Posted on by Mark Mortimer

Book Review: Reflections from Earth Orbit

Winston Scott in many ways is a typical NASA astronaut. He had a challenging and aimless youth. Then, through military training, he blossomed into a very capable pilot, instructor and astronaut. Uniquely, he grew up in a fairly impoverished black neighborhood of Miami where music, particularly by playing the trumpet, gave strength to his voice. Later, while at NASA, Scott was a mission specialist on STS-72 and on STS-87. For both he undertook experiments, worked with satellites and tested EVA techniques in the preparation for building the ISS. This is the background for his reflections.

The reflections themselves get presented they way family photographs are presented during a Sunday afternoon lunch at a friend’s house. The prose of the book is all in first person, past tense. Many large colour photographs accompany the narrative. The sensation is of the author standing beside you pointing at the photographs and then giving a rousing rendition of the surrounding activities. There is no real order of events. The book starts with Scott’s childhood, bounces to flight training, returns back to high school then on toward a shuttle launch, back to childhood memories and so on. As a reflection this is fine. As an autobiography, which this book isn’t, this is confusing. But, as long as the tea is fresh and the hot scones keep coming, reading this book is pleasant.

As a series of reflections, this book is strongly emotive. Memories of childhood security, cravings for model aeroplanes and musical embellishments counterpoint space based images of smoke from fires in Kuwait, sleeping where up and down have no meaning and empty blackness that dominates the visual senses. Absent however are Scott’s personal emotions. There is no evidence of love or hate, neither pain nor joy. The descriptions themselves whilst obviously from first person experience, have more the style of an art student than a master like Picasso. Further, the occasional use of quoted dialogue adds to the authenticity but seldom to the content.

This lack of content is where Scott misses his opportunity. From his unique background and recent views as a successful astronaut, he should have been able to build an inspiring compilation of powerful experiences. Their rendition could then have propelled other youths forward. However, he doesn’t. He waxes on about views he saw and events that transpired but he never equates these to feelings or to resolutions. There isn’t anything to grab on to and say, ‘gee, I can do that and maybe I can also ascend to the stars!’. Further, precious little technical information makes the text little use as a reference. Given these short comings, there really doesn’t seem to be significant value inside these pages. If you were to read without the tea and scones, there wouldn’t even be the satisfaction of a full belly.

An elder statesman’s best role can be to pass on knowledge. In so doing, they inspire and guide fledglings to new heights. William Scott book Reflections from Earth Orbit presents some unique and colourful descriptions from his experience as a NASA astronaut and an elder statesman. Provide this book as an incentive and it may just entice a young one to soar.

Click here to visit Amazon.com and read more reviews online or purchase a copy.

Posted on by Fraser Cain

Pandora and Prometheus

Prometheus and Pandora above the dark side of Saturn’s rings. Image credit: NASA/JPL/SSI. Click to enlarge
Saturn’s moons Prometheus and Pandora are captured here in a single image taken from less than a degree above the dark side of Saturn’s rings. Pandora is on the right, and Prometheus is on the left. Prometheus is 102 kilometers (63 miles) across. Pandora is 84 kilometers (52 miles) across.
The two moons are separated by about 69,000 kilometers (43,000 miles) in this view.

The F ring, extending farthest to the right, contains a great deal of fine, icy material that is more the size of dust than the boulders thought to comprise the dense B ring. These tiny particles are particularly bright from this viewing geometry, especially at right near the ansa, or edge.

At left of center, a couple of ringlets within the Encke gap (325 kilometers, or 200 miles wide) can also be easily seen due to their fine dust-sized material. The other dark features in the rings are density waves and bending waves.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Feb. 20, 2005, when Cassini was a mean distance of 1.85 million kilometers (1.15 million miles) from the moons. The image scale is about 11 kilometers (7 miles) per pixel on both moons.

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 . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

Strange White Streak on Titan

Unusual bright spot offers Titan mystery. Image credit: NASA/JPL/SSI. Click to enlarge
During a recent pass of Saturn’s moon Titan, one of more than 40 during Cassini’s planned four-year mission, the spacecraft acquired this infrared view of the bright Xanadu region and the moon’s south pole. Titan is 5,150 kilometers (3,200 miles) across.

