NuSTAR Mission Status Report: Observatory Unfurls its Unique Mast

\Artist's concept of NuSTAR in orbit. NuSTAR has a 33-foot (10-meter) mast that deploys

after launch to separate the optics modules (right) from the detectors in the focal plane (left).

Image credit: NASA/JPL-Caltech

› Full image and caption

June 21, 2012

PASADENA, Calif. -- NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, has successfully deployed its lengthy mast, giving it the ability to see the highest energy X-rays in our universe. The mission is one step closer to beginning its hunt for black holes hiding in our Milky Way and other galaxies.

"It's a real pleasure to know that the mast, an accomplished feat of engineering, is now in its final position," said Yunjin Kim, the NuSTAR project manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif. Kim was also the project manager for the Shuttle Radar Topography Mission, which flew a similar mast on the Space Shuttle Endeavor in 2000 and made topographic maps of Earth.

NuSTAR's mast is one of several innovations allowing the telescope to take crisp images of high-energy X-rays for the first time. It separates the telescope mirrors from the detectors, providing the distance needed to focus the X-rays. Built by ATK Aerospace Systems in Goleta, Calif., this is the first deployable mast ever used on a space telescope.

On June 21 at 10:43 a.m. PDT (1:43 p.m. EDT), nine days after launch, engineers at NuSTAR's mission control at UC Berkeley in California sent a signal to the spacecraft to start extending the 33-foot (10-meter) mast, a stable, rigid structure consisting of 56 cube-shaped units. Driven by a motor, the mast steadily inched out of a canister as each cube was assembled one by one. The process took about 26 minutes. Engineers and astronomers cheered seconds after they received word from the spacecraft that the mast was fully deployed and secure.

The NuSTAR team will now begin to verify the pointing and motion capabilities of the satellite, and fine-tune the alignment of the mast. In about five days, the team will instruct NuSTAR to take its "first light" pictures, which are used to calibrate the telescope.

Why did NuSTAR need such a long, arm-like structure? The answer has to do with the fact that X-rays behave differently than the visible light we see with our eyes. Sunlight easily reflects off surfaces, giving us the ability to see the world around us in color. X-rays, on the other hand, are not readily reflected: they either travel right through surfaces, as is the case with skin during medical X-rays, or they tend to be absorbed, by substances like your bone, for example. To focus X-rays onto the detectors at the back of a telescope, the light must hit mirrors at nearly parallel angles; if they were to hit head-on, they would be absorbed instead of reflected.

On NuSTAR, this is accomplished with two barrels of nested mirrors, each containing 133 shells, which reflect the X-rays to the back of the telescope. Because the reflecting angle is so shallow, the distance between the mirrors and the detectors is long. This is called the focal length, and it is maintained by NuSTAR's mast.

The fully extended mast is too large to launch in the lower-cost rockets required for relatively inexpensive Small Explorer class missions like NuSTAR. Instead NuSTAR launched on its Orbital Science Corporation's Pegasus rocket tucked inside a small canister. This rocket isn't as expensive as its bigger cousins because it launches from the air, with the help of a carrier plane, the L-1011 "Stargazer," also from Orbital.

NuSTAR is a Small Explorer mission led by the California Institute of Technology in Pasadena and managed by JPL for NASA's Science Mission Directorate in Washington. The spacecraft was built by Orbital Sciences Corporation, Dulles, Va. Its instrument was built by a consortium including Caltech; JPL; the University of California, Berkeley; Columbia University, New York; NASA's Goddard Space Flight Center, Greenbelt, Md.; the Danish Technical University in Denmark; Lawrence Livermore National Laboratory, Livermore, Calif.; and ATK Aerospace Systems, Goleta, Calif. NuSTAR will be operated by UC Berkeley, with the Italian Space Agency providing its equatorial ground station located at Malindi, Kenya. The mission's outreach program is based at Sonoma State University, Rohnert Park, Calif. NASA's Explorer Program is managed by Goddard. JPL is managed by Caltech for NASA.

