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Young Stars In Old Galaxies: A Cosmic Hide And Seek Game
Posted: Friday, June 28, 2002
Source: European Southern Observatory (ESO) (http://www.eso.org/)
Combining data from the NASA/ESA Hubble Space Telescope (HST) and the ESO Very Large Telescope (VLT), a group of European and American astronomers have made an unexpected, major discovery.
They have identified a huge number of "young" stellar clusters, only a few billion years old , inside an "old" elliptical galaxy (NGC 4365), probably aged some 12 billion years. For the first time, it has been possible to identify several distinct periods of star-formation in a galaxy as old as this one.
Elliptical galaxies like NGC 4365 have until now been considered to have undergone one early star-forming period and thereafter to be devoid of any star formation. However, the combination of the best and largest telescopes in space and on the ground has now clearly shown that there is more than meets the eye. This important new information will help to understand the early history of galaxies and the general theory of star formation in the Universe.
Do elliptical galaxies only contain old stars?
One of the challenges of modern astronomy is to understand how galaxies, those large systems of stars, gas and dust, form and evolve. In this connection, a central question has always been to learn when most of the stars in the Universe formed. Did this happen at a very early stage, within a few billion years after the Big Bang? Or were a significant number of the stars we now observe formed much more recently?
Spectacular collisions between galaxies take place all the time, triggering the formation of thousands or even millions of stars, cf. ESO PR Photo 29b/99 of the dramatic encounter between NGC 6872 and IC 4970. However, when looking at the Universe as a whole, most of its stars are found in large elliptical galaxies (this refers to their form) whose overall appearance has so far led us to believe that they, and their stars as well, are very old, indeed among the oldest objects in the Universe.
These elliptical galaxies do shine with the diffuse, reddish glow normally associated with stars that are many billions of years old. However, what is really the underlying mix of stars that produces this elderly appearance? Could perhaps a significant number of much younger stars be "hiding" among the older ones?
Whatever the case, this question must obviously be looked into, before it is possible to claim understanding of the evolution of these old galaxies. It is a very challenging investigation and it is only now that new and more detailed observations with the world's premier telescopes have been obtained that cast more light on this central question and thus on the true behaviour of some of the major building blocks of the Universe.
Cosmic archaeology
In order to identify the constitutents of the stellar "cocktail" in elliptical galaxies, a team of European and American astronomers [2] observed massive stellar clusters in and around several nearby galaxies. These clusters, referred to as "globular" because of their shape, are present in large numbers around most galaxies and together they form a kind of "skeleton" within their host galaxies.
These "bones" receive an imprint for every episode of star formation they undergo. Thus, by reading the ages of the globular clusters in a galaxy, it is possible to identify the past epoch(s) of active star formation in that galaxy.
This is like digging into the ruins of an ancient archaeological city site and to find those layers and establish those times when the city underwent bursts of building activity. In this way, by the study of the distribution and ages of the globular clusters in an elliptical galaxy, astronomers can reveal when many of its stars were formed.
A surprise discovery
The team combined images in visual light of a number of galaxies from Hubble's Wide Field and Planetary Camera 2 (WFPC2) with infrared images obtained with the multi-mode ISAAC instrument on the 8.2-m VLT ANTU telescope at the ESO Paranal Observatory (Chile). When measuring very accurately the colours of the globular clusters in one of these galaxies, NGC 4365 that is a member of the large Virgo Cluster of galaxies, they discovered to their great surprise that many of these clusters are only a few billion years old, i.e. much younger than the age of most other stars in that galaxy, roughly 12 billion years.
In fact, the astronomers were able to identify three major groups of globular clusters in NGC 4365. First, there is an old population of clusters of metal-poor stars, then there are some clusters of old, but metal-rich stars and now, seen for the first time, a third population of clusters with young and metal-rich stars.
"We needed the combination of the Hubble and the VLT with the latest space- and ground-based astronomical technology to break this new ground", says group leader Markus Kissler-Patig from the European Southern Observatory Headquarters in Garching (Germany). "Once we had found those young clusters, we then went on to observe them spectroscopically with another of the world's giant telescopes, the 10-m Keck on Hawaii - and this fully confirmed our results."