Southeast of Xanadu (and above the center in this view) is a peculiar semi-circular feature informally referred to by imaging scientists as “the Smile.” This surface feature is the brightest spot on Titan’s surface, not only to the imaging science subsystem cameras, but also to the visual and infrared mapping spectrometer instrument, which sees the surface at even longer wavelengths. The Smile is 560 kilometers (345 miles) wide.

At the landing site of the successful Huygens probe mission, brighter regions correspond to icy upland areas, while the darker regions are lowlands that possess a higher proportion of the organic byproducts of Titan’s atmospheric photochemistry. Those results seem to confirm the long-standing hypothesis that Xanadu is a relatively high region of less contaminated ice. However, the cause of the even brighter Smile is a mystery that is still under study.

Farther south, a field of bright clouds arcs around the pole, moving at a few meters per second. Around the limb (edge), Cassini peers through Titan’s smoggy, nitrogen-rich atmosphere.

North in this image is toward the upper left.

The image was taken with the Cassini spacecraft narrow-angle camera on June 4, 2005, at a distance of approximately 1.2 million kilometers (700,000 miles) from Titan using a spectral filter sensitive to wavelengths of infrared light centered at 938 nanometers. The image scale is 7 kilometers (4 miles) per pixel.

Original Source: NASA Astrobiology

Posted on by Fraser Cain

APEX Telescope Sees First Light

The APEX Telescope at Chajnantor. Image credit: ESO. Click to enlarge
The Atacama Pathfinder Experiment (APEX) project has just passed another major milestone by successfully commissioning its new technology 12-m telescope, located on the 5100m high Chajnantor plateau in the Atacama Desert (Chile). The APEX telescope, designed to work at sub-millimetre wavelengths, in the 0.2 to 1.5 mm range, has just performed its first scientific observations. This new front-line facility will provide access to the “Cold Universe” with unprecedented sensitivity and image quality.

Karl Menten, Director of the group for Millimeter and Sub-Millimeter Astronomy at the Max-Planck-Institute for Radio Astronomy (MPIfR) and Principal Investigator of the APEX project is excited: ” Among the first observations, we have obtained wonderful spectra, which took only minutes to take but offer a fascinating view of the highly complex organic chemistry in star-forming regions. In addition, we have also obtained exquisite images from the Magellanic Clouds and observed molecules in the active nuclei of several external galaxies. Traditionally, telescopes turn to weak extragalactic sources only after they are well in operation. With APEX, we could pick them amongst our first targets!”

Because sub-millimetre radiation from space is heavily absorbed by water vapour in the Earth’s atmosphere, APEX is located at an altitude of 5100 metres in the high Chilean Atacama desert on the Chajnantor plains, 50 km east of San Pedro de Atacama in northern Chile. The Atacama desert is one of the driest places on Earth, thus providing unsurpassed observing opportunities – at the costs of the demanding logistics required to operate a frontier science observatory at this remote place.

Along with the Japanese 10-m ASTE telescope, which is operating at a neighbouring, lower altitude location, APEX is the first and largest sub-millimetre facility under southern skies. With its precise antenna and large collecting area, it will provide, at this exceptional location, unprecedented access to a whole new domain in astronomical observations. Indeed, millimetre and sub-millimetre astronomy opens exciting new possibilities in the study of the first galaxies to have formed in the Universe and of the formation processes of stars and planets. APEX will, among other things, allow astronomers to study the chemistry and physical conditions of molecular clouds, that is, dense regions of gas and dust in which new stars are forming.

APEX follows in the footsteps of the 15m Swedish-ESO Submillimetre Telescope (SEST) which was operated at ESO La Silla from 1987 until 2003 in a collaboration between ESO and the Onsala Space Observatory. SEST operated in the wavelength range from 0.8 to 3 mm. Says Catherine Cesarsky, ESO’s Director General: “SEST was for a long time the only instrument of its kind in the southern hemisphere. With it, ESO and our collaborators have gained valuable operational experience with regard to ground-based observations in the non-optical spectral domain. With APEX, we offer the ESO community a most exciting new facility that will pave the way for ALMA.”

As its name implies, APEX is the pathfinder to the ALMA project. It is indeed a modified ALMA prototype antenna and is located at the future site of the ALMA observatory. ALMA is planned to consist of a giant array of 12-m antennas separated by baselines of up to 14 km and is expected to start operation by the end of the decade. It will bring to sub-millimetre astronomy the aperture synthesis techniques of radio astronomy, enabling precision imaging to be done on sub-arcsecond angular scales, and will so nicely complement the ESO VLT/VLTI observatory.

