What Are The Odds Of Finding Extraterrestrial Intelligent Life?

Source:

http://www.sciencedaily.com/releases/2008/04/080416110124.htm

ScienceDaily (Apr. 19, 2008) — Is there anybody out there? Probably not, according to a scientist from the University of East Anglia. A mathematical model produced by Prof Andrew Watson suggests that the odds of finding new life on other Earth-like planets are low, given the time it has taken for beings such as humans to evolve and the remaining life span of Earth.

Structurally complex and intelligent life evolved late on Earth and it has already been suggested that this process might be governed by a small number of very difficult evolutionary steps.
Prof Watson, from the School of Environmental Sciences, takes this idea further by looking at the probability of each of these critical steps occurring in relation to the life span of Earth, giving an improved mathematical model for the evolution of intelligent life.
According to Prof Watson a limit to evolution is the habitability of Earth, and any other Earth-like planets, which will end as the sun brightens. Solar models predict that the brightness of the sun is increasing, while temperature models suggest that because of this the future life span of Earth will be ‘only’ about another billion years, a short time compared to the four billion years since life first appeared on the planet.
“The Earth’s biosphere is now in its old age and this has implications for our understanding of the likelihood of complex life and intelligence arising on any given planet,” said Prof Watson.
“At present, Earth is the only example we have of a planet with life. If we learned the planet would be habitable for a set period and that we had evolved early in this period, then even with a sample of one, we’d suspect that evolution from simple to complex and intelligent life was quite likely to occur. By contrast, we now believe that we evolved late in the habitable period, and this suggests that our evolution is rather unlikely. In fact, the timing of events is consistent with it being very rare indeed.”
Prof Watson suggests the number of evolutionary steps needed to create intelligent life, in the case of humans, is four. These probably include the emergence of single-celled bacteria, complex cells, specialized cells allowing complex life forms, and intelligent life with an established language.
“Complex life is separated from the simplest life forms by several very unlikely steps and therefore will be much less common. Intelligence is one step further, so it is much less common still,” said Prof Watson.
His model, published in the journal Astrobiology, suggests an upper limit for the probability of each step occurring is 10 per cent or less, so the chances of intelligent life emerging is low – less than 0.01 per cent over four billion years.
Each step is independent of the other and can only take place after the previous steps in the sequence have occurred. They tend to be evenly spaced through Earth’s history and this is consistent with some of the major transitions identified in the evolution of life on Earth.
Adapted from materials provided by University of East Anglia.

Fausto Intilla - www.oloscience.com

Solar Flares Set The Sun Quaking

Source:

http://www.sciencedaily.com/releases/2008/04/080418090439.htm

ScienceDaily (Apr. 18, 2008) — Data from the ESA/NASA spacecraft SOHO shows clearly that powerful starquakes ripple around the Sun in the wake of mighty solar flares that explode above its surface. The observations give solar physicists new insight into a long-running solar mystery and may even provide a way of studying other stars.

The outermost quarter of the Sun’s interior is a constantly churning maelstrom of hot gas. Turbulence in this region causes ripples that criss-cross the solar surface, making it heave up and down in a patchwork pattern of peaks and troughs.
The joint ESA-NASA Solar and Heliospheric Observatory (SOHO) has proved to be an exceptional spacecraft for studying this phenomenon. Discovering how the ripples move around the Sun has provided valuable information about the Sun’s interior conditions. A class of oscillations called the 5-minute oscillations with a frequency of around 3 millihertz have proven particularly useful.
According to conventional thinking, the 5-minute oscillations can be thought of as the sound you would get from a bell sitting in the middle of the desert and constantly being touched by random sand grains, blown on the wind. But what Christoffer Karoff and Hans Kjeldsen, both at the University of Aarhus, Denmark, saw in the data, was very different.
“The signal we saw was like someone occasionally walking up to the bell and striking it, which told us that there was something missing from our understanding of how the Sun works,” Karoff says.
So they began looking for the culprit and discovered an unexpected correlation with solar flares. It seemed that when the number of solar flares went up, so did the strength of the 5-minute oscillations.
“The strength of the correlation was so strong that there can be no doubt about it,” says Karoff.
A similar phenomenon is known on Earth in the aftermath of large earthquakes. For example, after the 2004 Sumatra-Andaman Earthquake, the whole Earth rang with seismic waves like a vibrating bell for several weeks.
The correlation is not the end of the story. Now the researchers have to work to understand the mechanism by which the flares cause the oscillations. “We are not completely sure how the solar flares excite the global oscillations,” says Karoff.
In a broader context, the correlation suggests that, by looking for similar oscillations within other stars, astronomers can monitor them for flares. Already, Karoff has used high-technology instruments at major ground-based telescopes to look at other Sun-like stars. In several cases, he detected the tell-tale signs of oscillations that might originate from flares.
“Now we need to monitor these stars for hundreds of days,” he says. That will require dedicated spacecraft, such as the CNES mission with ESA participation, COROT. The hard work, it seems, is just starting.
Notes for editors:
‘Evidence that solar flares drive global oscillations in the Sun’ by C. Karoff & H. Kjeldsen will be published in The Astrophysical Journal letters on 1 May 2008.
Adapted from materials provided by European Space Agency.

