Posted on by Fraser Cain

Biggest Collision in the Universe

With ESA?s XMM-Newton observatory, an international team of scientists has observed a nearby head-on collision of two galaxy clusters that has smashed together thousands of galaxies and millions upon millions of stars. It is one of the most powerful events ever witnessed. Such collisions are second only to the Big Bang in total energy output.

The event details what the scientists are calling the ?perfect cosmic storm?: galaxy clusters that collided like two high-pressure weather fronts and created hurricane-like conditions, tossing galaxies far from their paths and churning shock waves of 100-million-degree gas through intergalactic space.

This unprecedented view of a merger in action crystallises the theory that the Universe built its magnificent hierarchal structure from the ?bottom up? – essentially through mergers of smaller galaxies and galaxy clusters into bigger ones.

“Here before our eyes we see the making of one of the biggest objects in the Universe,” said Dr Patrick Henry of the University of Hawaii, who led the study. “What was once two distinct but smaller galaxy clusters 300 million years ago is now one massive cluster in turmoil.?

Henry and his colleagues, Alexis Finoguenov and Ulrich Briel of the Max-Planck Institute for Extraterrestrial Physics in Germany, present these results in an upcoming issue of the Astrophysical Journal. The forecast for the new super-cluster, they said, is ‘clear and calm’ now that the worst of the storm has passed.

Galaxy clusters are the largest gravitationally bound structures in Universe, containing hundreds to thousands of galaxies. Our Milky Way galaxy is part of a small group of galaxies but is not gravitationally bound to the closest cluster, the Virgo Cluster. We are destined for a collision in a few thousand million years, though.

The cluster named Abell 754 in the constellation Hydra has been known for decades. However, to the scientists’ surprise, the new observation reveals that the merger may have occurred from the opposite direction than what was thought. They found evidence for this by tracing the wreckage today left in the merger’s wake, spanning a distance of millions of light years. While other large mergers are known, none has been measured in such detail as Abell 754.

For the first time, the scientists could create a complete ?weather map? of Abell 754 and thus determine a forecast. This map contains information about the temperature, pressure and density of the new cluster. As in all clusters, most the ordinary matter is in the form of gas between the galaxies and not locked up in the galaxies or stars themselves. The massive forces of the merging clusters accelerated intergalactic gas to great speeds. This resulted in shock waves that heat the gas to very high temperatures, which then radiated X-ray light, far more energetic than the visible light our eyes can detect. XMM-Newton, in orbit, detects this type of high-energy light.

The dynamics of the merger revealed by XMM-Newton point to a cluster in transition. “One cluster has apparently smashed into the other from the ‘north-west’ and has since made one pass through,” said Finoguenov. “Now, gravity will pull the remnants of this first cluster back towards the core of the second. Over the next few thousand million of years, the remnants of the clusters will settle and the merger will be complete.”

The observation implies that the largest structures in the Universe are essentially still forming in the modern era. Abell 754 is relatively close, about 800 million light years away. The construction boom may soon be over in a few more thousand million years though. A mysterious substance dubbed ‘dark energy’ appears to be accelerating the Universe’s expansion rate. This means that objects are flying apart from each other at an ever-increasing speed and that clusters may eventually never have the opportunity to collide with each other.

X-ray observations of galaxy clusters such as Abell 754 will help to better define dark energy and also dark matter, an ?invisible? and mysterious substance that appears to comprise over 80 percent of a galaxy cluster’s mass.

This observation was announced at a NASA Internet press conference today. A paper describing these results, by Patrick Henry and his collaborators, will be published in the Astrophysical Journal.

Original Source: ESA News Release

Posted on by Fraser Cain

Earliest Star Forming Galaxies Found

Detailed analyses of mankind’s deepest optical view of the universe, the Hubble Ultra Deep Field (HUDF), by several expert teams have at last identified what may turn out to be some of the earliest star-forming galaxies. Astronomers are now debating whether the hottest stars in these early galaxies may have provided enough radiation to “lift a curtain” of cold, primordial hydrogen that cooled after the big bang. This is a problem that has perplexed astronomers over the past decade, and NASA’s Hubble Space Telescope has at last glimpsed what could be the “end of the opening act” of galaxy formation. These faint sources illustrate how astronomers can begin to explore when the first galaxies formed and what their properties might be.