In order to operate at the shorter sub-millimetre wavelengths, APEX presents a surface of exceedingly high quality: after a series of high precision adjustments, the APEX project team was able to adjust the surface of the mirror with remarkable precision: over the 12m diameter of the antenna, the deviation from the perfect parabola is now less than 17 thousandths of a millimetre. This is smaller than one fifth of the average thickness of a human hair!

“From the engineering point of view, APEX is already a big success and its performance surpasses our expectations”, says APEX Project Manager Rolf G?sten. “This could only be achieved thanks to the highly committed teams from the constructor, from the MPIfR and from the APEX project whose endless hours of work, often at high altitudes, made this project become reality.”

In parallel to the construction and commissioning of the APEX telescope, a demanding cutting-edge technology program has been launched to provide the best possible detectors for this outstanding facility. For its first observations, APEX was equipped with state-of-the-art sub-millimetre spectrometers developed by MPIfR’s Division for Sub-Millimetre Technology and, more recently, with the first facility receiver built at Chalmers University (OSO).

APEX is a collaboration between the Max-Planck-Institute for Radio Astronomy (MPIfR), Onsala Space Observatory (OSO), and the European Organisation for Astronomical Research in the Southern Hemisphere (ESO). The telescope was designed and constructed by VERTEX Antennentechnik GmbH (Germany), under contract by MPIfR, and is based on a prototype antenna constructed for the ALMA project. Operation of APEX in Chajnantor is entrusted to ESO.

Background information on sub-millimetre astronomy and on the first APEX results can be found as PDF files on the APEX Fact Sheets page.

Original Source: ESO News Release

Posted on by Fraser Cain

Nicholson Crater on Mars

Perspective view of Nicholson Crater central peak. Image credit: ESA. Click to enlarge
This image, taken by the High Resolution Stereo Camera (HRSC) on board ESA?s Mars Express spacecraft, shows Nicholson Crater, located at the southern edge of Amazonis Planitia on Mars.

The HRSC obtained this image during orbit 1104 with a ground resolution of approximately 15.3 metres per pixel. The scene shows the region around Nicholson Crater, at approximately 0.0? South and 195.5? East.

Nicholson Crater, measuring approximately 100 kilometres wide, is located at the southern edge of Amazonis Planitia, north-west of a region called Medusae Fossae.

Located in the centre of this crater is a raised feature, about 55 kilometres long and 37 kilometres wide, which extends to a maximum height of roughly 3.5 kilometres above the floor of the crater.

At present, it is still unclear how this central feature was shaped and what kind of processes led to its formation. It is thought that the remnant hill could be composed of material from underground or was built as a result of atmospheric deposition.

The tall feature in the centre of this hill is the central peak of the crater, which forms when the surface material ?rebounds? after being compressed during the formation of an impact crater.

However, it is clear that this feature has been heavily sculpted after its creation, by the action of wind or even water.

Original Source: ESA Mars Express

Posted on by Fraser Cain

Martian Dust Devils Will Plague Astronauts

Dust devil tracks. Image credit: NASA/JPL. Click to enlarge
Ah, Martian summer! Finally, the days are long, just like on dear old Earth. And daytime highs rocket all the way up to a balmy 20?C (68?F) from the summer nighttime low of -90?C (-130?F), meaning you and your fellow astronauts can warm up your machinery earlier to get a good start on mining operations.

Dust devils on Mars form the same way they do in deserts on Earth. “You need strong surface heating, so the ground can get hotter than the air above it,” explains Lemmon. Heated less-dense air close to the ground rises, punching through the layer of cooler denser air above; rising plumes of hot air and falling plumes of cool air begin circulating vertically in convection cells. Now, if a horizontal gust of wind blows through, “it turns the convection cells on their sides, so they begin spinning horizontally, forming vertical columns–and starting a dust devil.”

Hot air rising through the center of the column powers the whirling air ever faster–fast enough to begin picking up sand. Sand scouring the ground then dislodges flour-fine dust, and the central column of hot rising air buoys that dust high aloft. Once prevailing horizontal winds begin pushing the dust devil across the ground, look out!

