August 25, 2006, 4:45 AM CT

Why Earth's Aurorae Shine

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.........

Posted by: Sean      Permalink         Source

August 23, 2006, 6:11 PM CT

Antarctic Ozone Hole

Twenty years ago this month, government and university scientists ventured to Antarctica to study the cause of a hole in the stratospheric ozone layer over the southernmost continent. Those observations were the first definitive demonstration that humans are capable of affecting the entire global climate system and led to the Montreal Protocol, the first treaty to address the Earth's environment.

Today, Susan Solomon and David Hoffman, who led the research team, met with colleagues from the National Oceanic and Atmospheric Administration (NOAA) and the National Science Foundation (NSF) at a news briefing in Washington, D.C., to reflect on the importance of the finding and discuss its implications for the future.

"The patient hasn't recovered," said Hoffman, who heads NOAA's global atmospheric monitoring program. "But it's not getting any sicker. We really have not seen any recovery in Antarctica," he said.

Hoffman also predicted it would take until 2060 for the ozone layer to heal completely, provided humans stop all release of man-made substances containing chlorine or bromine.

Their work began in 1986, when NSF, NOAA and NASA rapidly put together a research team, known as the National Ozone Expedition, or NOZE. The purpose was to discover the cause of a confimed depletion of ozone in the Earth's atmosphere over Antarctica. In just two months, the team led by Solomon of NOAA and Hoffman, who was then at the University of Wyoming, learned most of what we know about the ozone hole, especially the role chlorofluorocarbons, or CFCs, in destroying the ozone layer--which protects the Earth from ultraviolet radiation.........

Posted by: Sean      Permalink         Source

August 8, 2006, 9:44 PM CT

Learning From Near-impossible Missions

Projects for space scientists and astronomers taught LogicaCMG a lot about building mission-critical systems. Customers across the world have benefited from this experience.

"Your mission is almost impossible. If you choose to accept it, you'll have to land a small probe on the surface of Titan, Saturn's giant moon".

"We don't know what it's like there - no one has been before. Your mission is to gather data and get it back to Earth. There's only one chance to get it right".

"Oh, and there's one more thing. The spacecraft that will carry the probe to Saturn will take seven years to get to the launch point. The software to control the probe and its instruments must be tested before it leaves".

Perfect delivery.

LogicaCMG is used to briefs like this. The British company has been writing software for tough space missions ever since the European Space Agency was created.

In 1992 LogicaCMG was selected to develop software to control the Huygens probe's descent onto Titan. It also had to operate the scientific instruments and report their findings to mission control.

The probe would be launched on board the Cassini spacecraft in 1997. The descent would happen seven years later after a journey of 1.2 billion kilometres.........

Posted by: Sean      Permalink         Source

June 26, 2006, 11:08 PM CT

Epimetheus

Epimetheus Multimedia Gallery.

Epimetheus [ep-eh-MEE-thee-us] is an irregularly shaped moon covered with several large and small grooves, valleys and ridges. Several craters larger than 30 kilometers (18.6 miles) can be seen on its surface. The extensive cratering indicates that its surface must be several billion years old.

Epimetheus and Janus, another similarly shaped moon, share the same orbit. As these two moons approach each other they exchange momentum and trade orbits; the inner satellite becomes the outer and the outer moves to the inner position. This exchange happens about once every four years. Janus and Epimetheus may have formed from a disruption of a single parent to form co-orbital satellites. If this is the case, the disruption must have happened early in the history of Saturn's satellite system.........

Posted by: Sean      Permalink         Source

June 18, 2006, 12:04 AM CT

Asteroid Probe Offers New Views

A Japanese spacecraft has delivered an unprecedented look at one of the near-Earth asteroids that frequently fly by our planet.

Hayabusa, Japanese for "falcon," achieved a close encounter with asteroid 25143 Itokawa last November.

At 1,640 feet (500 meters) long, the asteroid is a small, rocky, "S-type" commonly found in the inner regions of the main asteroid belt (virtual solar system).

To some observers Itokawa resembles a lumpy potato. Others see a celestial sea otter with a small "head" and larger "body" (sea otter photo and profile).

Hayabusa hovered over the oddly shaped asteroid taking images and readings before achieving a daring touchdown in an attempt to capture the first ever asteroid-surface samples.........

Posted by: Sean      Permalink         Source

May 24, 2006, 6:49 PM CT

Clues To Milky Way Evolution

The measurements, released at an astrophysics workshop at the Aspen Center for Physics in Colorado and available today online to other astronomers, includes examination of old "fossil" stars that were born when our Milky Way galaxy was in its infancy. Team members posit that such data may eventually provide evidence to back up theories that our galaxy has -- over time -- "cannibalized" other, smaller galaxies and is "digesting" them.

