Sun's Ripples Reveal Clues to the Core

The core of the Sun holds secrets into how it and the planets formed billions of years ago, but the bright solar surface obscures the view of its heart.

Now after a 30-year search, astrophysicists may have detected hints of ripples on the surface, just a few yards high, that could finally help shed light on the mysterious core.

The results suggest the Sun's core rotates more slowly than theorists have predicted.

Long search:

Astronomers first detected waves on the solar surface 30 years ago. Soaring miles high, those "p-mode" waves are generated by sound running through the star. They hinted at the existence of far more subtle ripples driven by gravity. These "g-mode" waves are believed to occur when gas churning below the surface plunges even deeper and collides with denser material, sending ripples propagating through the interior and up to the surface--the equivalent of dropping a stone in a pond.

Scientists wanted to detect g-mode waves since they pass through the Sun's mysterious heart and carry vital information concerning internal activity. For instance, the speed at which the solar core rotates is uncertain. Knowing this detail could shed light on the birth of the entire solar system, because it represents the hub of rotation for the dusty cloud of matter that eventually formed the sun and planets.

Unfortunately, g-modes are badly degraded during their passage to the solar surface, and by the time they reach the exterior, they are little more than ripples a few yards high.

To make matters harder, the g-modes take between two and seven hours to rise and fall just once, which means astronomers are faced with having to detect a swell that moves just a few millimeters per second at most.

Finally, success:

Now, however, an international team of astronomers employing the ESA-NASA Solar and Heliospheric Observatory (SOHO) may have finally caught glimpses of these long-sought waves, findings detailed online May 3 in the journal Science.

The key was the telescope's Global Oscillation at Low Frequency (GOLF) instrument. This device looks for bright, distinctive signals given off by sodium vapor, allowing researchers to measure ripples on the Sun with great sensitivity. The g-modes are very distinct from the p-modes in terms of both size and the speed at which they rise and fall.

The instrument cannot distinguish lone g-modes. Instead, astrophysicist Rafael Garcia at DSM/DAPNIA/Service d'Astrophysique in France and his colleagues looked for the signature of a large number of these oscillations from 10 years of GOLF data.

"By analogy, imagine
that the Sun was an enormous piano playing all the notes simultaneously. Instead of looking for a particular note--middle C, for instance--it would be easier to search for all the C's, from all the octaves together," Garcia said. "So that's what we looked for, the cumulative effect of several g-modes."

What was learned:

The way the g-modes got distorted as they passed through the Sun have given the first hints of the core's rotation speed. The surface of the Sun rotates at different rates depending on location, with the equator spinning faster (about 25 days) than the poles (roughly 36 days).

"The core of the Sun seems to rotate about three to five times faster on average," Garcia told LiveScience.

Current theories of solar formation suggest the original cloud of matter that gave rise to the solar system had a high rate of rotation, a remnant of which "could exist in the deepest regions of the Sun," Garcia said. "It seems that the solar core rotation is slower than expected by those theories," he added.?

Garcia noted a magnetic field leftover from the solar system's formation could have contributed to slowing down the solar core. A new generation of instruments now being built that can measure individual g-modes--for instance, "the GOLF New-Generation prototype that could fly in the DynaMICCS spacecraft presented inside the Cosmic-Vision 2015-2025 ESA program"--could help provide the insight needed to explain the mysteries of the solar core, he said.

http://www.Livescience.com

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A Jovian Photo Feast of Jupiture

New images beamed back by a NASA spacecraft that flew by Jupiter earlier this year are giving scientists their most detailed glimpse yet of the gas giant and its moons.

On Feb. 28, New Horizons passed within 1.4 million miles (2.3 million kilometers) of Jupiter as part of a slingshot maneuver to give it a speed boost as it races toward its main target Pluto. During the move, the spacecraft snapped hundreds of images of the Jupiter system.

