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August 27, 2006, 9:18 PM CT

Low Altitude Flying With Coarse Maps

Low Altitude Flying With Coarse Maps This image provides views of Earth from the Moon on 2 September
What exactly determines the time of the SMART-1 impact? What causes the uncertainty in the impact time?

The SMART-1 spacecraft is currently expected to impact the Moon's surface on 3 September 2006, at 07:41 CEST (05:41 UT). However, it is also possible that the small satellite hits the Moon on the previous orbit at 02:37 CEST (00:37 UT). Why?

The time of impact has been determined by orbit predictions following the major thruster manoeuvres performed from 23 June to 2 July 2006 (plus a few trajectory correction manoeuvres performed on 27 and 28 July 2006) - aimed at changing the impact site from the lunar far-side to the lunar near-side, taking into account the Sun-Earth-Moon gravity perturbations. These make the SMART-1 orbit perilune (point of closest approach to the lunar surface) naturally drift down about one kilometre per orbit.

In determining the impact orbit, ESA's spacecraft control experts are also taking into account the tiny perturbations to the trajectory induced by the small hydrazine thrusters to offload the spacecraft reaction wheels, and some slight additional gravity perturbations. An additional slot is also available for a corrective manoeuvre on 1 and 2 September 2006 if needed, to maintain the impact time as planned and allow ground based observations.........

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August 27, 2006, 8:50 PM CT

Forecast Accuracy Gets Boost

Forecast Accuracy Gets Boost
An advanced forecasting model that predicts several types of extreme weather with substantially improved accuracy has been adopted for day-to-day operational use by civilian and military weather forecasters. The new computer model was created through a partnership that includes the National Oceanic and Atmospheric Administration (NOAA), the National Center for Atmospheric Research (NCAR), and more than 150 other organizations and universities in the United States and abroad.

The high-resolution Weather Research and Forecasting model (WRF) is the first model to serve as both the backbone of the nation's public weather forecasts and a tool for cutting-edge weather research. Because the model fulfills both functions, it is easier for research findings to be translated into improved operational models, leading to better forecasts.

The model was adopted for use by NOAA's National Weather Service (NWS) as the primary model for its one-to-three-day U.S. forecasts and as a key part of the NWS's ensemble modeling system for short-range forecasts. The U.S. Air Force Weather Agency (AFWA) also has used WRF for several areas of operations around the world.

"The Weather Research and Forecasting model development project is the first time researchers and operational scientists have come together to collaborate on a weather modeling project of this magnitude," says Louis Uccellini, director of NOAA's National Centers for Environmental Prediction.........

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August 25, 2006, 4:44 AM CT

Why Earth's Aurorae Shine

Why Earth's Aurorae Shine Aurorae over Canada
ESA's Cluster mission has established that high-speed flows of electrified gas, known as bursty bulk flows, in the Earth's magnetic field are the carriers of decisive amounts of mass, energy and magnetic perturbation towards the Earth during magnetic substorms. When substorms occur, energetic particles strike our atmosphere, causing aurorae to shine.

Such colourful aurorae regularly light the higher latitudes in the northern and southern hemisphere. They are caused mostly by energetic electrons spiralling down the Earth's magnetic field lines and colliding with atmospheric atoms at about 100 kilometres altitude. These electrons come from the magnetotail, a region of space on the night-side of Earth where the Sun's wind of particles pushes the Earth's magnetic field into a long tail.

At the tail's centre is a denser region known as the plasmasheet. Violent changes of the plasmasheet are known as magnetic substorms. They last up to a couple of hours and somehow hurl electrons and other charged particles earthwards. Apart from the beautiful light show, substorms also excite the Earth's ionosphere, perturbing the reception of GPS signals and communications between the Earth and orbiting satellites.

A key issue about substorms has been to determine how they fling material earthwards. The so called 'Bursty Bulk Flows' (BBFs), flows of gas that travel at over 300 kilometres per second through the plasmasheet, were discovered in the 1980s and became a candidate mechanism.........

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August 24, 2006, 9:49 PM CT

Microscopic passengers to hitch ride

Microscopic passengers to hitch ride
When space shuttle Atlantis rockets into space later this week, it will take along three kinds of microbes so researchers can study how their genetic responses and their ability to cause disease change.

