Posted on by Fraser Cain

Expedition 10 Lands Safely

After traveling more than 78 million miles aboard the International Space Station, Expedition 10 Commander and NASA ISS Science Officer Leroy Chiao and Flight Engineer Salizhan Sharipov returned to Earth today. With them was European Space Agency Astronaut Roberto Vittori, who had spent eight days aboard the orbiting complex doing research.

After a flawless descent by the ISS Soyuz 9 spacecraft, Chiao, Sharipov and Vittori landed on target in north-central Kazakhstan, about 53 miles (85 kilometers) northeast of Arkalyk, at 5:08 p.m. CDT. Recovery forces arrived at the site within minutes of the touchdown. The area was saturated from recent rains and melting winter snow, so the first members of the recovery team to reach the scene decided to fly the crew to Arkalyk to meet with remaining members of the recovery team.

The crew’s friends and families are expected to greet them upon their arrival at Star City, Russia, about eight hours after landing. Chiao and Sharipov will remain in Star City for a few weeks of post-flight debriefings and medical exams before returning to Houston in mid-May.

Chiao and Sharipov spent 192 days, 19 hours and 2 minutes in space. They launched on Oct. 13, on the same Soyuz spacecraft that brought them home. For six months, the pair maintained systems and conducted scientific research onboard the Station.

Among their accomplishments on the Station was replacing critical hardware in the Joint Quest Airlock, repairing U.S. spacesuits, submitting a scientific research paper on ultrasound use in space and voting for the first time in an American Presidential election from space. They completed two spacewalks, including experiment installation and tasks that prepared the Station for the arrival of a new European cargo ship next year.

Aboard the Station, the Expedition 11 crew, Commander Sergei Krikalev and Flight Engineer and NASA Station Science Officer John Phillips, are beginning a six-month mission that will include the resumption of Space Shuttle flights and two spacewalks from the Station. Expedition 11 is scheduled to return to Earth on Oct. 7, 2005.

Krikalev and Phillips will have light duty for the next three days as they rest after completing a busy handover period. For the past week, they have been learning about Station operations from the two men who called the ship home since October. Chiao and Sharipov briefed Krikalev and Phillips on day-to-day operations and gave them hands-on opportunities at Station maintenance: Chiao and Phillips restored functionality of the Quest for future spacewalks and practiced operating the Canadarm2 robotic arm.

Information on the crew’s activities aboard the Station, future launch dates, as well as Station sighting opportunities from anywhere on the Earth, is available on the Internet at:

http://www.nasa.gov/station

Original Source: NASA News Release

Posted on by Fraser Cain

Spitzer Discovers Early Galaxy Forming Region

The Spitzer Space Telescope (SST) is the fourth and final instrument in NASA’s Great Observatories series. The SST followed the Hubble Space Telescope (HST), Chandra X-Ray, and Compton Gamma Ray Observatories into space on August 25th, 2003. Placed in Earth-trailing heliocentric (solar) orbit, and working under a 2.5 plus year charter within NASA’s Origins Program, the SST revealed first public light in May of 2004 – giving the world a spectacular infrared view of the face-on grand spiral galaxy M51 in Canes Venatici.

Lord Rosse first described M51 as a “spiral nebula” in 1845. It wasn’t until Edwin Hubble resolved faint variable stars within another “M” – M31 – that M51 and other “spiral nebulae” achieved a rank equal with our own Milky Way – Galaxy!

But to name a thing is not to explain it. One of the toughest things to explain about anything is “How did it get to be what it is?”

Well before the release of SST’s image of M51, astronomers had already been given a “heads-up” on a rare instance of a class of distant objects in the heavens – an expansive region of gas and dust glowing faintly yet unattended by stellar light – just the kind of study that could revolutionize the way astronomers understand galaxy formation. NASA’s Origins Program had made a major hit and now the problem was to advance the runner to home using other sources of data…

In a paper entitled “Discovery of a Large ~ 200kpc Gaseous Nebula at z=~2.7 with the Spitzer Space Telescope” (published March 29, 2005), astrophysicist Arjun Dey of the National Optical Astronomy Observatory (NOAO) and colleagues from other organizations (including the SST operations center at the Jet Propulsion Laboratory) pulled together data from across the lower half of the em spectrum – radio to visible light – to paint a picture of early galaxy cluster formation associated with this excited (and exciting) region of dust and gas located some 11.3 BLY’s away in time and space.

In the words of the team, “We report the discovery of a very large spatially extended nebula associated with a luminous mid-infrared source.” To you and me that means they discovered “a long ago, and far away womb of early galactic birth”.

The object (SST24 J1434110+331733) was originally mapped using the SST’s MIPS and IRAC detectors during a mid-infrared survey of spring?s constellation Bootes in late January 2004. After data reduction by JPL personnel, it became clear that SST24 could offer some extremely significant insights into that mysterious era of galactic unfolding when young galaxies are ensconced in the stuff of star formation. But to penetrate this stuff would require expanding the picture of the region using light from across the em spectrum.

