Posted on by Fraser Cain

Neptune Kidnapped Triton from Another Planet

Neptune’s largest moon, Triton. Image credit: NASA. Click to enlarge
Neptune’s moon Triton is unique in the Solar System because it’s the only large moon that orbits in the opposite direction to its planet’s rotation. Researchers have developed a computer model that explains how Neptune could have captured Triton from another planet during a close approach. Under this scenario, Triton was originally part of a binary system with another planet. They got too close to Neptune and Triton was torn away.

Neptune’s large moon Triton may have abandoned an earlier partner to arrive in its unusual orbit around Neptune. Triton is unique among all the large moons in the solar system because it orbits Neptune in a direction opposite to the planet’s rotation (a “retrograde” orbit). It is unlikely to have formed in this configuration and was probably captured from elsewhere.

In the May 11 issue of the journal Nature, planetary scientists Craig Agnor of the University of California, Santa Cruz, and Douglas Hamilton of the University of Maryland describe a new model for the capture of planetary satellites involving a three-body gravitational encounter between a binary and a planet. According to this scenario, Triton was originally a member of a binary pair of objects orbiting the Sun. Gravitational interactions during a close approach to Neptune then pulled Triton away from its binary companion to become a satellite of Neptune.

“We’ve found a likely solution to the long-standing problem of how Triton arrived in its peculiar orbit. In addition, this mechanism introduces a new pathway for the capture of satellites by planets that may be relevant to other objects in the solar system,” said Agnor, a researcher in UCSC’s Center for the Origin, Dynamics, and Evolution of Planets.

With properties similar to the planet Pluto and about 40 percent more massive, Triton has an inclined, circular orbit that lies between a group of small inner moons with prograde orbits and an outer group of small satellites with both prograde and retrograde orbits. There are other retrograde moons in the solar system, including the small outer moons of Jupiter and Saturn, but all are tiny compared to Triton (less than a few thousandths of its mass) and have much larger and more eccentric orbits about their parent planets.

Triton may have come from a binary very similar to Pluto and its moon Charon, Agnor said. Charon is relatively massive, about one-eighth the mass of Pluto, he explained.

“It’s not so much that Charon orbits Pluto, but rather both move around their mutual center of mass, which lies between the two objects,” Agnor said.

In a close encounter with a giant planet like Neptune, such a system can be pulled apart by the planet’s gravitational forces. The orbital motion of the binary usually causes one member to move more slowly than the other. Disruption of the binary leaves each object with residual motions that can result in a permanent change of orbital companions. This mechanism, known as an exchange reaction, could have delivered Triton to any of a variety of different orbits around Neptune, Agnor said.

An earlier scenario proposed for Triton is that it may have collided with another satellite near Neptune. But this mechanism requires the object involved in the collision to be large enough to slow Triton down, but small enough not to destroy it. The probability of such a collision is extremely small, Agnor said.

Another suggestion was that aerodynamic drag from a disk of gas around Neptune slowed Triton down enough for it to be captured. But this scenario puts constraints on the timing of the capture event, which would have to occur early in Neptune’s history when the planet was surrounded by a gas disk, but late enough that the gas would disperse before it slowed Triton’s orbit enough to send the moon crashing into the planet.

In the past decade, many binaries have been discovered in the Kuiper belt and elsewhere in the solar system. Recent surveys indicate that about 11 percent of Kuiper belt objects are binaries, as are about 16 percent of near-Earth asteroids.

“These discoveries pointed the way to our new explanation of Triton’s capture,” Hamilton said. “Binaries appear to be a ubiquitous feature of small-body populations.”

The binary Pluto and its moon Charon and the other binaries in the Kuiper belt are especially relevant for Triton, as their orbits abut Neptune’s, he said.

“Similar objects have probably been around for billions of years, and their prevalence indicates that the binary-planet encounter that we propose for Triton’s capture is not particularly restrictive,” Hamilton said.

The exchange reaction described by Agnor and Hamilton may have broad applications in understanding the evolution of the solar system, which contains many irregular satellites. The researchers plan to explore the implications of their findings for other satellite systems.

This research was supported by grants from NASA’s Planetary Geology and Geophysics, Outer Planet Research, and Origins of Solar Systems programs.

Original Source: UC Santa Cruz

Posted on by Fraser Cain

Fast Winds Around Dying Stars

The Ant Nebula. Image credit: NASA/STScI. Click to enlarge
These photographs are composite images of various planetary nebulae created out of data from the Hubble Space Telescope and Chandra X-Ray Observatory. The Chandra data (in blue) shows the X-ray view while Hubble (red and green) reveals the optical view. As a massive star nears the end of its life, it expels material to surround itself in a dusty shroud. The intense ultraviolet radiation from the star heats up the material and forces it away at extremely high speeds. This creates the unusual shapes we see from Earth.