Some of those images, unveiled Tuesday during a NASA news conference, reveal never-before-seen features of the planet and its moons. New Horizon's principal investigator, Alan Stern, said New Horizon's Jupiter flyby was "successful beyond our wildest dreams."

"This is the eighth mission to Jupiter, and it gives us a chance for the first time to take these modern instruments in close where Cassini couldn't go and with the bandwidth that Galileo couldn't deliver to really unveil new views of the system," Stern said.

Among the new images is one showing Jupiter's high-altitude clouds and a haze at the planet's south pole probably formed by charged particles transported there during one of the gas giant's auroras.

Another image provides the best picture yet of Jupiter's charcoal-black rings. "Most people didn't realize Jupiter had rings. When you say rings, most people think of Saturn," said New Horizons scientist Jeff Moore of NASA's Ames Research Center. "By incredible good luck, we happened to be at the right trajectory with the right instruments to study these."

There are images capturing several simultaneous volcanic eruptions on Jupiter's moon Io and one of a volcanic plume jettisoned up 200 miles (320 kilometers) above the moon's surface. Another picture shows in stunning detail Jupiter's Little Red Spot, a new storm system that is smaller than the planet's famous Great Red Spot.

"It's sort of reminiscent of Van Gogh's 'Starry Night' painting," said Hal Weaver, a New Horizons project scientist at John Hopkins University. "But this is the real deal. It's not in somebody's imagination."

Stern's favorite image shows Jupiter's icy moon Europa rising above the Jupiter cloud tops. The shot is one of many the spacecraft was programmed to take for artistic, rather than scientific, purposes.

"I'd say if you haven't been to Jupiter yet, you have now, and New Horizon has taken you there," Stern said.

More to come
New Horizon's images are providing scientists with a bounty of new data to analyze, and there is still more to come. "We are only about 70 percent of the way through the playback," said John Spencer, New Horizon's deputy lead researcher. "The data is still coming down every morning. It's going to be kind of sad in a few weeks when we finally stop getting this daily fix of new exciting stuff and we have to actually sit down and write up our papers."

The Jupiter flyby came just 13 months after New Horizon's launch, and was a dress rehearsal for its rendezvous with Pluto in 2015. The instruments performed so well that the team will veer from its original plan and prepare for the Pluto mission early.

"We've really learned how to drive this spacecraft," Stern said. "The people that did the Jupiter encounter are now charged in the coming year and a half with designing and writing all the code for the spacecraft to execute during its Pluto encounter."

The original plan was to put New Horizon into hibernation for several years after the Jupiter flyby before waking it again to prepare for Pluto. "We've instead decided that the team is so expert now and they're at the peak of their performance that we're going to be designing and writing all the code in '07 and '08 and doing our first rehearsal of the Pluto encounter in 2009," Stern said.

http://www.msnbc.msn.com

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Gone With the Martian Wind

Mars is a very windy place?so windy, in fact, that bright, oxidized martian soil is being scoured away by martian winds and dust devils to reveal darker, sub-surface soil with the end result of making the whole planet warmer. Mars is experiencing its own brand of climate change. Is this related to planet earth?s greenhouse gas driven climate change? No. Is understanding the process important for our understanding of how planets evolve and change over time? Absolutely.


In early April of this year, a young Carl Sagan Center Principal Investigator named Lori Fenton, together with her colleagues at? NASA Ames Research Center and the USGS in Flagstaff Arizona, published an article in the journal Nature revealing the phenomenon of the rise in the martian global temperature over the past 20 years. The rise, less that 2? for both surface and air temperature, is still significant from a geologic perspective.

The mechanism for the warming is due to the change in brightness, or ?albedo? of the martian surface. The light, bright, oxidized martian surface soil reflects a significant amount of solar radiation, tending to keep Mars cool, just as wearing white on a hot summer?s day is cooling. The darker, more absorbent subsurface soil, revealed after a windstorm or dust devil passes through on Mars, retains more heat, just as wearing dark clothes will on that same hot summer?s day here on earth. The result of more exposed dark soil is that the temperature of Mars has gone up between one and two degrees over the last two decades.