Fausto Intilla - www.oloscience.com

Stellar Birth In The Galactic Wilderness

Source:

http://www.sciencedaily.com/releases/2008/04/080416141356.htm

ScienceDaily (Apr. 18, 2008) — A new image from NASA's Galaxy Evolution Explorer shows baby stars sprouting in the backwoods of a galaxy -- a relatively desolate region of space more than 100,000 light-years from the galaxy's bustling center.
The striking image, a composite of ultraviolet data from the Galaxy Evolution Explorer and radio data from the National Science Foundation's Very Large Array in New Mexico, shows the Southern Pinwheel galaxy, also known simply as M83.
In the new view, the main spiral, or stellar, disk of M83 looks like a pink and blue pinwheel, while its outer arms appear to flap away from the galaxy like giant red streamers. It is within these so-called extended galaxy arms that, to the surprise of astronomers, new stars are forming.
"It is absolutely stunning that we find such an enormous number of young stars up to 140,000 light-years away from the center of M83," said Frank Bigiel of the Max Planck Institute for Astronomy in Germany, lead investigator of the new Galaxy Evolution Explorer observations. For comparison, the diameter of M83 is only 40,000 light-years across.
Some of the "outback" stars in M83's extended arms were first spotted by the Galaxy Evolution Explorer in 2005. Remote stars were also discovered around other galaxies by the ultraviolet telescope over subsequent years. This came as a surprise to astronomers because the outlying regions of a galaxy are assumed to be relatively barren and lack high concentrations of the ingredients needed for stars to form.
The newest Galaxy Evolution Explorer observations of M83 (colored blue and green) were taken over a longer period of time and reveal many more young clusters of stars at the farthest reaches of the galaxy. To better understand how stars could form in such unexpected territory, Bigiel and his colleagues turned to radio observations from the Very Large Array (red). Light emitted in the radio portion of the electromagnetic spectrum can be used to locate gaseous hydrogen atoms, or raw ingredients of stars. When the astronomers combined the radio and Galaxy Evolution Explorer data, they were delighted to see they matched up.
"The degree to which the ultraviolet emission and therefore the distribution of young stars follows the distribution of the atomic hydrogen gas out to the largest distances is absolutely remarkable," said Fabian Walter, also of the Max Planck Institute for Astronomy, who led the radio observations of hydrogen in the galaxy.
The astronomers speculate that the young stars seen far out in M83 could have formed under conditions resembling those of the early universe, a time when space was not yet enriched with dust and heavier elements.
"Even with today's most powerful telescopes, it is extremely difficult to study the first generation of star formation. These new observations provide a unique opportunity to study how early generation stars might have formed," said co-investigator Mark Seibert of the Observatories of the Carnegie Institution of Washington in Pasadena.
M83 is located 15 million light-years away in the southern constellation Hydra.
Other investigators include: Barry Madore of The Observatories of the Carnegie Institution of Washington; Armando Gil de Paz of the Complutense University of Madrid, Spain; David Thilker of Johns Hopkins University, Baltimore; Elias Brinks of the University of Hertfordshire, England; and Erwin de Blok of the University of Cape Town, South Africa.
The California Institute of Technology in Pasadena leads the Galaxy Evolution Explorer mission and is responsible for science operations and data analysis. NASA's Jet Propulsion Laboratory, also in Pasadena, manages the mission and built the science instrument. Caltech manages JPL for NASA. The mission was developed under NASA's Explorers Program managed by NASA's Goddard Space Flight Center, Greenbelt, Md. Researchers sponsored by Yonsei University in South Korea and the Centre National d'Etudes Spatiales (CNES) in France collaborated on this mission.
The Very Large Array is part of the National Radio Astronomy Observatory, a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.
Adapted from materials provided by NASA/Jet Propulsion Laboratory.

Fausto Intilla - www.oloscience.com

Drifting Star Discovered: Implications For Star And Planet Formation Theory

Source:

http://www.sciencedaily.com/releases/2008/04/080415101016.htm

ScienceDaily (Apr. 17, 2008) — By studying in great detail the 'ringing' of a planet-harbouring star, a team of astronomers using ESO's 3.6-m telescope have shown that it must have drifted away from the metal-rich Hyades cluster. This discovery has implications for theories of star and planet formation, and for the dynamics of our Milky Way.
The yellow-orange star Iota Horologii, located 56 light-years away towards the southern Horologium ("The Clock") constellation, belongs to the so-called "Hyades stream", a large number of stars that move in the same direction.
Previously, astronomers using an ESO telescope had shown that the star harbours a planet, more than 2 times as large as Jupiter and orbiting in 320 days (ESO 12/99).
But until now, all studies were unable to pinpoint the exact characteristics of the star, and hence to understand its origin. A team of astronomers, led by Sylvie Vauclair from the University of Toulouse, France, therefore decided to use the technique of 'asteroseismology' to unlock the star's secrets.
"In the same way as geologists monitor how seismic waves generated by earthquakes propagate through the Earth and learn about the inner structure of our planet, it is possible to study sound waves running through a star, which forms a sort of large, spherical bell," says Vauclair.
The 'ringing' from this giant musical instrument provides astronomers with plenty of information about the physical conditions in the star's interior.
And to 'listen to the music', the astronomers used one of the best instruments available. The observations were conducted in November 2006 during 8 consecutive nights with the state-of-the-art HARPS spectrograph mounted on the ESO 3.6-m telescope at La Silla.
Up to 25 'notes' could be identified in the unique dataset, most of them corresponding to waves having a period of about 6.5 minutes.
These observations allowed the astronomers to obtain a very precise portrait of Iota Horologii: its temperature is 6150 K, its mass is 1.25 times that of the Sun, and its age is 625 million years. Moreover, the star is found to be more metal-rich than the Sun by about 50%.
These results show the power of asteroseismology when using a very precise instrument such as HARPS," says Vauclair. "It also shows that Iota Horologii has the same metal abundance and age as the Hyades cluster and this cannot be a coincidence."
The Hyades is an ensemble of stars that is seen with the unaided eye in the Northern constellation Taurus ("The Bull"). This open cluster, located 151 light-years away, contains stars that were formed together 625 million years ago.
The star Iota Horologii must have thus formed together with the stars of the Hyades cluster but must have slowly drifted away, being presently more than 130 light-years away from its original birthplace. This is an important result to understand how stars move on the galactic highways of the Milky Way.
This also means that the amount of metals present in the star is due to the original cloud from which it formed and not because it engulfed planetary material. "The chicken and egg question of whether the star got planets because it is metal-rich, or whether it is metal-rich because it made planets that were swallowed up is at least answered in one case," says Vauclair.
The astronomers' study is being published as a Letter to the Editor in Astronomy and Astrophysics ("The exoplanet-host star iota Horologii: an evaporated member of the primordial Hyades cluster", by S. Vauclair et al.). The team is composed of Sylvie Vauclair, Marion Laymand, Gérard Vauclair, Alain Hui Bon Hoa, and Stéphane Charpinet (LATT, Toulouse, France), François Bouchy (IAP, Paris, France), and Michaël Bazot (University of Porto, Portugal).
Adapted from materials provided by ESO.

Fausto Intilla - www.oloscience.com

NASA Extends Cassini's Grand Tour Of Saturn Two More Years

Source:

http://www.sciencedaily.com/releases/2008/04/080415133647.htm

ScienceDaily (Apr. 17, 2008) — NASA is extending the international Cassini-Huygens mission by two years. The historic spacecraft's stunning discoveries and images have revolutionized our knowledge of Saturn and its moons.
Cassini's mission originally had been scheduled to end in July 2008. The newly-announced two-year extension will include 60 additional orbits of Saturn and more flybys of its exotic moons. These will include 26 flybys of Titan, seven of Enceladus, and one each of Dione, Rhea and Helene. The extension also includes studies of Saturn's rings, its complex magnetosphere, and the planet itself.
"This extension is not only exciting for the science community, but for the world to continue to share in unlocking Saturn's secrets," said Jim Green, director, Planetary Science Division, NASA Headquarters, Washington. "New discoveries are the hallmarks of its success, along with the breathtaking images beamed back to Earth that are simply mesmerizing."
"The spacecraft is performing exceptionally well and the team is highly motivated, so we're excited at the prospect of another two years," said Bob Mitchell, Cassini program manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif.
Based on findings from Cassini, scientists think liquid water may be just beneath the surface of Saturn's moon Enceladus. That's why the small moon, only one-tenth the size of Titan and one-seventh the size of Earth's moon, is one of the highest-priority targets for the extended mission.
Cassini discovered geysers of water-ice jetting from the Enceladus surface. The geysers, which shoot out at a distance three times the diameter of Enceladus, feed particles into Saturn's most expansive ring. In the extended mission, the spacecraft may come as close as 25 kilometers (15 miles) from the moon's surface.
Cassini's observations of Saturn's largest moon, Titan, have given scientists a glimpse of what Earth might have been like before life evolved. They now believe Titan possesses many parallels to Earth, including lakes, rivers, channels, dunes, rain, snow, clouds, mountains and possibly volcanoes.
"When we designed the original tour, we really did not know what we would find, especially at Enceladus and Titan," said Dennis Matson, the JPL Cassini project scientist. "This extended tour is responding to these new discoveries and giving us a chance to look for more."
Unlike Earth, Titan's lakes, rivers and rain are composed of methane and ethane, and temperatures reach a chilly minus 180 degrees Celsius (minus 290 degrees Fahrenheit). Although Titan's dense atmosphere limits viewing the surface, Cassini's high-resolution radar coverage and imaging by the infrared spectrometer have given scientists a better look.
Other activities for Cassini scientists will include monitoring seasons on Titan and Saturn, observing unique ring events, such as the 2009 equinox when the sun will be in the plane of the rings, and exploring new places within Saturn's magnetosphere.
Cassini has returned a daily stream of data from Saturn's system for almost four years. Its travel scrapbook includes nearly 140,000 images, and information gathered during 62 revolutions around Saturn, 43 flybys of Titan and 12 close flybys of the icy moons.
More than 10 years after launch and almost four years after entering into orbit around Saturn, Cassini is a healthy and robust spacecraft. Three of its science instruments have minor ailments, but the impact on science-gathering is minimal. The spacecraft will have enough propellant left after the extended mission to potentially allow a third phase of operations. Data from the extended mission could lay the groundwork for possible new missions to Titan and Enceladus.
Cassini launched Oct. 15, 1997, from Cape Canaveral, Fla., on a seven-year journey to Saturn, traversing 3.5 billion kilometers (2.2 billion miles). It is one of the most scientifically capable spacecraft ever launched, with a record 12 instruments on the orbiter and six more instruments on the European Space Agency's Huygens probe, which piggybacked a ride to Titan on Cassini. Cassini receives electrical power from three radioisotope thermoelectric generators, which generate electricity from heat produced by the natural decay of plutonium. The spacecraft was captured into Saturn orbit in June 2004 and immediately began returning data to Earth.
Adapted from materials provided by National Aeronautics And Space Administration.

