Posted on by Fraser Cain

Brand New Martian Gullies

Before (2002) and after pictures of a new gully on a sand dune on Mars. Image credit: NASA/JPL. Click to enlarge.
New gullies that did not exist in mid-2002 have appeared on a Martian sand dune.

That’s just one of the surprising discoveries that have resulted from the extended life of NASA’s Mars Global Surveyor, which this month began its ninth year in orbit around Mars. Boulders tumbling down a Martian slope left tracks that weren’t there two years ago. New impact craters formed since the 1970s suggest changes to age-estimating models. And for three Mars summers in a row, deposits of frozen carbon dioxide near Mars’ south pole have shrunk from the previous year’s size, suggesting a climate change in progress.

“Our prime mission ended in early 2001, but many of the most important findings have come since then, and even bigger ones might lie ahead,” said Tom Thorpe, project manager for Mars Global Surveyor at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. The orbiter is healthy and may be able to continue studying Mars for five to 10 more years, he said.

Mars years are nearly twice as long as Earth years. The orbiter’s longevity has enabled monitoring of year-to-year patterns on Mars, such as seasonal dust storms and changes in the polar caps. “Mars is an active planet, and over a range of timescales changes occur, even in the surface,” said Dr. Michael Malin of Malin Space Science Systems, San Diego, principal investigator for the Mars Orbiter Camera on Mars Global Surveyor.

“To see new gullies and other changes in Mars surface features on a time span of a few years presents us with a more active, dynamic planet than many suspected before Mars Global Surveyor got there,” said Michael Meyer, Mars Exploration Program chief scientist, NASA Headquarters, Washington.

Two gullies appear in an April 2005 image of a sand-dune slope where they did not exist in July 2002. The Mars Orbiter Camera team has found many sites on Mars with fresh-looking gullies, and checked back at more than 100 gullied sites for possible changes between imaging dates, but this is the first such find. Some gullies, on slopes of large sand dunes, might have formed when frozen carbon dioxide, trapped by windblown sand during winter, vaporized rapidly in spring, releasing gas that made the sand flow as a gully-carving fluid.

At another site, more than a dozen boulders left tracks when they rolled down a hill sometime between the taking of images in November 2003 and December 2004. It is possible that they were set in motion by strong wind or by a “marsquake,” Malin said.

Some changes are slower than expected. Studies suggest new impact craters might appear at only about one-fifth the pace assumed previously, Malin said. That pace is important because crater counts are used to estimate the ages of Mars surfaces.

The camera has recorded seasonal patterns of clouds and dust within the atmosphere over the entire planet. In addition, other instruments on Mars Global Surveyor have provided information about atmospheric changes and year-to-year patterns on Mars as the mission has persisted. Daily mapping of dust abundance in Mars’ atmosphere by the Thermal Emission Spectrometer has shown dust over large areas during three Mars southern hemisphere summers in a row. However, the extent and duration of dust storms varied from year to year.

Mars Global Surveyor was launched Nov. 7, 1996; entered orbit around Mars Sept. 12, 1997; and returned the first Mars data from its science instruments Sept. 15, 1997. Beyond its own investigations, the orbiter provides support for other Mars missions, such as landing-site evaluations, atmospheric monitoring, communication relay and imaging of hardware on the surface. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington. JPL’s industrial partner is Lockheed Martin Space Systems, Denver, which built and operates the spacecraft.

For newly released images on the Internet, visit: http://www.nasa.gov/vision/universe/solarsystem/mgs-092005-images.html and http://www.msss.com/mars_images/moc/2005/09/20/ .

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Binary Star Baby Picture

The centre of this infrared image shows the higher mass primary star (pink) and its lower mass companion. Image credit: CfA. Click to enlarge.
Newborn stars are difficult to photograph. They tend to hide in the nebulous stellar nurseries where they formed, enshrouded by thick layers of dust. Now, Smithsonian astronomer T.K. Sridharan (Harvard-Smithsonian Center for Astrophysics) and his colleagues have photographed a pair of stellar twins in infrared light, which penetrates the dust. And these babies are whoppers, weighing several times the mass of the Sun.

Moreover, Sridharan’s images reveal a circumstellar disk surrounding the more massive of the two stars. The presence of a disk suggests that massive, multiple-star systems form the same way as the Sun, by gradually accreting material from a gaseous disk.

“This system is the youngest massive binary ever to be directly imaged – only about 100,000 years old,” said Sridharan.

Sridharan and his colleagues studied an object known as IRAS 20126+4104, located more than 5,000 light-years away in the constellation Cygnus the Swan. IRAS 20126+4104 was suspected of harboring a binary star because outflows from the region wobbled back and forth like a spinning top. The wobble hinted at the gravitational tug of an unseen companion.

On several exceptionally clear and steady nights, the researchers were able to take highly detailed infrared images of this object using the UKIRT telescope on Mauna Kea, Hawaii. Those images revealed not one but two stars, as well as a dark dust lane where the inner parts of the disk, known from previous radio-wavelength observations, appeared nearly edge-on in silhouette.