"Our research focuses on the oldest stars, and probes the earliest phases of the evolution of our home galaxy, the Milky Way," said Rosemary Wyse, a professor in the Henry A. Rowland Department of Physics and Astronomy in Johns Hopkins' Krieger School of Arts and Sciences and a member of the RAVE team. "The unprecedented sample available with RAVE will allow me -- and now, with the release of this data, others -- to test ideas of our origins laid out by various cosmological theories."

The team also includes members from the United States, Gera number of, Australia, Canada, the Netherlands, the United Kingdom, Slovenia, Italy, Switzerland and France.

The survey has been made possible by the unique capabilities of the "six-degree field" multi-object spectrograph on the 1.2-meter UK Schmidt Telescope of the Anglo-Australian Observatory, located at Siding Spring Observatory in New South Wales, Australia. This instrument is capable of obtaining spectroscopic information for as a number of as 150 stars at once, from an area of the sky equal to more than 150 times the area covered by the full moon.........

Posted by: Sean      Permalink         Source

May 23, 2006, 9:29 PM CT

Internet Astronomy

For a number of generations various human cultures have had great knowledge about the star constellations. However, these days most of the so-called modernized breed of human can't tell you much about what's around us in the infinite Universe. The funny thing is, technically we now know more about what's there than ever before, we've even got photos. With the Hubble Telescope we now have access to the most unbelievable pictures imaginable: galaxies, nebulae and millions of stars close up. You don't need to buy a book or DVD to see this stuff, just sit down at your computer and let the Internet take you on a galactic journey.

A lot of the images can be accessed for free just by finding the right sites. At http://wires.news.com.au/special/mm/030811-hubble.htm#panup2 you can watch a stream of beautiful visuals that are literally out of this world. The beauty of the photos, the fact that they are moving, and the musical accompaniment makes the whole trip quite ethereal. The other great aspect is the information the researchers have uncovered, mind-blowing ideas like the fact that some stars are 60 times brighter than our own sun, or the idea that there are thousands of stars in one tiny spot in the sky. The concept that galaxies are 150 million light years away-do you know how fast light travels?.........

Posted by: Sean      Permalink

May 23, 2006, 9:18 PM CT

The moon

Ignoring the occasional pre-telescopic appearance of exceptionally large sunspots, the Moon is the only heavenly body which shows features to the naked eye--the Man in the Moon. These features are permanent, and it was therefore obvious that the Moon always keeps its same face turned to us (eventhough there are minor perturbations that were not noticed until later). In the philosophy of Aristotle (384-322 BCE), these features presented somewhat of a problem. The heavens, starting at the Moon, were the realm of perfection, the sublunary region was the realm of change and corruption, and any resemblance between these regions was strictly ruled out. Aristotle himself suggested that the Moon partook perhaps of some contamination from the realm of corruption.

Eventhough Aristotle's natural philosophy was very influential in the Greek world, it was not without competitors and skeptics. Thus, in his little book On the Face in the Moon's Orb, the Greek writer Plutarch (46-120 CE) expressed rather different views on the relationship between the Moon and Earth. He suggested that the Moon had deep recesses in which the light of the Sun did not reach and that the spots are nothing but the shadows of rivers or deep chasms. He also entertained the possibility that the Moon was inhabited. In the following century, the Greek satirist Lucian (120-180 CE) wrote of an imaginary trip to the Moon, which was inhabited, as were the Sun and Venus.........

Posted by: Sean      Permalink         Source

May 23, 2006, 9:08 PM CT

Astronomy And Astrophysics

Astronomy, which etymologically means laws of the stars, is the science whose subject is the observation and explanation of events outside the earth. Astrophysics was born as the application of physics to the phenomena observed by astronomy, this was only possible once it was understood that the elements that made up the "celestial objects" were the same that made up the Earth, and that the same laws of physics applied. Nearly all astronomers now have a strong background in physics, and the results of observations are always put in an astrophysical context, so the distinction between astronomy and astrophysics almost doesn't exist anymore.

In the early part of its history, astronomy involved only the observation and predictions of the motions of the objects in the sky that could be seen with the naked eye. Greeks made some important contributions to astronomy, but the progress almost stopped during the middle ages, except for the work of some Arabic astronomers. The renaissance came to astronomy with the work of Copernicus, who proposed a heliocentric system. His work was defended, expanded and corrected by the likes of Galileo Galilei and Kepler. The latter of these was the first to provide a system which described correctly the details of the motion of the planets with the Sun at the centre. He didn't understand the reasons behind the laws he wrote down, however, and it was left to Newton's invention of celestial dynamics and his law of gravitation, the final explanation of the motions of the planets. Stars were found much later to be far away objects, and with the advent of spectroscopy it was proved that they were similar to our own sun, but with a range of temperatures, masses and sizes.........

Posted by: Sean      Permalink         Source

Older Blog Entries  

---