Fausto Intilla - www.oloscience.com

Gravity Wave 'Smoking Gun' Fizzles: Gravitational Radiation Can Be Produced More Than One Way

Source:

http://www.sciencedaily.com/releases/2008/04/080415143816.htm

ScienceDaily (Apr. 17, 2008) — A team of researchers from Case Western Reserve University has found that gravitational radiation—widely expected to provide "smoking gun" proof for a theory of the early universe known as "inflation"—can be produced by another mechanism.
According to physics scholars, inflation theory proposes that the universe underwent a period of exponential expansion right after the big bang. A key prediction of inflation theory is the presence of a particular spectrum of "gravitational radiation"—ripples in the fabric of space-time that are notoriously difficult to detect but believed to exist nonetheless.
"If we see a primordial gravitational wave background, we can no longer say for sure it is due to inflation," said Lawrence Krauss, the Ambrose Swasey Professor of Physics and Astronomy at Case Western Reserve.
At the same time the researchers find that gravitational waves are a far more sensitive probe of new physics near the highest energy scale of interest to particle physicists than previously envisaged. Thus their work provides strong motivation for the ongoing quest to detect primordial gravitational radiation.
Krauss, along with Case Western Reserve colleagues Katherine Jones-Smith, a graduate student, and Harsh Mathur, associate professor of physics, present these findings in an article "Nearly Scale Invariant Spectrum of Gravitational Radiation from Global Phase Transitions" published recently in Physical Review Letters.
Inflation theory arose in the 1980s as a means to explain some features of the universe that had previously baffled astronomers such as why the universe is so close to being flat and why it is so uniform. Today, inflation remains the best way to theoretically understand many aspects of the early universe, but most of its predictions are sufficiently malleable that consistency with observation cannot be considered unambiguous confirmation.
Enter gravitational radiation—the key prediction of inflation theory is the presence of a particular spectrum of gravitational radiation. Detection of this spectrum was regarded among physicists as "smoking gun" evidence that inflation did in fact occur, billions of years ago.
In 1992 Krauss, then at Yale, argued that another mechanism besides inflation could give rise to precisely the same spectrum of gravitational radiation as is predicted by inflation. The argument given by Krauss in 1992 provided a rough estimate of the spectrum.
Last year Krauss teamed up with Case Western Reserve colleagues, Jones-Smith, a graduate student in physics, and Mathur, associate professor of physics, to do a more complete calculation. They found that the exact calculation predicts the signal to be much stronger than the rough estimate.
Describing their results, Krauss said, "It is shocking and surprising when you find the answer is 10,000 times bigger than the rough estimate and could possibly produce a signal that mimics the kind produced by inflation."
Gravitational radiation is a prediction of Einstein's Theory of General Relativity. According to the theory, whenever large amounts of mass or energy are shifting around, it disrupts the surrounding space-time and ripples emanate from the region where the mass/energy shift.
These space-time ripples, known as gravitational radiation, are imperceptible on the human scale, but highly sensitive experiments (such as the Laser Interferometer Gravitational Wave Observatory (LIGO) in Livingston, La.) are designed precisely to look for such radiation and are the only hope for detecting them directly.
However, gravitational radiation from the early universe can also be detected indirectly through its effect on the cosmic microwave background (CMB) radiation (relic radiation from the Big Bang which permeates all space). The radiation from the CMB would become polarized in the presence of gravitational radiation. Detecting such polarized light is the mission of a satellite based experiment (Planck) set to launch in 2009.
The gravitational radiation produced by either inflation or the mechanism proposed by Jones-Smith, Krauss and Mathur would imprint itself on the CMB and be detected as polarization. Until now it was widely believed that a detection of polarized light from the CMB was a "smoking gun" for inflation theory. But with the publication of their recent paper in Physical Review Letters, Krauss and co-workers have raised the issue of whether that polarized light can be unambiguously tied to inflation.
The mechanism proposed by Krauss and coworkers invokes a phenomenon called "symmetry breaking" that is a central part of all theories of fundamental particle physics, including the so-called standard model describing the three non-gravitational forces known to exist. Here, a "scalar field" (similar to an electric or magnetic field) becomes aligned as the universe expands. But as the universe expands each region over which the field is aligned comes into contact with other regions where the field has a different alignment. When that happens the field relaxes into a state where it is aligned over the entire region and in the process of relaxing it emits gravitational radiation.
Adapted from materials provided by Case Western Reserve University.