This panel of composite images shows part of the unfolding drama of the last stages of the evolution of sun-like stars. Dynamic elongated clouds envelop bubbles of multimillion degree gas produced by high-velocity winds from dying stars. In these images, Chandra’s X-ray data are shown in blue, while green and red are optical and infrared data from Hubble.

Planetary nebulas – so called because some of them resemble a planet when viewed through a small telescope – are produced in the late stages of a sun-like star’s life. After several billion years of stable existence (the sun is 4.5 billion years old and will not enter this phase for about 5 billion more years) a normal star will expand enormously to become a bloated red giant. Over a period of a few hundred thousand years, much of the star’s mass is expelled at a relatively slow speed of about 50,000 miles per hour.

This mass loss creates a more or less spherical cloud around the star and eventually uncovers the star’s blazing hot core. Intense ultraviolet radiation from the core heats the circumstellar gas to ten thousand degrees, and the velocity of the gas flowing away from the star jumps to about a million miles per hour.

This high speed wind appears to be concentrated into opposing supersonic funnels, and produces the elongated shapes in the early development of planetary nebulas (BD+30-3639 appears spherical, but other observations indicate that it is viewed along the pole.) Shock waves generated by the collision of the high-speed gas with the surrounding cloud create the hot bubbles observed by Chandra. The origin of the funnel-shaped winds is not understood. It may be related to strong, twisted magnetic fields near the hot stellar core.

Original Source: Chandra X-Ray Observatory

Posted on by Fraser Cain

Spitzer View of Comet Chunks

The broken Comet 73P/Schwassman-Wachmann 3. Image credit: NASA/JPL-Caltech. Click to enlarge
As Comet 73P/Schwassman-Wachmann 3 is falling apart before our eyes, astronomers from around the world have been recording and studying the process. This recent photograph, released from the Spitzer Space Telescope, shows 45 of the comet’s 58 known fragments. The infrared telescope also has a great view of the cooler dust particles that fill in the trail between the comet chunks.

NASA’s Spitzer Space Telescope has snapped a picture of the bits and pieces making up Comet 73P/Schwassman-Wachmann 3, which is continuing to break apart on its periodic journey around the sun. The new infrared view shows several chunks of the comet riding along its own dusty trail of crumbs.

“Spitzer has revealed a trail of meteor-sized debris filling the comet’s orbit,” said Dr. William T. Reach of NASA’s Spitzer Science Center at the California Institute of Technology, Pasadena. Reach and his team recently observed the comet using Spitzer.

Comet 73P/Schwassman-Wachmann 3 consists of a collection of fragments that file along like ducks in a row around the sun every 5.4 years. This year, the bunch will pass by Earth beginning on May 12 before swinging by the sun on June 6. The fragments won’t get too close to Earth, about 7.3 million miles, or 30 times the distance between Earth and the moon, but they should be visible through binoculars in the countryside night skies.

The icy comet began falling apart in 1995 during one of its tropical trips to the sun. Astronomers believe that its crusty outer layer cracked due to the heat, allowing fresh ice to evaporate and split the comet apart.

During the past six weeks, amateur and professional astronomers have been watching the comet fall apart before their telescopes’ eyes. Spitzer viewed the broken comet from its quiet perch up in space May 4 to May 6, covering a portion of the sky that allowed it to spot 45 of the 58 known fragments.

The observatory’s infrared view also provides the first look at the dusty trail left by the disintegrating comet after it splintered apart in 1995. The trail is made up of comet dust, pebbles and rocks that occasionally rain down on Earth in what is called the Tau Herculid meteor shower. From May 19 to June 19, as Earth passes through the outskirts of the trail, only a weak meteor shower is expected, with just a few “shooting stars” visible in the night sky. A larger meteor shower might occur in 2022 if Earth crosses near the comet’s wake as predicted.

Spitzer’s infrared eyes were able to see the dusty comet bits lining the trail because the dust is warmed by sunlight and glows at infrared wavelengths. Most of the dust particles, specifically the millimeter-sized nuggets, had never been seen before. Reach said that these particles probably represent the natural deterioration of the comet over the years, a process commonly observed in intact comets.

The comet dust also adds up to more evidence for the “icy dirtball” theory of comets. In recent years, more and more astronomers are coming to think of comets not as snowballs coated in dust, but as dirtballs crusted with ice.