“Many people have seen the iconic Hubble Space Telescope images of circumstellar disks around low-mass stars. This image is the equivalent for high-mass stars,” said Sridharan.

Between them the two stars weigh more than 10 times the mass of the Sun. Sridharan calculates that the surrounding disk contains at least one-tenth of a solar mass, which is enough material to make 100 Jupiter-sized worlds. The disk may be even more massive. It extends outward for at least 850 astronomical units, or 80 billion miles (more than 20 times the distance to Pluto). Interestingly, the smaller companion star currently is located at the same distance from the primary star, hinting that the companion’s gravity may play a role in limiting the outer reaches of the disk.

Sridharan said that the next step in studying this intriguing twin system is to get higher-resolution observations using adaptive optics or interferometry. Such data will yield a better estimate of the companion’s mass and a detailed profile of the disk.

“We are currently following several leads to investigate this star system, so stay tuned,” Sridharan added.

Sridharan’s co-authors are S.J. Williams and G.A. Fuller of UMIST (Manchester, UK). This research was published in the Sept. 20, 2005, issue of The Astrophysical Journal Letters and is available online at http://arxiv.org/abs/astro-ph/0508342.

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: Harvard CfA News Release

Posted on by Fraser Cain

Halo of Blue Stars Around a Black Hole

Artist illustration of the heart of galaxy M31. Image credit: NASA. Click to enlarge.
Astronomers using NASA’s Hubble Space Telescope have identified the source of a mysterious blue light surrounding a supermassive black hole in our neighboring Andromeda Galaxy (M31). Though the light has puzzled astronomers for more than a decade, the new discovery makes the story even more mysterious.

The blue light is coming from a disk of hot, young stars. These stars are whipping around the black hole in much the same way as planets in our solar system are revolving around the Sun. Astronomers are perplexed about how the pancake-shaped disk of stars could form so close to a giant black hole. In such a hostile environment, the black hole’s tidal forces should tear matter apart, making it difficult for gas and dust to collapse and form stars. The observations, astronomers say, may provide clues to the activities in the cores of more distant galaxies.

By finding the disk of stars, astronomers also have collected what they say is ironclad evidence for the existence of the monster black hole. The evidence has helped astronomers rule out all alternative theories for the dark mass in Andromeda’s core, which scientists have long suspected was a black hole.

“Seeing these stars is like watching a magician pulling a rabbit out of a hat. You know it happened but you don’t know how it happened,” said Tod Lauer of the National Optical Astronomy Observatory in Tucson, Arizona. He and a team of astronomers, led by Ralf Bender of the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, and John Kormendy of the University of Texas in Austin, made the Hubble observations. The team’s results will be published in the Sept. 20, 2005 issue of the Astrophysical Journal.

Hubble Probes Strange Blue Light
Astronomer Ivan King of the University of Washington and colleagues first spotted the strange blue light in 1995 with the Hubble telescope. He thought the light might have come from a single, bright blue star or perhaps from a more exotic energetic process. Three years later, Lauer and Sandra Faber of the University of California at Santa Cruz used Hubble again to study the blue light. Their observations indicated that the blue light was a cluster of blue stars.

Now, new spectroscopic observations by Hubble’s Space Telescope Imaging Spectrograph (STIS) reveal that the blue light consists of more than 400 stars that formed in a burst of activity about 200 million years ago. The stars are tightly packed in a disk that is only a light-year across. The disk is nested inside an elliptical ring of older, cooler, redder stars, which was seen in previous Hubble observations.

The astronomers also used STIS to measure the velocities of those stars. They obtained the stars’ speeds by calculating how much their light waves are stretched and compressed as they travel around the black hole. Under the black hole’s gravitational grip, the stars are traveling very fast: 2.2 million miles an hour (3.6 million kilometers an hour, or 1,000 kilometers a second). They are moving so fast that it would take them 40 seconds to circle the Earth and six minutes to arrive at the Moon. The fastest stars complete an orbit in 100 years.

Andromeda’s active core probably made similar disks of stars in the past and may continue to make them.

“The blue stars in the disk are so short-lived that it is unlikely in the long 12-billion-year history of Andromeda that such a short-lived disk would appear now,” Lauer said. “That’s why we think that the mechanism that formed this disk of stars probably formed other stellar disks in the past and will trigger them again in the future. We still don’t know, however, how such a disk could form in the first place. It still remains an enigma.”

The astronomers credit Hubble’s superb vision for finding the disk.

“Only Hubble has the resolution in blue light to observe this disk,” said team member Richard Green of the National Optical Astronomy Observatory in Tucson. “It is so small and so distinct from the surrounding red stars that we were able to use it to probe into the very dynamical heart of Andromeda. These observations were taken by the members of our team that built STIS. We designed its visible channel specifically to seize such an opportunity ? to measure starlight closer to a black hole than in any other galaxy outside our own.”