A new important clue to the evolution of the Universe
This is a surprising discovery since the stars in giant elliptical galaxies were until now believed to have formed exclusively early on in the history of the Universe.
However, it is now clear that some of the old galaxies may have been hiding their true nature and have indeed experienced much more recent periods of major star formation.
This is priceless new information for the current attempts to understand the early history of galaxies and the general theory of star formation in the Universe.
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More information
The information presented in this Press Release is based on a research article that has been accepted for publication in the European journal "Astronomy & Astrophysics" ("Extragalactic Globular Clusters in the Near-Infrared: II. The Globular Cluster Systems of NGC 3115 and NGC 4365" by Thomas H. Puzia, Stephen E. Zepf, Markus Kissler-Patig, Michael Hilker, Dante Minniti and Paul Goudfrooij; astro-ph/0206147).
The full text of this ESO Press Release, with two photos and one animated-GIF prsentation, is available at:
http://www.eso.org/outreach/press-rel/pr-2002/pr-11-02.html
Editor's Note: The original news release can be found at http://www.eso.org/outreach/press-rel/pr-2002/pr-11-02.html
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Posted: Tuesday, June 25, 2002
Source: BBC News Online's Helen Briggs
http://news.bbc.co.uk/2/hi/science/nature/1334512.stm
Northern Europeans could be descended from as few as 50 individuals who survived the last ice age.
New DNA evidence suggests that a few hundred Stone Age hunter-gatherers were the ancestors of many modern day northern Europeans.
One theory is that the population expanded from a small enclave of foragers who retreated south to an area of the Balkans or Spain to escape the spread of the glaciers.
Some Europeans are descended from neolithic farmers
If true, northern Europeans share essentially the same genetic makeup as their bison-hunting forefathers.
According to Oxford University's Ryk Ward, the genetic data fits in surprisingly well with archaeological clues.
"Around 20,000 years ago, the population of Europe was forced to retreat into an area where there were no glaciers," says Professor Ward of the Institute of Biological Anthropology.
"From that population base, a very small number of individuals then became the ancestors of the current [northern] European population."
Out-of-Africa
He says it is impossible to specify exact numbers, but he believes that about 1,000 individuals gave rise to the modern northern European gene pool, and possibly as few as 50.
According to the joint US and UK team, northern Europeans diverged from their African roots as recently as 27,000 to 53,000 years ago.
"From a genetic standpoint, this is the first evidence that such a bottleneck occurred in Europeans," he told BBC News Online.
The evidence comes from a study of stretches of human DNA that contain individual variations of just a single letter in the genetic code.
Individual variation
Scientists are interested in studying these tiny molecular differences (single nucleotide polymorphisms or SNPs) because they could explain why some people are more susceptible to common diseases than others.
But they also provide a tool for studying our genetic history, by measuring the amount of shuffling of human DNA that has occurred over time.
Many scientists believe that humans arose in Africa, and then spread and conquered the rest of the world.
But during this long journey, the genetic history of the human race underwent a series of twists and turns.
Northern Europeans share SNPs with the Nigerian population, says Eric Lander of the MIT/Whitehead Center for Genomic Research in Cambridge, Massachusetts.
But he says the European samples show large clumps of unshuffled genetic material, suggesting a recent breeding bottleneck.
The study is reported in the 10 May issue of the journal Nature.
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Neanderthal clues from mammoth find Posted: Tuesday, June 25, 2002
BBC
An excavation at a quarry in Norfolk has revealed what could be one of the best-preserved Neanderthal sites ever found in the UK.
Among the finds at the site are the skeletons from three or possibly four mammoths, including two metre-long tusks.
However, it is unclear whether these beasts were hunted, or their meat simply scavenged from corpses.
The remains, which came to light during gravel extraction earlier this year, are likely to reveal much about Neanderthal life.