But even though Hubble has looked 95 percent of the way back to the beginning of time, astronomers agree that’s not far enough. “For the first time, we at last have real data to address this final frontier ? but we need more observations. We must push even deeper into the universe, unveiling what happened during the initial 5 percent of the remaining distance back to the big bang,” said Richard Ellis of the California Institute of Technology in Pasadena, Calif.

In the past couple decades astronomers have amassed evidence that we live in a reionized or “refried universe.” This so-called reionization epoch was a critical watershed for the evolving universe. During that early time cold hydrogen atoms drifting in space were pumped up with so much energy from the ultraviolet starlight that they were stripped of their electrons. The universe once again became transparent to light, like the Sun burning off a morning fog. This early period is called “reionization” because the primeval universe, which was hotter than our Sun, was initially ionized as a soup of hydrogen nuclei and free-moving electrons. As the universe cooled through the expansion of space, these electrons were captured by hydrogen nuclei to make neutral hydrogen. But the electrons were lost again when the first fiercely bright stars fired up.

The epoch of reionization is thought to have ended 0.5 to one billion years after the big bang. Constraints come from observations of quasars located with the Sloan Digital Sky Survey, and recent measures of polarization in the radiation emerging from the earliest phases of cosmic history recorded by the Wilkinson Microwave Anisotropy Probe (WMAP).

The major difficulty has been that galaxies at such a remote distance are very faint and are very hard to find. Only the most luminous galaxies can be relatively easily seen. Prior to the HUDF, astronomers did not have the sensitivity to accurately constrain the numbers of very distant sources at that epoch, and so there’s been a long-standing debate whether normal galaxies were really capable of doing the reionizing job.

The sensitivity of Hubble’s Advanced Camera for Surveys (ACS), combined with the penetrating power of the Near Infrared Camera and Multi-Object Spectrometer (NICMOS), finally revealed these long sough faint galaxies. The HUDF shows that close to a billion years after the big bang the early universe was filled with dwarf galaxies, but no fully formed galaxies like our Milky Way. After careful analysis, they have been sorted out as between 54 and 108 dim, red smudges sprinkled across the HUDF image. From a hierarchical point of view, this means the universe started out as a bunch of “mom & pop” stores, which merged into businesses, and then into giant corporations ? the majestic galaxies we see today.

HUDF research are being led by: Rodger Thompson (University of Arizona, Tucson, Ariz.) and collaborator Rychard Bouwens (University of California/Lick Observatory, Santa Cruz, Calif.) [see science papers 1, 2 and 3]; Haojing Yan (Spitzer Science Center, California Institute of Technology, Pasadena, Calif.) and Rogier Windhorst (Arizona State University, Tempe, Ariz.) [see science paper]; Massimo Stiavelli (Space Telescope Science Institute, Baltimore, MD.) [see science paper]; Andrew Bunker (University of Exeter and the University of Cambridge, UK) [see science papers 1 and 2]; and Sangeeta Malhotra and James Rhoads (Space Telescope Science Institute) [see science paper]. The teams used different techniques:

The Bunker team identified a list of 50 probable distant galaxies in the Ultra Deep Field and distributed details of their work within a day of the images becoming publicly available. They isolated their distant sample using techniques developed with earlier, less sensitive, Hubble images tested through spectroscopic observations undertaken with the 10-meter W.M. Keck observatory in Hawaii. Bunker’s team claims that the combined ultraviolet light from the galaxies located in the Ultra Deep Field is insufficient to reionize the universe. Perhaps the physics of star formation was different at these early times, or a further, yet more distant population is responsible.

The Stiavelli team shows that the same objects would be sufficient to reionize the universe, if they possessed much fewer heavier elements ? anything heavier than helium ? than those of present-day galaxies, and if the early galaxies contained more massive stars. Both these assumptions are reasonable at early epochs, since astronomers know that stars make the metals that exist in the universe. Early on, before most of the stars we see today had been formed, the amount of elements must have been much lower.