Solid Evidence for a Monster Black Hole
In addition to the discovery of the disk of stars, the astronomers used this uniquely close look at Andromeda to prove unambiguously that the galaxy hosts a central black hole. In 1988, in independent ground-based studies, John Kormendy and the team of Alan Dressler and Douglas Richstone discovered a central dark object in Andromeda that they believed was a supermassive black hole. This was the first strong case for what are now 40 detections of black holes, most of them made by Hubble. Those observations, however, did not definitively rule out other, very exotic, and far less likely, alternatives.

“There are compelling reasons to believe that these are supermassive black holes,” Kormendy said. “But extreme claims require extraordinarily strong evidence. We have to be sure that these are black holes and not dark clusters of dead stars.”

The STIS observations of Andromeda are so precise that astronomers have eliminated all other possibilities for what the central, dark object could be. They also calculated that the black hole’s mass is 140 million Suns, which is three times more massive than once thought.

So far, dark clusters have definitively been ruled out in only two galaxies, NGC 4258 and our galaxy, the Milky Way. “These two galaxies give us unambiguous proof that black holes exist,” Kormendy added. “But both are special cases ? NGC 4258 contains a disk of water masers that we observe with radio telescopes, and our galactic center is so close that we can follow individual stellar orbits. Andromeda is the first galaxy in which we can exclude all exotic alternatives to a black hole using Hubble and using the same techniques by which we find almost all supermassive black holes.”

“Studying black holes always was a primary mission of Hubble,” Kormendy said. “Nailing the black hole in Andromeda is without a doubt an important part of its legacy. It makes us much more confidant that the other central dark objects detected in galaxies are black holes, too.”

“Now that we have proven that the black hole is at the center of the disk of blue stars, the formation of these stars becomes hard to understand,” Bender added. “Gas that might form stars must spin around the black hole so quickly ? and so much more quickly near the black hole than farther out ? that star formation looks almost impossible. But the stars are there.”

A Galaxy’s Active Core
The black hole and the disk of stars are not the only pieces of architecture in Andromeda’s core. A team led by Lauer and Faber used Hubble in 1993 to discover that the galaxy appears to have a double cluster of stars at its center. This finding was a surprise, because two clusters should merge into one in only a few hundred thousand years. Scott Tremaine of Princeton University solved this problem by suggesting that the “double nucleus” was actually a ring of old, red stars. The ring looked like two star clusters because astronomers were only seeing the stars on the opposite ends of the ring. The ring is about five light-years from the black hole and its surrounding disk of blue stars. The disk and the ring are tilted at the same angle as viewed from Earth, suggesting that they may be related.

Although astronomers are surprised to find a blue disk of stars swirling around a supermassive black hole, they also say the puzzling architecture may not be that unusual.

“The dynamics within the core of this neighboring galaxy may be more common than we think,” Lauer explained. “Our own Milky Way apparently has even younger stars close to its own black hole. It seems unlikely that only the closest two big galaxies should have this odd activity. So this behavior may not be the exception but the rule. And we have found other galaxies that have a double nucleus.”

Original Source: Hubble News Release

Posted on by Fraser Cain

Oldest Meteorites Hint at Early Solar System

Different concentrations of elements in a meteorite: magnesium is green, calcium is yellow, aluminium is white, iron is red and silicon is blue. Image credit: Open University. Click to enlarge.
Researchers trying to work out how the planets formed have uncovered a new clue by analysing meteorites that are older than the Earth.

The research shows that the process which depleted planets and meteorites of so-called volatile elements such as zinc, lead and sodium (in their gaseous form) must have been one of the first things to happen in our nebula. The implication is that ‘volatile depletion’ may be an inevitable part of planet formation – a feature not just of our Solar System, but of many other planetary systems too.

The researchers at Imperial College London, who are funded by the Particle Physics and Astronomy Research Council (PPARC), reached their conclusions after analysing the composition of primitive meteorites, stony objects that are older than the Earth and which have barely changed since the Solar System was made up of fine dust and gas.

Their analysis, published today in the Proceedings of the National Academy of Sciences, shows that all the components that make up these rocks are depleted of volatile elements. This means that volatile element depletion must have occurred before the earliest solids had formed.

All of the terrestrial planets in the Solar System as far out as Jupiter, including Earth, are depleted of volatile elements. Researchers have long known that this depletion must have been an early process, but it was unknown whether it occurred at the beginning of the formation of the Solar System, or a few million years later.

It might be that volatile depletion is necessary to make terrestrial planets as we know them -as without it our inner solar system would look more like the outer solar system with Mars and Earth looking more like Neptune and Uranus with much thicker atmospheres.

Dr Phil Bland, from Imperial’s Department of Earth Science and Engineering, who led the research, explains: “Studying meteorites helps us to understand the initial evolution of the early Solar System, its environment, and what the material between stars is made of. Our results answer one of a huge number of questions we have about the processes that converted a nebula of fine dust and gas into planets.”