Neanderthals are thought to have lived during the last Ice Age - perhaps becoming most prevalent some time around 60,000 years ago.
They are believed to have colonised the south of England - which was then linked by land to continental Europe.
Relatively little is known about their habits or abilities, or even their precise relationship to humans.
Traces of them have not been found after approximately 30,000 years ago, and it is possible that they were unable to compete with Homo sapiens.
The exact date of the site has not yet been fixed, but is probably from some time between 40,000 and 60,000 years ago.
David Miles, Chief Archaeologist at English Heritage, said: "It is extremely rare to find any evidence of Neanderthals and even rarer to find it in association with mammoth remains.
"We may have discovered a butchery site, or, what would be even more exciting, first evidence in Britain of a Neanderthal hunting site which would tell us much about their organisational and social abilities."
Other finds on the site include a large number of finely-fashioned flint axes in an elongated "D-shape".
Microanalysis of any residues on their edges could tell researchers how they were used.
Archaeologists also found teeth from a woolly rhino and an Ice Age reindeer antler.
The site is thought to have been a series of ponds at that time, used as a watering place by both animals and Neanderthals.
Dr Mark White, a Palaeolithic archaeologist from Durham University, said: "It is valid to speculate that the Neanderthals had gone to this watering place because they knew they would find prey to kill."
However, the extent of their killing abilities are still in doubt. The presence of carcass beetles among the mammoth remains suggests that some, or all of the massive creatures found there died naturally.
Dr Bill Bosmier, who led the excavation team, suggested that Neanderthals had their fill after the carcasses had been partially stripped by hyenas or other carnivores.
"However, given the size of a mammoth and the quantity of meat on it, it is equally possible that one or more of the mammoths at the site could have been killed and butchered by Neanderthals without leaving cutmarks on the bones."
Work is continuing on all the animal remains and artefacts taken from the site, funded by the Aggregates Levy Sustainability Fund, which is administered by English Heritage, English Nature and the Countryside Agency.
It is the first grant awarded from the fund.
Reproduced from:
http://news.bbc.co.uk/hi/english/sci/tech/
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New Cellular Evolution Theory Rejects Darwinian Assumptions Posted: Tuesday, June 18, 2002
Source: University Of Illinois At Urbana-Champaign (http://www.uiuc.edu/)
CHAMPAIGN, Ill. — Life did not begin with one primordial cell. Instead, there were initially at least three simple types of loosely constructed cellular organizations. They swam in a pool of genes, evolving in a communal way that aided one another in bootstrapping into the three distinct types of cells by sharing their evolutionary inventions. The driving force in evolving cellular life on Earth, says Carl Woese, a microbiologist at the University of Illinois at Urbana-Champaign, has been horizontal gene transfer, in which the acquisition of alien cellular components, including genes and proteins, work to promote the evolution of recipient cellular entities.
Woese presents his theory of cellular evolution, which challenges long-held traditions and beliefs of biologists, in the June 18 issue of the Proceedings of the National Academy of Sciences.
Cellular evolution, he argues, began in a communal environment in which the loosely organized cells took shape through extensive horizontal gene transfer. Such a transfer previously had been recognized as having a minor role in evolution, but the arrival of microbial genomics, Woese says, is shedding a more accurate light. Horizontal gene transfer, he argues, has the capacity to rework entire genomes. With simple primitive entities this process can "completely erase an organismal genealogical trace."
His theory challenges the longstanding Darwinian assumption known as the Doctrine of Common Descent – that all life on Earth has descended from one original primordial form.
"We cannot expect to explain cellular evolution if we stay locked in the classical Darwinian mode of thinking," Woese said. "The time has come for biology to go beyond the Doctrine of Common Descent."
"Neither it nor any variation of it can capture the tenor, the dynamic, the essence of the evolutionary process that spawned cellular organization," Woese wrote in his paper.
Going against traditional thinking is not new to Woese, a recipient of the National Medal of Science (2000), and holder of the Stanley O. Ikenberry Endowed Chair at Illinois.