The Yan and Windhorst team started from the objects that are seen, and then carefully estimated the fraction of fainter galaxies that are not seen, even in the Hubble Ultra Deep Field. They found that the number of dwarf galaxies rapidly increases at fainter levels in the HUDF. This is like a cosmic “stock- market chart” but with very few large corporations and numerous “mom-and-pop corner stores.” Yan and Windhorst conclude that this steep increase of the faint dwarf galaxy population collectively generates enough ultraviolet light to finish reionizing the universe by redshift 6, even if the amount of heavier elements was similar to that of present-day galaxies.

The HUDF NICMOS Treasury team (Thompson/Illingworth) has taken the UDF data and other ACS survey data to get the best possible estimate of the relative numbers of bright and faint galaxies around redshift 6, only 900 million years after the big bang. The papers, led by Rychard Bouwens, show that faint galaxies dominate at this epoch, compared to more recent times, and are likely to have played a significant role in the late stages of reionization. The team has also used the HUDF NICMOS data to detect a small sample of galaxies at higher redshifts (at z=7-8), 200 million years closer in time to the big bang. The amount of reionizing light at redshifts 7-8 appears to be lower than what is seen only 200 million years later at redshift 6.

The Malhotra and Rhoads team have found a “sheet” of galaxies in the HUDF. They find that the galaxy density near redshift z=5.9 (look-back time of 12.5 billion years) is four times the galaxy density in the rest of the surveyed HUDF “core sample.” This supports theories of galaxy formation which predict that dense regions should be the first sites of galaxy formation. This evidence for an over density was bolstered by a complementary study, undertaken by Malhotra, Rhoads, and JunXian Wang, which uses the Cerro Tololo Inter-American Observatory to obtain a map of galaxies over a much wider area than the HUDF. Even with its lower sensitivity and more limited coverage in distance, this map shows that “extra” galaxies are spread like a sheet, with the HUDF located near one edge of the structure. “The presence of such structures doubtlessly affected the reionization of the universe, because the ultraviolet light that separated intergalactic hydrogen atoms into protons and electrons would have been more intense where galaxies are more common. It is then likely that reionization proceeded at different speeds in different regions of the early universe,” says Rhoads. This Hubble team used spectra to measure the distances of these galaxies very precisely.

The WFC3 built for Hubble is expected to see ten times as many distant infrared galaxies as the NICMOS. When launched, the JWST will have the light-gathering power to peruse an even earlier universe and actually see the very first stars and star clusters, which remain beyond even Hubble’s reach. These still hypothesized ultra-bright stars formed only 200 million years after the big bang (at redshift z=20, and as deduced from the WMAP image of the cosmic microwave background). They are currently believed to have heated the universe so much back then, that smaller, normal stars had to wait for the hydrogen gas to re-cool and condense before they could form.

Original Source: Hubble News Release

Posted on by Fraser Cain

Mystery at the Heart of the Milky Way

A mystery lurking at the centre of our own Milky Way galaxy – an object radiating high-energy gamma rays – has been detected by a team of UK astronomers working with international partners. Their research, published today (September 22nd) in the Journal Astronomy and Astrophysics, was carried out using the High Energy Stereoscopic System (H.E.S.S.), an array of four telescopes, in Namibia, South-West Africa.

The Galactic Centre harbours a number of potential gamma-ray sources, including a supermassive black hole, remnants of supernova explosions and possibly an accumulation of exotic ‘dark matter’ particles, each of which should emit the radiation slightly differently. The radiation observed by the H.E.S.S. team comes from a region very near Sagittarius A*, the black hole at the centre of the galaxy. According to most theories of dark matter, it is too energetic to have been created by the annihilation of dark matter particles. The observed energy spectrum best fits theories of the source being a giant supernova explosion, which should produce a constant stream of radiation.

Dr. Paula Chadwick of the University of Durham said, “We know that a giant supernova exploded in this region 10,000 years ago. Such an explosion could accelerate cosmic gamma rays to the high energies we have seen – a billion times more energy than the radiation used for X-rays in hospitals. But further observations will be needed to determine the exact source.”

