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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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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Climate Catastrophes In The Solar System

Earth sits between two worlds that have been devastated by climate catastrophes. In the effort to combat global warming, our neighbours can provide valuable insights into the way climate catastrophes affect planets.

From what scientists know now, it is possible that Venus and Mars started out a lot like Earth. At some point in time, each planet followed a path that changed its climate. The transition was from Earth-like to either a cloudy inferno (Venus) or a frigid desert (Mars). Data from Venus Express and Mars express is now helping scientists determine if, when and why each planet passed the point of no-return.

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Earthlike Look Alike

On Tuesday, astronomers announced the discovery of Gliese 581 C, an "Earthlike" planet 20 light-years outside our solar system. The New York Times, among othOn Tuesday, astronomers announced the discovery of Gliese 581 C, an "Earthlike" planet 20 light-years outside our solar system. The New York Times, among other news organizations, repeated the word Earthlike in headlines. What does it mean to say that a planet is "Earthlike"?

It's small, rocky, not too hot, not too cold, and it might be able to support life. In general, an Earthlike planet should be no more than 10 times as massive as the Earth, but big enough that its atmosphere doesn't drift off. (The newly discovered planet is roughly five Earth masses.) For comparison, Jupiter is 100 times Earth's mass. The planet also needs to have a rocky core. Big balls of gas like Jupiter aren't likely to be conducive to living organisms. But most importantly, to be capable of supporting life a planet must have a surface temperature that can sustain water in liquid form. (We can't know for sure, but it's safe to assume that alien life-forms would need water to survive.)

A planet's temperature is determined by a planet's distance from the star around which it orbits: It should be close enough that water doesn't freeze, but far enough away that it doesn't boil off. (The star in question, Gliese 581, is dim compared to our sun, but the planet orbits close enough to it that water can probably maintain liquid form.) Planets such as Neptune, a giant ball of ice and rock surrounded by a thick envelope of gas, could never support life, since so little heat penetrates its atmosphere. In the case of Gliese 581 C, scientists have a good idea of the planet's temperature and mass but can only speculate about its composition.

er news organizations, repeated the word Earthlike in headlines. What does it mean to say that a planet is "Earthlike"?

It's small, rocky, not too hot, not too cold, and it might be able to support life. In general, an Earthlike planet should be no more than 10 times as massive as the Earth, but big enough that its atmosphere doesn't drift off. (The newly discovered planet is roughly five Earth masses.) For comparison, Jupiter is 100 times Earth's mass. The planet also needs to have a rocky core. Big balls of gas like Jupiter aren't likely to be conducive to living organisms. But most importantly, to be capable of supporting life a planet must have a surface temperature that can sustain water in liquid form. (We can't know for sure, but it's safe to assume that alien life-forms would need water to survive.)

A planet's temperature is determined by a planet's distance from the star around which it orbits: It should be close enough that water doesn't freeze, but far enough away that it doesn't boil off. (The star in question, Gliese 581, is dim compared to our sun, but the planet orbits close enough to it that water can probably maintain liquid form.) Planets such as Neptune, a giant ball of ice and rock surrounded by a thick envelope of gas, could never support life, since so little heat penetrates its atmosphere. In the case of Gliese 581 C, scientists have a good idea of the planet's temperature and mass but can only speculate about its composition.

http://www.slate.com

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NASA Predicts Nongreen Plants On Other Planets

NASA scientists believe they have found a way to predict the color of plants on planets in other solar systems.


To the left of this post is an illustration of what plants may look like on different planets. (Credit: Caltech illustration by Doug Cummings)Ads by Google Advertise on this site


Green, yellow or even red-dominant plants may live on extra-solar planets, according to scientists whose two scientific papers appear in the March issue of the journal, Astrobiology. The scientists studied light absorbed and reflected by organisms on Earth, and determined that if astronomers were to look at the light given off by planets circling distant stars, they might predict that some planets have mostly non-green plants.

"We can identify the strongest candidate wavelengths of light for the dominant color of photosynthesis on another planet," said Nancy Kiang, lead author of the study and a biometeorologist at NASA's Goddard Institute for Space Studies, New York. Kiang worked with a team of scientists from the Virtual Planetary Laboratory (VPL) at the California Institute of Technology, Pasadena, Calif. VPL was formed as part of the NASA Astrobiology Institute (NAI), based at the NASA Ames Research Center in California's Silicon Valley.

"This work broadens our understanding of how life may be detected on Earth-like planets around other stars, while simultaneously improving our understanding of life on Earth," said Carl Pilcher, director of the NAI at NASA Ames. "This approach -- studying Earth life to guide our search for life on other worlds -- is the essence of astrobiology."

Kiang and her colleagues calculated what the stellar light would look like at the surface of Earth-like planets whose atmospheric chemistry is consistent with the different types of stars they orbit. By looking at the changes in that light through different atmospheres, researchers identified colors that would be most favorable for photosynthesis on other planets.

This new research narrows the range of colors that scientists would expect to see when photosynthesis is occurring on extrasolar planets. Each planet will have different dominant colors for photosynthesis, based on the planet's atmosphere where the most light reaches the planet's surface. The dominant photosynthesis might even be in the infrared.

"This work will help guide designs for future space telescopes that will study extrasolar planets, to see if they are habitable, and could have alien plants," said Victoria Meadows, an astronomer who heads the VPL. The VPL team is using a suite of computer models to simulate Earth-size planets and their light spectra as space telescopes would see them. The scientists' goal is to discover the likely range of habitable planets around other stars and to find out how these planets might appear to future planet-finding missions.

On Earth, Kiang and colleagues surveyed light absorbed and reflected by plants and some bacteria during photosynthesis, a process by which plants use energy from sunlight to produce sugar. Organisms that live in different light environments absorb the light colors that are most available. For example, there is a type of bacteria that inhabit murky waters where there is little visible light, and so they use infrared radiation during photosynthesis.

Scientists have long known that the chlorophyll in most plants on Earth absorbs blue and red light and less green light. Therefore, chlorophyll appears green. Although some green color is absorbed, it is less than the other colors. Previously, scientists thought plants are not efficient as they could be, because they do not use more green light.

According to scientists, the Sun has a specific distribution of colors of light, emitting more of some colors than others. Gases in Earth's air also filter sunlight, absorbing different colors. As a result, more red light particles reach Earth's surface than blue or green light particles, so plants use red light for photosynthesis. There is plenty of light for land plants, so they do not need to use extra green light. But not all stars have the same distribution of light colors as our Sun. Study scientists say they now realize that photosynthesis on extrasolar planets will not necessarily look the same as on Earth.

"It makes one appreciate how life on Earth is so intimately adapted to the special qualities of our home planet and Sun," said Kiang.

Note: This story has been adapted from a news release issued by NASA/Goddard Space Flight Center.

http://www.sciencedaily.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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