronomical units, or 465 million miles. These points, one leading and the other trailing Jupiter, are places were the gravitational attraction of the sun and Jupiter are balanced, allowing debris to collect like dust bunnies in the corner of a room. Hundreds of asteroids have been discovered in the leading (L4) and trailing (L5) points, each orbiting around that point as if in an eddy.

The asteroid 617 Patroclus, originally discovered at L5 and named in 1906, was found to have a companion in 2001, and so far is the only known Trojan binary. The discoverers were not able to estimate the orbit of the components because they had too few observations.

As experienced asteroid hunters, Marchis and his colleagues in August this year discovered the first triple asteroid system, 87 Sylvia, much closer to the sun in the main asteroid belt between Mars and Jupiter, and used a powerful 8-meter telescope of the European Southern Observatory’s Very Large Telescope in Chile to study the three objects. They were able to chart the orbits of the asteroids to estimate the density of Sylvia, from which they concluded it is a rubble-pile of loosely, packed rock.

The French and American team tried the same technique with the much more distant Patroclus, employing imaging data from the Keck II Laser Guide Star System at the W. M. Keck Observatory on Mauna Kea, which yields a sharp resolution impossible with any other ground-based telescope.

“Before, we could only look at objects near a bright reference star, limiting the use of adaptive optics to a small percentage of the heavens,” Marchis said. “Now, we can use adaptive optics to view almost any point on the sky.”

The laser guide star system uses a laser beam to excite sodium atoms within a small spot in the upper atmosphere. This artificial “star” is used to measure atmospheric turbulence, which is then removed by the movable mirrors of the Keck adaptive optics system.

With the system providing an unparalleled 58 milliarcsecond resolution, the Keck team made five observations in the infrared between November 2004 and July 2005. Marchis and his colleagues determined that the density of Patroclus and its companion, which are about the same size and circle around their center of mass every 4.3 days at a distance of 680 kilometers (423 miles), was very low: 0.8 grams per cubic centimeter, about one third that of rock and light enough to float in water. Assuming a rocky composition similar to that of Jupiter’s moons Callisto and Ganymede, the components of the system would have to be very loosely packed – about half empty space, an internal characteristic which is not expected for a same-size binary system, the researchers concluded.

The team suggests a more reasonable composition of water ice with only 15 percent open space, which makes these objects similar to comets and small Kuiper Belt objects, which have been determined to have densities less than water.

Marchis suspects that the binary system formed when a single large asteroid was torn asunder by the gravitational tug of Jupiter.

“The Patroclus system displays similar characteristics to the binary Near Earth Asteroids, which are believed to have formed during an encounter with a terrestrial planet by tidal splitting,” he said. “In the case of a Trojan asteroid, it is only when the work of our collaborators was published recently that we could suggest that this encounter was with Jupiter.”

Because in Homer’s Iliad, Patroclus was Achilles’ companion and a hero of the Trojan War, Achilles would have been an appropriate name for one of the two asteroids, which are about the same size. However, another asteroid already has the name Achilles, so Marchis and his collaborators proposed naming the smallest member of the binary system Menoetius, after the father of Patroclus. The Committee on Small Body Names of the International Astronomical Union has tentatively accepted the name. The asteroid designated Menoetius is about 112 kilometers (70 miles) in diameter, while Patroclus is about 122 kilometers (76 miles) wide.

In addition to Marchis, the team included astronomy professor Imke de Pater and postdoctoral fellow Michael H. Wong of UC Berkeley; Daniel Hestroffer, Pascal Descamps, J??bf?r??bf?me Berthier and Fr??bf?d??bf?ric Vachier of the Institut de M??bf?canique C??bf?leste et de Calculs des ??bf?ph??bf?m??bf?rides (IMCCE); and Antonin Bouchez, Randall Campbell, Jason Chin, Marcos van Dam, Scott Hartman, Erik Johansson, Robert Lafon, David Le Mignant, Paul Stomski, Doug Summers and Peter Wizinovich of the W. M. Keck Observatory.

The project was supported by grants from the National Science Foundation through the Science and Technology Center for Adaptive Optics and by the National Aeronautics and Space Administration. Most of the data were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership between the California Institute of Technology, the University of California and NASA, with additional observations obtained at the Gemini Observatory operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership.