In part the need to have other looks at SST24 was driven by the limited aperture of SST’s 0.84 meter mirror and those long wavelengths associated with infrared light. At best, the SST revealed the central third of the nebulosity. (Instruments aboard the SST are limited to 6 arc seconds detail resolution.) Three onboard detectors (the Infrared Array Camera -IRAC, Infrared Spectrograph – IRS, and Multiband Imaging Photometer for Spitzer – MIPS) image and analyze infrared light in the mid to far-infrared wavelengths (3.6-160 micrometers).

Although light observed using the three SST instruments mostly originates from “warm” objects (gases and dust), light from near-optical sources can also be seen after expansionary redshift over vast distances. Interestingly, one particular bright line in that same “near-optical light” was first flagged for astronomical use by astrophysicist Lyman Spitzer – namesake of the SST itself – one of the leading 20th century proponents of infrared astronomy.

Joined with data from other instruments, Dey and his team put together a compelling case for an active galactic nuclei (AGN) within SST24. If verified such an AGN would demonstrate that black holes play an important role in early galaxy evolution. Such an example may very well revolutionize our understanding of galaxy formation by making AGN’s more the cause – rather than the effect – of galaxy group formation…

Visual data used by the team associated with SST24 was collected using the 4m and 2.1m telescopes of the NOAO in Kitt Peak, Arizona. These instruments improved SST resolution by a factor of almost eight times. Other data available in optical light extended the picture of SST24’s energy output. During May and June of 2004, spectrographic information on SST24 (along with foreground and background objects) was gathered in finely-tuned and precisely oriented 1 arc second strips through the 10 meter Keck I instrument on Mauna Kea, Hawaii.

From the paper’s abstract, “The bright mid-infrared source was first detected in observations made using the Spitzer Space Telescope. Existing broad-band imaging data from the NOAO Deep Wide-Field Survey revealed the mid-infrared source to be associated with a diffuse, spatially-extended, optical counterpart… Spectroscopy and further imaging … reveals the optical source is almost purely line-emitting nebula with little if any, detectable diffuse continuum emission.”

Typically, mature galaxies display a full spectrum of light generated by blackbody radiation from stellar photospheres. Such broadband spectra are usually reinforced by narrow, bright emission lines associated with atomic excitation. But SST24’s spectrum is dominated by a single narrow band of radiation. That band – though redshifted some 3.7 times due to 11.3 BLY’s of recession – associates with the “Lyman Alpha” frequency emitted by hydrogen gas. Usually such Lyman-alpha clouds irradiate by stimulation from distant background quasars. But in the case of SST24, another mechanism may be involved – a black hole source within the nebula itself.

In piecing together SST24’s structure, the science team determined that its AGN is offset from the center of the cloud by nearly one-tenth the cloud’s full extent. Although it is unclear what impact this offset has on galaxy formation, the fact of it must be incorporated into how we model galaxy group formation in the future.

Spectrographic shifts in Lyman alpha light also indicate that the central 100 KLY region of SST24 slowly revolves and contains the mass equivalent of some 6 trillion suns – some 5x that of our own Milky Way and Whirlpool (M51) galaxies combined. SST24 includes a region of space easily encompassing the entire Milky Way and all twelve satellite galaxies.

But SST24 is not totally devoid of star formation. The team reports that “a young star forming galaxy lies near the northern end of the nebula.” That galaxy is reddened by dust, has the same redshift as the Lyman-alpha radiation, plus broad-band radiation associated with star formation. This galaxy gives no indication of having an AGN. Because of this we may soon learn that AGN?s may not play a role essential to the formation of all galaxies.

Although radio-frequency examination of SST24 is difficult (due to resolution issues at long wavelengths), the team points out that its mid-infrared to radio-wave density ratio, “shows remarkable similarity to starburst galaxies…” For this reason parts of SST24 mat be passing through an era of rapid stellar evolution that could quickly lead to the revelation of a full-blown galaxy rich with luminous breeder stars…

SST24 is not the only Lyman-alpha cloud ever detected, but those few discovered are thought extraordinary by the science team: “The rarity of these >100kpc lyman-alpha clouds, their association with powerful AGN and galaxy overdensities, and their energetics all suggest that these regions are the formation sites of the most massive galaxies. If so, understanding the physical conditions and energetics of these systems can provide important insights into the massive galaxy formation process.”

Written by Jeff Barbour

Posted on by Fraser Cain

Wallpaper: 15 Years of Hubble

When NASA’s Hubble Space Telescope was launched in 1990, astronomers anticipated great discoveries, ranging from finding black holes to looking back billions of years toward the beginning of time. Now, 15 years later, the versatile telescope continues to deliver exciting new science, including helping to prove the existence of dark energy, tracing enigmatic gamma-ray bursts to distant galaxies, and sampling the atmospheres of far-flung planets. To celebrate Hubble’s 15th anniversary, new breathtaking images will be released of a majestic spiral galaxy teeming with newborn stars and an eerie-looking spire of gas and dust.

The new image of the well-known spiral galaxy M51 (known as the Whirlpool Galaxy), showcases a spiral galaxy’s classic features, from its curving arms, where newborn stars reside, to its yellowish central core, a home for older stars. A feature of considerable added interest is the companion galaxy located at the end of one of the spiral arms. The new photograph of the Eagle Nebula shows a tall, dense tower of gas that is being sculpted by ultraviolet light from a group of massive, hot stars.