In the late 1970s Woese identified the Archaea, a group of microorganisms that thrive primarily in extremely harsh environments, as a separate life form from the planet's two long-accepted lines – the typical bacteria and the eukaryotes (creatures like animals, plants, fungi and certain unicellular organisms, whose cells have a visible nucleus). His discovery eventually led to a revision of biology books around the world.
The three primary divisions of life now comprise the familiar bacteria and eukaryotes, along with the Archaea. Woese argues that these three life forms evolved separately but exchanged genes, which he refers to as inventions, along the way. He rejects the widely held notion that endosymbiosis (which led to chloroplasts and mitochondria) was the driving force in the evolution of the eukaryotic cell itself or that it was a determining factor in cellular evolution, because that approach assumes a beginning with fully evolved cells.
His theory follows years of analysis of the Archaea and a comparison with bacterial and eukaryote cell lines.
"The individual cell designs that evolved in this way are nevertheless fundamentally distinct, because the initial conditions in each case are somewhat different," Woese wrote in his introduction. "As a cell design becomes more complex and interconnected a critical point is reached where a more integrated cellular organization emerges, and vertically generated novelty can and does assume greater importance."
Woese calls this critical point in a cell's evolutionary course the Darwinian Threshold, a time when a genealogical trail, or the origin of a species, begins. From this point forward, only relatively minor changes can occur in the evolution of the organization of a given type of cell.
To understand cellular evolution, one must go back beyond the Darwinian Threshold, Woese said.
His argument is built around evidence "from the three main cellular information processing systems" – translation, transcription and replication – and he suggests that cellular evolution progressed in that order, with translation leading the way.
The pivotal development in the evolution of modern protein-based cells, Woese said, was the invention of symbolic representation on the molecular level – that is, the capacity to "translate" nucleic acid sequence into amino acid sequence.
Human language is another example of the evolutionary potential of symbolic representation, he argues. "It has set Homo sapiens entirely apart from its (otherwise very close) primitive relatives, and it is bringing forth a new level of biological organization," Woese wrote.
The advent of translation, he said, caused various archaic nucleic-based entities to begin changing into proteinaceous ones, emerging as forerunners of modern cells as genes and other individual components were exchanged among them. The three modern types of cellular organization represent a mosaic of relationships: In some ways one pair of them will appear highly similar; in others a different pair will.
This, Woese said, is exactly what would be expected had they individually begun as distinct entities, but during their subsequent evolutions they had engaged in genetic cross-talk – they had indulged in a commerce of genes.
Editor's Note: The original news release can be found at http://www.news.uiuc.edu/scitips/02/0617evoltion.html
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Newfound Planetary System Has "Hometown" Look Posted: Friday, June 14, 2002
Source: National Science Foundation (http://www.nsf.gov/)
After 15 years of observation and a lot of patience, the world's premier planet-hunting team has found a planetary system that reminds them of our home solar system.
Geoffrey Marcy, astronomy professor at the University of California, Berkeley, and astronomer Paul Butler of the Carnegie Institution of Washington, today announced the discovery of a Jupiter-like planet orbiting a Sun-like star at nearly the same distance as the Jovian system orbits our sun.
"All other extrasolar planets discovered up to now orbit closer to the parent star, and most of them have had elongated, eccentric orbits. This new planet orbits as far from its star as our own Jupiter orbits the sun,” said Marcy. The National Science Foundation (NSF) and NASA fund the planet-hunting team.
The star, 55 Cancri in the constellation Cancer, was already known to have one planet, announced by Butler and Marcy in 1996. That planet is a gas giant slightly smaller than the mass of Jupiter and whips around the star in 14.6 days at a distance only one-tenth that from Earth to the sun.
Using as a yardstick the 93-million mile Earth-sun distance, called an astronomical unit or AU, the newfound planet orbits at 5.5 AU, comparable to Jupiter's distance from our sun of 5.2 AU (about 512 million miles). Its slightly elongated orbit takes it around the star in about 13 years, comparable to Jupiter's orbital period of 11.86 years. It is 3.5 to 5 times the mass of Jupiter.