Professor Ian Halliday, Chief Executive of the Particle Physics and Astronomy Research Council (PPARC) which funds UK involvement in H.E.S.S. said; “Science continues to throw out the unexpected as we push back the frontiers of knowledge.” Halliday added “The centre of our Galaxy is a mysterious place, home to exotic phenomena such as a black hole and dark matter. Finding out which of these sources produced the gamma-rays will tell us a lot about the processes taking place in the very heart of the Milky Way.”

However, the team’s theory doesn’t fit with earlier results obtained by the Japanese /Australian CANGAROO instrument or the US Whipple instrument. Both of these have detected high-energy gamma rays from the Galactic Centre in the past (observations from 1995-2002), though not with the same precision as H.E.S.S, and they were unable to pinpoint the exact location as H.E.S.S. has now done, making it harder to deduce the source. These previous results have different characteristics to the H.E.S.S. observations. It is possible that the gamma-ray source at the Galactic Centre varies over the timescale of a year, suggesting that the source is in fact a variable object, such as the central black hole.

The H.E.S.S. team hopes to unravel the mystery with further observations of the Galactic Centre over the next year or two. The full array of four telescopes will be inaugurated on September 29th 2004.

Original Source: PPARC News Release

Posted on by Fraser Cain

Glaciers Speed Up When Ice Breaks Away

Since 2002, when the Larsen B ice shelf broke away from the coast of the Antarctic Peninsula, scientists have witnessed profound increases in the flow of nearby glaciers into the Weddell Sea. These observations were made possible through NASA, Canadian and European satellite data.

Two NASA-funded reports, appearing in the Geophysical Research Letters journal, used different techniques to arrive at similar results. Researchers from NASA’s Jet Propulsion Laboratory (JPL), Pasadena, Calif., NASA’s Goddard Space Flight Center (GSFC), Greenbelt, Md., and the National Snow and Ice Data Center (NSIDC), Boulder, Colo., said the findings prove ice shelves act as “brakes” on the glaciers that flow into them. The results also suggest climate warming can rapidly lead to rises in sea level.

Large ice shelves in the Antarctic Peninsula disintegrated in 1995 and 2002, as a result of climate warming. Almost immediately after the 2002 Larsen B ice shelf collapse, researchers observed nearby glaciers flowing up to eight times faster than prior to the breakup. The speed-up also caused glacier elevations to drop, lowering them by as much as 38 meters (124 feet) in six months.

“Glaciers in the Antarctic Peninsula accelerated in response to the removal of the Larsen B ice shelf,” said Eric Rignot, a JPL researcher and lead author of one of the studies. “These two papers clearly illustrate, for the first time, the relationship between ice shelf collapses caused by climate warming, and accelerated glacier flow,” Rignot added.

Rignot’s study used data from European Space Agency Remote Sensing Satellites (ERS) and Canadian Space Agency RADARSAT satellite. The United States and Canada share a joint agreement on RADARSAT, which NASA launched.

Scambos and colleagues used five Landsat 7 images of the Antarctic Peninsula from before and after the Larsen B breakup. The images revealed crevasses on the surfaces of glaciers. By tracking the movement of crevasses in sequence from one image to the next, the researchers were able to calculate velocities of the glaciers.

The surfaces of glaciers dropped rapidly as the flow sped up, according to ICESat measurements. “The thinning of these glaciers was so dramatic that it was easily detected with ICESat, which can measure elevation changes to within an inch or two,” said Christopher Shuman, a GSFC researcher and a co-author on the Scambos paper.

The Scambos study examined the period right after the Larsen B ice shelf collapse to try to isolate the immediate effects of ice shelf loss on the glaciers. Rignot’s study used RADARSAT to take monthly measurements that are continuing. Clouds do not limit RADARSAT measurements, so it can provide continuous, broad velocity information.

