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February 4, 2007, 8:20 PM CT

mammoth cloud engulfing Titan's North Pole

mammoth cloud engulfing Titan's North Pole Cassini's visual and infrared mapping spectrometer (VIMS) has imaged a huge cloud system covering the north pole of Titan.
A giant cloud half the size of the United States has been imaged on Saturn's moon Titan by the Cassini spacecraft. The cloud may be responsible for the material that fills the lakes discovered last year by Cassini's radar instrument.

Cloaked by winter's shadow, this cloud has now come into view as winter turns to spring. The cloud extends down to 60 degrees north latitude, is roughly 2400 kilometers in diameter and engulfs almost the entire north pole of Titan.

The new image was acquired on 29 December 2006, by Cassini's visual and infrared mapping spectrometer (VIMS). Scientific models predicted this cloud system but it had never been imaged with such details before.

"We knew this cloud had to be there but were amazed at its size and structure," said Dr. Christophe Sotin of the University of Nantes, France, a member of the visual and infrared mapping spectrometer team and distinguished visiting scientist at NASA's Jet Propulsion Laboratory, Pasadena, California. "This cloud system may be a key element in the global formation of organics and their interaction with the surface."

The same cloud system seen on 29 December 2006, was still there two weeks later during the flyby which took place on 13 January 2007, even though observing conditions were slightly less favorable than in December.........

Posted by: Edwin      Read more         Source


January 30, 2007, 4:44 AM CT

Hot Stuff On Saturn

Hot Stuff On Saturn
UCL researchers have reported findings in the journal 'Nature' that rule out a long-held theory about why the Gas Giants like Saturn have such hot outer atmospheres.

Along with colleagues from Boston University, the team from UCL Physics & Astronomy found that the upper atmospheres of the giant planets in our solar system do not heat up in the same way as here on Earth.

A simple calculation to give the expected temperature of a planet's upper atmosphere balances the amount of sunlight absorbed by the energy lost to the lower atmosphere. However, the calculated values don't tally with the actual observations of the gas giants - they are consistently much hotter.It has long been thought that the culprit behind the heating process was the ionosphere, being driven by the planet's magnetic field, or magnetosphere. On the Earth this is seen in the auroral region where the spectacular Aurora Borealis, or Northen Lights, show where this energy transfer is taking place.

By analogy, it was believed the heating effect on the gas giants would be similar. The 'auroral zone' heating would then somehow be distributed to lower latitudes, though this is difficult to do because the high spin rates of these planets tends to prevent north-south movement.

The UCL team was investigating this redistribution when they reached their surprising conclusion. By using numerical models of Saturn's atmosphere, the researchers found that there, the net effects of the winds driven by polar energy inputs is not to heat the atmosphere, but to actually cool it equatorward of the heated region.........

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January 24, 2007, 5:53 PM CT

The Sun May Have A Dimmer Switch

The Sun May Have A Dimmer Switch
THERE'S a dimmer switch inside the sun that causes its brightness to rise and fall on timescales of around 100,000 years - exactly the same period as between ice ages on Earth. So says a physicist who has created a computer model of our star's core.

Robert Ehrlich of George Mason University in Fairfax, Virginia, modelled the effect of temperature fluctuations in the sun's interior. According to the standard view, the temperature of the sun's core is held constant by the opposing pressures of gravity and nuclear fusion. However, Ehrlich believed that slight variations should be possible.

He took as his starting point the work of Attila Grandpierre of the Konkoly Observatory of the Hungarian Academy of Sciences. In 2005, Grandpierre and a collaborator, Gábor Ágoston, calculated that magnetic fields in the sun's core could produce small instabilities in the solar plasma. These instabilities would induce localised oscillations in temperature.

Ehrlich's model shows that whilst most of these oscillations cancel each other out, some reinforce one another and become long-lived temperature variations. The favoured frequencies allow the sun's core temperature to oscillate around its average temperature of 13.6 million kelvin in cycles lasting either 100,000 or 41,000 years. Ehrlich says that random interactions within the sun's magnetic field could flip the fluctuations from one cycle length to the other.........

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January 15, 2007, 7:15 PM CT

The Eagle Nebula In Infrared

The Eagle Nebula In Infrared Credit: NASA/JPL-Caltech/N. Flagey (IAS/SSC) & A. Noriega-Crespo (SSC/Caltech)
In visible light, the whole thing looks like an eagle. The region was captured recently in unprecedented detail in infrared light by the robotic orbiting Spitzer Space Telescope (SSC). Shown above, the infrared image allows observers to peer through normally opaque dust and so better capture the full complexity of the Eagle Nebula star forming region.