Professor Monica Grady, a planetary scientist from the Open University and member of PPARC’s Science Committee adds, “This research shows how looking at the tiniest of fragments of material can help us answer one of the biggest questions asked: ‘How did the Solar System form?’. It is fascinating to see how processes that took place over 4.5 billion years ago can be traced in such detail in laboratories on Earth today.

For planetary scientists, the most valuable meteorites are those that are found immediately after falling to earth, and so are only minimally contaminated by the terrestrial environment. The researchers analysed around half of the approximately 45 primitive meteorite falls in existence around the world, including the Renazzo meteorite which was found in Italy in 1824.

Dr Phil Bland is a member of the Impacts and Astromaterials Research Centre (IARC), which combines planetary science researchers from Imperial College London and the Natural History Museum.

Original Source: PPARC News Release

Posted on by Fraser Cain

Wide Image of the Virgo Cluster of Galaxies

Deep, wide field view of the Virgo Cluster showing a diffuse web of galaxies. Image credit: Chris Mihos et al. Click to enlarge.
Case Western Reserve University astronomers have captured the deepest wide-field image ever of the nearby Virgo cluster of galaxies, directly revealing for the first time a vast, complex web of “intracluster starlight” — nearly 1,000 times fainter than the dark night sky — filling the space between the galaxies within the cluster. The streamers, plumes and cocoons that make up this extremely faint starlight are made of stars ripped out of galaxies as they collide with one another inside the cluster, and act as a sort of “archaeological record” of the violent lives of cluster galaxies.

The Virgo image was captured through Case’s newly refurbished 24-inch Burrell Schmidt telescope, built in the 1930s and located at the Kitt Peak National Observatory in Arizona. Over the course of 14 dark moonless nights, the researchers took more than 70 images of the Virgo Cluster, then used advanced image processing techniques to combine the individual images into a single image capable of showing the faint intracluster light.

“When we saw all this very faint starlight in the image, my first reaction was WOW!,” project leader Chris Mihos said. “Then I began to worry about all the things we could have done wrong.” Many effects, such as stray light from nearby stars, from instruments in the observatory and even from the changing brightness of the night sky could all contaminate the image and lead to inaccurate results. “But as we corrected for each of these contaminants, not only did the faint starlight not disappear, it became even more apparent. That’s when we knew we had something big.”

The new image gives dramatic evidence of the violent life and death of cluster galaxies. Drawn together into giant clusters over the course of cosmic time by their mutual gravity, galaxies careen around in the cluster, smashing into other galaxies, being stripped apart by gravitational forces and even being cannibalized by the massive galaxies which sit at the cluster’s heart. The force of these encounters literally pulls many galaxies apart, leaving behind ghostly streams of stars adrift in the cluster, a faint tribute to the violence of cluster life.

“From computer simulations, we’ve long suspected this web of intracluster starlight should be there,” says Mihos, associate professor of astronomy at Case, “but it’s been extremely hard to map it out because it’s so faint.” Mihos and graduate students Craig Rudick (Case) and Cameron McBride (University of Pittsburgh, and former Case undergraduate) have developed computer simulations that track how clusters of galaxies evolve over time, to study exactly how this intracluster starlight is created.

“With the data from the telescope, we see how a cluster looks today,” Mihos explains. “But with computer simulations, we can watch how a cluster evolves over 10 billion years of time. By comparing the simulation to the real features we now see in Virgo, we can learn how the cluster formed and what happened to its many galaxies.” For example, the fact that the intracluster light in Virgo is so complex and irregular lends credence to the theory of “hierarchical assembly,” where clusters grow sporadically when groups of galaxies fall into the cluster, rather than through the smooth, slow addition of galaxies one by one.

To detect the faint intracluster light, upgrades were needed to Case’s Burrell Schmidt telescope, originally part of the original Warner and Swasey Observatory in Cleveland until its move to Kitt Peak in 1979. The improvements included the installation of a new camera system and upgrades to the telescope to make it more structurally stable and reduce unwanted scattered light.

“It’s like ‘The Little Engine that Could’,” says Case astronomer Paul Harding, who directed the refurbishment of the telescope. “It’s the smallest telescope on the mountain, but with these upgrades it’s capable of some pretty incredible science.” The telescope’s wide field of view — enough to fit three full moons across the image – proved crucial to the project, allowing the team to map out the intracluster light over a much larger part of the Virgo Cluster than would be possible using larger telescopes with their much smaller fields of view.
The Virgo Cluster of galaxies — so named because it appears in the constellation of Virgo — is the nearest galaxy cluster to the Earth, at a distance of approximately 50 million light years. The cluster contains more than 2,000 galaxies, the brightest of which can be seen with the aide of a small telescope.