Original Source: UC Berkeley News Release

Posted on by Fraser Cain

Most Milky Way Stars Are Single

An artist’s illustration of a rocky planet orbiting around a red dwarf star. Image credit: ESO Click to enlarge
Common wisdom among astronomers holds that most star systems in the Milky Way are multiple, consisting of two or more stars in orbit around each other. Common wisdom is wrong. A new study by Charles Lada of the Harvard-Smithsonian Center for Astrophysics (CfA) demonstrates that most star systems are made up of single stars. Since planets probably are easier to form around single stars, planets also may be more common than previously suspected.

Astronomers have long known that massive, bright stars, including stars like the sun, are most often found to be in multiple star systems. This fact led to the notion that most stars in the universe are multiples. However, more recent studies targeted at low-mass stars have found that these fainter objects rarely occur in multiple systems. Astronomers have known for some time that such low-mass stars, also known as red dwarfs or M stars, are considerably more abundant in space than high-mass stars.

By combining these two facts, Lada came to the realization that most star systems in the Galaxy are composed of solitary red dwarfs.

“By assembling these pieces of the puzzle, the picture that emerged was the complete opposite of what most astronomers have believed,” said Lada.

Among very massive stars, known as O- and B-type stars, 80 percent of the systems are thought to be multiple, but these very bright stars are exceedingly rare. Slightly more than half of all the fainter, sun-like stars are multiples. However, only about 25 percent of red dwarf stars have companions. Combined with the fact that about 85 percent of all stars that exist in the Milky Way are red dwarfs, the inescapable conclusion is that upwards of two-thirds of all star systems in the Galaxy consist of single, red dwarf stars.

The high frequency of lone stars suggests that most stars are single from the moment of their birth. If supported by further investigation, this finding may increase the overall applicability of theories that explain the formation of single, sun-like stars. Correspondingly, other star-formation theories that call for most or all stars to begin their lives in multiple-star systems may be less relevant than previously thought.

“It’s certainly possible for binary star systems to ‘dissolve’ into two single stars through stellar encounters,” said astronomer Frank Shu of National Tsing Hua University in Taiwan, who was not involved with this discovery. “However, suggesting that mechanism as the dominant method of single-star formation is unlikely to explain Lada’s results.”

Lada’s finding implies that planets also may be more abundant than astronomers realized. Planet formation is difficult in binary star systems where gravitational forces disrupt protoplanetary disks. Although a few planets have been found in binaries, they must orbit far from a close binary pair, or hug one member of a wide binary system, in order to survive. Disks around single stars avoid gravitational disruption and therefore are more likely to form planets.

Interestingly, astronomers recently announced the discovery of a rocky planet only five times more massive than Earth. This is the closest to an Earth-size world yet found, and it is in orbit around a single red dwarf star.

“This new planet may just be the tip of the iceberg,” said Lada. “Red dwarfs may be a fertile new hunting ground for finding planets, including ones similar in mass to the earth.”

“There could be many planets around red dwarf stars,” stated astronomer Dimitar Sasselov of CfA. “It’s all in the numbers, and single red dwarfs clearly exist in great numbers.”

“This discovery is particularly exciting because the habitable zone for these stars – the region where a planet would be the right temperature for liquid water – is close to the star. Planets that are close to their stars are easier to find. The first truly Earth-like planet we discover might be a world orbiting a red dwarf,” added Sasselov.

This research has been submitted to The Astrophysical Journal Letters for publication and is available online at http://arxiv.org/abs/astro-ph/0601375

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

Original Source: CfA News Release

Posted on by Fraser Cain

Neutron Star Swapping Leads to Gamma-Ray Bursts

M15 has a double neutron star system that will eventually merge violently. Image credit: NOAO Click to enlarge
Gamma-ray bursts are the most powerful explosions in the universe, emitting huge amounts of high-energy radiation. For decades their origin was a mystery. Scientists now believe they understand the processes that produce gamma-ray bursts. However, a new study by Jonathan Grindlay of the Harvard-Smithsonian Center for Astrophysics (CfA) and his colleagues, Simon Portegies Zwart (Astronomical Institute, The Netherlands) and Stephen McMillan (Drexel University), suggests a previously overlooked source for some gamma-ray bursts: stellar encounters within globular clusters.

“As many as one-third of all short gamma-ray bursts that we observe may come from merging neutron stars in globular clusters,” said Grindlay.

