Back to the main page

Archives Of Astronomy Blog

Subscribe To Astronomy Blog RSS Feed  RSS content feed What is RSS feed?

February 5, 2006, 11:34 PM CT

The Huygens Landing: One Year Ago

The Huygens Landing: One Year Ago
One year ago, on 14 January 2005, ESA's Huygens probe reached the upper layer of Titan's atmosphere and landed on the surface after a parachute descent 2 hours and 28 minutes later.

As part of the joint NASA/ESA/ASI mission to Saturn and its moons, the Huygens probe was sent from the Cassini spacecraft to explore Titan, Saturn's largest moon. Titan's organic chemistry may be like that of the primitive Earth around 4000 million years ago, and may hold clues about how life began on our planet.

The Huygens mission

The Huygens mission has been an outstanding engineering and scientific success, one of the most complex and scientifically rewarding space missions to date. The touchdown on the surface of Titan marked the farthest a man-made spacecraft has successfully landed away from Earth.

Clear images of the surface of Titan were obtained below 40 km altitude - revealing an extraordinary world, resembling Earth in a number of respects, particularly in meteorology, geomorphology and fluvial activity, but with different ingredients. The images show good evidence for erosion due to liquid flows, possibly methane.

Huygens enabled studies of the atmosphere and surface, including the first in-situ sampling of the organic chemistry and the aerosols below 150 km. These confirmed the presence of a complex organic chemistry, which reinforces the idea that Titan is a promising place to observe the molecules that may have been the precursors of the building blocks of life on Earth.........

Posted by: Edwin      Permalink

February 2, 2006, 10:42 PM CT

The Big Bang

The Big Bang
In physical cosmology, the Big Bang is the scientific theory that the Universe emerged from an enormously dense and hot state about 13.7 billion years ago. The Big Bang is a consequence of the observed Hubble's law velocities of distant galaxies that when taken together with the cosmological principle imply that space is expanding as per the Friedmann-Lemaître model of general relativity. Extrapolated into the past, these observations show that the Universe has expanded from a primeval state, in which all the matter and energy in the Universe was at an immense temperature and density. Physicists do not widely agree on what happened before this, eventhough general relativity predicts a gravitational singularity.

The term Big Bang is used both in a narrow sense to refer to a point in time when the observed expansion of the Universe (Hubble's law) began-calculated to be 13.7 billion (1.37 × 1010) years ago-and in a more general sense to refer to the prevailing cosmological paradigm explaining the origin and expansion of the Universe, as well as the composition of primordial matter through nucleosynthesis as predicted by the Alpher-Bethe-Gamow theory.

One consequence of the Big Bang is that the conditions of today's Universe are different from the conditions in the past or in the future. From this model, George Gamow in 1948 was able to predict, at least qualitatively, the existence of cosmic microwave background radiation (CMB). The CMB was discovered in the 1960s and further validated the Big Bang theory over its chief rival, the steady state theory.........

Posted by: Edwin      Permalink

January 31, 2006, 0:35 AM CT

XMM-Newton scores 1000

XMM-Newton scores 1000
ESA's X-ray observatory, continues its quest for the unknown. This month, after five years of operations, the mission saw the publication of its 1000th scientific paper, corresponding to an equivalent number of results, in top-class scientific journals. This is not the only record-breaking figure for this X-ray 'hunter' mission.

There are several ways to measure the scientific success of a mission. One is certainly to look at the use the scientific community makes of the data obtained by the mission, and at the number, novelty and significance of the results so produced.

From the very beginning of its operations in early 2000, hundreds of researchers all around the world have been subscribing to 'book' observing time with XMM-Newton, eager to obtain data and new clues about the hidden and powerful phenomena taking place in the Universe - black holes, birth and death of stars, active galactic nuclei.

Each of the five calls for observation proposals issued so far by ESA towards the scientific community, resulted in a subscription exceeding by seven times the observing slots available. More than 1600 astronomers, an estimated 20 per cent of the world-wide community, had participated to provide their ideas for using XMM-Newton to target highly energetic, exotic and still mysterious space objects.........

Posted by: Edwin      Permalink

January 28, 2006, 6:16 PM CT

Proof Of Extended Magnetic Activity In Space

Proof Of Extended Magnetic Activity In Space
Writing in the journal Nature, the British, French and American team claims that these observations provide the first good evidence that a process known as 'magnetic reconnection' can occur over extended areas in space.

Magnetic reconnection is a physical process in which oppositely directed magnetic fields are annihilated and the energy stored in them is converted to beams of energetic atomic particles. This reconnection process is believed to drive the dynamics of the Earths magnetosphere and is responsible for phenomena such as solar flares and the aurora.

