|Hypergiant Star Disks! |
Galactic RAVE-in! Fat Glamour?
Grabens of Mars! Man In The Moon!
Ancient Man: Love Not War!
|Hypergiant Star Disks! |
This illustration compares the size of a gargantuan star and its surrounding dusty
disk (top) to that of our solar system. Monstrous disks like this one were discovered
around two "hypergiant" stars by NASA's Spitzer Space Telescope. Astronomers
believe these disks might contain the early "seeds" of planets or, possibly, leftover
debris from planets that already formed. (RIT)
Rochester Institute of Technology News Release
February 8, 2006 - The discovery of dusty disks - the building blocks of planets -around two of the most massive stars known suggests that planets might form and survive in surprisingly hostile environments.
The discovery was made through NASA's Spitzer Space Telescope observations of two hypergiant stars in the Large Magellanic Cloud--the Milky Way's nearest neighboring galaxy--by a team led by Joel Kastner, a professor at Rochester Institute of Technology's Chester F. Carlson Center for Imaging Science. His team's findings will appear in the Feb. 10 issue of Astrophysical Journal Letters.
So far, searches for planets outside the solar system have been restricted to sun-like stars. All of these stars are older, dimmer and cooler objects than hypergiants, which are extraordinarily large and luminous but shorter-lived by billions of years.
Kastner and his team used infrared spectra obtained by Spitzer to study a population of dying stars.
They added a new direction to their project when Spitzer's infrared spectrograph revealed unexpected information. Spitzer's sensitive spectrometer, which breaks down infrared radiation into component wavelengths as a prism splits visible light into a rainbow, indicated that a third of the stars in the population thought to be in decline--including two massive and exceedingly luminous hypergiants--were actually younger stars in varying stages of development.
The curious spectra of these two hypergiants (R126 and R66) - with one star being 70 times bigger than the sun - led Kastner to reexamine the stars' classifications as dying. The shape of the spectra, or the amount of light from different wavelengths, is characteristic of flattened disks of dust orbiting the stars.
The two stars' similar spectra differ in detail, with one encircled by dust in crystalline form, the other by more shapeless, amorphous dust grains. This expands the range of known conditions under which complex dust grains and molecules can form and persist around stars, Kastner says.
Kastner describes the complex mixture of dust detected around the stars as the "tip of the iceberg," probably signaling that the disks of debris surrounding the stars are similar to the solar system's Kuiper Belt, a vast, distant collection of comet- and even Pluto-like objects. "To explain the very strong infrared radiation we detected, the stars we observed would have to host especially large Kuiper belts," he says.
He adds: "If Kuiper belts are the smoking guns of planetary formation around stars, it seems that these stars, as massive as they are, may be forming planets."
Hypergiants are only a few million years old and have a relatively short lifespan as far as stars go, considering the billions of years it will take the sun to expire.
"These planetary systems, if they do form and exist, are short lived because these massive stars explode as supernovae," Kastner says. "So it's amazing that the raw material for planets could be found in such a hostile environment."
Kastner's study highlights only two of more than a dozen or so known examples of very massive stars in the Large Magellanic Cloud that are bright infrared sources. The next phase of the study will use new Spitzer spectra of the additional hypergiant stars to determine how many more are encircled by dusty disks and why only some of these disks contain crystalline dust grains.
"We've discovered a new class of object, and we need to use Spitzer to measure the infrared spectra of a lot more of these objects to learn how unique they really are," Kastner says.
Kastner's team includes Catherine Buchanan from RIT and B. Sargent and W.J. Forrest from the University of Rochester.
Rochester Institute of Technology - http://www.rit.edu
|Galactic RAVE-in! |
Johns Hopkins University News Release
February 10, 2006 - An international team of astronomers released to the public the first data collected as part of the Radial Velocity Experiment, an ambitious spectroscopic survey aimed at measuring the speed, temperature, surface gravity and composition of up to a million stars passing near the sun.
The measurements, released at an astrophysics workshop at the Aspen Center for Physics in Colorado and available today online to other astronomers, includes examination of old "fossil" stars that were born when our Milky Way galaxy was in its infancy.
Team members posit that such data may eventually provide evidence to back up theories that our galaxy has -- over time -- "cannibalized" other, smaller galaxies and is "digesting" them.