The pictures are among the largest and sharpest views taken by Hubble. The images, taken by Hubble’s Advanced Camera for Surveys, are 20 times larger than a photograph taken by a typical digital camera. The new images are so sharp that they could be enlarged to billboard size and still retain the stunning details.

Mural-sized images of both celestial objects will be unveiled at 100 museums, planetariums, and science centers across the country, from Guam to Maine. The 4-foot-by-6-foot image of M51 and the 3-foot-by-6-foot photograph of the Eagle Nebula will be on display at all the sites. A list of these sites is available on http://hubblesite.org/about_us/unveiling.shtml.

If you cannot see the pictures at a museum or planetarium, catch them on the new “Gallery” at http://hubblesite.org/gallery. Views of M51 and the Eagle Nebula, along with more than 1,000 other glorious Hubble images, can be savored from the comfort of your home. If you want some Hubble pictures to hang in your home, then go to “Astronomy Print Shop.” Choose from a list of Hubble images that are specially formatted for printing. Select the image, the size you want (from 4 inches by 6 inches to 16 inches by 20 inches), and download it. Then take it to your favorite print shop to make a copy suitable for framing.

Looking for information about Hubble and its discoveries that is written for children? Then go to the Amazing Space education website at http://amazing-space.stsci.edu. Children can read a story tailored just for them on Hubble’s 15th anniversary, entitled “Hubble’s Picture Book of the Universe.” The story is under “The Star Witness,” a section of the website offering Hubble news written for children. Children also can take a journey through the eras of telescope history by going to Amazing Space’s “Online Explorations” and clicking on “Telescopes from the Ground Up.” This newest addition to Amazing Space traces the fascinating history of telescope evolution from the technological advancements to the people who made the telescopes.

Hubble was placed into Earth-orbit on April 25, 1990. For the first time, a large telescope that sees in visible light began orbiting above Earth’s distorting atmosphere, which blurs starlight and makes images appear fuzzy. Astronomers anticipated great discoveries from Hubble. The telescope has delivered as promised and continues serving up new discoveries. During its 15 years of viewing the universe, the telescope has taken more than 700,000 snapshots of celestial objects such as galaxies, dying stars, and giant gas clouds, the birthplace of stars. Astronomers are looking forward to more great discoveries by Hubble.

Original Source: Hubble News Release

Posted on by Mark Mortimer

Book Review: Night Sky Atlas

Of course the stars have been with people since people have been on Earth. Wandering along the ecliptic in an annual cycle allowed those with good memories to see the stars arc across the night sky, disappear and then reappear perhaps months later. Those with a good imagination then came along and, perhaps after reviewing the shapes of clouds, went on to name groups of stars; Leo the lion, the Big Dipper and Orion the hunter. These names represent the basic coordinates in star maps and also the basic orientation for astronomers when discussing their latest night time observations. A star map is essential for quickly learning this built up information and, with its knowledge, provides a common basis for discussing night time delights.

Robin Scagell in his book provides maps of the night skies. First he outlines the coordinate system; orbits, declination, right ascension, and ecliptics. Maps in semi-circular segments then illustrate the stars. A group of six illustrate the northern hemisphere. One pair gives a north and south view for a January evening at about midnight and with a false horizon drawn for a number of latitudes. Another shows May and a third pair shows September. Three other pairs show the segments if viewed from the southern hemisphere. These maps are quite small about 10 cm in diameter and show the constellations, names of significant stars and a washed area that represents the contribution from the Milky Way.

The main value of this book is the use of these guide maps with following detailed maps. Much like a road map that has blow ups with greater details, each of the semi-circular segments has four or five links to higher fidelity maps. And these higher fidelity maps are the purpose for the book’s larger format as these are each also a semicircle of diameter about 30 cm. Now it’s a bit curious as to how semi-circles divided to semi-circles, perhaps there’s a fair amount of overlap. Anyway these higher fidelity maps each appear twice. The first shows stars in black on a white background as well as constellation boundaries. The second is a photo-realistic image (stars as white dots on a black background) which show the night sky as a viewer would see it. In total there are eight pairs of these higher fidelity maps.

Following the maps are sections on what to see, sort of like a tourist’s map for a city. The moon gets large attention with lots of clear, fine scale photographs. Four, full page quarter circle maps provide place names on a shaded relief. The sun and each planet also have write-ups and pictures though, not surprisingly, the amount of information is inversely proportional to the distance from Earth. Of course these have no maps as no amateur astronomer has equipment able to discern geographic features except perhaps a little of Mars (the ice caps).

The final chapter of the book does get back into maps. Fifty of the most important constellations (presumably according to the author) have a small map (about 10cm by 10cm) alongside a write-up of the interesting features; galaxies, nebulae and other deep sky objects. This is a particularly good chapter with in-depth information much as a large city map presents details on tourist sections and popular sites. Once centring a constellation in the eyepiece of your favourite telescope, using this map quickly allows a viewer to identify features as well as their relative positions. Hence the constellation Pegasus becomes the stars Sadalbari, Matar and Enif. And thus the learning of the night sky via the maps in this book, quickens.