Until now, a full description of reconnection has proved elusive because in-situ observations were only made within the Earth's magnetosphere, the band of space surrounding Earth that protects it from most of the Sun's particles. In this area the thin electrical current sheets in which reconnection occurs extend over a short scale, allowing only evidence of patchy reconnection to be found. Researchers needed observations on a much larger scale to prove that reconnection over distances of thousands of kilometres can occur as predicted.

This evidence was provided in 2002, when the team discovered that reconnection could take place in the solar wind, a stream of particles ejected from the atmosphere of the Sun. Here, unlike in the magnetosphere, the current sheets occur over much greater distances. This gave scientists the opportunity to test the theory of large-scale reconnection.........

Posted by: Edwin      Permalink

January 25, 2006, 9:15 PM CT

Discovery Of Small, Rocky, Extrasolar World

Discovery Of Small, Rocky, Extrasolar World
Using a relatively new planet-hunting technique that can spot worlds one-tenth the mass of our own, scientists have discovered a potentially rocky, icy body that may be the smallest planet yet found orbiting a star outside our solar system.

The discovery suggests the technique, gravitational microlensing, may be an exceptional technology for finding distant planets with traits that could support life.

"This is an important breakthrough in the quest to answer the question 'Are we alone?'" said Michael Turner, assistant director for the National Science Foundation (NSF) mathematical and physical sciences directorate. "The team has discovered the most Earth-like planet yet, and more importantly, has demonstrated the power of a new technique that is sensitive to detecting habitable planets. It can probe a much greater portion of our galaxy and is complementary to other techniques".

Located more than 20,000 light years away in the constellation Sagittarius, close to the center of our Milky Way galaxy, planet OGLE-2005-BLG-390Lb is approximately five-and-a-half times the mass of Earth.

Orbiting a star one-fifth the mass of the sun at a distance almost three times that of Earth's orbit, the newly discovered planet is frigid: the estimated surface temperature is -364 degrees Fahrenheit (-220 degrees Celsius).........

Posted by: Edwin      Permalink

January 18, 2006, 9:37 PM CT

Size of a Small, Frost World

Size of a Small, Frost World
Observing a very rare occultation of a star by Pluto's satellite Charon from three different sites, including Paranal, home of the VLT, astronomers were able to determine with great accuracy the radius and density of the satellite to the farthest planet. The density, 1.71 that of water, is indicative of an icy body with about slightly more than half of rocks. The observations also put strong constraints on the existence of an atmosphere around Charon.

Since its discovery in 1978, Charon and Pluto have appeared to form a double planet, rather than a planet-satellite couple. Actually, Charon is about twice as small as Pluto in size, and about eight times less massive. However, there have been considerable discussions concerning the precise radii of Pluto and Charon, as well as about the presence of a tenuous atmosphere around Charon.

In August 2004, Australian amateur astronomer Dave Herald predicted that the 15-magnitude star UCAC2 26257135 should be occulted by Charon on 11 July 2005. The occultation would be observable from some parts of South America, including Cerro Paranal, in the northern Atacama Desert, the location of ESO's Very Large Telescope (VLT).

Stellar occultations have proved to be powerful tools to both measure sizes - at km-level accuracy, i.e. a factor ten better than what is feasible with other techniques - and detect very tenuous atmosphere - at microbar levels or less. Unfortunately, in the case of Charon, such occultations are extremely rare, owing to the very small angular diameter of the satellite on the sky: 55 milli-arcsec, i.e. the size of a one Euro coin observed from 100 km away!.........

Posted by: Brooke      Permalink

January 17, 2006, 0:22 AM CT

German Technology for Hubble's Successor

German Technology for Hubble's Successor
Carl Zeiss Optronics, in Oberkochen, Gera number of, and the Max Planck Institute for Astronomy in Heidelberg (MPIA), are developing the main fine mechanical optical technology for two instruments to be part of the James Webb Space Telescope (JWST). Over the next eight years, under administration of the European Space Agency and NASA in the USA, the JWST (with a mirror of 6.5 metres) will shape up to be the successor to the legendary HUBBLE Space Telescope. Carl Zeiss and the Max Planck Institute signed a contract on November 29 to co-operate in their work on the MIRI and NIRSpec instrumentation of the JWST.

The JAMES WEBB Space Telescope is going to replace the Hubble Space Telescope in the next few decades as the most important tool for astronomical observation. The most important scientific goal of the mission is to discover the "first light" of the early universe - the formation of the first stars out of the slowly cooling Big Bang. The light from these first stars and galaxies has shifted into the infrared spectrum because its wavelength has stretched out some twenty times, as the universe has been expanding. The infrared (warm) radiation of the telescope and its instruments could disturb these weak cosmic signals. In order to prevent this, the telescope has to be essentially deep frozen.........