“By measuring the brightness and extent of the debris trail, we are trying to find out whether most of the comet’s mass disintegrates into vapors from evaporating ice, the house-sized chunks seen in images from the Hubble Space Telescope, or the meteor-sized debris seen in the Spitzer images,” said Reach.

Reach and his team will continue to study the Spitzer data for clues to how the comet broke up. Their infrared data will tell them the sizes of the major fragments, which might indicate whether the comet did, as believed, crack under the thermal stress.

Comet 73P/Schwassman-Wachmann 3 should be dimly visible through binoculars on a clear night between the Cygnus and Pegasus constellations from May 12 to May 28. For more information about viewing the comet or the meteors, visit http://science.nasa.gov/headlines/y2006/24mar_73p.htm. None of the comet’s fragments pose a danger to Earth. For more information, see http://www.nasa.gov/mission_pages/hubble/Comet_73P.html.

Members of Reach’s team include: Dr. Michael Kelley of the University of Minnesota, Twin Cities; Dr. Carey M. Lisse of the Johns Hopkins University’s Applied Physics Laboratory, Laurel, Md.; Dr. Mark Sykes of Planetary Science Institute, Tucson, Ariz.; and Dr. Masateru Ishiguro of the Institute of Space and Astronautical Science, Japan.

NASA’s Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology. Spitzer’s multi-band imaging photometer, which made the observations, was built by Ball Aerospace Corporation, Boulder, Colo.; the University of Arizona, Tucson; and Boeing North American, Canoga Park, Calif. The instrument’s principal investigator is Dr. George Rieke of the University of Arizona.

Original Source: NASA Spitzer Telescope

Posted on by Fraser Cain

Solar Forecasting Decades Out


Solar astronomers are predicting a very low solar cycle 15 years from now, based on recent observations of the Sun. In the last few years, the Sun’s Great Conveyor Belt – which transfers hot plasma around the star – has slowed to half its normal speed. According to simulations, the speed of this conveyor translates into sunspot activity 20 years in the future. Solar Cycle 25, which peaks in the year 2022, should be one of the weakest ever observed.
The Sun’s Great Conveyor Belt has slowed to a record-low crawl, according to research by NASA solar physicist David Hathaway. “It’s off the bottom of the charts,” he says. “This has important repercussions for future solar activity.”

The Great Conveyor Belt is a massive circulating current of fire (hot plasma) within the Sun. It has two branches, north and south, each taking about 40 years to perform one complete circuit. Researchers believe the turning of the belt controls the sunspot cycle, and that’s why the slowdown is important.

“Normally, the conveyor belt moves about 1 meter per second??bf?walking pace,” says Hathaway. “That’s how it has been since the late 19th century.” In recent years, however, the belt has decelerated to 0.75 m/s in the north and 0.35 m/s in the south. “We’ve never seen speeds so low.”

According to theory and observation, the speed of the belt foretells the intensity of sunspot activity ~20 years in the future. A slow belt means lower solar activity; a fast belt means stronger activity. The reasons for this are explained in the Science@NASA story Solar Storm Warning.

“The slowdown we see now means that Solar Cycle 25, peaking around the year 2022, could be one of the weakest in centuries,” says Hathaway.

This is interesting news for astronauts. Solar Cycle 25 is when the Vision for Space Exploration should be in full flower, with men and women back on the Moon preparing to go to Mars. A weak solar cycle means they won’t have to worry so much about solar flares and radiation storms.

On the other hand, they will have to worry more about cosmic rays. Cosmic rays are high-energy particles from deep space; they penetrate metal, plastic, flesh and bone. Astronauts exposed to cosmic rays develop an increased risk of cancer, cataracts and other maladies. Ironically, solar explosions, which produce their own deadly radiation, sweep away the even deadlier cosmic rays. As flares subside, cosmic rays intensify-yin, yang.

Hathaway’s prediction should not be confused with another recent forecast: A team led by physicist Mausumi Dikpata of NCAR has predicted that Cycle 24, peaking in 2011 or 2012, will be intense. Hathaway agrees: “Cycle 24 will be strong. Cycle 25 will be weak. Both of these predictions are based on the observed behavior of the conveyor belt.”

How do you observe a belt that plunges 200,000 km below the surface of the sun?

“We do it using sunspots,” Hathaway explains. Sunspots are magnetic knots that bubble up from the base of the conveyor belt, eventually popping through the surface of the sun. Astronomers have long known that sunspots have a tendency to drift??bf?from mid solar latitudes toward the sun’s equator. According to current thinking, this drift is caused by the motion of the conveyor belt. “By measuring the drift of sunspot groups,” says Hathaway, “we indirectly measure the speed of the belt.”