“If you were standing next to the Spirit rover right now [in Gusev Crater] in the middle of the day, you might see half a dozen dust devils,” says Lemmon. Each Martian spring or summer day, dust devils begin appearing about 10 AM as the ground heats, and start abating about 3 PM as the ground cools (Mars’s solar day of 24 hours 39 minutes is only 39 minutes longer than Earth?s). Although the exact frequency and duration of Martian dust devils is unknown, photographs from Mars Global Surveyor in orbit reveal innumerable wandering tracks at all latitudes on the planet. These tracks crisscross the surface where dust devils have scoured away loose surface material to reveal different-colored soil beneath.

Moreover, actual dust devils have been photographed from orbit–some of them as large as 1 to 2 kilometers across at their base and (from their shadows) clearly towering 8 to 10 km high.

What intrigues Farrell from having chased dust devils in the Arizona desert, however, is the strange fact that terrestrial dust devils are electrically charged–and Martian dust devils might be, too.

Dust devils get their charge from grains of sand and dust rubbing together in the whirlwind. When certain pairs of unlike materials rub together, one material gives up some of its electrons (negative charges) to the other material. Such separation of electric charges is called triboelectric charging, the prefix “tribo” (pronounced TRY-bo) meaning “rubbing.” Triboelectric charging makes your hair stand on end when you rub a balloon against your head. Dust and sand, like plastic and hair, form a tribolelectric pair. (Dust and sand aren’t necessarily made of the same stuff, notes Lemmon, because “dust can be blown in from anywhere.”) Smaller dust particles tend to charge negative, taking away electrons from the larger sand grains.

Because the rising central column of hot air that powers the dust devil carries the negatively-charged dust upward and leaves the heavier positively-charged sand swirling near the base, the charges get separated, creating an electric field. “On Earth, with instruments we’ve measured electric fields on the order of 20 thousand volts per meter (20 kV/m),” Farrell says. That’s peanuts compared to the electric fields in terrestrial thunderstorms, where lightning doesn’t flash until electric fields get 100 times greater–enough to ionize (break apart) air molecules.

But a mere 20 kV/m “is very close to the breakdown of the thin Martian atmosphere,” Farrell points out. More significantly, Martian dust devils are so much bigger than their terrestrial counterparts that their stored electrical energy may be much higher. “How would those fields discharge?” he asks. “Would you have Martian lightning inside the dust devils?” Even if lightning wouldn’t ordinarily occur naturally, the presence of an astronaut or rover or habitat might induce filamentary discharges, or local arcing. “The thing you’d really have to watch out for is corners, where electric fields can get very strong,” he adds. “You might want to make your vehicle or habitat rounded.”

Another consideration for astronauts on Mars would be “radio static as charged grains hit bare-wire antennas,” Farrell warns. And after the dust devil passed over and was gone, a lasting souvenir of its passage would be an increased adhesion of dust to spacesuits, vehicles, and habitats via electrostatic cling–the same phenomenon that causes socks to stick together when pulled out of a clothes dryer–making cleanup difficult before reentering a habitat.

Because Martian dust devils can tower 8 to 10 kilometers high, planetary meteorologists now think the devils may be responsible for throwing so much dust high into the Martian atmosphere. Importantly for astronauts, that dust may be carrying negative charges high into the atmosphere as well. Charge building up at the storm top could pose a hazard to a rocket taking off from Mars, as happened to Apollo 12 in November 1969 when it lifted off from Florida during a thunderstorm: the rocket exhaust ionized or broke down the air molecules, leaving a trail of charged molecules all the way down to the ground, triggering a lightning bolt that struck the spacecraft.

“Early sea navigators, like Columbus, understood that their ships had to be designed for extreme weather conditions,” Farrell points out. “To design a mission to Mars, we need to know the extremes of Martian weather–and those extremes appear to be in the form of dust storms and devils.”

Original Source: NASA News Release

Posted on by Fraser Cain

Discovery Won’t Launch Before Sunday

Space Shuttle Discovery on the launch pad. Image credit: NASA. Click to enlarge
NASA announced the earliest the Return to Flight Space Shuttle mission (STS-114) could launch is 2:14 p.m. EDT, Sunday, July 17. Mission Management Team and engineering meetings took place last night and today at NASA’s Kennedy Space Center.

Team members reviewed data and possible troubleshooting plans for the liquid hydrogen tank low-level fuel cut-off sensor. The sensor failed a routine pre-launch check during the launch countdown Wednesday, causing mission managers to scrub Discovery’s first launch attempt.