"We haven't yet found an exact solar system analog, which would have a circular orbit and a mass closer to that of Jupiter. But this shows we are getting close, we are at the point of finding planets at distances greater than 4 AU from the host star,” said Butler.
“I think we will be finding more of them among the 1,200 stars we are now monitoring," he added.
The team shared its data with Greg Laughlin, assistant professor of astronomy and astrophysics at the University of California, Santa Cruz. His dynamical calculations show that an Earth-sized planet could survive in a stable orbit between the two gas giants. For the foreseeable future, existence of any such planet around 55 Cancri will remain speculative.
Marcy, Butler and their team also announced a total of 15 new planets today, including the smallest ever detected: a planet circling the star HD49674 in the constellation Auriga at a distance of .05 AU, one-twentieth the distance from Earth to the sun. Its mass is about 15 percent that of Jupiter and 40 times that of Earth. This brings the total number of known planets outside our solar system to 91.
Discovery of a second planet orbiting 55 Cancri culminates 15 years of observations with the 3-meter (118-inch) telescope at Lick Observatory, owned and operated by the University of California. The team also includes Debra Fischer, UC Berkeley; Steve Vogt, UC Santa Cruz; Greg Henry, Tennessee State University, Nashville; and Dimitri Pourbaix, the Institut d'Astronomie et d'Astrophysique, Université Libre de Bruxelles.
Marcy and Butler used a technique that measures the slight Doppler shift in starlight caused by a wobble in the star’s position, due to the gravitational tug of an orbiting planet. By observing over a period of years, they can infer a planet’s approximate mass and orbital size and period.
The star 55 Cancri is 41 light years from Earth and is about 5 billion years old. Further data are needed to determine whether yet another planet is orbiting it, because the two known planets do not explain all the observed Doppler wobbling. One possible explanation is a Saturn-mass planet orbiting about .24 AU from the star.
For more information, see: http://exoplanets.org
An artist's concept and animation will be available June 13 at: http://www.jpl.nasa.gov/images/newplanets
Editor's Note: The original news release can be found at http://www.nsf.gov/od/lpa/news/02/pr0254.htm
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Chandra Detects First Possible Evidence Of Gravity's Effect On Neutron Star's Radiation Posted: Wednesday, June 12, 2002
Source: NASA/Marshall Space Flight Center (http://www.msfc.nasa.gov)
With NASA's Chandra X-ray Observatory, astronomers have detected features that may be the first direct evidence of the effect of gravity on radiation from a neutron star. This finding, if confirmed, could enable scientists to measure the gravitational field of neutron stars and determine whether they contain exotic forms of matter not seen on Earth.
A team led by George Pavlov of Penn State University in University Park observed 1E 1207.4-5209, a neutron star in the center of a supernova remnant about 7,000 light years from Earth. The results were presented on June 6, 2002, at the American Astronomical Society in Albuquerque, N.M.
Pavlov's group found two dips, or absorption features, in the spectrum of X-rays from the star. If these dips are due to the absorption of X-rays near the star by helium ions in a strong magnetic field, they indicate that the gravitational field reduces the energies of X-rays escaping from near the surface of a neutron star.
"This interpretation is consistent with the data," said Pavlov, "but the features may be a blend of many other features. More precise measurements, preferably with Chandra's grating spectrometer, are needed."
"These absorption features may be the first evidence of the effect of gravity on radiation near the surface of an isolated neutron star," said Pavlov. "This is particularly important because it would allow us to set limits on the type of matter that comprises this star."
Neutron stars are formed when a massive star runs out of fuel and its core collapses. A supernova explosion occurs and the collapsed core is compressed to a hot object about 12 miles in diameter, with a thin atmosphere of hydrogen and possibly heavier ions in a gravitational field 100 billion times as strong as Earth's.
These objects, which have a density of more than 1 billion tons per teaspoonful, are called neutron stars because they have been thought to be composed mostly of neutrons. Although neutron stars have been studied extensively for more than three decades, their exact nature is still unknown.