The 'Microbe' experiment, part of the STS-115 space shuttle mission scheduled for launch Aug. 27, will study three common microorganisms -- Salmonella typhimurium, Pseudomonas aeruginosa and Candida albicans -- that have been identified as potential threats to crew health. Sending these microbes into space will allow researchers to investigate the microbes' genetic adaptation and ability to cause infectious disease in microgravity, and to better understand the astronauts' space environment. The results of this experiment will help NASA researchers evaluate the risks to astronauts on future exploration missions planned to go to the moon and Mars.

"Spaceflight holds tremendous potential for the development of novel therapeutics, vaccines and diagnostics to treat, prevent and control infectious diseases," said Cheryl A. Nickerson, Ph.D., the experiment's principal investigator and a researcher at the Biodesign Institute at Arizona State University, Tempe. "Our Microbe experiment will be the first to investigate the effects of spaceflight on the disease-causing potential and gene expression profiles of disease-causing microbes." NASA Ames Research Center, Moffett Field, Calif., developed the Microbe payload for flight.........

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August 24, 2006, 9:11 PM CT

Pluto is not a planet

Pluto is not a planet Pluto
The "United Nations" of astronomers has announced a new definition of what a planet is, slightly revising the description preferred by an international panel including an MIT professor that was tasked with the challenge.

Members of the International Astronomical Union (IAU) voted on August 24 to define a planet as an object that is in orbit around the sun, is large enough for its own gravity to pull it into a nearly spherical shape, and has cleared the neighborhood around its orbit -- in other words, it has no other large bodies crossing its path.

The third condition was added to the draft definition of a planet submitted to the IAU about a week ago by MIT's Richard Binzel and his colleagues. Binzel, a professor of planetary science in the Department of Earth, Atmospheric and Planetary Sciences, took responsibility for presenting the final version of the resolution at the time of the final vote.

This means that while Pluto will still be considered a planet, it will technically be a dwarf planet because it is smaller than Mercury. It will be joined in that category by Ceres and 2003 UB313 (a temporary name for an object discovered only three years ago). More "dwarf planets" are expected to be announced by the IAU in the coming months and years.

As a result of the new definition, our solar system now contains eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, plus the three dwarf planets led by Pluto.........

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August 23, 2006, 9:17 PM CT

Supercomputers To Study Atoms Linked To Black Holes

Supercomputers To Study Atoms Linked To Black Holes
Super-hot atoms in space hold the key to an astronomical mystery, and an Ohio State University astronomer is leading an effort to study those atoms here on Earth.

Anil Pradhan, professor of astronomy, and his team have used supercomputers to perform the most precise energy calculations ever made for these atoms and their properties. As a result, astronomers -- in particular, those hunting black holes -- will have a better idea of what they are looking at when they examine faraway space matter using X-ray telescopes.

The results appear in the recent issue of the Journal of Physics B: Atomic, Molecular and Optical Physics. And while the paper's subject matter is highly technical, it tells a story that weaves together atomic physics, Einstein's theory of relativity, cutting-edge astronomical observations, and some of the world's fastest supercomputers.

Astronomers have spied seas of super-hot atoms in plasma form, circling the centers of very bright galaxies, called active galactic nuclei. The plasma is believed to be a telltale sign of a black hole; the black hole itself is invisible, but any material spiraling into it should be very hot, and shine brightly with X-rays.

Before anyone can prove definitively whether active galaxies contain black holes, astronomers need to measure the energy levels of the excited atoms in the plasma very precisely, and match the measurements with what they know about atomic physics.........

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August 22, 2006, 6:59 PM CT

Close-up on Cuvier crater ridge

Close-up on Cuvier crater ridge
This high-resolution image, taken by the Advanced Moon Imaging Experiment (AMIE) on board ESA's SMART-1 spacecraft, shows the young crater 'Cuvier C' on the Moon.

Click for high resolution image

AMIE obtained this sequence on 18 March 2006 from a distance of 591 kilometres from the surface, with a ground resolution of 53 metres per pixel. The imaged area is centred at a latitude of 50.1º South and a longitude of 11.2º East, with a field of view of 27 km. The North is on the right of the image.

"This image shows the resolving power of the SMART-1 camera to measure the morphology of rims and craters in order to diagnose impact processes", says SMART-1 Project scientist Bernard Foing, "or to establish the statistics of small craters for lunar chronology studies".