Using historical sunspot records, Hathaway has succeeded in clocking the conveyor belt as far back as 1890. The numbers are compelling: For more than a century, “the speed of the belt has been a good predictor of future solar activity.”

If the trend holds, Solar Cycle 25 in 2022 could be, like the belt itself, “off the bottom of the charts.”

Original Source: NASA News Release

Posted on by Fraser Cain

We’re Safe from Gamma Ray Bursts

Gamma ray burst host galaxies. Image credit: NASA/ESA/STScI. Click to enlarge
If a gamma ray burst happened near the Earth, it would make for a very bad day: our ozone layer would be stripped away, worldwide climate would change dramatically, and life would struggle to survive. Fortunately, it looks like they don’t happen in galaxies like our Milky Way. Researchers have found that bursts tend to occur in small irregular galaxies that lack heavier chemical elements.

A gamma-ray burst (GRB) occurring in our own galaxy could decimate life on Earth, destroying the ozone layer, triggering climate change and drastically altering life’s evolution. However, the good news is that results published online in the journal Nature show that the likelihood of a natural disaster due to a GRB is much lower than previously thought.

Long-duration GRBs are powerful flashes of high-energy radiation that arise from some of the biggest explosions of extremely massive stars. Astronomers have analysed a total of 42 long duration GRBs ??bf? those lasting more than two seconds ??bf? in several Hubble Space Telescope (HST) surveys.

They have found that the galaxies from which they originate are typically small, faint and misshapen (irregular) galaxies, while only one was spotted from a large spiral galaxy similar to the Milky Way. In contrast, supernovae (also the result of collapsing massive stars) were found to lie in spiral galaxies roughly half of the time.

These results, published in the May 10 online edition of the journal Nature, indicate that GRBs form only in very specific environments, which are different from those found in the Milky Way.

Andrew Fruchter, at the Space Telescope Science Institute, the lead author of the paper said, “Their occurrence in small irregulars implies that only stars that lack heavy chemical elements (elements heavier than hydrogen and helium) tend to produce long-duration GRBs.”

This means that long bursts happened more often in the past when galaxies did not have a large supply of heavy elements. Galaxies build up a stockpile of heavier chemical elements through the ongoing evolution of successive generations of stars. Early generation stars formed before heavier elements were abundant in the universe.

The authors also found that the locations of GRBs differed from the locations of supernovae (which are a much more common variety of exploding star). GRBs were far more concentrated on the brightest regions of their host galaxies, where the most massive stars reside. Supernovae, on the other hand, occur throughout their host galaxies.

“The discovery that long-duration GRBs lie in the brightest regions of their host galaxies suggests that they come from the most massive stars ??bf? perhaps 20 or more times as massive as our Sun,” said Andrew Levan of the University of Hertfordshire, a co-author of the study.

However, massive stars abundant in heavy elements are unlikely to trigger GRBs because they may lose too much material through stellar “winds” off their surfaces before they collapse and explode. When this happens, the stars don’t have enough mass left to produce a black hole, a necessary condition to trigger GRBs. The energy from the collapse escapes along a narrow jet, like a stream of water from a hose. The formation of directed jets, that concentrate energy along a narrow beam, would explain why GRBs are so powerful.

If a star loses too much mass, it may only leave behind a neutron star that cannot trigger a GRB. On the other hand, if the star loses too little mass, the jet cannot burn its way through the star. This means that extremely high-mass stars that puff away too much material may not be candidates for long bursts. Likewise, neither are the stars that give up too little material.

“It’s a Goldilocks scenario,” said Fruchter. “Only supernovae whose progenitor stars have lost some, but not too much mass, appear to be candidates for the formation of GRBs??bf?.

“People have, in the past, suggested that it might be possible to use GRBs to follow the locations of star formation. This obviously doesn’t work in the universe as we see it now, but, when the universe was young, GRBs may well have been more common, and we may yet be able to use them to see the very first stars to form after the Big Bang,” added Levan.

Original Source: RAS News Release

Posted on by Fraser Cain

Venus Express is in the Final Orbit

Artist’s view of Venus Express at Venus. Image credit: ESA. Click to enlarge
After a month of maneuvering, ESA’s Venus Express has reached its final science orbit. The spacecraft made its final maneuver on May 6, firings its engines to tighten its orbit to one that ranges between 66,000 and 250 km (41,000 and 155 miles) above the planet. Its scientific instruments will now be turned on and tested over the course of May. This will make the spacecraft ready for its science phase, due to begin on June 4, 2006.