Fausto Intilla - www.oloscience.com

Ghosts Of Galaxies: Lingering Star Streams Skirt Two Nearby Spiral Galaxies

Source:

http://www.sciencedaily.com/releases/2008/04/080415160358.htm

ScienceDaily (Apr. 16, 2008) — An international team of astronomers has identified huge star streams in the outskirts of two nearby spiral galaxies. For the first time, they have obtained a panoramic overview of an example of galactic cannibalism similar to that involving the Sagittarius dwarf galaxy in the vicinity of the Milky Way.
The detection of these immense stellar fossils confirms the predictions of the cold dark matter model of cosmology, which proposes that present-day grand design spiral galaxies were formed from the merging of less massive stellar systems.
The first of these debris structures surrounds the galaxy NGC 5907, located 40 million light-years from Earth and formed from the destruction of one of its dwarf satellite galaxies at least four thousand million years ago. According to the research team, the dwarf galaxy has lost the greater part of its mass in the form of stars, star clusters and dark matter, all of which has become strewn out along its orbit, giving rise to a complicated assembly of criss-crossing galactic fossils whose radius exceeds 150 000 light-years.
“Our results provide a fresh insight itno this spectacular phenomenon surrounding spiral galaxies and show that haloes contain fossil dwarf galaxies, thus providing us with a unique opportunity to study the final stages in the assembly of galaxies like ours,” maintains David Martínez, a researcher at the Instituto de Astrofísica de Canarias (IAC) leading the team that carried out the observations.
The astronomers’ search has not been able to find the main bodies of the devoured galaxies, which leads them to conclude that they have by now been completely destroyed. “These star streams are very difficult to detect and have a very low density of stars,” comments Martínez. “It is this that gives them their ghostly aspect. Hence, being related with the death of a dwarf galaxy, they may be considered as the ghosts of now vanished galaxies.”
The team has discovered another huge, tenuous stream in the shape of a loop in the galaxy NGC 4013, almost 50 million light-years away in the constellation Ursa Major. Its ghostly trail stretches more than 80 000 light-years from the nucleus and is made up of old, metal-poor stars. Although its three-dimensional geometry is unknown, it possesses a structure very similar to that of the Monoceros tidal stream, a ring of stars surrounding the Milky Way that was formed through the destruction of a dwarf galaxy three thousand million years ago.
Jorge Peñarrubia, a theoretical astrophysicist at the University of Victoria (Canada) and member of the team, specializes in modelling these star streams. According to Peñarrubia, “fitting theoretical models to these star streams enables us to reconstruct their history and describe one of the most mysterious and controversial components of galaxies: dark matter.”
Astrophotographers join the chase
For the job of seeking out and detecting the streams, the team has enlisted the help of the renowned astrophotographer R. Jay Gabany, whose contribution towards obtaining the images “has been decisive,” says Martínez, “a fact that underlines yet again the great contribution made by amateurs.”
For years, R. Jay Gabany has obtained spectacular colour images of the deep sky with small robotic telescopes in New Mexico and Australia. His images have been published in the best popular astronomy magazines in the world. His work on this project demonstrates the potential contribution of amateur astronomers to XXI century astronomy. With the new technologies, they are capable of participating in highly competitive scientific projects at an international level.
Adapted from materials provided by Instituto de Astrofísica de Canarias.