For more information, visit http://www.nasa.gov/nustar and http://www.nustar.caltech.edu/.

Whitney Clavin 818-354-4673

Jet Propulsion Laboratory, Pasadena, Calif.

whitney.clavin@jpl.nasa.gov

2012-183

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NuSTAR X-ray Telescope Launched ON Mission TO Search for Black Holes

06/13/2012 12:43 PM Filed in: Space News | Space Science

By WILLIAM HARWOOD

CBS News

A small X-ray telescope was boosted into orbit at noon EDT today by an air-launched Pegasus XL rocket Wednesday, the first step in an ambitious low-cost mission to study supermassive black holes believed to be lurking at the cores of galaxies like Earth's Milky Way and to probe the creation of heavy elements in the cataclysmic death throes of massive stars.

The innovative telescope, built around an extendable 33-foot-long Tinkertoy-like mast with nested X-ray mirrors on one end and sensitive detectors on the other, also will study the mechanisms responsible for stellar explosions and look for clues about what powers the energetic jets of particles blasted away from some black holes that apparently can disrupt star formation and even galactic evolution.

While X-ray telescopes sensitive to lower energies have been operated with great success, the $180 million Nuclear Spectroscopic Telescope Array, or NuStar, is the first space telescope designed to focus higher-energy X-rays like those used for medical imaging and dental X-rays.

NuSTAR images are expected to be "10 times crisper and a hundred times more sensitive than any we've had of the cosmos to date," said Fiona Harrison, the principal investigator at the California Institute of Technology. "This will enable Nu-STAR to study some of the hottest, densest and most energetic phenomenon in the universe."

The mission got underway with a dramatic pre-dawn launch from an L-1011 jet at an altitude of about 40,000 feet above the Pacific Ocean some 120 miles south of the Kwajalein Atoll in the Marshall Islands. Tucked into the nose cone of a three-stage solid-fuel Pegasus XL rocket, the NuSTAR spacecraft was dropped like a bomb at 12 p.m EDT (GMT-4; 4 a.m. Thursday local time). After a five-second fall, the first stage of the winged Pegasus booster ignited with a rush of flame to begin the steep climb to orbit.

Orbital Sciences Corp. of Dulles, Va., provided the carrier aircraft, the Pegasus XL booster and the NuSTAR satellite to NASA and the mission operations team at the California Institute of Technology under a "Small Explorer" program contract valued at nearly $180 million. The Pacific Ocean launch zone was selected to enable the spacecraft to reach a scientifically favorable orbit tilted just six degrees to the equator.

All three stages of the Pegasus booster operated normally, falling away as planned as their propellants were exhausted. Thirteen minutes after launch, NuSTAR was released into its operational 375-mile-high orbit. A few minutes after that, the telescope's transmitter was activated and telemetry confirmed the successful deployment of its five-segment solar array.

This was the 41st launch of a Pegasus rocket and the 31st using the more powerful XL version. Overall, Pegasus rockets have launched more than 70 satellites since 1990, with 27 successful missions in a row over the past 15 years.

"Today was a great day for NuSTAR, a great day for Pegasus, a great day for the entire launch team," said Tim Dunn, NASA's assistant launch director. "We thank Orbital Sciences for the ride, and we're ready to get into the science operation of the NuSTAR mission."

Over the next six days, engineers plan to activate and check out NuSTAR's attitude control system, star trackers, solar array drive electronics and instruments. Then, seven days after launch, commands will be sent to deploy the critical open-framework mast that provides the required separation between the telescope's X-ray mirrors and its detectors.

Unlike optical telescopes that use mirrors to bounce starlight to detectors, penetrating X-rays are focused by cylindrical, nested mirrors that cause a very slight deviation in the trajectory of the incoming radiation. A relatively long focal length is required to achieve the sensitivity astronomers need.

NuSTAR's ability to detect high-energy X-rays is the result of improved mirror and detector technology. But its ability to be launched by a small, relatively low-cost rocket is the result of an innovative design incorporating an extendable mast, built by ATK Aerospace Systems, that was originally developed for a shuttle radar mapping mission.