The Case findings are reported in the paper “Diffuse Light in the Virgo Cluster” to be published in the September 20th issue of The Astrophysical Journal Letters. Along with Mihos team researchers included Case astronomers Heather Morrison and Paul Harding, and John Feldmeier, a National Science Foundation Fellow at the National Optical Astronomy Observatory in Tucson, Ariz. (and formerly of Case).

The wide-field image of the Virgo Cluster, along with movies of computer simulations of galaxies and galaxy clusters, can be found at http://astroweb.case.edu/hos/Virgo.

Original Source: Case Western University News Release

Posted on by Fraser Cain

Methane Release Raised Earth Temperatures 180 Million Years Ago

Western Hemisphere. Image credit: NASA Click to enlarge
Open University researchers have uncovered startling new evidence about an extreme period of a sudden, fatal dose of global warming some 180 million years ago during the time of the dinosaurs. The scientists’ findings could provide vital clues about climate change happening today and in the future.

The OU Department of Earth Sciences team, PhD student Dave Kemp and supervisors Drs. Angela Coe and Anthony Cohen, along with Dr. Lorenz Schwark of the University of Cologne, discovered evidence suggesting that vast amounts of methane gas were released to the atmosphere in three massive ‘methane burps’ or pulses. The addition of methane, a greenhouse gas, to the atmosphere had a severe impact on the environment, warming Earth about 10 C, and resulting in the extinction of a large number of species on land and in the oceans.

Dr Angela Coe says: “We’ve known about this event for a few years through earlier work by our team and others, but there’s been a great deal of uncertainty about its precise size, duration, and underlying cause. What our present study shows is that this methane release was not just one event, but 3 consecutive pulses. Importantly, our data demonstrate that each individual pulse was very rapid. Also, whilst the methane release was very quick, we’ve found that the recovery took much longer, occurring over a few hundred thousand years”.

The methane came from gas hydrate, a frozen mixture of water and methane found in huge quantities on the seabed. This hydrate suddenly melted, allowing the methane to escape. The OU researchers based their findings on geochemical analyses of mudrocks that are preserved along the Yorkshire coast near Whitby, UK, and date from the Jurassic Period of geological time.

Dave Kemp, whose PhD is funded by the Natural Environment Research Council (NERC), says: “The methane was released because slight wobbles in the Earth’s orbit periodically bring our planet closer to the Sun, warming the oceans sufficiently to melt the vast reserves of hydrate. We believe that this effect was compounded by warming from greenhouse gases from volcanoes. After the methane was released into the atmosphere from the seabed it reacted rapidly with oxygen to form carbon dioxide. Carbon dioxide is also a powerful greenhouse gas that persists in the atmosphere for many hundreds of years, and it was this gas which caused such a massive global warming effect”.

Dr Anthony Cohen adds: “One of the most important aspects of the study is that it provides an accurate timescale for how the Earth, and life, reacted to a sudden increase in atmospheric carbon dioxide. Today we are releasing large amounts of carbon dioxide to the atmosphere, primarily through the burning of fossil fuels. It is possible that the rate at which carbon dioxide is being added to the atmosphere now actually outstrips the rate at which it was added 180 million years ago. Given that the effects were so devastating then, it is extremely important to understand the details of past events in order to better comprehend present-day climate change. With this information, we are better informed about what action needs to be taken to mitigate or avoid some of the potential detrimental future effects”.

NASA Astrobiology

Posted on by Fraser Cain

Ghostly Spokes in the Rings

An image showing faint, narrow spokes in the outer B ring. Image credit: NASA/JPL/SSI Click to enlarge
Scientists are celebrating the first Cassini spacecraft sighting of spokes, the ghostly radial markings discovered in Saturn’s rings by NASA’s Voyager spacecraft 25 years ago.

A sequence of images taken on the side of the rings not illuminated by the sun has captured a few faint, narrow spokes in the outer B ring, about 3,500 kilometers long and about 100 kilometers wide (2,200 miles by 60 miles).

The images can be seen at: http://www.nasa.gov/cassini, http://saturn.jpl.nasa.gov and http://ciclops.org .

Previously, scientists believed the visibility of spokes depended on the elevation of the sun above the rings. The less sunlight, the more visible the spokes. For this reason, they weren’t expecting to see spokes until later in the mission when the sun angle will be low.

In Voyager images from 25 years ago, the spokes appeared dark when seen at low sun angles and bright when seen at high sun angles. This behavior indicated that they were comprised of extremely small icy particles. Since Voyager days, spokes had been seen in images taken by NASA’s Hubble Space Telescope. The new Cassini images were taken at very high sun angles, where small particles can brighten substantially, making them more visible.

Determining the timing in the appearance of spokes will be of intense interest and will require monitoring spoke activity from a variety of geometries over several years. “Cassini has found that the Saturn Kilometric Radiation period has changed since Voyager, which though hard to believe, may mean that the rotation of Saturn’s interior has changed,” said Dr. Carolyn Porco, Cassini imaging team leader at the Space Science Institute in Boulder, Colo., and one of the first individuals to study spokes in Voyager images. “That would be a finding of enormous consequence, so we’ll be looking very closely to see if the frequency of spoke activity has changed too.”