In particular, the three famous pillars near the image center are seen bathed in dust likely warmed by a supernova explosion. The warm dust is digitally assigned the false color of red. Also visible, near the bottom of the image, is ten light-year long pillar sometimes dubbed the Fairy of Eagle Nebula. The greater Eagle emission nebula, tagged M16, lies about 6500 light years away, spans about 20 light-years, and is visible with binoculars toward the constellation of Serpens.........

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January 9, 2007, 8:45 PM CT

Universe's Oldest Objects

Universe's Oldest Objects
The deepest reaches of space are permeated by a cloak of infrared radiation, an uneven energy swath generated by long-dead objects from the early universe.

Now, scientists have teased apart overlapping signals from that cosmic infrared background, building upon an earlier study to show that uneven patches of energy may actually be clusters of the first objects to emerge from the Big Bang.

The astronomers believe the objects are either extremely bright stars more than 1,000 times more massive than our sun, or quasars, large black holes that consume enormous amounts of gas and debris and re-emit the materials in almost unparalleled bursts of energy. If the patches are star clusters, they may be the first galaxies, smaller than most known galaxies yet containing a mass on the scale of 1 million suns.

With a grant from the National Science Foundation, scientists studied archival data from the calibration of the NASA Spitzer telescope and conducted several stages of cleaning to remove signals from more recent galaxies and other objects to get to the underlying signals.

"Observing the cosmic infrared background is like watching distant fireworks from within a brightly lit city," said lead author Alexander Kashlinsky of NASA's Goddard Space Flight Center in Greenbelt, Md. "It's as if we have turned off the city lights one by one to see the bursts more clearly. While we can't resolve each spark in the fireworks, we can see the large scale structures and their glow".........

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January 8, 2007, 9:32 PM CT

New Stars Shed Light On The Past

New Stars Shed Light On The Past
new image from the Hubble Space Telescope shows N90, one of the star-forming regions in the Small Magellanic Cloud. The rich populations of infant stars found here enable astronomers to examine star forming processes in an environment that is very different from that in our own Milky Way.

This new image taken with the Advanced Camera for Surveys onboard the NASA/ESA Hubble Space Telescope depicts bright blue newly formed stars that are blowing a cavity in the centre of a fascinating star-forming region known as N90.

N90 is located in the wing of the Small Magellanic Cloud, in the constellation of Tucana, approximately 200,000 light-years away from the Earth. Its proximity makes it an exceptional laboratory to perform in-depth studies of star formation processes and their evolution in an environment close to that in the early Universe. Dwarf galaxies such as the Small Magellanic Cloud, with small numbers of stars compared to our own Milky Way, are considered to be the primitive building blocks of larger galaxies. The study of star formation within this dwarf galaxy is particularly interesting to astronomers because its primitive nature means that it lacks a large percentage of the heavier elements that are forged in successive generations of stars through nuclear fusion.........

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January 7, 2007, 9:00 PM CT

Black Hole In Tiny 'Dwarf' Galaxy

Black Hole In Tiny 'Dwarf' Galaxy Dwarf galaxy, VCC128, at the center, and the enlargement at right shows a double nucleus that suggests the presence of a black hole.
Credit: NASA/Hubble Space Telescop
Astronomers have found evidence of a supermassive black hole at the heart of a dwarf elliptical galaxy about 54 million light years away from the Milky Way galaxy where Earth resides.

It is only the second time a supermassive black hole has been discerned in a dwarf galaxy, and only the third time that astronomers have observed a double nucleus at the heart of a galaxy, said Victor P. Debattista, a postdoctoral researcher in astronomy at the University of Washington.

The galaxy, called VCC128, lies in the Virgo Cluster and is about 1 percent the size of the Milky Way. All of its stars combined would equal 100 million to 1 billion of our suns, Debattista said.

"It's a very small galaxy, on the outskirts of the cluster," he said. "It is effectively the smallest galaxy in which there is a supermassive black hole".

Black holes lie at the center of many galaxies, and have gravitational fields so powerful that nothing - not even light - can escape. A supermassive black hole is so large that its mass equals anywhere between 100,000 and 10 billion of our suns.

Debattista is the lead author of a poster detailing the discovery being presented today at the American Astronomical Society national meeting in Seattle. Co-authors are Ignacio Ferreras of Kings College in London, Anna Pasquali of the Max-Planck-Institut für Astronomie in Germany, Anil Seth at the Harvard-Smithsonian Center for Astrophysics in Boston, Sven De Rijcke of the Universiteit Gent in Belgium, and Lorenzo Morelli of Pontificia Universidad Catolica in Chile. The work was funded by a grant from the National Science Foundation, a Brooks Prize Fellowship at the UW and the Fund for Scientific Research in Belgium.........