Earlier X-ray telescopes, sensitive to lower energies, were built around fixed structures and required large launch vehicles. NASA's Chandra X-ray Observatory, for example, weighed more than six tons and was launched by the shuttle Columbia. NuSTAR weighs just 770 pounds. The mast providing the required separation between mirror and detectors was designed to fit inside a 3.3-foot-tall canister at launch.

Assuming the 25-minute mast deploy sequence works properly next week, engineers will carefully align the optics and detectors. Science operations are expected to begin in about 30 days.

"One of NuSTAR's primary science goals is to study black holes (and) the extreme physics, the fascinating physics that occurs very close to the black hole where spacetime is severely distorted and particles are accelerated close to the speed of light," Harrison said. "And also to understand how black holes are distributed throughout the universe."

While galactic blacks holes initially were thought to be rare, "in the last 15 years, we understand that there is a very massive black hole at the center of every galaxy like our Milky Way," Harrison said. "And not only that, these black holes influence the way these galaxies grow and form."

While black holes are, by definition, invisible due to gravity so intense not even light can escape, they can be detected by looking for the radiation that is generated as gas and dust are sucked in and heated to extreme temperatures by friction with other in-falling material.

"What you're actually seeing is the dust and gas, the material in the galaxy, that's attracted by the black hole's gravity," Harrison said. "Close to the black hole, it organizes itself into a disk and friction turns this gravitational energy into heat. The material heats up such that when you're closest to the black hole, just a few times further away than the event horizon itself, the material is radiating high energy X-rays."

Combining NuSTAR's images with those captured by other, lower-energy X-ray telescopes, scientists will be able to "study the entire X-ray spectrum," Harrison said, "we can watch atoms circulate in the closest orbits near the black hole, we can observe how spacetime distorts our view of these objects and tell things like how fast the black hole is spinning."

NuSTAR will also focus on a variety of other energetic phenomenon, including the mechanisms responsible for the creation of heavy elements in supernova explosions and those powering the unimaginable jets of particles boosted to near light speed in the vicinity of black holes and other collapsed bodies like neutron stars and spinning pulsars, the left-over cores of stars destroyed in supernova blasts.

NuSTAR's state-of-the-art mirrors and detectors will help astronomers bring their views of the high-energy universe into much sharper focus.

"It's like you're trying to read a book without your glasses," Harrison said. "You know there's text there, but you can't make out the letters. Currently, we can make out about 2 percent of this cosmic text. But with NuSTAR, we'll be able to make out the majority of the story, we'll be able to image the sky, read the story and understand things like how galaxies form, how black holes grow and the history of the high energy universe."

The mission is expected to last at least two years.

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Revolutionary Instrument Propels Astronomical Imaging to New Extremes

Figure 1. Gemini South’s first light image from GeMS/GSAOI shows extreme detail in the central part of the globular star cluster NGC 288. North is up

, East is right. For more technical details on this image and others see the technical companion article here.

High Resolution PNG | In Black & White

Figure 2. Gemini South laser guide star system propagating as the Milky Way rises.

High Resolution JPG

Figure 3. The Gemini South laser guide star “constellation” (upper left) is captured in this image by the lead of Gemini’s Optical Systems Group Maxime Boccas and Adaptive Optics Scientist Benoit Neichel. The image shows the 50-watt laser beam as it shines upward toward the atmospheric sodium layer about 90 kilometers above the earth’s surface to create a pattern of five artificial guide stars used to sample atmospheric turbulence for the Gemini Observatory’s GeMS adaptive optics system. The yellow-orange beam visible from lower right to upper left is caused by scattering of the laser's light by the Earth's lower atmosphere. The 30-second exposure was obtained on the night of January 21-22, 2011 and used a 500mm f/5.6 Celestron telescope with a Canon Rebel XT camera at an ISO setting of 1600. Image Credit: Gemini Observatory/AURA