According to Rignot’s study, the Hektoria, Green and Evans glaciers flowed eight times faster in 2003 than in 2000. They slowed moderately in late 2003. The Jorum and Crane glaciers accelerated two-fold in early 2003 and three-fold by the end of 2003. Adjacent glaciers, where the shelves remained intact, showed no significant changes according to both studies. The studies provide clear evidence ice shelves restrain glaciers, and indicate present climate is more closely linked to sea level rise than once thought, Scambos added.

Original Source: NASA News Release

Posted on by Fraser Cain

Mars Rovers Get a Mission Extension

As NASA’s Spirit and Opportunity rovers resumed reliable contact with Earth, after a period when Mars passed nearly behind the Sun, the space agency extended funding for an additional six months of rover operations, as long as they keep working.

Both rovers successfully completed their primary three-month missions on the surface of Mars in April and have already added about five months of bonus exploration during the first extension of their missions.

“Spirit and Opportunity appear ready to continue their remarkable adventures,” said Andrew Dantzler, solar system division director at NASA Headquarters, Washington. “We’re taking advantage of that good news by adding more support for the teamwork here on Earth that’s necessary for operating the rovers.”

Neither rover drove during a 12-day period this month, while radio transmissions were unreliable because of the Sun’s position between the two planets. Daily planning and commanding of rover activities recommenced Monday for Opportunity and today for Spirit.

“It is a relief to get past this past couple of weeks,” said Jim Erickson, project manager for both rovers at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “Not only were communications disrupted, but the rovers were also going through the worst part of Mars southern-hemisphere winter from a solar-energy standpoint.”

“Although Spirit and Opportunity are well past warranty, they are showing few signs of wearing out,” Erickson said. “We really don’t know how long they will keep working, whether days or months. We will do our best to continue getting the maximum possible benefit from these great national resources.”

Rover science team members will spend less time at JPL during the second mission extension. They are able to attend daily planning meetings by teleconferencing from their home institutions in several states and in Europe. “All 150 science team members and collaborators have been provided the tools to be able to participate remotely,” said JPL’s Dr. John Callas, science manager for the rover project. Workstations researchers used at JPL are at their home institutions. Planning tools include video feeds, workstation display remote viewing, and audio conferencing.

Besides reducing costs, remote operations allow scientists to spend more time at home. “We get back to more normal lives, back to our families, and we still get to explore Mars every day,” said Dr. Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator.

Another change in operations is a shift from seven days per week to five days per week from October through December. This accommodates a temporary trim of about 20 percent in the project’s engineering team to about 100 members. The rovers’ reduced energy supply, during the rest of the martian winter, makes the inactive days valuable for recharging batteries. By January, the energy situation will have improved for the solar-powered rovers, provided they are still operating. The team size will rebound to support daily operations.

As Mars emerges from behind the Sun, Spirit is partway up the west spur of highlands called the “Columbia Hills,” a drive of more than 3 kilometers (2 miles) from its landing site. Opportunity is inside stadium-size “Endurance Crater,” headed toward the base of a stack of exposed rock layers in “Burns Cliff,” and a potential exit route on the crater’s south side.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA’s Science Mission Directorate, Washington. Images and additional information about the project are available on the Web at http://marsrovers.jpl.nasa.gov and http://athena.cornell.edu. For information about NASA programs on the Internet, visit http://www.nasa.gov.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

NASA Awards Jupiter Icy Moons Mission

NASA’s Jet Propulsion Laboratory (JPL), Pasadena, Calif., selected Northrop Grumman Space Technology, Redondo Beach, Calif., as the contractor for co-designing the proposed Prometheus Jupiter Icy Moons Orbiter (JIMO) spacecraft. The contract award is for approximately $400 million, covering work through mid-2008.

The Prometheus JIMO mission is part of an ambitious mission to orbit and explore three planet-sized moons, Callisto, Ganymede and Europa, of Jupiter. The moons may have vast oceans beneath their icy surfaces. A nuclear reactor would enable the mission, which would launch in the next decade.

JIMO would be the first NASA mission using nuclear electric propulsion, which would enable the spacecraft to orbit each icy world to perform extensive investigations of their composition, history, and potential for sustaining life.