Fausto Intilla
www.oloscience.com

Milky Way's Giant Black Hole 'Awoke From Slumber' 300 Years Ago

Source:

http://www.sciencedaily.com/releases/2008/04/080415111724.htm

ScienceDaily (Apr. 16, 2008) — Using NASA, Japanese, and European X-ray satellites, a team of Japanese astronomers has discovered that our galaxy’s central black hole let loose a powerful flare three centuries ago.
The finding helps resolve a long-standing mystery: why is the Milky Way’s black hole so quiescent? The black hole, known as Sagittarius A* (pronounced "A-star"), is a certified monster, containing about 4 million times the mass of our Sun. Yet the energy radiated from its surroundings is billions of times weaker than the radiation emitted from central black holes in other galaxies.
"We have wondered why the Milky Way’s black hole appears to be a slumbering giant," says team leader Tatsuya Inui of Kyoto University in Japan. "But now we realize that the black hole was far more active in the past. Perhaps it’s just resting after a major outburst."
The new study, which will appear in the Publications of the Astronomical Society of Japan, combines results from Japan’s Suzaku and ASCA X-ray satellites, NASA’s Chandra X-ray Observatory, and the European Space Agency’s XMM-Newton X-ray Observatory.
The observations, collected between 1994 and 2005, revealed that clouds of gas near the central black hole brightened and faded quickly in X-ray light as they responded to X-ray pulses emanating from just outside the black hole. When gas spirals inward toward the black hole, it heats up to millions of degrees and emits X-rays. As more and more matter piles up near the black hole, the greater the X-ray output.
These X-ray pulses take 300 years to traverse the distance between the central black hole and a large cloud known as Sagittarius B2, so the cloud responds to events that occurred 300 years earlier. When the X-rays reach the cloud, they collide with iron atoms, kicking out electrons that are close to the atomic nucleus. When electrons from farther out fill in these gaps, the iron atoms emit X-rays. But after the X-ray pulse passes through, the cloud fades to its normal brightness.
Amazingly, a region in Sagittarius B2 only 10 light-years across varied considerably in brightness in just 5 years. These brightenings are known as light echoes. By resolving the X-ray spectral line from iron, Suzaku’s observations were crucial for eliminating the possibility that subatomic particles caused the light echoes.
"By observing how this cloud lit up and faded over 10 years, we could trace back the black hole’s activity 300 years ago," says team member Katsuji Koyama of Kyoto University. "The black hole was a million times brighter three centuries ago. It must have unleashed an incredibly powerful flare."
This new study builds upon research by several groups who pioneered the light-echo technique. Last year, a team led by Michael Muno, who now works at the California Institute of Technology in Pasadena, Calif., used Chandra observations of X-ray light echoes to show that Sagittarius A* generated a powerful burst of X-rays about 50 years ago -- about a dozen years before astronomers had satellites that could detect X-rays from outer space. "The outburst three centuries ago was 10 times brighter than the one we detected," says Muno.
The galactic center is about 26,000 light-years from Earth, meaning we see events as they occurred 26,000 years ago. Astronomers still lack a detailed understanding of why Sagittarius A* varies so much in its activity. One possibility, says Koyama, is that a supernova a few centuries ago plowed up gas and swept it into the black hole, leading to a temporary feeding frenzy that awoke the black hole from its slumber and produced the giant flare.
Launched in 2005, Suzaku is the fifth in a series of Japanese satellites devoted to studying celestial X-ray sources and is managed by the Japan Aerospace Exploration Agency (JAXA). This mission is a collaborative effort between Japanese universities and institutions and NASA Goddard.
Adapted from materials provided by NASA/Goddard Space Flight Center.

Fausto Intilla
www.oloscience.com

Space Radiation May Cause Prolonged Cellular Damage To Astronauts

Source:

http://www.sciencedaily.com/releases/2008/04/080415164332.htm

ScienceDaily (Apr. 16, 2008) — With major implications for long-duration space travel, a study from the Lombardi Comprehensive Cancer Center at Georgetown University Medical Center demonstrates that the high-energy radiation found in space may lead to premature aging and prolonged oxidative stress in cells. The findings suggest that astronauts may be at increased risk of colon cancer due to exposure to the high linear energy transfer (LET) radiation found in space.

"Radiation exposure, either intentional or accidental, is inevitable during our lifetimes," says Kamal Datta, M.D., assistant professor at Lombardi and the study's lead author. "But with plans for a mission to Mars, we need to understand more about the nature of radiation in space. There is currently no conclusive information for estimating the risk that astronauts may experience."
The kickoff of Project Constellation -- the National Aeronautics and Space Administration (NASA) program to return humans to the moon and travel to Mars -- has led to increased scrutiny of radiation exposures during space travel. A 2004 report from the National Academies suggested that cancer incidence may be higher in the astronaut population as compared to the general U.S. population, and the National Research Council published a report last month that recommended increased research into the radiation exposures experienced by astronauts during space travel, as well as development of new radiation shielding technologies.
Current risk estimates for radiation exposure rely exclusively on the cumulative dose a person receives in his or her lifetime. The Lombardi study suggests that a more accurate risk assessment should include not only dose, but also the quality of radiation.
To conduct the study, Datta and his team measured the level of free radicals present as well as the expression of stress response genes in the cells of mice exposed to high-LET radiation similar to that found in space. The researchers concluded that the cellular environment of the gastrointestinal tract was highly oxidative -- or full of free radicals -- for prolonged periods of time, a state which is conducive to cancer development.
The free radicals produced by the radiation causes damage to cells' DNA, and as this damage accumulates, it can lead to mutations -- and in some cases, malignant tumors. The prolonged exposure to free radicals creates ample opportunity for DNA damage to accumulate within individual cells. In fact, Datta and his team observed that the stress response continued for as long as two months after exposure to the high-LET radiation.
In addition the cellular damage from oxidative stress, the researchers also found that the mice exposed to the high-LET radiation aged prematurely. Datta says the mice's coats became prematurely grey, an observation the team plans to follow-up with MRI brain scans.
The Lombardi study, funded by NASA and presented at the 2008 American Association for Cancer Research annual meeting, compared these effects to those from low-LET radiation, such as gamma rays. Low-LET radiation is often used in medical imaging and radiotherapies for cancer, so humans are more often exposed to this class of radiation. The study showed that low-LET radiation did not create an oxidative environment in cells, though both types of radiation did induce a pro-inflammatory response.
High-LET radiation is found in solar flares and is made up of high-energy protons, charged iron particles, and some gamma radiation. The earth's atmosphere blocks the majority of this radiation, preventing exposure to these particles in normal life. High-LET radiation is known to cause a great deal of damage in a localized area, whereas the impact of low-LET tends to be more diffuse within a tissue.
Co-authors on the study include Kathryn Doiron and Albert J. Fornace, Jr, M.D., both of Georgetown's Lombardi Comprehensive Cancer Center.
Adapted from materials provided by Georgetown University Medical Center.