The sensor protects the Shuttle’s main engines by triggering shutdown if fuel runs unexpectedly low. The sensor is one of four inside the liquid hydrogen section of the External Tank (ET).

A new official launch date will be scheduled once a troubleshooting plan is complete and engineers are working on a solution. Space Shuttle Program managers plan meetings tomorrow to discuss the problem and finalize the troubleshooting plan.

The launch control team began troubleshooting while the liquid oxygen and liquid hydrogen was drained from the ET last night. The No. 2 liquid hydrogen sensor in the ET’s liquid hydrogen tank continued to read ‘wet’ and did not transition to a ‘dry’ indication once the tank was completely drained.

Following de-tanking operations, the same commands that were sent during the launch countdown were repeated while draining. While going through commands, sensor No. 2 continued to show ‘wet’ instead of ‘dry.’ The firing room reissued commands, and the sensor went to ‘dry’ as it should. Another round of commands was sent and sensor No. 2 performed as expected, with all sensors in the ‘dry’ state. Space Shuttle Discovery remains at Launch Pad 39B. The Rotating Service Structure was put back around the vehicle last night.

The STS-114 crew, led by Commander Eileen Collins, remains at Kennedy Space Center while engineers assess the problem. During their 12-day Return to Flight mission to the International Space Station, Discovery’s seven crew members will test new techniques and equipment designed to make Space Shuttle missions safer. They’ll also deliver supplies and make repairs to the Space Station.

For the latest information about the STS-114 mission, visit: http://www.nasa.gov/returntoflight

Original Source: NASA News Release

Posted on by Fraser Cain

Satellite Can Tell When Ice is Melting

Resolute Bay seen by the Hyperion instrument aboard Earth Observing-1. Image credit: NASA. Click to enlarge
Spring thaw in the Northern Hemisphere was monitored by a new set of eyes this year — an Earth-orbiting NASA spacecraft carrying a new version of software trained to recognize and distinguish snow, ice, and water from space.

Using this software, the Space Technology 6 Autonomous Sciencecraft Experiment autonomously tracked changes in the cryosphere, the section of Earth that is frozen, and relayed the information and images back to scientists.

The software, developed by engineers at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., controls the Earth Observing-1 spacecraft. NASA’s Goddard Space Flight Center, Greenbelt, Md, manages the satellite. The software has taken more than 1,500 images of frozen lakes in Minnesota, Wisconsin, Quebec, Tibet and the Italian Alps, along with sea ice in Arctic and Antarctic bays.

While other spacecraft only capture images when they receive explicit commands to do so, for the last year Earth Observing-1 has been making its own decisions. Based on general guidelines from scientists, the spacecraft automatically tracks events such as volcano eruptions, floods and ice formation. The most recent software upgrade allows the spacecraft to accurately recognize cryosphere changes such as ice melting.

Previously, scientists spent several months developing software for Earth Observing-1 to detect changes in snow, water and ice. The new software is capable of learning by itself, and it took only a few hours for scientists to train it to recognize cryosphere changes. In fact, the new software has learned to classify the images so well that scientists plan to use it for the remainder of the mission.

“This new software is capable of a rudimentary form of learning, much the way a child learns the names of new objects,” said Dominic Mazzoni, the JPL computer scientist who developed the software. “Instead of programming the software using a complicated series of commands and mathematical equations, scientists play the role of a teacher, repeatedly showing the computer different images and giving feedback until it has correctly learned to tell them apart.”

On Earth Observing-1, the software searches for specific cryospheric events and reprograms the spacecraft to capture additional images of the event.

“The software has exceeded all of our expectations,” said Dr. Steve Chien, JPL principal investigator for the Autonomous Sciencecraft Experiment. “We have demonstrated that a spacecraft can operate autonomously, and the software has taken literally hundreds of images without ground intervention.”

Similar software has been used to distinguish between different types of clouds in images captured by JPL’s Multi-angle Imaging SpectroRadiometer, an instrument on NASA’s Terra spacecraft. Automatically identifying types of clouds from space will help scientists better understand Earth’s global energy balance and predict future climate trends.

Future versions of the software also might be used to track dust storms on Mars, search for ice volcanoes on Jupiter?s moon Europa, and monitor activity on Jupiter’s volcanically active moon Io. NASA’s New Millennium Program developed both the satellite and the software. The program is responsible for testing new technologies in space.