The JIMO mission, integrated with the Vision for Space Exploration, also develops and demonstrates technologies and capabilities in direct support to implement the Vision, including space nuclear electric power systems and nuclear electric propulsion systems.

“We have assembled an exceptional team of professionals to take us into the next phase of the mission. To see the mission evolve is rewarding, and I am confident a good team is in place to move us forward,” said John Casani, project manager for the JIMO mission at JPL.

Under the contract, Northrop Grumman will work with a government team to complete the preliminary design for the spacecraft. The work includes developing hardware, software and test activities for the design of the non-nuclear portion of the spacecraft. It also includes developing the interfaces for the spacecraft, space reactor, and science instruments. The contractor is responsible for the integration of government-owned and provided technologies into the spacecraft. They are also responsible for assembly, integration, and testing of the space system in accordance with applicable government requirements.

The government team will co-design the spacecraft with the contractor. NASA will supply the launch vehicle. The Department of Energy’s Office of Naval Reactors, Washington, will own and be responsible for the space reactor.

The government team includes JPL, NASA’s Ames Research Center, Moffett Field, Calif.; Glenn Research Center, Cleveland; Kennedy Space Center, Fla.; Langley Research Center, Hampton, Va.; and Marshall Space Flight Center, Huntsville, Ala. Also the Office of Naval Reactors, which includesing Knolls Atomic Power Laboratory, Schenectady, N.Y.; Bettis Laboratory, Pittsburgh; and supporting Department of Energy national laboratories.

The mission instruments will be procured competitively via a NASA Announcement of Opportunity. Three crosscutting themes, identified by a NASA-chartered science definition team, drive the proposed JIMO investigations.

The themes are: evaluate the degree subsurface oceans are present on these moons; study the chemical composition of the moons, including organic materials, and the surface processes that affect them; and scrutinize the entire Jupiter system, particularly the interactions between Jupiter, the moons’ atmospheres and interiors.

JIMO is managed by JPL and is part of NASA’s Prometheus Program, a program studying a series of initiatives to develop power systems and technologies for space exploration in support of the Vision for Space Exploration.

JPL, a division of the California Institute of Technology, manages the proposed JIMO mission for NASA’s Exploration Systems Mission Directorate, Washington.

For more information about the mission or NASA, visit:
http://spacescience.nasa.gov/missions/prometheus.htm
NASA JIMO Mission
http://www.nasa.gov

Original Source: NASA JPL News Release

Posted on by Fraser Cain

SpaceShipOne’s Engine Designer Working with NASA

SpaceDev has begun designing a reuseable, piloted, sub-orbital space ship that could be scaled up to safely and economically transport passengers to and from low earth orbit, including the International Space Station. The name of the vehicle is the ?SpaceDev Dream Chaser.?

SpaceDev?s founding chairman and CEO, Jim Benson, recently signed a Space Act Memorandum of Understanding (MOU) with NASA Ames Research Center director, Dr. Scott Hubbard. This non-binding MOU confirms the intention of the two parties to explore novel, hybrid rocket propulsion based hypersonic test beds for routine human space access. The parties will explore collaborative partnerships to investigate the potential of using SpaceDev?s proven hybrid propulsion and other technologies, and a low cost, private space program development approach, to establish and design new piloted small launch vehicles and flight test platforms to enable near-term, low-cost routine space access for NASA and the United States. One possibility for collaboration is the SpaceDev Dream Chaser? project, which is currently being discussed with NASA Ames.

Unlike the more complex SpaceShipOne, for which SpaceDev provides critical proprietary hybrid rocket motor propulsion technologies, the SpaceDev Dream Chaser? would be crewed and take-off vertically, like most launch vehicles, and will glide back for a normal horizontal runway landing.

?This project is one small step for SpaceDev, but could evolve into one giant leap for affordable, commercial human space flight,? said Jim Benson. ?I have been waiting for almost fifty years for commercial space flight, and have concluded that SpaceDev, through our unbroken string of successful space technology developments, now has the technical capability and know-how, along with our partners, and when fully funded, to quickly develop a safe and affordable human space flight program, beginning with sub-orbital flights in the near future, and building up to reliable orbital public space transportation hopefully by the end of this decade.?