Less than one month after insertion into orbit, and after sixteen loops around the planet Venus, ESA’s Venus Express spacecraft has reached its final operational orbit on 7 May 2006.

Already at 21:49 CEST on 6th May, when the spacecraft communicated to Earth through ESA’s ground station at New Norcia (Australia), the Venus Express ground control team at ESA’s European Spacecraft Operations Centre (ESOC) in Darmstadt (Germany) received advanced confirmation that final orbit was to be successfully achieved about 18 hours later.

Launched on 9 November 2005, Venus Express arrived to destination on 11 April 2006, after a five-month interplanetary journey to the inner solar system. The initial orbit – or ‘capture orbit’ – was an ellipse ranging from 330 000 kilometres at its furthest point from Venus surface (apocentre) to less than 400 kilometres at its closest (pericentre).

As of the 9-day capture orbit, Venus Express had to perform a series of further manoeuvres to gradually reduce the apocentre and the pericentre altitudes over the planet. This was achieved by means of the spacecraft main engine – which had to be fired twice during this period (on 20 and 23 April 2006) – and through the banks of Venus Express’ thrusters – ignited five times (on 15, 26 and 30 April, 3 and 6 May 2006).

“Firing at apocentre allows the spacecraft to control the altitude of the next pericentre, while firing at the pericentre controls the altitude of the following apocentre,” says Andrea Accomazzo, Spacecraft Operations Manager at ESOC. “It is through this series of operations that we reached the final orbit last Sunday, about one orbital revolution after the last ‘pericentre change manoeuvre’ on Saturday 6 May”.

Venus Express entered its target orbit at apocentre on 7 May 2006 at 15:31 (CEST), when the spacecraft was at 151 million kilometres from Earth. Now the spacecraft is running on an ellipse substantially closer to the planet than during the initial orbit. The orbit now ranges between 66 000 and 250 kilometres over the Venus and it is polar. The pericentre is located almost above the North pole (80º North latitude), and it takes 24 hours for the spacecraft to travel around the planet.

“This is the orbit designed to perform the best possible observations of Venus, given the scientific objectives of the mission. These include global observations of the Venusian atmosphere, of the surface characteristics and of the interaction of the planetary environment with the solar wind,” says Hakan Svedhem, Venus Express Project Scientist. “It allows detailed high resolution observations near pericentre and the North Pole, and it lets us study the very little explored region around the South Pole for long durations at a medium scale,” he concluded.

Until beginning of June, Venus Express will continue its ‘orbit commissioning phase’, started on 22 April this year. “The spacecraft instruments are now being switched on one by one for detailed checking, which we will continue until mid May. Then we will operate them all together or in groups” said Don McCoy, Venus Express Project Manager. “This allows simultaneous observations of phenomena to be tested, to be ready when Venus Express’ nominal science phase begins on 4 June 2006,” he concluded.

Original Source: ESA Portal

Posted on by Fraser Cain

Measuring the Background Light of the Universe

Artist’s impression of the Extragalactic Background Light emission and absorption. Image credit: HESS Collaboration. Click to enlarge
The Universe is filled with a diffuse glow of radiation coming from all the stars and galaxies. This cosmic fog is actually hard to detect because we have much brighter objects nearby that can wash it out; like how the city lights obscure the stars at night. One way to measure this radiation is by using the radiation from quasars, which are extremely bright and distant. The high-energy radiation from the quasars loses energy as it passes through this background radiation, and this can be measured.

All throughout space, a cosmic background light shimmers. Stars, galaxies – all kinds of sources – contribute to it; the light is their leftovers, in fact. Now, astrophysicists have discovered that this light is hardly as intense as anyone had guessed. The researchers used two distant quasars as “probes”, and recorded their gamma spectra using the H.E.S.S. telescopes in Namibia. These spectra turned out to be just a bit reddened; the background light seemed to only lightly obfuscate the quasars’ radiation. These observations do not just shed light on the background light – but on topics as great as the birth and development of galaxies (Nature, April 20, 2006).

Stars, galaxies, quasars, and many other objects contribute to the fog of radiation in the universe. It permeates all of intergalactic space; it is the “leftover” light that all these objects emit. Extragalactic background light – EBL – covers up epochs worth of stellar activity, from the time the first stars were created to the present. Scientists have been trying for a long time to measure this emission. Doing that directly is not easy, however, and extremely inaccurate, because Earth’s atmosphere, the Solar System, and the Milky Way send out radiation which gets in the way of observing weak EBL.