For more information on the Autonomous Sciencecraft Experiment on the Internet, visit: http://ase.jpl.nasa.gov .

For more information on the New Millennium Program on the Internet, visit: http://nmp.jpl.nasa.gov .

For information about the Earth Observing-1 spacecraft on the Internet, visit: http://eo1.gsfc.nasa.gov .

Original Source: NASA News Release

Posted on by Fraser Cain

Planet Found in Triple Star System

Artist’s animation shows the view from a hypothetical moon in orbit around the planet. Image credit: NASA. Click to enlarge
A NASA-funded astronomer has discovered a world where the sun sets over the horizon, followed by a second sun and then a third. The new planet, called HD 188753 Ab, is the first known to reside in a classic triple-star system.

“The sky view from this planet would be spectacular, with an occasional triple sunset,” said Dr. Maciej Konacki (MATCH-ee Konn-ATZ-kee) of the California Institute of Technology, Pasadena, Calif., who found the planet using the Keck I telescope atop Mauna Kea mountain in Hawaii. “Before now, we had no clues about whether planets could form in such gravitationally complex systems.”

The finding, reported in this week’s issue of Nature, suggests that planets are more robust than previously believed.

“This is good news for planets,” said Dr. Shri Kulkarni, who oversees Konacki’s research at Caltech. “Planets may live in all sorts of interesting neighborhoods that, until now, have gone largely unexplored.” Kulkarni is the interdisciplinary scientist for NASA’s planned SIM PlanetQuest mission, which will search for signs of Earth-like worlds.

Systems with multiple stars are widespread throughout the universe, accounting for more than half of all stars. Our Sun’s closest star, Alpha Centauri, is a member of a trio.

“Multiple-star systems have not been popular planet-hunting grounds,” said Konacki. “They are difficult to observe and were believed to be inhospitable to planets.”

The new planet belongs to a common class of extrasolar planets called “hot Jupiters,” which are gas giants that zip closely around their parent stars. In this case, the planet whips every 3.3 days around a star that is circled every 25.7 years by a pirouetting pair of stars locked in a 156-day orbit.

The circus-like trio of stars is a cramped bunch, fitting into the same amount of space as the distance between Saturn and our Sun. Such tight living quarters throw theories of hot Jupiter formation into question. Astronomers had thought that hot Jupiters formed far away from their parent stars, before migrating inward.

“In this close-knit system, there would be no room at the outskirts of the parent star system for a planet to grow,” said Konacki.

Previously, astronomers had identified planets around about 20 binary stars and one set of triple stars. But the stars in those systems had a lot of space between them. Most multiple-star arrangements are crowded together and difficult to study.

Konacki overcame this challenge using a modified version of the radial velocity, or “wobble,” planet-hunting technique. In the traditional wobble method, a planet’s presence is inferred by the gravitational tug, or wobble, it induces in its parent star. The strategy works well for single stars or far-apart binary and triple stars, but could not be applied to close-star systems because the stars’ light blends together.

By developing detailed models of close-star systems, Konacki was able to tease apart the tangled starlight. This allowed him to pinpoint, for the first time, the tug of a planet on a star snuggled next to other stars. Of 20 systems examined so far, HD 188753, located 149 light-years away, was the only one found to harbor a planet.

Hot Jupiters are believed to form out of thick disks, or “doughnuts,” of material that swirl around the outer fringes of young stars. The disk material clumps together to form a solid core, then pulls gas onto it. Eventually, the gas giant drifts inward. The discovery of a world under three suns contradicts this scenario. HD 188753 would have sported a truncated disk in its youth, due to the disruptive presence of its stellar companions. That leaves no room for HD 188753’s planet to form, and raises a host of new questions.

The masses of the three stars in HD 188753 system range from two-thirds to about the same mass as our Sun. The planet is slightly more massive than Jupiter.

For artist’s concepts and other graphics, visit http://planetquest.jpl.nasa.gov/ . For information about NASA and agency programs on the Web, visit http://www.nasa.gov/home/index.html .

Original Source: NASA News Release

Posted on by Fraser Cain

Superwinds Seen in Distant Galaxies

An artist’s impression of a Superwind in a young massive galaxy. Image credit: PPARC/David Hardy. Click to enlarge
A team of astronomers, led by the University of Durham, has discovered the aftermath of a spectacular explosion in a galaxy 11.5 billion light years away. Their observations, reported today (14th July 2005) in the journal Nature provide the most direct evidence yet of a galaxy being almost torn apart by explosions that produce a stream of high-speed material known as “Superwinds”. The observations were made using the 4.2 metre William Herschel Telescope on La Palma in which the UK is a major stakeholder.