?I am delighted that we will be working with SpaceDev to help meet the goals of The Vision for Space Exploration,? said G. Scott Hubbard, director of NASA Ames Research Center, located in California?s Silicon Valley. ?Near-term, low-cost, crewed and uncrewed routine space access is a key for realizing the nation?s Exploration Vision. I look forward to a long and fruitful partnership with SpaceDev to explore the technologies for a new class of exciting launch vehicles for future space exploration.?

The sub-orbital SpaceDev Dream Chaser is derived from an existing X-Plane concept and will have an altitude goal of approximately 160 km (about 100 miles) and will be powered by a single, high performance hybrid rocket motor, under parallel development by SpaceDev for the SpaceDev Streaker?, a family of small, expendable launch vehicles, designed to affordably deliver small satellites to low earth orbit. The SpaceDev Dream Chaser will use motor technology being developed for the SpaceDev Streaker? booster stage, the most powerful motor in the Streaker family. The SpaceDev Dream Chaser motor will produce approximately 100,000 pounds of thrust, about six times the thrust of the SpaceShipOne motor, but less than one-half the thrust of the 250,000 pounds of thrust produced by hybrid rocket motors developed several years ago by the American Rocket Company (AMROC).

SpaceDev?s non-explosive hybrid rocket motors use synthetic rubber as the fuel, and nitrous oxide for the oxidizer to make the rubber burn. Traditional rocket motors use two liquids, or a solid propellant that combines the fuel and oxidizer, but both types of rocket motors are explosive, and all solid motors produce copious quantities of toxic exhaust. SpaceDev?s hybrid rocket motors are non-toxic and do not detonate like solid or liquid rocket motors.

Original Source: SpaceDev News Release

Posted on by Fraser Cain

Keeping the Rings In Line

Saturn’s moon Prometheus is seen shepherding the inner edge of Saturn’s F ring. Prometheus is 102 kilometers (63 miles) across and was captured in a close-up view by the Cassini spacecraft near the time of orbital insertion at Saturn PIA06098. A number of clumps are visible here along the arcing F ring.

The image was taken with the Cassini spacecraft narrow angle camera on Aug. 5, 2004, at a distance of 8.2 million kilometers (5.1 million miles) from Saturn through a filter sensitive to visible green light. The image scale is 49 kilometers (33 miles) per pixel. Contrast was slightly enhanced to aid visibility.

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, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

For more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and the Cassini imaging team home page, http://ciclops.org .

Original Source: NASA JPL News Release

Posted on by Mark Mortimer

Book Review: Sun Observer’s Guide

Our sun produces vast amounts of energy through nuclear reactions. Due to this energy and the sun’s huge mass, the sun consists mostly of sub atomic particles and ionized atoms especially hydrogen and helium. These rocket and careen within the sun and then via convection and radiation they work their way out through the surface, the photosphere, and onward throughout the solar system. The photosphere, tenuous as it is, can be seen to resemble porridge with a fairly homogeneous mix of small light and dark patches. Occasionally, a large dark spot occurs. Seemingly harmless, this spot is quite often a burst of energy and matter that sends an energetic stream of particles and radiation out from the sun. Perhaps harmless in appearance these spots can disrupt radio traffic, fail electrical power grids and knock out satellites. But on the good side, these spots are the main subjects for sun observers.

Using sun spots, observers can assign a latitude and longitude coordinate system to the sun. They can define the sun’s rotation rate and its ‘mood’. A sullen sun may have only one or even no sunspots on its surface. At other times, the playful sun could have hundreds of sunspots. This activity cycles through its minimum and maximum over an eleven year period. However the sun can quiet down for a longer time. Between 1645 and 1715 there was almost no sun spot activity. We refer to this time as a little ice age here on Earth due to the much cooler temperatures experienced. Of course, the opposite can happen. Unusually high sun spot activity occurred in the years 1000 to 1250 and a warmer climate allowed Vikings to settle in Greenland. So, not only are sun spots the main characteristic of our sun, they also have a direct influence on the earth’s climate. There can’t be a much better reason for observers to continue their studies!