One way out of this problem is observing quasars – the cosmic energy factories which have a huge black hole in their middle. These “gravity traps” swallow up gas around them and spit some of it back as plasma, accelerated to nearly the speed of light. It is radiation bundled out of protons, electrons, and electromagnetic waves. Often, it can be hundreds of times wider than its mother galaxy. If this “quasar spray” heads in the direction of Earth, the radiation can appear quite strong – astronomers call this a “blazar”.

The two objects which H.E.S.S. researchers observed are both blazars. How to use them as probes? They send out very energetic gamma light particles, which lose strength on their way to Earth when they hit EBL photons. This causes the original blazar gamma spectrum to redden – like when the Sun nears the horizon at dusk and the Earth’s atmosphere disperses more of the blue part of the sunlight than the red. The thicker the atmosphere, the redder the sun. Reddening depends on the thickness of the medium. This fact is the key to investigating the composition of EBL.

Luigi Costamante of the Max Planck Institute for Nuclear Physics in Heidelberg says “the main problem is that energy distribution in quasars can take many different forms. Until now, we could not really say whether any observed spectrum looks red because it truly had a strong reddening, or if it was that way from the beginning.”

This problem has been solved thanks to the gamma spectra of two quasars — H 2356-309 and 1ES 1101-232. These objects are more distant than any sources observed until now. The sensitivity of the H.E.S.S. telescope made it possible to investigate them. It turns out that EBL’s intensity is not strong enough to redden quasar light; the spectra are too blue, and contain too many higher-energy gamma rays.

H.E.S.S. data has allowed the scientists to derive the maximum intensity of the diffused light. It is near the lowest limit resulting from the sum of the light of single galaxies visible in an optical telescope. That answers a question that has puzzled astronomers for years: is diffuse light created above all by the radiation from the first stars? The H.E.S.S. results seem to eliminate this possibility. There is also little room for contributions from other sources, like normal galaxies. Looking more closely at intergalactic space gives new perspectives on investigating gamma rays outside our own galaxy.

Original Source: Max Planck Society

Posted on by Fraser Cain

Air From Moonrocks

A focusing lens to produce oxygen and slug from a vacuum moondust filled chamber. Image credit: NASA. Click to enlarge
When astronauts return to the Moon, to explore and eventually build a moon base, they’re going to need oxygen… and lots of it. Fortunately lunar soil – or regolith – is almost half oxygen. NASA researchers are using a technique called vacuum pyrolysis, where the regolith is heated until it releases oxygen. Light from the Sun was focused by a lens to heat lunar soil to 2,500 degrees C. As much as 20% of the soil was converted to free oxygen, and the leftover slag could be used for bricks, radiation shielding or pavement.

An early, persistent problem noted by Apollo astronauts on the Moon was dust. It got everywhere, including into their lungs. Oddly enough, that may be where future Moon explorers get their next breath of air: The moon’s dusty layer of soil is nearly half oxygen.

The trick is extracting it.

“All you have to do is vaporize the stuff,” says Eric Cardiff of NASA’s Goddard Space Flight Center. He leads one of several teams developing ways to provide astronauts oxygen they’ll need on the Moon and Mars. (See the Vision for Space Exploration.)

Lunar soil is rich in oxides. The most common is silicon dioxide (SiO2), “like beach sand,” says Cardiff. Also plentiful are oxides of calcium (CaO), iron (FeO) and magnesium (MgO). Add up all the O’s: 43% of the mass of lunar soil is oxygen.

Cardiff is working on a technique that heats lunar soils until they release oxygen. “It’s a simple aspect of chemistry,” he explains. “Any material crumbles into atoms if made hot enough.” The technique is called vacuum pyrolysis–pyro means “fire”, lysis means “to separate.”

“A number of factors make pyrolysis more attractive than other techniques,” Cardiff explains. “It requires no raw materials to be brought from Earth, and you don’t have to prospect for a particular mineral.” Simply scoop up what’s on the ground and apply the heat.

In a proof of principle, Cardiff and his team used a lens to focus sunlight into a tiny vacuum chamber and heated 10 grams of simulated lunar soil to about 2,500 degrees C. Test samples included ilmenite and Minnesota Lunar Simulant, or MLS-1a. Ilmenite is an iron/titanium ore that Earth and the Moon have in common. MLS-1a is made from billion-year-old basalt found on the north shore of Lake Superior and mixed with glass particles that simulate the composition of the lunar soil. Actual lunar soil is too highly prized for such research now.