Fausto Intilla - www.oloscience.com

Radiation Risks For Astronauts On A Mission To Mars

Source:

http://www.sciencedaily.com/releases/2008/04/080414094156.htm

ScienceDaily (Apr. 14, 2008) — The European Space Agency (ESA) has chosen the GSI accelerator facility to assess radiation risks that astronauts will be exposed to on a Mars mission. GSI was selected because its accelerator is the only one in Europe able to create ion beams similar to those found in space. To determine possible health risks of manned space flights, scientists from all over Europe have been asked to investigate the effects of ion beams in human cells and organs. The first experiments will be launched this year and subsequently continued at GSI’s planned FAIR accelerator system.

Astronauts flying to the moon or Mars would be constantly bombarded by cosmic rays, whose health risks are not known in detail. Unlike the situation in space, the earth’s surface is largely shielded from cosmic rays by the planet’s atmosphere and magnetic field. In general, radiation can damage human cells and their genetic material. In addition to causing cancer, it can directly kill cells, which can later result in extensive damage in tissues including the brain.
The aim of the planned research activities is to quantitatively examine the biological effects of ion beams on the human genome and to determine how these effects would manifest themselves over time. For these tests, scientists will irradiate molecules and cell and tissue samples. The results of the research could then be used to develop optimized radiation shields for space exploration, which are a prerequisite for conducting safe missions to Mars.
The ion beams found in space have a wide variety of sources and can be derived from all types of elements, ranging from the lightest, hydrogen, to the heaviest, uranium. GSI’s accelerator facility can generate all types of ion beams, making it particularly well-suited for the planned research project. The research possibilities will be greatly expanded in the future by the FAIR accelerator facility, which will be able to produce even more energetic and intense ion beams.
Scientists are invited by ESA to submit proposals for experiments at GSI. The internationally leading scientists on the Biophysics & Radio-Biology Program Advisory Committee will begin reviewing initial applications in May, and the first experiments could be conducted as early as the end of this year.
Adapted from materials provided by Helmholtz Association of German Research Centres.

Fausto Intilla

www.oloscience.com

NASA Spacecraft Fine Tunes Course For Mars Landing

Source:

http://www.sciencedaily.com/releases/2008/04/080411091532.htm

ScienceDaily (Apr. 14, 2008) — NASA engineers have adjusted the flight path of the Phoenix Mars Lander, setting the spacecraft on course for its May 25 landing on the Red Planet.