Gamma-ray bursts (GRBs) come in two distinct “flavors.” Some last up to a minute, or even longer. Astronomers believe those long GRBs are generated when a massive star explodes in a hypernova. Other bursts last for only a fraction of a second. Astronomers theorize that short GRBs originate from the collision of two neutrons stars, or a neutron star and a black hole.

Most double neutron star systems result from the evolution of two massive stars already orbiting each other. The natural aging process will cause both to become neutron stars (if they start with a given mass), which then spiral together over millions or billions of years until they merge and release a gamma-ray burst.

Grindlay’s research points to another potential source of short GRBs – globular clusters. Globular clusters contain some of the oldest stars in the universe crammed into a tight space only a few light-years across. Such tight quarters provoke many close stellar encounters, some of which lead to star swaps. If a neutron star with a stellar companion (such as a white dwarf or main-sequence star) exchanges its partner with another neutron star, the resulting pair of neutron stars will eventually spiral together and collide explosively, creating a gamma-ray burst.

“We see these precursor systems, containing one neutron star in the form of a millisecond pulsar, all over the place in globular clusters,” stated Grindlay. “Plus, globular clusters are so closely packed that you have a lot of interactions. It’s a natural way to make double neutron-star systems.”

The astronomers performed about 3 million computer simulations to calculate the frequency with which double neutron-star systems can form in globular clusters. Knowing how many have formed over the galaxy’s history, and approximately how long it takes for a system to merge, they then determined the frequency of short gamma-ray bursts expected from globular cluster binaries. They estimate that between 10 and 30 percent of all short gamma-ray bursts that we observe may result from such systems.

This estimate takes into account a curious trend uncovered by recent GRB observations. Mergers and thus bursts from so-called “disk” neutron-star binaries – systems created from two massive stars that formed together and died together – are estimated to occur 100 times more frequently than bursts from globular cluster binaries. Yet the handful of short GRBs that have been precisely located tend to come from galactic halos and very old stars, as expected for globular clusters.

“There’s a big bookkeeping problem here,” said Grindlay.

To explain the discrepancy, Grindlay suggests that bursts from disk binaries are likely to be harder to spot because they tend to emit radiation in narrower blasts visible from fewer directions. Narrower “beaming” might result from colliding stars whose spins are aligned with their orbit, as expected for binaries that have been together from the moment of their birth. Newly joined stars, with their random orientations, might emit wider bursts when they merge.

“More short GRBs probably come from disk systems – we just don’t see them all,” explained Grindlay.

Only about a half dozen short GRBs have been precisely located by gamma-ray satellites recently, making thorough studies difficult. As more examples are gathered, the sources of short GRBs should become much better understood.

The paper announcing this finding was published in the January 29 online issue of Nature Physics. It is available online at http://www.nature.com/nphys/index.html and in preprint form at http://arxiv.org/abs/astro-ph/0512654.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

Original Source: CfA News Release

Posted on by Fraser Cain

Dione’s Tectonic Faults

False colour view of Dione. Image credit: NASA/JPL/SSI Click to enlarge
This view highlights tectonic faults and craters on Dione, an icy world that has undoubtedly experienced geologic activity since its formation.

To create the enhanced-color view, ultraviolet, green and infrared images were combined into a single black and white picture that isolates and maps regional color differences. This “color map” was then superposed over a clear-filter image. The origin of the color differences is not yet understood, but may be caused by subtle differences in the surface composition or the sizes of grains making up the icy soil.

This view looks toward the leading hemisphere on Dione (1,126 kilometers, or 700 miles across). North is up and rotated 20 degrees to the right.

See Dione Has Her Faults (Monochrome) for a similar monochrome view.

All images were acquired with the Cassini spacecraft narrow-angle camera on Dec. 24, 2005 at a distance of approximately 151,000 kilometers (94,000 miles) from Dione and at a Sun-Dione-spacecraft, or phase, angle of 99 degrees. Image scale is 896 meters (2,940 feet) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

Stardust Placed Into Hibernation

An artist’s conception of Stardust spacecraft. Image credit: NASA/JPL Click to enlarge
NASA’s Stardust spacecraft was placed into hibernation mode yesterday. Stardust successfully returned to Earth samples of a comet via its sample return capsule on Jan. 15. The spacecraft has logged almost seven years of flight.