In their tests, “as much as 20 percent of the simulated soil was converted to free oxygen,” Cardiff estimates.

What’s leftover is “slag,” a low-oxygen, highly metallic, often glassy material. Cardiff is working with colleagues at NASA’s Langley Research Center to figure out how to shape slag into useful products like radiation shielding, bricks, spare parts, or even pavement.

The next step: increase efficiency. “In May, we’re going to run tests at lower temperatures, with harder vacuums.” In a hard vacuum, he explains, oxygen can be extracted with less power. Cardiff’s first test was at 1/1,000 Torr. That is 760,000 times thinner than sea level pressure on Earth (760 Torr). At 1 millionth of a Torr — another thousand times thinner — “the temperatures required are significantly reduced.”

Cardiff is not alone in this quest. A team led by Mark Berggren of Pioneer Astronautics in Lakewood, CO, is working on a system that harvests oxygen by exposing lunar soil to carbon monoxide. In one demonstration they extracted 15 kg of oxygen from 100 kg of lunar simulant–an efficiency comparable to Cardiff’s pyrolysis technique: more.

D.L. Grimmett of Pratt & Whitney Rocketdyne in Canoga Park, CA, is working on magma electrolysis. He melts MLS-1 at about 1,400 deg. C, so it is like magma from a volcano, and uses an electric current to free the oxygen: more.

Finally, NASA and the Florida Space Research Institute, through NASA’s Centennial Challenge, are sponsoring MoonROx, the Moon Regolith Oxygen competition. A $250,000 prize goes to the team that can extract 5 kg of breathable oxygen from JSC-1 lunar simulant in just 8 hours.

The competition closes June 1, 2008, but the challenge of living on other planets will last for generations.

Got any hot ideas?

Original Source: NASA News Release

Posted on by Fraser Cain

Milky Way is Consuming Many Galaxies

The Field of Streams. Image credit: Vasily Belokurov/SDSS-II. Click to enlarge
The Milky Way is continuing to consume entire galaxies, and the evidence is right there in the night sky. After analyzing data from the Sloan Digital Sky Survey, astronomers have found many streams of stars – all that remains from these gobbled up galaxies. As a satellite galaxy merges with the Milky Way, it’s slowly torn apart as it sinks into the galactic halo. Streams of stars are unraveled like a ball of yarn, and these continue to orbit the Milky Way, distinct from the orbital movements of the rest of the stars in our galaxy.

A new map of stars in the Milky Way Galaxy, constructed with data from the Sloan Digital Sky Survey (SDSS-II), reveals a night sky criss-crossed with streams of stars, left behind by satellite galaxies and star clusters spiraling to their deaths.

Analyzing five years of data spanning nearly one-quarter of the sky, Cambridge University (UK) researchers Vasily Belokurov and Daniel Zucker created a dramatic new image of the outer Milky Way, using stellar colors eliminating the redder, nearby stars that would otherwise swamp the view of background structures. They found so many trails of stars in their high contrast image that they named the area the “Field of Streams.”

Satellite galaxies orbiting the Milky Way are literally ripped apart by the tidal forces of our galaxy. As these satellites sink in gravitational quicksand, their stars are torn from them in giant streams that trace their orbital paths — just like meteor streams lie along the paths of defunct comets in the Solar system.

Dominating the Field of Streams image is the enormous, arching stream of the Sagittarius dwarf galaxy. The Sagittarius dwarf was discovered more than a decade ago and other researchers have previously mapped its long tidal stream in other regions of the sky.

But the new SDSS-II data had a remarkable surprise in store.

“The stream appears forked,” said Belokurov. “We are seeing different wraps superimposed on the sky, as the stream goes around the galaxy two or three times.”

Because of the multiple wraps, the observations provide strong new constraints on the dark matter halo of the Milky Way, according to Mike Fellhauer of Cambridge University. “The leading theories of dark matter predict that the Galaxy’s halo should be flattened, like a rugby football. But our simulations only match the forked Sagittarius stream if the inner halo is round, like a soccer ball.”

In addition to the Sagittarius arches, the Field shows faint trails of stars torn from globular clusters, and other rings, trails, and lumps that appear to be the remains of disrupted dwarf galaxies. “There are more streams here than in a river delta,” commented Zucker.

Prominent among these is the Monoceros stream, discovered previously by SDSS-II scientists Heidi Jo Newberg of Rensselaer Polytechnic Institute and Brian Yanny of the Fermi National Accelerator Laboratory. The multiple rings of stars are all that remain from a dwarf satellite that was absorbed by the Milky Way long ago.