"We are not even sure that neutron stars are composed of neutrons," said Divas Sanwal, also of Penn State, and lead author on a paper describing the team's results. "They could be largely composed of subatomic particles called pions or kaons, or even free quarks."
One key to narrow the range of possibilities is to measure the strength of gravity on the surface of a neutron star by observing its effect on X-rays from very near the surface of the star. According to Einstein's theory of General Relativity, attraction of photons by a star's gravitational field results in a lower energy of the photon (longer wavelength of radiation) when detected by a distant observer. The measurement of this gravitational redshift relates the mass to the radius of the star, and it will test the theories for the various possible forms of dense matter.
The team, which also includes Slava Zavlin of Max Plank Institute for Extraterrestrial Physics, Germany, and Marcus Teter of Penn State, considered several possible explanations for the absorption features observed from 1E 1207. The strength and X-ray energy of the features make it improbable that they are due to intervening interstellar material or absorption due to electrons or ions circling in a strong magnetic field. The most likely hypothesis, they conclude, is that the features are due to absorption by helium ions in a magnetic field about a hundred trillion times more intense than the Earth's magnetic field. In this case, the gravitational redshift reduces the energy of the X-rays by 17 percent.
Pavlov and his colleagues observed 1E 1027 with Chandra's Advanced CCD Imaging Spectrometer on January 6, 2000, and again on January 5, 2002, each time for approximately 30,000 seconds.
The ACIS instrument was built for NASA by Penn State and the Massachusetts Institute of Technology, Cambridge, Mass. under the leadership of Gordon Garmire of Penn State. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the Office of Space Science, Washington, D.C. TRW, Inc., Redondo Beach, Calif., is the prime contractor for the spacecraft. The Smithsonian's Chandra X-ray Center controls science and flight operations from Cambridge.
Images associated with this release are available on the World Wide Web at:
http://chandra.harvard.edu
AND
http://chandra.nasa.gov
Editor's Note: The original news release can be found at http://www1.msfc.nasa.gov/NEWSROOM/news/releases/2002/02-146.html
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100,000-Year Climate Pattern Linked To Sun's Magnetic Cycles Posted: Friday, June 7, 2002
Source: Dartmouth College (http://www.dartmouth.edu/)
HANOVER, N.H. – Thanks to new calculations by a Dartmouth geochemist, scientists are now looking at the earth's climate history in a new light. Mukul Sharma, Assistant Professor of Earth Sciences at Dartmouth, examined existing sets of geophysical data and noticed something remarkable: the sun's magnetic activity is varying in 100,000-year cycles, a much longer time span than previously thought, and this solar activity, in turn, may likely cause the 100,000-year climate cycles on earth. This research helps scientists understand past climate trends and prepare for future ones.
Published in the June 10 issue of Earth and Planetary Science Letters (Elsevier, volume 199, issues 3-4), Sharma's study combined data on the varying production rates of beryllium 10, an isotope found on earth produced when high-energy galactic cosmic rays bombard our atmosphere, and data on the past variations in the earth's magnetic field intensity. With this information, Sharma calculated variations in solar magnetic activity going back 200,000 years, and he noticed a pattern.
Over the last 1 million years, the earth's climate record has revealed a 100,000-year cycle oscillating between relatively cold and warm conditions, and Sharma's data on the sun's magnetic activity corresponded to the earth's ice age history.
"Surprisingly, it looks like solar activity is varying in longer time spans than we realized," says Sharma. "We knew about the shorter cycles of solar activity, so maybe these are just little cycles within a larger cycle. Even more surprising is the fact that the glacial and interglacial periods on earth during the last 200,000 years appear to be strongly linked to solar activity."
Sharma's calculations suggest that when the sun is magnetically more active, the earth experiences a warmer climate, and vice versa, when the sun is magnetically less active, there is a glacial period. Right now, the earth is in an interglacial period (in between ice ages) that began about 11,000 years ago, and as expected, this is also a time when the estimated solar activity appears to be high.