Posted by: Edwin      Read more         Source


January 7, 2007, 7:12 AM CT

A new way to spin up pulsars

A new way to spin up pulsars The progression of spiral formation in a supernova, which eventually results in a pulsar's spin.
A team of scientists using Oak Ridge National Laboratory supercomputers has discovered the first plausible explanation for a pulsar's spin that fits the observations made by astronomers. Anthony Mezzacappa of the Department of Energy lab's Physics Division and John Blondin of North Carolina State University explain their results in the Jan. 4 issue of the journal Nature. According to three-dimensional simulations they performed at the Leadership Computing Facility, located at ORNL, the spin of a pulsar is determined not by the spin of the original star, but by the shock wave created when the star's massive iron core collapses.

That shock wave is inherently unstable, a discovery the team made in 2002, and eventually becomes cigar-shaped instead of spherical. The instability creates two rotating flows-one in one direction directly below the shock wave and another, inner flow, that travels in the opposite direction and spins up the core.

"The stuff that's falling in toward the center, if it hits this shock wave that is not a sphere any more but a cigar-shaped surface, will be deflected," Mezzacappa said. "When you do this in 3-D, you find that you wind up with not only one flow, but two counterrotating flows".

The asymmetrical flows establish a "sloshing" motion that, in the complex 3-D models, accounts for the pulsars observed spin velocities from once every 15 to 300 milliseconds, which is much slower than previous models predicted.........

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December 28, 2006, 9:59 PM CT

Finding a Different Mars Underneath

Finding a Different Mars Underneath
Mars is showing scientists its older, craggier face buried beneath the surface, thanks to a pioneering sounding radar co-sponsored by NASA aboard the European Space Agency's Mars Express orbiter.

Observations by the first project to explore a planet by sounding radar strongly suggest that ancient impact craters lie buried beneath the smooth, low plains of Mars' northern hemisphere. The technique uses echoes of waves that have penetrated below the surface.

"It's almost like having X-ray vision," said Dr. Thomas R. Watters of the National Air and Space Museum's Center for Earth and Planetary Studies, Washington. "Besides finding previously unknown impact basins, we've also confirmed that some of the subtle topographic depressions mapped previously in the lowlands are related to impact features".

Studies of how Mars evolved aid understanding of early Earth. Some signs of the forces at work a few billion years ago are more evident on Mars because, on Earth, many of them have been obliterated during Earth's more active resurfacing by tectonic activity.

Watters and nine co-authors report the findings in the Dec. 14, 2006 issue of the journal Nature.

The researchers used the orbiter's Mars Advanced Radar for Subsurface and Ionospheric Sounding, which was provided to the European Mars mission by NASA and the Italian Space Agency. The instrument transmits radio waves that pass through the Martian surface and bounce off features in the subsurface with electrical properties that contrast with those of materials that buried them.........

Posted by: Edwin      Read more         Source


December 18, 2006, 9:01 PM CT

Stars Can Be Strange

Stars Can Be Strange Astronomers are debating whether the matter in these stars is composed of free quarks or crystals of sub-nuclear particles, rather than neutrons.
According to the "Strange Matter Hypothesis," which gained popularity in the paranormal 1980's, nuclear matter, too, can be strange. The hypothesis suggests that small conglomerations of quarks, the infinitesimally tiny particles that attract by a strong nuclear force to form neutrons and protons in atoms, are the true ground state of matter. The theory has captivated particle physicists worldwide, including one of Washington University's own.

Mark Alford, Ph.D., Washington University in St. Louis assistant professor of physics in Arts & Sciences, and collaborators from MIT and the Lawrence Berkeley National Laboratory and Los Alamos National Laboratory, have used mathematical modeling to discover some properties of theoretical "strange stars," composed entirely of quark matter. Alford and his colleagues have found that under the right conditions the surface of a strange star could fragment into blobs of quark material called "strangelets," forming a rigid halo that contradicts traditional strange star models. This means that collapsed stars' nuclear leftovers, like the famously resplendent Crab Nebula, could be stranger than physicists think.

Alford and his colleagues recently published their findings in Physical Review D 73, 114016 (2006). The standard account of the dramatic death of a heavy star is that, after exploding in a supernova that rivals a whole galaxy in brightness, what is left is a "neutron star," a profoundly dense remnant, made mostly of neutrons, with a mass one and a half times that of our sun, crammed into an area with the radius of Saint Louis.........

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