“We sang our spacecraft to sleep today with a melody of digital ones and zeros,” said Tom Duxbury, Stardust project manager at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “Stardust has performed flawlessly these last seven years and 2.88 billion miles and deserves a rest for a while, like the rest of the team.”

The “song” was actually a series of commands that was sent up to the spacecraft yesterday, Jan. 29 at 4 p.m. Pacific time (7 p.m. Eastern time). The commands deactivated all but a few essential systems, such as Stardust’s solar arrays and receive antenna – which will remain powered on. This long-term hibernation state could allow for almost indefinite (tens of years) out-of-contact operations while maintaining the spacecraft health.

“Placing Stardust in hibernation gives us options to possibly reuse it in the future,” said Dr. Tom Morgan, Stardust Program Executive at NASA Headquarters, Washington. “The mission has already been a great success, but if at all possible we may want to add even more scientific dividends to this remarkable mission’s record of achievement.”

The Stardust spacecraft is currently in an orbit that travels from a little closer to the Sun than that of the Earth to well beyond the orbit of Mars. It will next fly past Earth on January 14, 2009, at a distance of about 1 million kilometers (621,300 miles).

NASA’s Stardust sample return mission successfully concluded its prime mission on Jan. 15, 1006, when its sample return capsule carrying cometary and interstellar particles successfully touched down at 2:10 a.m. Pacific time (3:10 a.m. Mountain time) in the desert salt flats of the Utah Test and Training Range.

Stardust scientists at NASA’s Johnson Space Center in Houston are currently analyzing what could be considered a treasure-trove of cometary and interstellar dust samples that exceeded their grandest expectations. Scientists believe these precious samples will help provide answers to fundamental questions about comets and the origins of the solar system.

NASA’s Jet Propulsion Laboratory, Pasadena, Calif., manages the Stardust mission for NASA’s Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, developed and operated the spacecraft.

For information about the Stardust mission on the Web, visit www.nasa.gov/stardust. For information about NASA and agency programs on the Web, visit http://www.nasa.gov/home .

Original Source: NASA News Release

Posted on by Fraser Cain

The Smell of Moondust

Apollo 17 astronaut Jack Schmitt, with his spacesuit grayed by moondust. Image credit: NASA Click to enlarge
Moondust. “I wish I could send you some,” says Apollo 17 astronaut Gene Cernan. Just a thimbleful scooped fresh off the lunar surface. “It’s amazing stuff.”

Feel it?it’s soft like snow, yet strangely abrasive.

Taste it?”not half bad,” according to Apollo 16 astronaut John Young.

Sniff it?”it smells like spent gunpowder,” says Cernan.

How do you sniff moondust?

Every Apollo astronaut did it. They couldn’t touch their noses to the lunar surface. But, after every moonwalk (or “EVA”), they would tramp the stuff back inside the lander. Moondust was incredibly clingy, sticking to boots, gloves and other exposed surfaces. No matter how hard they tried to brush their suits before re-entering the cabin, some dust (and sometimes a lot of dust) made its way inside.

Once their helmets and gloves were off, the astronauts could feel, smell and even taste the moon.

The experience gave Apollo 17 astronaut Jack Schmitt history’s first recorded case of extraterrestrial hay fever. “It’s come on pretty fast,” he radioed Houston with a congested voice. Years later he recalls, “When I took my helmet off after the first EVA, I had a significant reaction to the dust. My turbinates (cartilage plates in the walls of the nasal chambers) became swollen.”

Hours later, the sensation faded. “It was there again after the second and third EVAs, but at much lower levels. I think I was developing some immunity to it.”

Other astronauts didn’t get the hay fever. Or, at least, “they didn’t admit it,” laughs Schmitt. “Pilots think if they confess their symptoms, they’ll be grounded.” Unlike the other astronauts, Schmitt didn’t have a test pilot background. He was a geologist and readily admitted to sniffles.

Schmitt says he has sensitive turbinates: “The petrochemicals in Houston used to drive me crazy, and I have to watch out for cigarette smoke.” That’s why, he believes, other astronauts reacted much less than he did.

But they did react: “It is really a strong smell,” radioed Apollo 16 pilot Charlie Duke. “It has that taste — to me, [of] gunpowder — and the smell of gunpowder, too.” On the next mission, Apollo 17, Gene Cernan remarked, “smells like someone just fired a carbine in here.”