Porco’s analysis of spokes in the early 1980s found that these narrow arrangements of small particles came and went with a period equal to that of the powerful bursts of radio waves, called Saturn Kilometric Radiation, discovered by Voyager and coming from Saturn’s magnetic field. This association indicated that spokes were a phenomenon involving electromagnetic effects due to Saturn’s magnetic field.

There is no commonly accepted theory for the creation of spokes. Some ideas suggest that spokes result from meteoroid impacts onto the rings; others suggest that they are created by instability in Saturn’s magnetic field, which surrounds the planet, near the rings. Whatever the cause, imaging team members will study the new spoke images and maintain their vigil for additional spoke sightings.

Cassini also completed a flyby of Saturn’s moon Titan on Wednesday, Sept. 7. During that flyby, one of two solid-state recorders on board the spacecraft failed to record science data as planned. The spacecraft team is troubleshooting the cause of the anomaly, and early indications point to a software problem that would be correctable with no long-term impacts. About half of the planned science data was received.

This was Cassini’s eighth flyby out of 45 Titan flybys planned in the nominal four-year tour.

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 Cassini-Huygens mission for NASA’s Science Mission Directorate, Washington. 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.

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

Shoreline Found on Titan

The boundary of the bright (rough) region and the dark (smooth) region appears to be a shoreline. Image credit: NASA/JPL/SSI Click to enlarge
Images returned during Cassini’s recent flyby of Titan show captivating evidence of what appears to be a large shoreline cutting across the smoggy moon’s southern hemisphere. Hints that this area was once wet, or currently has liquid present, are evident.

“We’ve been looking for evidence of oceans or seas on Titan for some time. This radar data is among the most telling evidence so far for a shoreline,” said Steve Wall, radar deputy team leader from NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

The new radar images can be seen at: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .

The images show what looks like a shoreline dividing a distinct bright and dark region roughly 1,700 kilometers long by 170 kilometers wide (1,060 by 106 miles). Directly to the right of a bright and possibly rough area is one that is very dark and smooth.

“This is the area where liquid or a wet surface has most likely been present, now or in the recent past, said Wall. “Titan probably has episodic periods of rainfall or massive seepages of liquid from the ground.”

The brightness patterns in the dark area indicate that it may once have been flooded with liquid that may now have partially receded. Bay-like features also lead scientists to speculate that the bright-dark boundary is most likely a shoreline.

“We also see a network of channels that run across the bright terrain, indicating that fluids, probably liquid hydrocarbons, have flowed across this region,” said Dr. Ellen Stofan, Cassini associate radar team member from Proxemy Research, Laytonsville, Md.

Taken together with the two other radar passes in October 2004 and February 2005, these very high resolution images have identified at least two distinct types of drainage and channel formation on Titan. Some channels in images from this pass are long and deep, with angular patterns and few tributaries, suggesting that fluids flow over great distances. By contrast, others show channels that form a denser network that might indicate rainfall.

Dr. Larry Soderblom with the U.S. Geological Survey in Flagstaff, Ariz., said, “It looks as though fluid flowed in these channels, cutting deeply into the icy crust of Titan. Some of the channels extend over 100 kilometers (60 miles). Some of them may have been fed by springs, while others are more complicated networks that were likely filled by rainfall.”

Titan has an environment somewhat similar to that of Earth before biological activity forever altered the composition of Earth’s atmosphere. The major difference on Titan, however, is the absence of liquid water, and Titan’s very low temperature. With a thick, nitrogen-rich atmosphere, Titan was until recently presumed to hold large seas or oceans of liquid methane. Cassini has been in orbit around Saturn for a year and has found no evidence for these large seas.

Cassini encountered an anomaly with one of two solid-state recorders during the Sept. 7 close flyby, resulting in some data not being recorded. Half of the data from the flyby was received, much to the delight of anxious scientists. The spacecraft team is troubleshooting the cause, and early indications point to a software problem that would be correctable with no long-term impacts.

This was Cassini’s eighth out of 45 Titan flybys planned in the nominal four-year tour. The next radar pass will be Oct. 26 when the team will focus on the Huygens probe landing site close to the equator.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA?s Science Mission Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL. The radar instrument team is based at JPL, working with team members from the United States and several European countries.

Original Source: NASA/JPL/SSI News Release

Posted on by Mark Mortimer

Book Review: The Rocket Company

The particular dream of this book is where people end up easily, routinely and safely flying into space from Earth. In real life, many people and corporations address this topic seemingly at regular intervals. NASA has its own unique capability to start projects along this road only to shy away just before culmination. Jules Verne had his plans, purely fictional ideas for travelling to the moon. Wernher Von Braun had his own plans and dreams. Most daydreamers look at only certain aspects. Engineers, of course, focus on resolving technical issues. Economists might envision profits greater than any known on Earth. Philosophers vouchsafe interstellar travel as the ultimate test for humankind, and dream to pass the test. Within the mind, such events and circumstances can easily shape into a solid looking mirage. Often, that is exactly where they stay, as reality tends to be a lot different and usually much more challenging.