As an atlas this book is good but not great. I put it to the test, went out, got my bearings using the Big Dipper and then looked in the book. Note I’m no expert. However, this being April made the large scale maps very difficult. The nearest map (May at Midnight) did not do my view justice. Going to the higher fidelity maps was no help as I couldn’t get an appreciation of the scale. However, starting with the constellation Big Dipper (or Ursa Major), I was able to learn more about the local sky group. More large scale maps would have helped. Also, in looking at the higher fidelity maps, I only referred to the high contrast, black on white views; never the photo-realistic ones. Nevertheless this book is an effective night sky atlas for those looking without aid or those using binoculars or small telescopes.

Travelling to visit the grandparents, planning for a vacation or going out to view stars at night all have much better results when undertaken with an appropriate map. Robin Scagell in his book, Night Sky Atlas provides the guidance for viewing the moon, planets, stars and other deep sky objects. So don’t get lost in the big, diamond endowed, velvet cloth that descends over us every evening, get this book and travel away.

See more reviews or order a copy online from Amazon.com

Review by Mark Mortimer.

Posted on by Fraser Cain

Hot Spots Seen on Neutron Stars

Thanks to data from ESA?s XMM-Newton spacecraft, European astronomers have observed for the first time rotating ?hot spots? on the surfaces of three nearby neutron stars.

This result provides a breakthrough in understanding the ?thermal geography? of neutron stars, and provides the first measurement of very small-sized features on objects hundreds to thousands light-years away. The spots vary in size from that of a football field to that of a golf course.

Neutron stars are extremely dense and fast-rotating stars mainly composed of neutrons. They are extremely hot when they are born, being remnants of supernovae explosions. Their surface temperature is thought to gradually cool down with time, decreasing to less than one million degrees after 100 000 years.

However, astrophysicists had proposed the existence of physical mechanisms by which the electromagnetic energy emitted by neutron stars could be funnelled back into their surface in certain regions. Such regions, or ?hot spots?, would then be reheated and reach temperatures much higher than the rest of the cooling surface. Such peculiar ?thermal geography? of neutron stars, although speculated, could never be observed directly before.

Using XMM-Newton data, a team of European astronomers have observed rotating hot spots on three isolated neutron stars that are well-known X-ray and gamma-ray emitters. The three observed neutron stars are ?PSR B0656-14?, ?PSR B1055-52?, and ?Geminga?, respectively at about 800, 2000 and 500 light-years away from us.

As for normal stars, the temperature of a neutron star is measured through its colour that indicates the energy the star emits. The astronomers have divided the neutron star surfaces into ten wedges and have measured the temperature of each wedge. By doing so, they could observe rise and fall of emission from the star?s surface, as the hot spots disappear and appear again while the star rotates. It is also the first time that surface details ranging in size from less than 100 metres to about one kilometre are identified on the surface of objects hundreds to thousands light-years away.

The team think that the hot spots are most probably linked to the polar regions of the neutron stars. This is where the star?s magnetic field funnels charged particles back towards the surface, in a way somehow similar to the ?Northern lights?, or aurorae, seen at the poles of planets which have magnetic fields, such as Earth, Jupiter and Saturn.

?This result is a first, and a key to understand the internal structure, the dominant role of the magnetic field treading the star interior and its magnetosphere, and the complex phenomenology of neutron stars,? says Patrizia Caraveo, of the Istituto Nazionale di Astrofisica (IASF), Milan, Italy.

?It has been possible only thanks to the new capabilities provided by the ESA XMM-Newton observatory. We look forward to applying our method to many more magnetically isolated neutron stars,? concludes Caraveo.

However, there is still a puzzle for the astronomers. If the three ?musketeers? are predicted to have polar caps of comparable dimensions, why then are the hot spots observed in the three cases so different in size, ranging from 60 metres to one kilometre? What mechanisms rule the difference? Or does this mean some of the current predictions on neutron stars magnetic fields need to be revised?

The result, by Andrea De Luca, Patrizia Caraveo, Sandro Mereghetti, Matteo Negroni (IASF) and Giovanni Bignami of CESR, Toulouse and University of Pavia, is published in the 20 April 05 issue of the Astrophysical Journal (http://www.journals.uchicago.edu/ApJ, vol. 623:1051-1069).

Original Source: ESA News Release

Posted on by Fraser Cain

Earthquake Should Show a Gravity Scar

Image credit: ESA
A new ESA study predicts that the devastating Sumatran earthquake, which resulted in the tragic tsunami of 26 December 2004, will have left a ?scar? on Earth?s gravity that could be detected by a sensitive new satellite, due for launch next year.

The Sumatran earthquake measured 9 on the Richter scale and caused widespread devastation and death when it struck unexpectedly late last year. Thankfully, earthquakes of this magnitude are rare events, taking place perhaps once every two decades.

Seismological data suggests that, during the event, the seafloor on either side of a fault line running for 1000 km along the bottom of the Indian Ocean dramatically changed height, producing a ledge, 6 metres high. Such a large-scale movement will change the gravitational field of the Earth. Roberto Sabadini and Giorgio Dalla Via, University of Milan, and colleagues have calculated this change. They found that the Earth?s gravity altered, in an instant, by as much as is expected from six years’ worth of melting at the Patagonian Ice Fields in southernmost South America.