High Resolution JPG

Gemini Observatory Press Release

For immediate release on January 5, 2012

Science Contacts:

• François Rigaut

  • Gemini Adaptive Optics Senior Scientist

  • Gemini Observatory, La Serena, Chile

  • Phone: +56-51-205 784

  • frigaut"at"gemini.edu

• Benoit Neichel

  • Adaptive Optics Scientist

  • Gemini Observatory, La Serena, Chile

  • Phone: +56-51-205 642

  • bneichel"at"gemini.edu

Media Contacts:

• Peter Michaud

  • Public Information and Outreach Manager

  • Gemini Observatory, Hilo, Hawai'i

  • Phone: (808) 974-2510

  • Cell: (808) 936-6643

  • pmichaud"at"gemini.edu

• Antonieta Garcia

  • Media Specialist

  • Gemini Observatory, La Serena, Chile

  • Phone: +56-51-205 628

  • agarcia"at"gemini.edu

Gemini’s next-generation adaptive optics system produces highest-resolution with largest field-of-view ever captured from the ground using laser guide star technology.

For images and additional technical background information, see: www.gemini.edu/node/11718.

On December 16, 2011, a decade of hard work culminated at the Gemini South telescope in Chile, when a next-generation adaptive optics (AO) system produced its first ultra-sharp wide field image. The first target image showed a portion of a dense cluster of stars called NGC 288. This first light image reveals details at nearly the theoretical limit of Gemini’s large 8-meter mirror over an unprecedented large patch of the night sky.

The crispness of the first-light image clearly demonstrates the potential of the system, which is poised to provide astronomers with a powerful new tool for the study of a wide range of phenomena: from black holes at the centers of galaxies to the life histories of stars.

Called the Gemini Multi-conjugate adaptive optics System (GeMS for short), it uses five artificial guide stars made by a laser to provide extreme clarity over the largest area of night sky ever captured in a single AO observation — an area of the night sky which is 10 times larger than that covered by any other existing AO system in the world.

The reaction to this achievement has been swift and positive. When Space Telescope Science Institute director Matt Mountain saw the first light image, he praised the GeMS instrument team: “Incredible! You have truly revolutionized ground-based astronomy!”

Mountain was the director of the Gemini Observatory when the GeMS project began a decade ago. He also put together the original team, selecting François Rigaut as the lead scientist to develop the GeMS instrument.

Rigaut was in the Observatory’s control room high in the Chilean Andes when the new infrared image first appeared on the viewing monitor.

“We couldn’t believe our eyes!” Rigaut recalls. “The image of NGC 288 revealed thousands of pinpoint stars. Its resolution is Hubble-quality – and from the ground this is phenomenal.”

Rigaut explained that with the new gain in angular resolution the crowded city of stars captured in the first light image appears no more densely populated than a typical field in the Milky Way. “This is somewhat uncharted territory: no one has ever made images so large with such a high angular resolution.”

University of Toronto astronomer Roberto Abraham, one of a community of hundreds of astronomers worldwide who uses the 8-meter Gemini telescopes for cutting-edge research, was less reserved:

“This is fan-freaking-tastic!!!!!!!” he wrote.

The first light observing run culminated a decade-long effort in instrument planning and development. “We were lucky to have clear weather and stable atmospheric conditions that night,” said Gemini AO scientist Benoit Neichel. “Even despite interruptions of the laser propagation due to satellites and planes passing by, we obtained our first image with the system. It was surprisingly crisp and large, with an exquisitely uniform image quality.”

Gemini’s new system overcomes two limitations that have plagued the previous generation of AO systems: (1) a limited number of stars bright enough to guide on; and (2) a small field-of-view (the size of the patch of sky observed in a single observation).

While not a new solution, lasers have proved to be an effective solution to the first problem. When no "natural" guide star is available, an artificial one is created using a powerful laser emitting the well-known orange color used in some streetlights. This laser guide star technology is currently being used by observatories around the world, including both Gemini telescopes in Chile and Hawai‘i.