In The Rocket Company, Stiennon and Hoerr put paper to their daydreaming engineering ways. Their premise for getting people safely and effectively space faring begins with an investors group with pocket books just large enough to bank role everyone’s needs. Next, the investors go hire the best engineers with well above typical salary levels and then give them all the babysitting they need to build their rocket ship. Rather than just listing the systems, sub-systems and components, the authors do an excellent job of introducing production elements at appropriate times. First the flight trajectory defines the requirements. Market cases frame the payload size. Then many of the main elements of the craft get analysed and defined. The analysis does include a lot of engineer speak which is great for said specialists but not so much for others.

However, don’t let the preceding fool you into thinking this book is a dry rendition of systems engineering case studies. It is not. The authors artfully and smoothly wrap all the engineer speak into a fictional package that makes reading it a pleasure. The frame of reference for the reader is of looking over the shoulder of the company’s chief documenter. From this first person perspective, the reader is treated to people discussing the pro’s and con’s of various fuel mixtures, we listen to shouting in the boardroom while options are discussed and we taste the thrill of watching the test vehicle successfully launch.

By using this fictional surround to convey their impression of requirements and resolutions, the authors ensure that somewhat dry subject matter gets a fresh and interesting face. They introduce problems like slowing a feedback response to be compatible with human characteristics. Then, they present discussions amongst the fictional characters on some juicy historical similarities. Last, they sum up the issue by having the company’s expert engineer give the appropriate answer for this difficulty. And this is the beauty of fiction and daydreaming as the results work first time.

By using a person in a fictional company to present technical parameters studies, the authors successfully walk a very challenging tight rope. On one side is the chasm of detail. If they fell there, the book would likely have reams of tables of weight, cost and capability. This way they’d have a true technical reference but a very dry and dated one. On the other side of the rope, the chasm leads to pure fiction. That is, the authors provide a good story but what value is it in actually getting people into space? Skilfully though, the authors place the readers between these two gaping pitfalls and nicely balance the rocket design and business case with the fictional encounters of people living the lives within a fictitious company.

In consideration, there must be something people are just missing. We’ve put humans on the moon, we’ve dug tunnels joining Britain to France, and we’ve raised buildings towering high into the sky. So why are we still moribund on this planet? Many answers jump forth, but let the book The Rocket Company by Patrick Stiennon and David Hoerr show you one avenue to escape this tribulation. Sometimes dreams can turn into reality. This is one which many people would happily wish to come true.

Review by Mark Mortimer

Read more reviews online, or purchase a copy from Amazon.com.

Posted on by Fraser Cain

What’s Up This Week – September 19 – September 25, 2005

Cassini image of Saturn. Image credit: NASA/JPL. Click to enlarge.
Monday, September 19 – On this day in 1848, William Boyd was watching Saturn – and discovered its moon – Hyperion. If you’re up early this morning, why not take a look at the “Ring King”? It’s making a very spectacular pass through the constellation of Cancer right now and is wonderfully close to the M44! If you’re looking telescopically, be sure to power up for the Cassini Division and even small telescopes can spot its many moons.

Also today in 1988, Israel launched its first satellite. How long has it been since you’ve watched an ISS pass or an iridium flare? Both are terrific events that don’t require any special equipment to be seen. Be sure to check with Heaven’s Above for accurate times and passes in your location and enjoy!

Since we will only have a short time until the Moon rises tonight, let’s follow the progress of a variable star over the next week. Eta Aquilae is one of the most fascinating stars in the sky to watch and it doesn’t even require a telescope. Just look less than one fist-width due south of Altair…

Discovered by Pigot in 1784, this cepheid class variable has a precision change rate of over a magnitude in a period of 7.17644 days. During this time it will reach of maximum of magnitude 3.7 and decline slowly over 5 days to a minimum of 4.5… Yet it only takes two days to brighten again! This period of expansion and contraction makes Eta very unique. To help gauge these changes, compare Eta to Beta on Altair’s same southeast side. When Eta is at maximum, it will be about equal in brightness.

Tuesday, September 20 – On this night in 1948, the 48″ Schmidt telescope at Mt. Palomoar was busy taking pictures. The first photographic plate was being exposed on a galaxy by the same man who ground and polished the corrector plate for this scope – Hendricks. His object of choice was reproduced as panel 18 in the Hubble Atlas of Galaxies and tonight we’ll join his vision as we take a look at the fantastic M31 – Andromeda Galaxy.