Beryllium 10 is useful for studying the geology from hundreds of thousands of years ago mainly because it has a half-life of about one and a half million years. In addition, there are two key factors that have affected beryllium 10 production over the last 200,000 years: the earth's magnetic field and the sun's magnetic activity. When there are high-intensity solar magnetic storms, more charged particles are interacting with cosmic rays, and less beryllium 10 is produced. Likewise, the earth's magnetic field changes the flux of cosmic rays into and out of the atmosphere.
Since the production rate of beryllium 10 and earth's magnetic field intensity are known for the last 200,000 years, Sharma could calculate solar magnetic activity for this time period.
"I took sets of existing, independent data and made new comparisons and calculations," says Sharma. Then he went a step further to make a connection with the history of ice ages by looking at oxygen isotopes in the oceans, which reveal the history of how much ice was at the poles and are therefore a measure of average global surface temperature.
"I compared the estimated past variations in the solar activity with those of the oxygen isotopes in the ocean. Although there is a strong relationship between solar activity and oxygen isotopic variations, it is too early to say exactly what is the mechanism though which the sun is influencing the terrestrial climate."
One explanation of the 100,000-year cycle was offered by the Milankovitch Theory of Ice Ages in the 1940s, which suggested that the cyclical variations in the earth's orbit around the sun result in the earth receiving varying amounts of solar radiation that, in turn, control the climate. This explanation is under dispute because the variations of the solar energy in relation to the changes in orbit are very small. Other current research focuses on past variations in the sun's irradiance, or heat intensity (as opposed to the magnetic activity).
Sharma notes that more analysis is needed to test his theory. "I've only looked at 200,000 years. My calculations need to be verified for a million years, for instance. Plus, regarding the current global warming debate, it still needs to be examined if the role of solar activity will exacerbate the rising temperatures that result from carbon dioxide buildup in the atmosphere."
This work was supported by Dartmouth College, the Max Planck Institute and by a grant from the National Science Foundation.
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Black Holes In Distant Galaxies Point To Wild Youth Posted: Wednesday, June 5, 2002
Source: NASA/Marshall Space Flight Center (http://www.msfc.nasa.gov)
Like 'flower power' tattoos on aging ex-hippy baby boomers, unexpectedly large numbers of neutron stars and black holes in elliptical galaxies suggest some of these galaxies lived through a much wilder youth. The discovery by NASA's Chandra X-ray Observatory may require a revision of how elliptical galaxies evolved.
"For the first time, Chandra has allowed us to distinguish hundreds of star-like sources that are black holes and neutron stars in distant elliptical galaxies," said Craig Sarazin of the University of Virginia who presented his team's findings on three elliptical galaxies, known as NGC 4697, NGC 4649, and NGC 1553, today at the American Astronomical Society meeting in Albuquerque, N.M. "The black holes and neutron stars we now see in these elliptical galaxies are reminders of their very active past."
Black holes and neutron stars are the "stellar corpses" of the brightest, most massive and short-lived stars. The presence of numerous neutron stars and black holes shows that these galaxies once contained many very bright, massive stars. This is in marked contrast to the present populations of lower-mass, faint, old stars that now dominate elliptical galaxies.
The black holes and neutron stars found by Chandra in these galaxies appear to be members of binary star systems. The strong pull of gravity from the collapsed star pulls material off the normal star. This material emits large amounts of X-rays as it falls into the black hole or neutron star.
The Chandra observations also show that most of the binary star systems that contain black holes are not scattered randomly among the stars in the elliptical galaxies. Instead, most of the X-ray binaries are located in "globular star clusters," round balls of stars, containing about one million stars in a region of the galaxy where typically only one would be found.
The high fraction of black hole binaries found in globular star clusters suggests that the black holes captured a single star or pulled it away from its original companion. Normally, the distances between stars in galaxies are too great for capture to occur, but in the extraordinarily dense environment of globular clusters they may be much more common.
"Chandra has shown us that the birthplace of these exotic black hole binary systems are in the dense globular clusters," said Joel Bregman, a collaborator at the University of Michigan, Ann Arbor.