Schmitt says, “All of the Apollo astronauts were used to handling guns.” So when they said ‘moondust smells like burnt gunpowder,’ they knew what they were talking about.

To be clear, moondust and gunpowder are not the same thing. Modern smokeless gunpowder is a mixture of nitrocellulose (C6H8(NO2)2O5) and nitroglycerin (C3H5N3O9). These are flammable organic molecules “not found in lunar soil,” says Gary Lofgren of the Lunar Sample Laboratory at NASA’s Johnson Space Center. Hold a match to moondust–nothing happens, at least, nothing explosive.

What is moondust made of? Almost half is silicon dioxide glass created by meteoroids hitting the moon. These impacts, which have been going on for billions of years, fuse topsoil into glass and shatter the same into tiny pieces. Moondust is also rich in iron, calcium and magnesium bound up in minerals such as olivine and pyroxene. It’s nothing like gunpowder.

So why the smell? No one knows.

ISS astronaut Don Pettit, who has never been to the moon but has an interest in space smells, offers one possibility:

“Picture yourself in a desert on Earth,” he says. “What do you smell? Nothing, until it rains. The air is suddenly filled with sweet, peaty odors.” Water evaporating from the ground carries molecules to your nose that have been trapped in dry soil for months.

Maybe something similar happens on the moon.

“The moon is like a 4-billion-year-old desert,” he says. “It’s incredibly dry. When moondust comes in contact with moist air in a lunar module, you get the ‘desert rain’ effect–and some lovely odors.” (For the record, he counts gunpowder as a lovely odor.)

Gary Lofgren has a related idea: “The gases ‘evaporating’ from the moondust might come from the solar wind.” Unlike Earth, he explains, the moon is exposed to the hot wind of hydrogen, helium and other ions blowing away from the sun. These ions hit the moon’s surface and get caught in the dust.

It’s a fragile situation. “The ions are easily dislodged by footsteps or dustbrushes, and they would be evaporated by contact with warm air inside the lunar module. Solar wind ions mingling with the cabin’s atmosphere would produce who-knows-what odors.”

Want to smell the solar wind? Go to the moon.

Schmitt offers yet another idea: The smell, and his reaction to it, could be a sign that moondust is chemically active.

“Consider how moondust is formed,” he says. “Meteoroids hit the moon, reducing rocks to jagged dust. It’s a process of hammering and smashing.” Broken molecules in the dust have “dangling bonds”–unsatisfied electrical connections that need atomic partners.

Inhale some moondust and what happens? The dangling bonds seek partners in the membranes of your nose. You get congested. You report strange odors. Later, when the all the bonds are partnered-up, these sensations fade.

Another possibility is that moondust “burns” in the lunar lander’s oxygen atmosphere. “Oxygen is very reactive,” notes Lofgren, “and would readily combine with the dangling chemical bonds of the moondust.” The process, called oxidation, is akin to burning. Although it happens too slowly for smoke or flames, the oxidation of moondust might produce an aroma like burnt gunpowder. (Note: Burnt and unburnt gunpowder do not smell the same. Apollo astronauts were specific. Moondust smells like burnt gunpowder.)

Curiously, back on Earth, moondust has no smell. There are hundreds of pounds of moondust at the Lunar Sample Lab in Houston. There, Lofgren has held dusty moon rocks with his own hands. He’s sniffed the rocks, sniffed the air, sniffed his hands. “It does not smell like gunpowder,” he says.

Were the Apollo crews imagining things? No. Lofgren and others have a better explanation:

Moondust on Earth has been “pacified.” All of the samples brought back by Apollo astronauts have been in contact with moist, oxygen-rich air. Any smelly chemical reactions (or evaporations) ended long ago.

This wasn’t supposed to happen. Astronauts took special “thermos” containers to the moon to hold the samples in vacuum. But the jagged edges of the dust unexpectedly cut the seals of the containers, allowing oxygen and water vapor to sneak in during the 3-day trip back to Earth. No one can say how much the dust was altered by that exposure.

Schmitt believes “we need to study the dust in situ–on the moon.” Only there can we fully discover its properties: Why does it smell? How does it react with landers, rovers and habitats? What surprises await?

NASA plans to send people back to the moon in 2018, and they’ll stay much longer than Apollo astronauts did. The next generation will have more time and better tools to tackle the mystery.

We’ve only just begun to smell the moondust.

Original Source: NASA News Release