Gemini solved the field-of-view problem with a technique called Multi-Conjugate Adaptive Optics (MCAO). By using five laser guide stars (rather than a single one as in other systems), tomographic atmospheric modeling techniques borrowed from medical imaging, and several deformable mirrors, MCAO extends the field-of-view of AO systems by 10 times or more; it also produces images with exquisitely uniform image quality across the entire field-of-view. The Gemini Multi-Conjugate Adaptive Optics System (GeMS) is the first of its kind to combine laser guide stars with MCAO, which opens up more of the nighttime sky for detailed study.

“MCAO is game-changing,” Abraham said. "It’s going to propel Gemini to the next echelon of discovery space as well as lay a foundation for the next generation of extremely large telescopes. Gemini is going to be delivering amazing science while paving the way for the future.”

GeMS development started at Gemini in the early 2000s. The system was assembled in the Gemini instrumentation laboratories over the past four years and uses an infrared imager called the Gemini South AO Imager (GSAOI) built at the Australian National University. The GeMS team field-tested it on the telescope during several commissioning periods in 2011, and performed the final tests in mid-December.

GeMS work will continue through the first half of 2012. Testing will focus on stability, performance optimization, and integration into operations. It will gradually be opened to the Gemini astronomy community during 2012.

The Gemini Observatory is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência e Tecnologia (Brazil), and SECYT (Argentina)

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SpaceX: Dragon ISS Bound

by Jason Rhian on August 16, 2011 from UniverseToday.com

Space Exploration Technologies (SpaceX) is preparing its next Dragon spacecraft for a trip to the International Space Station (ISS). SpaceX has worked over the last several months to make sure that the spacecraft is set for the Nov. 30 launch date that has given to the commercial space company. If all goes according to plan, a little more than a week after launch – the Dragon will dock with the ISS.

NASA has technically agreed to allow SpaceX to combine all of the tests and demonstration activities that were originally slated to take place on two separate flights (COTS demo missions 2 and 3). SpaceX is working to further maximize the cost-effectiveness of this mission by including additional payloads in the Falcon 9’s second stage. These will be deployed after the Dragon separates from the rocket.

“SpaceX has been making steady progress towards our next launch,” said SpaceX’s Communications Director Kirstin Brost-Grantham. “There are a number of challenges associated with berthing with the International Space Station, but challenges are the norm here. With each mission we are making history.”

NASA is waiting to provide final approval of the mission’s combines objectives once any and all potential risks that are associated with the secondary payloads have been worked out.

There is a lot riding on the Commercial Orbital Transportation Services (COTS) contract. If crew members on the orbiting laboratory can access the Dragon’s contents and the spacecraft conducts all of its requirements properly – it will go a long way to proving the viability of NASA’s new path toward using commercial spacecraft and it could usher in a new era of how space flight is conducted.

It is hoped that private-public partnerships could lower the cost related to access-to-orbit and in so doing also help to increase the reliability, safety and frequency of space flight.

SpaceX has been working from milestone to milestone in getting the next mission ready to launch. Just this week the company conducted what is known as a wet dress rehearsal or WDR of the Falcon 9 rocket out at Cape Canaveral Air Force Station’s Space Launch Complex 40 (SLC 40). The Falcon 9 was loaded with propellant and went through all of the operations that lead up to launch – right down to T-1 second. At that point, the launch team stands down and the Falcon 9 is detanked.

SpaceX last launched from SLC 40 last December, during the intervening months the company has worked to upgrade the launch pad. New liquid oxygen or LOX tanks have been installed. These new tanks should streamline loading time from 90 minutes – to under 30 minutes. It is hoped that these efforts will allow the Falcon 9 to move from the hangar to liftoff – in under an hour.

SpaceX has launched the Falcon 9 twice and the Dragon spacecraft once – each completed the primary objectives successfully and helped to establish SpaceX as a leader in the NewSpace movement. SpaceX has inked many lucrative contracts, both domestic and foreign as a result. Besides the COTS contract, SpaceX is also one of the companies that has a contract under the Commercial Crew Development contract (phase-02) or CCDev-02.