One of the main benefits of observing the sun is that minimal equipment is required. Some observations are achievable with binoculars and a few sheets of paper. A small refractor telescope is better than binoculars, but due to the sun’s energy, small is actually better than large. And using paper with appropriate grids and scales on it aids in locating and sizing sun spots that do appear. Then, using the techniques described in this book, a viewer can characterize and record their observations in a manner that is useful for their own benefit and in a manner that would be advantageous to professional bodies, if the observer wanted to share their work. This isn’t that far fetched, as the author herself contributes as an amateur and then works with an organization that makes use of amateur observations.

Aside from sun spots, the other great viewing attraction of the sun is its eclipse. Because of its rarity and its spectacular sight, the eclipse draws people from everywhere in the world. If you are fortunate enough to be on a path of totality, you will see the sun go through a number of distinct phases. It starts with an annular eclipse, where the moon moves to block the sun’s light. When the moon almost exactly covers the sun only some of the photosphere is visible at the moon’s edges and the moon appears to have a ring of fire about its circumference. Should a valley on the moon allow a ray of light to sparkle and flash in the sun’s normal white colour with the beads somewhat like a diamond ring. At totality the photosphere is completely blocked and the ghostly corona shimmers and shines in vibrant ribbons floating around the ring of the moon. Then these phases repeat themselves in reverse order, as the moon continues in its orbit past the sun. The solar eclipse is truly worth travelling to see.

To learn a bit about the sun and of the pleasures in viewing it then Pam Spence’s book, Sun Observer’s Guide, is a handy reference. Sometimes it can be repetitive in its instructions and there is very little on why the sun does what it does. However, there is more than sufficient detail on how to look, what to look for and what the value is of the observations. The unaided and unknowing eye may consider the sun a rock steady source of light and heat, but an educated viewer, with the help of this book, will know better.

To read more reviews, or order the book online, visit Amazon.com.

Review by Mark Mortimer

Posted on by Fraser Cain

Methane and Water Overlap on Mars

Recent analyses of ESA?s Mars Express data reveal that concentrations of water vapour and methane in the atmosphere of Mars significantly overlap. This result, from data obtained by the Planetary Fourier Spectrometer (PFS), gives a boost to understanding of geological and atmospheric processes on Mars, and provides important new hints to evaluate the hypothesis of present life on the Red Planet.

PFS observed that, at 10-15 kilometres above the surface, water vapour is well mixed and uniform in the atmosphere. However, it found that, close to the surface, water vapour is more concentrated in three broad equatorial regions: Arabia Terra, Elysium Planum and Arcadia-Memnonia.

Here, the concentration is two to three times higher than in other regions observed. These areas of water vapour concentration also correspond to the areas where NASA?s Odyssey spacecraft has observed a water ice layer a few tens of centimetres below the surface, as Dr Vittorio Formisano, PFS principal investigator, reports.

New in-depth analysis of PFS data also confirms that methane is not uniform in the atmosphere, but concentrated in some areas. The PFS team observed that the areas of highest concentration of methane overlap with the areas where water vapour and underground water ice are also concentrated. This spatial correlation between water vapour and methane seems to point to a common underground source.

Initial speculation has taken the underground ice layer into account. This could be explained by the ?ice table? concept, in which geothermal heat from below the surface makes water and other material move towards the surface. It would then freeze before getting there, due to the very low surface temperature (many tens of degrees Celsius below zero).

Further investigations are needed to fully understand the correlation between the ice table and the presence and distribution of water vapour and methane in the atmosphere.

In other words, can the geothermal processes which ?feed? the ice table also bring water vapour and other gases, like methane, to the surface? Can there be liquid water below the ice table? Can forms of bacterial life exist in the water below the ice table, producing methane and other gases and releasing them to the surface and then to the atmosphere?

The PFS instrument has also detected traces of other gases in the Martian atmosphere. A report on these is currently under peer review. Further studies will address whether these gases can be linked to water and methane and help answer the unresolved questions. In-situ observations by future lander missions to Mars may provide a more exhaustive solution to the puzzle.

Original Source: ESA News Release