Such a change is very intriguing and has never before been seen on any planet. The martian atmosphere is significantly thinner than that on earth. It?s similar to what is found on our home planet at about 100,000 feet. Even so, the winds that result from the movement of even such a thin atmosphere are clearly strong enough to have a profound impact on the planet. Comparative planetologists and climate modelers will be monitoring Mars closely for the next 20 years and beyond, trying to discern if there is some sort of pattern to the changes and if the trend seems to be continuing. The truth is, we have only begun to monitor and record such data and are just beginning to track changes as they unfold.


Mars dust devils have been in space news before now. In fact, the Mars Rover twins, Spirit and Opportunity, owe their lives to the quixotic martian winds. Gusts of wind and dust devils pass over the solar arrays on the intrepid robotic explorers just often enough to scour away the ubiquitous martian dust from the surface of their mission prolonging solar arrays and sweep away the dust build-up, allowing the 4 year old batteries to recharge. This helpful process was completely unforeseen.


With new high resolution instruments on Mars, thanks to the Mars Reconnaissance Orbiter, and advanced landers and rovers in the pipeline with Phoenix Scout and Mars Science Laboratory due to launch in the next few years, we will continue to get information on martian winds and weather and discover just what else is gone with the wind.

http://www.space.com

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Chandra Sees Remarkable Eclipse Of Black Hole

Chandra observations of the galaxy NGC 1365 have captured a remarkable eclipse of the supermassive black hole at its center. A dense cloud of gas passed in front of the black hole, which blocked high-energy X-rays from material close to the black hole. This serendipitous alignment allowed astronomers to measure the size of the disk of material around the black hole, a relatively tiny structure on galactic scales.


The Chandra image contains a bright X-ray source in the middle, which reveals the position of the supermassive black hole. An optical view of the galaxy from the European Space Observatory's Very Large Telescope shows the context of the Chandra data.

NGC 1365 contains a so-called active galactic nucleus, or AGN. Scientists believe that the black hole at the center of the AGN is fed by a steady stream of material, presumably in the form of a disk.

Material just about to fall into a black hole should be heated to millions of degrees before passing over the event horizon, or point of no return. The process causes the disk of gas around the central black hole in NGC 1365 to produce copious X-rays, but the structure is much too small to resolve directly with a telescope.

However, astronomers were able to measure the disk's size by observing how long it took for the black hole to go in and out of the eclipse. This was revealed during a series of observations of NGC 1365 obtained every two days over a period of two weeks in April 2006. During five of the observations, high-energy X-rays from the central X-ray source were visible, but in the second one -- corresponding to the eclipse -- they were not.

Note: This story has been adapted from a news release issued by Chandra X-ray Center.

http://www.sciencedaily.com/

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Galaxy Evolution

This animation shows an artist's concept of Z Camelopardalis (Z Cam), a stellar system featuring a collapsed, dead star, or white dwarf, and a companion star. The white dwarf, the bright white object within the disk on the left, sucks matter from its more sedate companion star, on the right. The stolen material forms a rotating disk of gas and dust around the white dwarf. After a certain amount of material accumulates, the star erupts in a huge nova explosion, known as a "classical nova." After that explosion, the star continues to flare up with smaller bursts, which is why Z Cam is known today as a recurrent dwarf Nova. The remnants of the classical nova explosion form a ghostly shell, which provides lingering evidence of the violent outburst. The animation ends with an image taken by NASA's Galaxy Evolution Explorer on Jan. 25, 2004, when the star system was undergoing a period of relative calm.

Astronomers divide exploding binary star systems into two classes -- recurrent dwarf novae, which erupt in smaller, "hiccup-like" blasts, and classical novae, which undergo huge explosions. A link between the two types of novae had been predicted, but the observations from the Galaxy Evolution Explorer bolster the theory that some binary systems undergo both types of explosions.

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