The Russian Hubble?

by Steve Nerlich on August 4, 2011 - UniverseToday.com

This is hardly breaking news, but there’s a new Russian space telescope in town. With a name like an anime character, Spektr R was launched on 18 July 2011 and its 10 metre carbon fibre dish was deployed a week later. It’s a radio telescope and – via a very large baseline array project known as RadioAstron – it will become arguably the world’s biggest radio telescope – and by a very long shot.

Following so closely after the Space Shuttle fleet’s retirement, the media has latched onto the idea that this represents a major step up from the Hubble Space Telescope and a further indication of the USA’s decline from space. But, nah…

Don’t get me wrong, when fully operational RadioAstron will be the biggest ever interferometer and is likely to deliver some great science when it gets up to speed. Well done, Roscosmos. But the various comparisons made between it and Hubble are a little spurious.

RadioAstron’s angular resolution is reported as 7 microarc seconds (or 0.000007 arcseconds) while Hubble’s resolution is generally reported as 0.05 arc seconds – so RadioAstron is reported as having over a thousand times more resolution. Well, sort of – but not really.

Firstly, the 10 metre radio mirror of Spektr R is designed to detect (stifles laughter) centimetre range wavelength light, while Hubble’s 2.4 metre mirror, is capable of detecting wavelengths in the visible light range of 350-790 nanometre range (and some non-visible infrared light too).

Angular resolution arises from the relationship between the wavelength of light you are observing and the size of your aperture. So, at the single instrument level Hubble rules supreme in the resolution stakes.

The resolution assigned to RadioAstron (the telescope array) arises from the ‘virtual’ dish diameter created by Spektr R’s orbit, when arrayed with ground-based radio telescopes – which may eventually include Earth’s largest dish, the 300 metre Arecibo dish and Earth’s largest steerable dish, the 110 metre Greenbank radio telescope.

Spektr R will orbit the Earth via a highly elliptical orbit with a perigee of 10,000 kilometres and an apogee of 390,000 kilometres – so giving an elliptical orbit with a semi-major axis of 200,000 kilometres. That sounds like one big dish, huh… although it isn’t, really – just virtually.

Don’t get me wrong, there is a huge increase in information to be gained from arraying Spektr R’s one data point with other ground based observatories’ data points. But nonetheless, it is just radio light conveyed information – which just can’t deliver the level of detail that nanometre wavelength visible light can carry.

That’s why you can usefully create radio telescope arrays, but you can’t gain much value from arraying visible light telescopes (at least not yet). The information conveyed by radio light is spread widely enough so that you can estimate the information it is carrying from just detecting it at two widely spread detectors – and then superimposing that data. The fine detailed information contained in visible light is just too complex to allow this.

So putting up RadioAstron up as a contender to the beloved Hubble Space Telescope makes no sense. It is a totally different scientific project that will deliver totally different – and hopefully awesome – scientific data. Ad astra. If we want a step up from Hubble, we need to get the James Webb Space Telescope back into production.

Tagged as: RadioAstron

Most Distant Astronomical Object Recordholders by Redshift (z) from Wikipedia

Objects in this list were found to be the most distant known object at the time of determination of their distance. This is frequently not the same as the date of their discovery.

Distances to astronomical objects may be determined through parallax measurements, use of standard candles such as cepheid variables or Type Ia supernovas, or redshift measurement. Spectroscopic redshift measurement is preferred, while photometric redshift measurement is also used.

List of the Most Distant Objects by Year of Object Discovery

This list contains a list of most distant objects by year of discovery of the object, not the determination of its distance. Objects may have been discovered without distance determination, and were subsequently found to be the most distant known at that time.

First seen by amateur astronomers back in December, the powerful seasonal storm that has since bloomed into a planet-wrapping swath of churning clouds has gotten some scrutiny by Cassini and the European Southern Observatory’s Very Large Telescope array situated high in the Chilean desert.