Seasoned amateur astronomers can literally point to the sky and show you the location of the M31, but perhaps you have never tried. Believe it or not, this is an easy galaxy to see unaided from even a modest dark sky site. Simply look to the east well after twilight and identify the large diamond-shaped pattern of stars that stretches around a handspan. This is the “Great Square of Pegasus”. The northernmost star is Alpha, and it is here we will begin our hop. Stay with the north chain of stars and look four finger-widths away for an easily seen star. The next along the chain is about three finger-widths away… And we’re almost there. Two more finger-widths to the north and you will see a dimmer star that looks like it has something smudgy nearby. That’s no cloud… That’s the Andromeda Galaxy. Congratulations. You didn’t even need a telescope.

Now get out those optics and enjoy one of the finest, largest and brightest in the sky!

Wednesday, September 21 – With plenty of time to spare before the Moon rises tonight, let’s head on to Capricornus and drop about four finger-widths south of its northeastern most star – Delta – and have a look at M30.

Discovered in 1764 by Charles Messier, binocular observers will spot this small, but attractive, globular cluster easily in the same field with star 41. For telescopic observers, you will find a dense core region and many chains of resolvable stars in this 40,000 light year distant object. Power up.

Tonight, watch as the Moon rises about two hours after sunset. Around a half hour later, you will see Mars join the show as well.

Thursday, September 22 – Today is the Autumnal Equinox, and will occur at 6:23 p.m. EDT. This marks the first day of the Fall season for the Northern Hemisphere and we astronomers welcome back earlier dark skies!

On this universal date for viewers in Hawaii, and most portions of Australia and New Zealand, the Moon will occult one of the Plieades’ stars – Alcyone. What a great event! Be sure to check this IOTA webpages for times in your area.

Now let’s get some more practice in Capricornus, as tonight we’ll take on a more challenging target with confidence. Locate the centermost bright star in the northern half of the constellation – Theta – because we’re headed for the “Saturn Nebula”.

Three finger-widths north of Theta you will see dimmer Nu, and only one finger-width west is NGC 7009. Nicknamed the “Saturn Nebula”, this wonderful blue planetary is around 8th magnitude and achievable in small scopes and large binoculars. Even at moderate magnification, you will see the elliptical shape which gave rise to its moniker. With larger scopes, those “ring like” projections become even clearer, making this challenging object well worth the hunt. You can do it!

Friday, September 23 – Check out the western skyline tonight about a half hour after sunset. The bright planet – Jupiter – is now almost lost, but in 1846 on this day, Johann Galle of the Berlin Observatory found another. This was the first time that Neptune was seen and identified visually.

Thanks to tonight’s much darker skies, you too, will have the same opportunity. Start by identifying Theta once again. Two finger-widths away to the northeast is dim star 29. Now, using your binoculars or finderscope, between them you will see another star and this is our marker. When you have located that star, Neptune is just to its northeast and will be the brightest object in the field with the exception of our marker star. It’s just that easy!

On this day in 1962, the prime time cartoon “The Jetsons” first premiered. Think of all the technology this inspired as tonight we kick back to watch the Alpha Aurigid meteor shower. Relax, face northeast and look for the radiant near Capella. The fall rate is around 12 per hour, and they are fast and leave trails!

Saturday, September 24 – In 1970, the first unmanned, automated return of lunar material to the Earth occurred on this day when the Soviet’s Luna 16 returned with three ounces of the Moon. If we think back, the lowest passing of that Moon to the south occured not long ago. By tomorrow morning it will have reached its highest point just before the Sun rises and will be nearly overhead.

For viewers in Northern Europe, the Moon will occult bright star 136 Taurii on this universal date. Be sure to check this IOTA webpages for a listing of times and locations in your area.

For the rest of us, we’ve got around four hours to play before the Moon brightens the skies. So, are we ready to try for the “Helix”?

Located in a sparsely populated area of the sky, this intriguing target is about a fist width due northwest of bright Formalhaut and about a fingerwidth west of Upsilon Aquarii. While the NGC 7293 is also a planetary nebula, its entirely different than most… It’s a very large and more faded edition of the M57! On a clear, dark night it can be spotted with binoculars since it spans almost one quarter a degree of sky. Using a telescope, stay at lowest power and widest field, because it is so large. It you have an OIII filter, this faded “ring” becomes a braided treat!

Sunday, September 25 – Now, are you ready for something really exciting? There’s a new comet in town and its name is 2005/P3 SWAN. At close to magnitude 10, this is not a comet you are going to see in binoculars or a small telescope, but for those with larger instruments and a northern position, you are going to like this!

Now, mind you… Ursa Major is now a morning constellation for most of us, but 2005/P3 SWAN will be mixing it up with both the Owl Nebula and the M108! The predicted path charts put it about 1 degree southeast of the M97. Happy Hunting!

The skies are getting darker and the times are getting earlier. Let the galaxy hunt begin! Until next week, may all your journeys be at light speed…. ~Tammy Plotner