Through Superwinds, galaxies are thought to blast a significant part of their gas into intergalactic space at speeds of up to several hundred miles per second. The driving force behind them is the explosion of many massive stars during an intense burst of star formation early in the galaxy’s life, possibly assisted by energy from a super massive black hole growing at its heart.

Superwinds are vital to the theory of galaxy formation for several reasons: firstly, they limit the sizes of galaxies by preventing further star formation – without them theoretical models indicate far more very bright galaxies than are actually seen in the Universe today. Secondly, they carry heavy elements – Star dust – far from their production sites in stars out into intergalactic space, providing raw material for planets and life across the Universe. Whilst the theories predicted Superwinds of this kind existed, previously observed examples were much smaller phenomena in nearby galaxies. These observations provide some of the most direct evidence yet for the existence of large-scale, galaxy-wide superwinds so far back in the history of the Universe.

The discovery of the Superwind was made by observing the gas in the halo of a galaxy (known as “LAB-2”), which at over 300,000 light years across is about three times larger than the disk of our own Milky Way galaxy. The astronomers discovered that light from hot glowing hydrogen gas is dimmed in a very specific way across the entire galaxy.

“We believe that the dimming is caused by a shell of cooled material which has been swept-up from the surroundings by a galaxy-wide Superwind explosion,” said Dr. Richard Wilman of the University of Durham. “Based on the uniformity of the absorption across the galaxy, it appears that the explosion was triggered several hundred million years earlier. This allows time for the gas to cool and to slow down from its high ejection speed, and thus to produce the absorption. As we see it, the shell is probably a few hundred thousand light years in front of its parent galaxy,” added Dr. Wilman.

Astronomers have long been puzzled about why key elements for the formation of planets and ultimately life (such as carbon, oxygen and iron) are so widely distributed throughout the Universe; only 2 billion years after the Big Bang, the remotest regions of intergalactic space have been enriched with them. The Superwind observed in this galaxy shows how such blast waves can travel through space carrying the elements formed deep within galaxies.

Crucial to the discovery and its interpretation was the ability to obtain detailed information on the gas in two-dimensions across the whole galaxy. This was made possible by a technique known as integral field spectroscopy, which is only just reaching maturity on the world’s largest telescopes.

Dr Joris Gerssen, a key member of the Durham team, explains, “Most astronomical spectroscopy is performed by placing a small aperture, or a narrow slit on the target, which for complex, extended sources such as this galaxy gives a rather incomplete picture”.

To overcome this the astronomers used an integral field spectrograph called ‘Sauron’ for a large survey of nearby galaxies, built at the Observatoire de Lyon by a collaboration of French, Dutch and UK astronomers.

Dr Gerssen added,” “Sauron is truly unique and its high efficiency means that it can more than hold its own against instruments on the world’s largest telescopes, some twice the size of the William Herschel Telescope. Nevertheless, the sheer distance of our target galaxy meant that Sauron had to stare at it for over 15 hours in order to make this discovery”.

“Sauron has provided us with the best evidence so far for an extensive outflow from a galaxy undergoing a huge starburst. These measurements are among the first steps towards understanding the physics of galaxy formation.,” commented Prof. Roger Davies, University of Oxford, one of the institutes involved on Sauron,” and we look forward to using similar two-dimensional spectrographs being built for 8m telescopes; these will probe the galaxy formation process to even earlier times.”

To date, observational evidence for Superwinds in young galaxies in the distant Universe has been largely indirect and circumstantial; efforts have focussed on searching for their subtle statistical signatures in large surveys of galaxies and intergalactic gas.

According to Prof. Richard Bower, from the University of Durham’s Institute of Computational Cosmology who initiated the research, “Astronomers have observed high-speed outflows in distant star-forming galaxies for several years, but never before have we been able to gauge their true scale from observations of a single galaxy. By taking advantage of the highly extended emission source of this galaxy, we can see the outflow as a kind of silhouette against the whole galaxy. This suggests that Superwinds are truly galaxy-wide in scale, and that they really are as important as our theories require.”

Original Source: PPARC News Release