It may seem surprising that Earth?s gravity is not equally strong at all points of the globe. Instead, it varies by a small fraction due to the presence of such things as mountains or deep ocean trenches. The tides and ocean circulation patterns also affect the gravity, as does the rotation of the Earth itself, which bulges out the planet?s equator and makes its diameter 21 kilometres wider than the pole-to-pole distance.

In order to measure the deviations from the average level of gravity, Earth scientists invented the concept of the geoid. This is a bit like a hi-tech version of ?sea level?, which is often used to give an absolute height measure. Today?s modern measurements need something more accurate, however.

The geoid is a hypothetical surface, on which the gravitational pull of the Earth is the same everywhere. It wraps itself around the Earth, moving away from the real surface when it is over areas of greater density and therefore stronger gravity. Over less dense regions, the geoid moves closer to the real surface.

When material is moved around, either instantaneously in an earthquake or gradually as in a melting ice field, the Earth?s gravity in the local region changes and so does the height of the geoid. In the Sumatran earthquake, Sabadini and Dalla Via found that the total geoid movement was some 18 mm ? a lot for a geoid!

ESA?s Gravity Field and Ocean Circulation Explorer (GOCE) is designed to sensitively investigate the gravitational field of the Earth from orbit. As the spacecraft passes over regions of stronger and weaker gravitational pull, it will bob up and down. Such deviations are far below the perceptible limits of humans but GOCE is equipped with a device called a gradiometer than can detect these ultra-subtle differences. By measuring the deviations in the geoid, scientists can gain a unique window into our planet.

?This work is at the frontier of geophysics and the perfect complement to seismology,? says Sabadini, ?Seismology is good for detecting the slip of earthquake faults and the location of the epicentre, geoid monitoring can determine how much mass is actually being moved around.?

It can also be used in the quest to understand climate change as ocean circulation also affects the geoid. Changes in climate, which in turn affect the ocean circulation pattern, will show up as a yearly change in the geoid. With so much to offer, the GOCE satellite is scheduled to launch in 2006. A paper on the Sumatran Earthquake by Roberto Sabadini, Giorgio Dalla Via, Masja Hoogland, Abdelkrim Aoudia is published in EOS, the journal of the American Geophysical Union.

Original Source: ESA News Release

Posted on by Fraser Cain

False Colour Titan

This false-color composite was created with images taken during the Cassini spacecraft’s closest flyby of Titan on April 16, 2005.

It was created by combining two infrared images (taken at 938 and 889 nanometers) with a visible light image (taken at 420 nanometers). Green represents areas where Cassini is able to see down to the surface. Red represents areas high in Titan’s stratosphere where atmospheric methane is absorbing sunlight. Blue along the moon’s outer edge represents visible violet wavelengths at which the upper atmosphere and detached hazes are better seen.

A similar false-color image showing the opposite hemisphere of Titan was created from images taken during Cassini’s first close flyby of the smoggy moon in October 2004 (see PIA06139). At that time, clouds could be seen near Titan’s south pole, but in these more recent observations no clouds are seen.

North on Titan is up and tilted 30 degrees to the right.

The images used to create this composite were taken with the Cassini spacecraft wide angle camera on April 16, 2005, at distances ranging from approximately 173,000 to 168,200 kilometers (107,500 to 104,500 miles) from Titan and from a Sun-Titan-spacecraft, or phase, angle of 56 degrees. Resolution in the images approximately 10 kilometers per pixel.

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

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

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Don’t Breathe the Moon Dust

This is a true story.

In 1972, Apollo astronaut Harrison Schmidt sniffed the air in his Lunar Module, the Challenger. “[It] smells like gunpowder in here,” he said. His commander Gene Cernan agreed. “Oh, it does, doesn’t it?”

The two astronauts had just returned from a long moonwalk around the Taurus-Littrow valley, near the Sea of Serenity. Dusty footprints marked their entry into the spaceship. That dust became airborne–and smelly.

Later, Schmidt felt congested and complained of “lunar dust hay fever.” His symptoms went away the next day; no harm done. He soon returned to Earth and the anecdote faded into history.

But Russell Kerschmann never forgot. He’s a pathologist at the NASA Ames Research Center studying the effects of mineral dust on human health. NASA is now planning to send people back to the Moon and on to Mars. Both are dusty worlds, extremely dusty. Inhaling that dust, says Kerschmann, could be bad for astronauts.

“The real problem is the lungs,” he explains. “In some ways, lunar dust resembles the silica dust on Earth that causes silicosis, a serious disease.” Silicosis, which used to be called “stone-grinder’s disease,” first came to widespread public attention during the Great Depression when hundreds of miners drilling the Hawk’s Nest Tunnel through Gauley Mountain in West Virginia died within half a decade of breathing fine quartz dust kicked into the air by dry drilling–even though they had been exposed for only a few months. “It was one of the biggest occupational-health disasters in U.S. history,” Kerschmann says.

This won’t necessarily happen to astronauts, he assures, but it’s a problem we need to be aware of–and to guard against.