Posted by: Jaison      Permalink

January 17, 2006, 0:18 AM CT

Possible Comet Dust Around Dead Star

Possible Comet Dust Around Dead Star An artist's concept of a comet being torn to shreds around a dead star
NASA's Spitzer Space Telescope has spotted what may be comet dust sprinkled around the white dwarf star G29-38, which died approximately 500 million years ago.

The findings suggest the dead star, which most likely consumed its inner planets, is still orbited by a ring of surviving comets and possibly outer planets. This is the first observational evidence that comets can outlive their suns.

"Astronomers have known for decades that stars are born, have an extended middle age, and then wither away or explode. Spitzer is helping us understand how planetary systems evolve in tandem with their parent stars," said David Leisawitz, NASA's Spitzer program scientist.

Astronomers believe white dwarfs are shrunken skeletons of stars that were once similar to Earth's sun. As the stars aged over billions of years, they grew brighter and eventually swelled in size to become red giants. Millions of years later, the red giants shed their outer atmospheres, leaving behind white dwarfs.

If any planets did orbit in these systems, the red giants would have engulfed at least the inner ones. Only distant outer planets and an orbiting icy outpost of comets would have survived.

"The dust seen by Spitzer around G29-38 was probably generated relatively recently when one such outlying comet may have been knocked into the inner region of the system and ripped into dust shreds by the tidal forces of the star," said astronomer William Reach of the Spitzer Science Center at the California Institute of Technology in Pasadena, Calif.........

Posted by: Brooke      Permalink

January 15, 2006, 8:05 PM CT

Stardust Capsule Back Home

Stardust Capsule Back Home
NASA's Stardust sample return mission returned safely to Earth when the capsule carrying cometary and interstellar particles successfully touched down Jan. 15 at 2:10 a.m. Pacific time (3:10 a.m. Mountain time) in the desert salt flats of the U.S. Air Force Utah Test and Training Range.

"Ten years of planning and seven years of flight operations were realized early this morning when we successfully picked up our return capsule off of the desert floor in Utah," said Tom Duxbury, Stardust project manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "The Stardust project has delivered to the international science community material that has been unaltered since the formation of our solar system".

Stardust released its sample return capsule at 9:57 p.m. Pacific time (10:57 p.m. Mountain time) last night. The capsule entered the atmosphere four hours later at 1:57 a.m. Pacific time (2:57 a.m. Mountain time). The drogue and main parachutes deployed at 2:00 and 2:05 a.m. Pacific time, respectively (3:00 and 3:05 a.m. Mountain time).

"I have been waiting for this day since the early 1980s when Deputy Principal Investigator Dr. Peter Tsou of JPL and I designed a mission to collect comet dust," said Dr. Don Brownlee, Stardust principal investigator from the University of Washington, Seattle. "To see the capsule safely back on its home planet is a thrilling accomplishment".........

Posted by: Brooke      Permalink

January 13, 2006, 6:46 PM CT

Mysterious Clouds in Antarctica

Mysterious Clouds in Antarctica The Rothera research station in Antarctica
A new study, funded in part by the Naval Research Laboratory and the National Aeronautics and Space Administration (NASA) reports that exhaust from the space shuttle can create high-altitude clouds over Antarctica mere days following launch, providing valuable insight to global transport processes in the lower thermosphere[mhs1]. The same study also finds that the shuttle's main engine exhaust plume carries small quantities of iron that can be observed from the ground, half a world away.

The international team of authors of the study, to appear in the July 6 issue of Geophysical Research Letters, used the STS-107 Shuttle mission as a case study to show that exhaust released in the lower thermosphere, near 110 kilometers altitude, can form Antarctic polar mesospheric clouds (PMCs). The thermosphere is the highest layer in our atmosphere, with the mesosphere (between 50-90 kilometers above the Earth), stratosphere, and troposphere below.

New observations presented by the research team from the Global Ultraviolet Imager (GUVI) on NASA's Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) satellite reveal transport of the STS-107 exhaust into the southern hemisphere just two days after the January 2003 launch. Water from the exhaust ultimately led to a significant burst of PMCs during the 2002-2003 southern polar summer, observed by the Solar Backscatter Ultraviolet (SBUV) satellite experiment. The inter-hemispheric transport followed by Antarctic PMC formation were unexpected.........

Posted by: Brooke      Permalink

Older Blog Entries   1   2   3   4   5   6   7   8   9   10   11   12