The image above shows three views of Saturn acquired on January 19: one by amateur astronomer Trevor Barry taken in visible light and the next two by the VLT’s infrared VISIR instrument – one taken in wavelengths sensitive to lower atmospheric structures one sensitive to higher-altitude features.

While the storm band can be clearly distinguished in the visible-light image, it’s the infrared images that really intrigue scientists. Bright areas can be seen along the path of the storm, especially in the higher-altitude image, marking large areas of upwelling warmer air that have risen from deep within Saturn’s atmosphere.

Normally relatively stable, Saturn’s atmosphere exhibits powerful storms like this only when moving into its warmer summer season about every 29 years. This is only the sixth such storm documented since 1876, and the first to be studied both in thermal infrared and by orbiting spacecraft.

The initial vortex of the storm was about 5,000 km (3,000 miles) wide and took researchers and astronomers by surprise with its strength, size and scale.

“This disturbance in the northern hemisphere of Saturn has created a gigantic, violent and complex eruption of bright cloud material, which has spread to encircle the entire planet… nothing on Earth comes close to this powerful storm.”

– Leigh Fletcher, lead author and Cassini team scientist at the University of Oxford in the United Kingdom.

The origins of Saturn’s storm may be similar to those of a thunderstorm here on Earth; warm, moist air rises into the cooler atmosphere as a convective plume, generating thick clouds and turbulent winds. On Saturn this mass of warmer air punched through the stratosphere, interacting with the circulating winds and creating temperature variations that further affect atmospheric movement.

The temperature variations show up in the infrared images as bright “stratospheric beacons”. Such features have never been seen before, so researchers are not yet sure if they are commonly found in these kinds of seasonal storms.

“We were lucky to have an observing run scheduled for early in 2011, which ESO allowed us to bring forward so that we could observe the storm as soon as possible. It was another stroke of luck that Cassini’s CIRS instrument could also observe the storm at the same time, so we had imaging from VLT and spectroscopy of Cassini to compare. We are continuing to observe this once-in-a-generation event.”

– Leigh Fletcher

A separate analysis using Cassini’s visual and infrared mapping spectrometer confirmed the storm is very violent, dredging up larger atmospheric particles and churning up ammonia from deep in the atmosphere. Other Cassini scientists are studying the evolving storm and a more extensive picture will emerge soon.

Read the NASA article here, or the news release from ESO here.

This false-color infrared image, obtained by NASA's Cassini spacecraft, shows clouds of large ammonia ice particles dredged up by a powerful storm in Saturn's northern hemisphere. Large updrafts dragged ammonia gas upward more than 30 miles (50 kilometers) from below. The ammonia then condensed into large crystals in the frigid upper atmosphere. This storm is the most violent ever observed at Saturn by an orbiting spacecraft.

Cassini's visual and infrared mapping spectrometer obtained these images on Feb. 24, 2011. Scientists colorized the image by assigning red to brightness detected from the 4.08-micron wavelength, green to brightness from the 0.90-micron wavelength, and blue to brightness from the 2.73-micron wavelength. Large particles (red) reflect sunlight well at 4.08 microns. Particles at high altitude (green) reflect sunlight well at 0.9 microns. Particles comprised of ammonia -- especially large ones -- do not reflect 2.73-micron sunlight well, but instead absorb light at this wavelength.

The storm here shows up as yellow, demonstrating that it has a large signal in both red and green colors. This indicates the cloud has large particles and extends upward to relatively high altitude. In addition, the lack of blue in the feature indicates that the storm cloud has a substantial component of ammonia crystals. The head of the storm is particularly rich in such particles, as created by powerful updrafts of ammonia gas from depth in the throes of Saturn’s thunderstorm.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency (ASI). NASA’s Jet Propulsion Laboratory in Pasadena, Calif., manages the mission for NASA's Science Mission Directorate at the agency's headquarters in Washington. The Cassini orbiter was designed, developed and assembled at JPL. The visual and infrared mapping spectrometer was built by JPL, with a major contribution by ASI. The visual and infrared mapping spectrometer science team is based at the University of Arizona, Tucson. JPL is a division of the California Institute of Technology in Pasadena.