Quartz, the main cause of silicosis, is not chemically poisonous: “You could eat it and not get sick,” he continues. “But when quartz is freshly ground into dust particles smaller than 10 microns (for comparison, a human hair is 50+ microns wide) and breathed into the lungs, they can embed themselves deeply into the tiny alveolar sacs and ducts where oxygen and carbon dioxide gases are exchanged.” There, the lungs cannot clear out the dust by mucous or coughing. Moreover, the immune system’s white blood cells commit suicide when they try to engulf the sharp-edged particles to carry them away in the bloodstream. In the acute form of silicosis, the lungs can fill with proteins from the blood, “and it’s as if the victim slowly suffocates” from a pneumonia-like condition.

Lunar dust, being a compound of silicon as is quartz, is (to our current knowledge) also not poisonous. But like the quartz dust in the Hawk’s Nest Tunnel, it is extremely fine and abrasive, almost like powdered glass. Astronauts on several Apollo missions found that it clung to everything and was almost impossible to remove; once tracked inside the Lunar Module, some of it easily became airborne, irritating lungs and eyes.

Martian dust could be even worse. It’s not only a mechanical irritant but also perhaps a chemical poison. Mars is red because its surface is largely composed of iron oxide (rust) and oxides of other minerals. Some scientists suspect that the dusty soil on Mars may be such a strong oxidizer that it burns any organic compound such as plastics, rubber or human skin as viciously as undiluted lye or laundry bleach.

“If you get Martian soil on your skin, it will leave burn marks,” believes University of Colorado engineering professor Stein Sture, who studies granular materials like Moon- and Mars-dirt for NASA. Because no soil samples have ever been returned from Mars, “we don’t know for sure how strong it is, but it could be pretty vicious.”

Moreover, according to data from the Pathfinder mission, Martian dust may also contain trace amounts of toxic metals, including arsenic and hexavalent chromium–a carcinogenic toxic waste featured in the docudrama movie Erin Brockovich (Universal Studios, 2000). That was a surprising finding of a 2002 National Research Council report called Safe on Mars: Precursor Measurements Necessary to Support Human Operations on the Martian Surface.

The dust challenge would be especially acute during windstorms that occasionally envelop Mars from poles to equator. Dust whips through the air, scouring every exposed surface and sifting into every crevice. There’s no place to hide.

To find ways of mitigating these hazards, NASA is soon to begin funding Project Dust, a four-year study headed by Masami Nakagawa, associate professor in the mining engineering department of the Colorado School of Mines. Project Dust will study such technologies as thin-film coatings that repel dust from tools and other surfaces, and electrostatic techniques for shaking or otherwise removing dust from spacesuits.

These technologies, so crucial on the Moon and Mars, might help on Earth, too, by protecting people from sharp-edged or toxic dust on our own planet. Examples include alkaline dust blown from dry lakes in North American deserts, wood dust from sawmills and logging operations, and, of course, abrasive quartz dust in mines.

The road to the stars is surprisingly dusty. But, says Kerschmann, “I strongly believe it’s a problem that can be controlled.”

Original Source: Science@NASA Story

Posted on by Fraser Cain

Solar Wind Flows From Magnetic Funnels on the Sun

A Chinese-German team of scientists have identified the magnetic structures in the solar corona where the fast solar wind originates. Using images and Doppler maps from the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer and magnetograms delivered by the Michelson Doppler Imager (MDI) on the space-based Solar and Heliospheric Observatory (SOHO) of ESA and NASA, they observed solar wind flowing from funnel-shaped magnetic fields which are anchored in the lanes of the magnetic network near the surface of the Sun. These observations are presented in the April 22 issue of Science magazine. The research leads to a better understanding of the magnetic nature of the sources of the solar wind, a stream of tenuous and hot plasma (electrically conductive gas) that affects the Earth’s space environment.

The solar wind consists of protons, alpha particles (two-fold ionized helium), heavy ions and electrons flowing from the surface of the Sun with speeds ranging from 300 to 800 km/s. The heavy ions in the coronal source regions emit radiation at certain ultraviolet wavelengths. When they flow towards Earth, as they do when tracing the nascent solar wind, the wavelengths of the ultraviolet emission become shorter, a phenomenon called the Doppler effect, which is well known in its acoustic variant, for example, from the change in tone of the horn of a police car while approaching to or receding from the listener. In the solar case, plasma motion towards us, which means away from the solar surface, is detected as blue shift in the ultraviolet spectrum, and thus can be used to identify the beginning of the solar wind outflow.

A SUMER ultraviolet spectrum is similar to what is seen when a prism separates white light into a rainbow of distinct colors. The ultraviolet radiation is however invisible to the human eye and cannot penetrate the Earth’s atmosphere. By analyzing ultraviolet emission obtained by SUMER on the space observatory SOHO from space, solar physicists can learn a great deal about the Sun and infer the gas temperature, chemical composition, and motion in the various atmospheric layers.

“The fine magnetic structure of the source region of solar wind has remained elusive” said first author Prof. Chuanyi Tu, from the Department of Geophysics of the Peking University in Beijing, China. “For many years, solar and space physicists have observed fast solar wind streams coming from coronal regions with open magnetic field lines and low light intensity, the so called coronal holes. However, only by combining complex observations from SOHO in a novel way have we been able to infer the properties of the sources inside coronal holes. The fast solar wind seems to originate in coronal funnels with a speed of about 10 km/s at a height of 20,000 kilometers above the photosphere”.