Cuvier C, a crater about 10 kilometres across, is visible in the lower right part of the image. Cuvier C is located at the edge of the larger old crater Cuvier, a crater 77 kilometres in diameter. The upper left quadrant of the image contains the smooth floor of Cuvier, only one fourth of which is visible in this image.

Crater Cuvier was named after the creator of the comparative anatomy, Georges Cuvier, a 19th century French naturalist (1769 - 1832).........

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August 22, 2006, 5:02 AM CT

First Direct Evidence For Dark Matter

First Direct Evidence For Dark Matter This composite image shows the galaxy cluster 1E0657-556, also known as the "bullet cluster",
Astronomers have discovered first direct proof that dark matter exists.

University of Arizona astronomers and their colleagues got side-on views of two merging galaxy clusters in observations made with state-of-the-art optical and X-ray telescopes.

"Nature gave us this fantastic opportunity to see hypothesized dark matter separated from ordinary matter in this merging system," said UA astronomer Douglas Clowe, leader of the study.

"Previous to this observation, all of our cosmological models were based on an assumption that we couldn't prove: that gravity behaves the same way on the cosmic scale as on Earth," Clowe said. "The clusters we've looked at in these images are a billion times larger than the largest scales at which we can measure gravity at present, which are on the scale of our solar system".

Douglas Clowe.

Clowe added, "What's amazing about this is that the process of galaxy clusters merging is thought to go on all of time. That's how galaxy clusters gain mass. But the fact that we caught this thing only 100 million years after it occurred -- so recently that it barely registers on the cosmic time scale -- is tremendous luck."

Astronomers have known since the 1930s that most of the universe must be made up of something other than normal matter, the stuff that makes stars, planets, all things and creatures. Given the way that galaxies move through space and scientists' understanding of gravity, astronomers theorize that the universe must contain about five times more dark matter than normal matter.........

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August 20, 2006, 9:44 PM CT

Hubble Sees Faintest Stars

Hubble Sees Faintest Stars ancient globular star cluster NGC 6397
The NASA/ESA Hubble Space Telescope has uncovered what astronomers are reporting as the dimmest stars ever seen in any globular star cluster.

Globular clusters are spherical concentrations of hundreds of thousands of stars. Seeing the whole range of stars in this area will yield insights into the age, origin, and evolution of the cluster.

These clusters formed early in the 13.7-thousand-million-year-old universe. The cluster observed by Hubble, called NGC 6397, is one of the closest globular star clusters to Earth.

Eventhough astronomers have conducted similar observations since Hubble was launched, a team led by Harvey Richer of the University of British Columbia, Vancouver, is reporting that they have at last unequivocally reached the faintest stars. Richer's team announced their findings on 17 August at the 2006 International Astronomical Union General Assembly in Prague, Czech Republic, and in the 18 August edition of the journal Science.

"We have run out of hydrogen-burning stars in this cluster. There are no fainter such stars waiting to be discovered," said Richer. "We have discovered the lowest-mass stars capable of supporting stable nuclear reactions in this cluster. Any less massive ones faded early in the cluster's history and by now are too faint to be observed."........

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August 20, 2006, 2:59 PM CT

Astronomers proclaim Pluto is a planet

Astronomers proclaim Pluto is a planet
Yes, Virginia, Pluto is a planet.

And it's about to be joined by several more, thanks to a new definition of the word "planet" announced recently by the world's astronomers through the International Astronomical Union (IAU).

The seven-person international panel that spent two years defining the difference between planets and smaller "solar system bodies" such as comets and asteroids includes an MIT astronomer.

If the definition is approved this week at the IAU General Assembly in Prague, our solar system will include 12 planets, with more to come. They include the eight classical planets that dominate the system, three planets in a new and growing category of "plutons" - Pluto-like objects - and Ceres. Pluto remains a planet and is the prototype for the new category of plutons.

"It's time to rewrite the textbooks," said Richard Binzel, an MIT professor of planetary science in the Department of Earth, Atmospheric and Planetary Sciences.

As per the new draft definition, two conditions must be satisfied for an object to be called a planet. First, the object must be in orbit around a star, while not being itself a star. Second, the object must be large enough (or, to be more technically correct, massive enough) for its own gravity to pull it into a nearly spherical shape.........

Posted by: Edwin      Permalink         Source

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