Crossing the Field is an enigmatic, new stream of stars extending over 70 degrees on the sky, whose original source remains unknown.

“Some of these ‘murdered’ galaxies have been named,” explained SDSS-II team member Wyn Evans of Cambridge, “but this galactic corpse hasn’t been identified yet. We’re looking for it right now.”

These new discoveries add weight to a picture in which galaxies like the Milky Way are built up from the merging and accretion of smaller galaxies.

“We’ve known about merging for some time,” said Yanny, “but the Field of Streams gives us a striking demonstration of multiple merger events going on the Milky Way galaxy right now. This is happening all over the Universe, as big galaxies grow by tearing up smaller ones into streams.”

These streams also provide new tests of the nature of dark matter itself, according to theorist James Bullock of University of California at Irvine; Bullock was not part of the SDSS team.

“The fact that we can see a ‘Field of Streams’ like this suggests that dark matter particles are very ‘cold’, or slow moving. If the dark matter was made up of ‘warm,’ fast moving particles, we wouldn’t expect these thin streams to hang around long enough for us to find them.”

Original Source: RAS News Release

Posted on by Fraser Cain

Two Milky Way Companion Galaxies Found

An artist’s impression of the Milky way galaxy. Image credit: NASA. Click to enlarge
Astronomers have turned up two new companion galaxies to the Milky Way by looking through images in the Sloan Digital Sky Survey. The first is about 640,000 light years away in the constellation Canes Venatici – the most remote satellite galaxy ever discovered. The second is smaller and dimmer, and located in the constellation Bootes. It has a squashed structure because it’s being distorted by the Milky Way’s gravitational tides.

The Sloan Digital Sky Survey (SDSS-II) announced today (May 8) the discoveries of two new, very faint companion galaxies to the Milky Way.

The first was found in the direction of the constellation Canes Venatici (the Hunting Dog) by SDSS-II researcher Daniel Zucker at Cambridge University (UK). His colleague Vasily Belokurov discovered the second in the constellation Bootes (the Herdsman).

“I was poring over the survey’s map of distant stars in the Northern Galactic sky – what we call a Field of Streams — and noticed an overdensity in Canes Venatici,” Zucker explained. “Looking further, it proved to be a previously unknown dwarf galaxy. It’s about 640,000 light years (200 kiloparsecs) from the Sun. This makes it one of the most remote of the Milky Way’s companion galaxies.”

Zucker emailed Belokurov with the news, and, just as discoveries often build upon one another, Belokurov excitedly emailed back a few hours later with the discovery of a new, even fainter dwarf galaxy. The new galaxy in Bootes, which Belokurov called ‘Boo,’ shows a distorted structure that suggests it is being disrupted by the Milky Way’s gravitational tides. “Something really bashed Boo about,” said Belokurov.

Although the dwarf galaxies are in our own cosmic backyard, they are hard to discover because they are so dim. In fact, the new galaxy in Bootes is the faintest galaxy so far discovered, with a total luminosity of only about 100,000 Suns. But because of its distance (640,000 light years) it appears almost invisible to most telescopes. The previous dimness record holder was discovered last year in Ursa Major using SDSS-II data.

New galactic neighbors are exciting in their own right, but the stakes in searches for ultra-faint dwarfs are especially high because of a long-standing conflict between theory and observations. The leading theory of galaxy formation predicts that hundreds of clumps of “cold dark matter” should be orbiting the Milky Way, each one massive enough in principle to host a visible dwarf galaxy. But only about ten dwarf companions have been found to date.

One possibility is that the galaxies in the smaller dark matter clumps are too faint to have appeared in previous searches, but might be detectable in deep surveys like SDSS-II.

“It’s like panning for gold. Our view of the sky is enormous, and we’re looking for very small clumps of stars,” explained Cambridge University astronomer Wyn Evans, a member of the SDSS-II research team. Added collaborator Mark Wilkinson: “Finding and studying these small galaxies is really important. From their structure and their motions, we can learn about the properties of dark matter, as well as measure the mass and the gravity field of the Milky Way”.

The new discoveries are part of the SEGUE project (Sloan Extension for Galactic Understanding and Exploration), one of the three component surveys of SDSS-II. SEGUE will probe the structure and stellar make-up of the Milky Way Galaxy in unprecedented detail.

“I’m confident there are more dwarf galaxies out there and SEGUE will find them,” said Heidi Newberg of Rensselaer Polytechnic Institute, co-chair of SEGUE.

Original Source: RAS News Release