“The fast solar wind starts to flow out from the top of funnels in coronal holes with a flow speed of about 10 km/s”, states Prof. Tu. “This outflow is seen as large patches in Doppler blue shift (hatched areas in the above figure) of a spectral line emitted by Ne+7 ions at a temperature of 600,000 Kelvin, which can be used as a good tracer for the hot plasma flow. Through a comparison with the magnetic field, as extrapolated from the photosphere by means of the MDI magnetic data, we found that the blue-shift pattern of this line correlates best with the open field structures at 20,000 km.”

The SUMER spectrometer scrutinized the sources of the solar wind by observing ultraviolet radiation coming from a large area of the northern polar region of the Sun. “The clear identification of the detailed magnetic structure of the source, now being revealed as coronal funnels, and the determination of the release height and initial speed of the solar wind are important steps in solving the problems of mass supply and basic acceleration. We can now focus our attention on studying further plasma conditions and physical processes that occur in the expanding coronal funnels and in their narrow necks anchored in the magnetic network”, says Prof. Eckart Marsch, co-author of the Science paper.

Solving the nature and origin of the solar wind is one of the main goals for which SOHO was designed. It has long been known to the astronomical community that the fast solar wind comes from coronal holes. What is new here is the discovery that these flows start in coronal funnels, which have their source located at the edges of the magnetic network. Just below the surface of the Sun there are large convection cells. Each cell has magnetic fields associated with it, which are concentrated in the network lanes by magneto-convection, where the funnel necks are anchored. The plasma, while still being confined in small loops, is brought by convection to the funnels and then released there, like a bucket of water is emptied into an open water channel.

“Previously it was believed that the fast solar wind originates on any given open field line in the ionization layer of the hydrogen atom slightly above the photosphere”, says Prof. Marsch, “However, the low Doppler shift of an emission line from carbon ions shows that bulk outflow has not yet occurred at a height of 5,000 km. The solar wind plasma is now considered to be supplied by plasma stemming from the many small magnetic loops, with only a few thousand kilometers in height, crowding the funnel. Through magnetic reconnection plasma is fed from all sides to the funnel, where it may be accelerated and finally form the solar wind.”

The SUMER instrument was built under the leadership of Dr. Klaus Wilhelm, who is also a co-author of the paper, at the Max Planck Institute for Solar System Research (formerly Max Planck Institute for Aeronomy) in Lindau, Germany, with key contributions from the Institut d’Astrophysique Spatiale in Orsay, France, the NASA Goddard Space Flight Center in Greenbelt, Maryland,the University of California in Berkeley, and with financial support from German, French, USA and Swiss national agencies. SOHO has been operating for almost ten years at a special vantage point in space 1.5 milion kilometers from the Earth, on the sunward side of the Earth. SOHO is a project of international collaboration between the European Space Agency and NASA. It was launched on an Atlas II-AS rocket from NASA’s Kennedy Space Center, Florida, in December 1995 and is operated from the Goddard Space Flight Center.

Original Source: Max Planck Society News Release

Posted on by Fraser Cain

Nebula N214C

The nebula N214 [1] is a large region of gas and dust located in a remote part of our neighbouring galaxy, the Large Magellanic Cloud. N214 is a quite remarkable site where massive stars are forming. In particular, its main component, N214C (also named NGC 2103 or DEM 293), is of special interest since it hosts a very rare massive star, known as Sk-71 51 [2] and belonging to a peculiar class with only a dozen known members in the whole sky. N214C thus provides an excellent opportunity for studying the formation site of such stars.

Using ESO’s 3.5-m New Technology telescope (NTT) located at La Silla (Chile) and the SuSI2 and EMMI instruments, astronomers from France and the USA [3] studied in great depth this unusual region by taking the highest resolution images so far as well as a series of spectra of the most prominent objects present.

N214C is a complex of ionised hot gas, a so-called H II region [4], spreading over 170 by 125 light-years (see ESO PR Photo 12b/05). At the centre of the nebula lies Sk-71 51, the region’s brightest and hottest star. At a distance of ~12 light-years north of Sk-71 51 runs a long arc of highly compressed gas created by the strong stellar wind of the star. There are a dozen less bright stars scattered across the nebula and mainly around Sk-71 51. Moreover, several fine, filamentary structures and fine pillars are visible.

The green colour in the composite image, which covers the bulk of the N214C region, comes from doubly ionised oxygen atoms [5] and indicates that the nebula must be extremely hot over a very large extent.

The Star Sk-71 51 decomposed
The central and brightest object in ESO PR Photo 12b/05 is not a single star but a small, compact cluster of stars. In order to study this very tight cluster in great detail, the astronomers used sophisticated image-sharpening software to produce high-resolution images on which precise brightness and positional measurements could then be performed (see ESO PR Photo 12c/05). This so-called “deconvolution” technique makes it possible to visualize this complex system much better, leading to the conclusion that the tight core of the Sk-71 51 cluster, covering a ~ 4 arc seconds area, is made up of at least 6 components.

From additional spectra taken with EMMI (ESO Multi-Mode Instrument), the brightest component is found to belong to the rare class of very massive stars of spectral type O2 V((f*)). The astronomers derive a mass of ~80 solar masses for this object but it might well be that this is a multiple system, in which case, each component would be less massive.