"Globular clusters appear to be the 'singles bars' of the stellar world," said Sarazin, "where a lonely black hole can go to find a companion."
Other members of the research team include Elizabeth L. Blanton, Scott W. Randall, and Gregory R. Sivakoff, all of University of Virginia, and Jimmy Irwin of University of Michigan.
The observations were made with Chandra's Advanced CCD Imaging Spectrometer, which was built for NASA by Penn State and the Massachusetts Institute of Technology, Cambridge, Mass. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the Office of Space Science, Washington, D.C. TRW, Inc., Redondo Beach, Calif., is the prime contractor for the spacecraft. The Smithsonian's Chandra X-ray Center controls science and flight operations from Cambridge.
Images associated with this release are available on the World Wide Web at:
http://chandra.harvard.edu
AND
http://chandra.nasa.gov
Editor's Note: The original news release can be found at http://www1.msfc.nasa.gov/NEWSROOM/news/releases/2002/02-144.html
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Black Hole Dynamo May Be Cosmos' Ultimate Electricity Generator Posted: Tuesday, June 4, 2002
Source: Los Alamos National Laboratory (http://www.lanl.gov/)
ALBUQUERQUE, N.M., June 3, 2002 - Researchers at the U.S. Department of Energy's Los Alamos National Laboratory believe that magnetic field lines extending a few million light years from galaxies into space may be the result of incredibly efficient energy-producing dynamos within black holes that are somewhat analogous to an electric motor. Los Alamos researchers Philipp Kronberg, Quentin Dufton, Stirling Colgate and Hui Li today discussed this finding at the American Astronomical Society meeting in Albuquerque, N.M.
By interpreting radio waves emanating from the gigantic magnetic fields, the researchers were able to create pictures of the fields as they extended from an object believed to be a black hole at the center of a galaxy out into regions of intergalactic space. Because the class of galaxies they studied are isolated from other intergalactic objects and gas - which could warp, distort or compress the fields - the fields extend a distance of up to ten million light years.
The energy in these huge magnetic fields is comparable to that released into space as light, X-rays and gamma rays. In other words, the black hole energy is being efficiently converted into magnetic fields. The mechanism is not yet fully understood, but Kronberg and his colleagues believe a black hole accretion disk could be acting similarly to an electric motor.
Colgate and Los Alamos colleagues Vladimir Pariev and John Finn have developed a model to perhaps explain what is happening. They believe that the naturally magnetized accretion disk rotating around a black hole is punctured by clouds of stars in the vicinity of the black hole, like bullet holes in a flywheel. This, in turn, leads nonlinearly to a system similar to an electric generator that gives rise to a rotating, but invisible magnetic helix.
In this way, huge amounts of energy are carried out and away from the center of a galaxy as a set of twisted magnetic field lines that eventually appear via radio waves from luminous cloud formations on opposite sides of the galaxy.
The Los Alamos researchers are calculating methods by which enormous amounts of expelled magnetic energy are converted into heat - manifested in the form of a relativistic gas of cosmic rays that create radio energy that can be detected by radio telescopes such as the Very Large Array. Although the exact mechanism is still a mystery, the Los Alamos researchers believe that a sudden reconnection or fusing of the magnetic field lines creates and accelerates the cosmic rays.
The researchers still don't understand why this fast magnetic field reconnection occurs. But understanding the mechanism could have important applications here on Earth such as creating a system of magnetic confinement for a fusion energy reactor.
The Los Alamos research is supported by the Laboratory Directed Research and Development Program and the Institute of Geophysics and Planetary Physics. The Natural Sciences and Engineering Research Council of Canada also provided support.
Los Alamos recently joined Southwest Universities consortium, which is hoping to build a very low frequency radio telescope called "LOFAR" in New Mexico or West Texas. The new telescope will be an excellent instrument for detecting hidden magnetic energy of the type the Los Alamos research team is interested in studying.
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Editor's Note: The original news release can be found at http://www.lanl.gov/worldview/news/releases/archive/02-062.shtml
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