"This is our first trajectory maneuver targeting a specific location in the northern polar region of Mars," said Brian Portock, chief of the Phoenix navigation team at NASA's Jet Propulsion Laboratory in Pasadena, Calif. The mission's two prior trajectory maneuvers, made last August and October, adjusted the flight path of Phoenix to intersect with Mars.
NASA has conditionally approved a landing site in a broad, flat valley informally called "Green Valley." A final decision will be made after NASA's Mars Reconnaissance Orbiter takes additional images of the area this month.
The orbiter's High Resolution Imaging Science Experiment camera has taken more than three dozen images of the area. Analysis of those images prompted the Phoenix team to shift the center of the landing target 13 kilometers (8 miles) southeastward, away from slightly rockier patches to the northwest. Navigators used that new center for planning today's maneuver.
The landing area is an ellipse about 62 miles by about 12 miles (100 kilometers by 20 kilometers). Researchers have mapped more than five million rocks in and around that ellipse, each big enough to end the mission if hit by the spacecraft during landing. Knowing where to avoid the rockier areas, the team has selected a scientifically exciting target that also offers the best chances for the spacecraft to set itself down safely onto the Martian surface.
"Our landing area has the largest concentration of ice on Mars outside of the polar caps. If you want to search for a habitable zone in the arctic permafrost, then this is the place to go," said Peter Smith, principal investigator for the mission, at the University of Arizona, Tucson.
Phoenix will dig to an ice-rich layer expected to lie within arm's reach of the surface. It will analyze the water and soil for evidence about climate cycles and investigate whether the environment there has been favorable for microbial life.
"We have never before had so much information about a Mars site prior to landing," said Ray Arvidson of Washington University in St. Louis. Arvidson is chairman of the Phoenix landing-site working group and has worked on Mars landings since the first successful Viking landers in 1976.
"The environmental risks at landing -- rocks and slopes -- represent the most significant threat to a successful mission. There's always a chance that we'll roll snake eyes, but we have identified an area that is very flat and relatively free of large boulders," said JPL's David Spencer, Phoenix deputy project manager and co-chair of the landing site working group.
Today's trajectory adjustment began by pivoting Phoenix 145 degrees to orient and then fire spacecraft thrusters for about 35 seconds, then pivoting Phoenix back to point its main antenna toward Earth. The mission has three more planned opportunities for maneuvers before May 25 to further refine the trajectory for a safe landing at the desired location.
In the final seven minutes of its flight on May 25, Phoenix must perform a challenging series of actions to safely decelerate from nearly 21,000 kilometers per hour (13,000 mph). The spacecraft will release a parachute and then use pulse thrusters at approximately 914 meters (3,000 feet) from the surface to slow to about 8 kilometers per hour (5 mph) and land on three legs.
"Landing on Mars is extremely challenging. In fact, not since the 1970s have we had a successful powered landing on this unforgiving planet. There's no guarantee of success, but we are doing everything we can to mitigate the risks," said Doug McCuistion, director of NASA's Mars Exploration Program at NASA Headquarters in Washington.
For more information about Phoenix, visit: http://www.nasa.gov/phoenix and http://phoenix.lpl.arizona.edu/.
The Phoenix mission is led by Peter Smith of the University of Arizona, Tucson, with project management at JPL and development partnership at Lockheed Martin, Denver. International contributions are provided by the Canadian Space Agency; the University of Neuchatel, Switzerland; the universities of Copenhagen and Aarhus, Denmark; the Max Planck Institute, Germany; and the Finnish Meteorological Institute.
Adapted from materials provided by NASA/Jet Propulsion Laboratory.

Fausto Intilla - www.oloscience.com

NASA Sets Sights On Lunar Dust Exploration Mission

Source: http://www.sciencedaily.com/releases/2008/04/080411092032.htm

ScienceDaily (Apr. 13, 2008) — NASA is preparing to send a small spacecraft to the moon in 2011 to assess the lunar atmosphere and the nature of dust lofted above the surface.

Called the Lunar Atmosphere and Dust Environment Explorer (LADEE), the mission will launch before the agency's moon exploration activities accelerate during the next decade. LADEE will gather detailed information about conditions near the surface and environmental influences on lunar dust. A thorough understanding of these influences will help researchers understand how future exploration may shape the lunar environment and how the environment may affect future explorers.
"LADEE represents a low-cost approach to science missions, enabling faster science return and more frequent missions," said Ames Director S. Pete Worden. "These measurements will provide scientific insight into the lunar environment, and give our explorers a clearer understanding of what they'll be up against as they set up the first outpost and begin the process of settling the solar system."
LADEE is a cooperative effort with NASA's Ames Research Center at Moffett Field, Calif., Goddard Space Flight Center in Greenbelt, Md., and Marshall Space Flight Center in Huntsville, Ala. The total cost of the spacecraft is expected to be approximately $80 million.
Ames will manage the mission, build the spacecraft and perform mission operations. Goddard will perform environmental testing and launch vehicle integration. The mission will be established within Marshall's newly created Lunar Science Program Office. Marshall will draw upon experience gained from managing a larger suite of low-cost, small satellite missions through NASA's Discovery and New Frontiers Program.
LADEE will fly to the moon as a secondary payload on the Discovery mission called Gravity Recovery and Interior Laboratory (GRAIL), which is designed to take ultra-precise gravity field measurements of the moon. Current plans call for the GRAIL and LADEE spacecraft to launch together on a Delta II rocket and separate after they are on a lunar trajectory. LADEE will take approximately four months to travel to the moon, then undergo a month-long checkout phase and begin 100 days of science operations.
LADEE is one of many activities to support lunar exploration planned by NASA's Science Mission Directorate in Washington. Last year, NASA also established a lunar science institute at Ames. Research teams will address current topics in basic lunar science and possible astronomical, solar and Earth science investigations that could be performed from the moon. In addition, NASA is preparing for scientific investigations following the planned launch later this year of the Lunar Reconnaissance Orbiter (LRO). After a 30-year hiatus, LRO represents NASA's first step toward returning humans to the moon.
Adapted from materials provided by National Aeronautics and Space Administration.

Fausto Intilla - www.oloscience.com