Stellar populations
From the unique images obtained and reproduced as ESO PR Photo 12b/05, the astronomers could study in great depth the properties of the 2341 stars lying towards the N214C region. This was done by putting them in a so-called colour-magnitude diagram, where the abscissa is the colour (representative of the temperature of the object) and the ordinate the magnitude (related to the intrinsic brightness). Plotting the temperature of stars against their intrinsic brightness reveals a typical distribution that reflects their different evolutionary stages.

Two main stellar populations show up in this particular diagram (ESO PR Photo 12d/05): a main sequence, that is, stars that like the Sun are still centrally burning their hydrogen, and an evolved population. The main sequence is made up of stars with initial masses from roughly 2-4 to about 80 solar masses. The stars that follow the red line on ESO PR Photo 12d/05 are main sequence stars still very young, with an estimated age of about 1 million years only. The evolved population is mainly composed of much older and lower mass stars, having an age of 1,000 million years.

From their work, the astronomers classified several massive O and B stars, which are associated with the H II region and therefore contribute to its ionisation.

A Blob of Ionised Gas
A remarkable feature of N214C is the presence of a globular blob of hot and ionised gas at ~ 60 arc seconds (~ 50 light-years in projection) north of Sk-71 51. It appears as a sphere about four light-years across, split into two lobes by a dust lane which runs along an almost north-south direction (ESO PR Photo 12d/05). The blob seems to be placed on a ridge of ionised gas that follows the structure of the blob, implying a possible interaction.

The H II blob coincides with a strong infrared source, 05423-7120, which was detected with the IRAS satellite. The observations indicate the presence of a massive heat source, 200,000 times more luminous than the Sun. This is more probably due to an O7 V star of about 40 solar masses embedded in an infrared cluster. Alternatively, it might well be that the heating arises from a very massive star of about 100 solar masses still in the process of being formed.

“It is possible that the blob resulted from massive star formation following the collapse of a thin shell of neutral matter accumulated through the effect of strong irradiation and heating of the star Sk-71 51”, says Mohammad Heydari-Malayeri from the Observatoire de Paris (France) and member of the team.”Such a “sequential star formation” has probably occurred also toward the southern ridge of N214C”.

Newcomer to the Family
The compact H II region discovered in N214C may be a newcomer to the family of HEBs (“High Excitation Blobs”) in the Magellanic Clouds, the first member of which was detected in LMC N159 at ESO. In contrast to the typical H II regions of the Magellanic Clouds, which are extended structures spanning more than 150 light years and are powered by a large number of hot stars, HEBs are dense, small regions usually “only” 4 to 9 light-years wide. Moreover, they often form adjacent to or apparently inside the typical giant H II regions, and rarely in isolation.

“The formation mechanisms of these objects are not yet fully understood but it seems however sure that they represent the youngest massive stars of their OB associations”, explains Frederic Meynadier, another member of the team from the Observatoire de Paris. “So far only a half-dozen of them have been detected and studied using the ESO telescopes as well as the Hubble Space Telescope. But the stars responsible for the excitation of the tightest or youngest members of the family still remain to be detected.”

More information
The research made on N214C has been presented in a paper accepted for publication by the leading professional journal, Astronomy and Astrophysics (“The LMC H II Region N214C and its peculiar nebular blob”, by F. Meynadier, M. Heydari-Malayeri and Nolan R. Walborn). The full text is freely accessible as a PDF file from the A&A web site.

Notes
[1]: The letter “N” (for “Nebula”) in the designation of these objects indicates that they were included in the “Catalogue of H-alpha emission stars and nebulae in the Magellanic Clouds” compiled and published in 1956 by American astronomer-astronaut Karl Henize (1926 – 1993).

[2]: The name Sk-71 51, is the abbreviation of Sanduleak -71 51. The American astronomer Nicholas Sanduleak, while working at the Cerro Tololo Observatory, published in 1970 an important list of objects (stars and nebulae showing emission-lines in their spectra) in the Magellanic Clouds. The “-71” in the star’s name is the declination of the object, while the “51” is the entry number in the catalogue.

[3]: The team of astronomers consists of Frederic Meynadier and Mohammad Heydari-Malayeri (LERMA, Paris Observatory, France), and Nolan R. Walborn (Space Telescope Science Institute, USA).

[4]: A gas is said to be ionised when its atoms have lost one or more electrons – in this case by the action of energetic ultraviolet radiation emitted by very hot and luminous stars close by. The heated gas shines mostly in the light of ionized hydrogen (H) atoms, leading to an emission nebula. Such nebulae are referred to as “H II regions”. The well-known Orion Nebula is an outstanding example of that type of nebula, cf. ESO PR Photos 03a-c/01 and ESO PR Photo 20/04.

[5]: The hotter the central object of an emission nebula, the hotter and more excited will be the surrounding nebula. The word “excitation” refers to the degree of ionization of the nebular gas. The more energetic the impinging particles and radiation, the more electrons will be lost and higher is the degree of excitation. In N214C, the central cluster of stars is so hot that the oxygen atoms are twice ionized, i.e. they have lost two electrons.

Original Source: ESO News Release