For more information about the Cassini-Huygens mission, visit http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov/home/index.cfm.

Credit: NASA/JPL/Univ. of Arizona

Tagged as: Cassini, ESO, infrared, NASA, Saturn, Solar System, storm, VLT

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Astronomy Without A Telescope – SLoWPoKES

by Steve Nerlich on May 14, 2011 from www.UniverseToday.com

The Sloan Low-mass Wide Pairs of Kinematically Equivalent Stars (SLoWPoKES) catalog was recently announced, containing 1,342 common proper motion pairs (i.e. binaries) – which are all low mass stars in the mid-K and mid-M stellar classes – in other words, orange and red dwarves.

These low mass pairs are all at least 500 astronomical units distance from each other – at which point the mutual gravitation between the two objects gets pretty tenuous – or so Newton would have it. Such a context provides a test-bed for something that lies in the realms of ‘fringe science’ – that is, Modified Newtonian Dynamics, or MoND.

The origin of MoND theory is generally attributed to a paper by Milgrom in 1981, which proposed MoND as an alternative way to account for the dynamics of disk galaxies and galactic clusters. Such structures can’t obviously hold together, with the rotational velocities they possess, without the addition of ‘invisible mass’ – or what these days we call dark matter.

MoND seeks to challenge a fundamental assumption built into both Newton’s and Einstein’s theories of gravity – where the gravitational force (or the space-time curvature) exerted by a massive object recedes by the inverse square of the distance from it. Both theories assume this relationship is universal – it doesn’t matter what the mass is or what the distance is, this relationship should always hold.

In a roundabout way, MoND proposes a modification to Newton’s Second Law of Motion – where Force equals mass times acceleration (F=ma) – although in this context, a is actually representing gravitational force (which is expressed as an acceleration).

If a expresses gravitational force, then F expresses the principle of weight. So for example, you can easily exert a sufficient force to lift a brick off the surface of the Earth, but it’s unlikely that you will be able to lift a brick, with the same mass, off the surface of a neutron star.

Anyhow, the idea of MoND is that by allowing F=ma to have a non-linear relationship at low values of a, a very tenuous gravitational force acting across a great distance might still be able to hold something in a loose orbit around a galaxy, despite the principle of a linear F=ma relationship predicting that this shouldn’t happen.

MoND is fringe science, an extraordinary claim requiring extraordinary evidence, since if Newton’s or Einstein’s theories of gravity cannot be assumed to universal, a whole bunch of other physical, astrophysical and cosmological principles start to unravel.

Also, MoND doesn’t really account for other observational evidence of dark matter – notably the gravitational lensing seen in different galaxies and galactic clusters – a degree of lensing that exceeds what is expected from the amount of visible mass that they contain.

In any case, Hernandez et al have presented a data analysis drawn from the SLoWPoKES database of widely spread low-mass binaries, suggestive that MoND might actually work at scales of around 7000 astronomical units. Now, since this hasn’t yet been picked up by Nature, Sci. Am. or anyone else of note – and since some hack writer at Universe Today is just giving it a ‘balanced’ review here, it may be premature to consider that a major paradigm of physics has been overturned.

Nonetheless, the concept of ‘missing mass’ and dark matter has been kicked around for close on 90 years now – with no-one seemingly any closer to determining what the heck this stuff is. On this basis, it is reasonable to at least entertain some alternate views.

Further reading:

Dhital et al Sloan Low-mass Wide Pairs of Kinematically Equivalent Stars (SLoWPoKES): A Catalog of Very Wide, Low-mass Pairs (note that this paper makes no reference to the issue of MoND).

Hernandez et al The Breakdown of Classical Gravity?

Tagged as: Modified Newtonian dynamics

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