"Our research focuses on the oldest stars, and probes the earliest phases of the evolution of our home galaxy, the Milky Way," said Rosemary Wyse, a professor in the Henry A. Rowland Department of Physics and Astronomy in Johns Hopkins' Krieger School of Arts and Sciences and a member of the RAVE team. "The unprecedented sample available with RAVE will allow me -- and now, with the release of this data, others -- to test ideas of our origins laid out by various cosmological theories."
The team also includes members from the United States, Germany, Australia, Canada, the Netherlands, the United Kingdom, Slovenia, Italy, Switzerland and France.
The survey has been made possible by the unique capabilities of the "six-degree field" multi-object spectrograph on the 1.2-meter UK Schmidt Telescope of the Anglo-Australian Observatory, located at Siding Spring Observatory in New South Wales, Australia. This instrument is capable of obtaining spectroscopic information for as many as 150 stars at once, from an area of the sky equal to more than 150 times the area covered by the full moon.
"The data we are making public today is twice the sample size of any previous survey, and has extremely high quality," Wyse said. "Other astronomers can definitely use these data in their work. All they have to do is go to our Web site and download it."
Stars in our Milky Way galaxy (NASA)
The RAVE survey measures the velocities of stars along the line of sight, something that has previously been difficult to obtain for such large samples of stars. Data from RAVE's first year of operation consists of information from some 25,000 stars, including measurement of their brightness, color and motion across the sky.
"This data set will provide a unique resource for all astronomers working in the field of galactic evolution and, with our public data release, the astronomical community can participate in our endeavor," says Tomaz Zwitter of the Ljubljana University in Slovenia and project scientist of the RAVE survey. "This first sample by itself is already two times the size of the previous largest survey of stars near the sun."
Matthias Steinmetz, director of the Astrophysical Institute Potsdam, and leader of the RAVE collaboration, predicted that "the full RAVE survey will provide a vast resource of stellar motions and chemical abundances, allowing us to answer fundamental questions of the formation and evolution of our galaxy."
Funding for RAVE is provided by the National Science Foundation for Johns Hopkins, and by the national research councils of other team members' countries, as well as by private sources.
RAVE - http://www.rave-survey.org
Johns Hopkins University - http://www.jhu.edu
|Fat Glamour? |
University of Chicago Press Journals
February 10, 2006 - Waifish models have long been accused of setting unrealistic beauty standards and lowering self-esteem.
Some companies, such as Dove, have switched to using more realistic-looking models in conjunction with empowering messages.
However, an important new study in the March 2006 issue of the Journal of Consumer Research reveals that, contrary to many assumptions, looking at moderately heavy models actually lowers most women's self-esteem, while looking at moderately thin models raises it.
"We demonstrated that exposure to thin models does not necessarily have a negative impact on one's self-esteem," explain Dirk Smeesters (Tilburg University) and Naomi Mandel (Arizona State University). "On the contrary, exposure to moderately thin (but not extremely thin) models has a positive impact on one's self-esteem."
In the first part of the study, participants selected four representative models in each category – extremely thin, moderately thin, moderately heavy, and extremely heavy – from a larger sample of images. These images were then shown to randomly chosen women in conjunction with a "lexical decision trial" – that is, the participants were timed as they responded to words related to thinness and heaviness.
Looking at moderately thin or extremely heavy models led to an increase in self-perception of thinness and an increase in self-esteem. By contrast, seeing extremely thin or moderately heavy models focused women's thoughts on how heavy they felt.
These results shed light on why magazines featuring only plus-sized models don't have the success of the magazine that feature slim models: "…campaigns featuring moderately heavy 'real women' might not be as inspirational (or effective) as expected," conclude Smeesters and Mandel.
University of Chicago Press Journals - http://www.journals.uchicago.edu
|Grabens of Mars |
This perspective view, looking down and to the north shows
pits and tectonic ‘grabens’ in the Phlegethon Catena region
of Mars. (ESA/ DLR/ FU Berlin - G. Neukum)
European Space Agency News Release
February 9, 2006 - These images, taken by the High Resolution Stereo Camera (HRSC) on board ESA’s Mars Express spacecraft, show pits and tectonic ‘grabens’ in the Phlegethon Catena region of Mars.
The HRSC obtained these images during orbit 1217 with a ground resolution of approximately 11.9 metres per pixel. The scenes show the region of Phlegethon Catena, centred at approximately 33.9° South and 253.1° East.
Located south-east of the Alba Patera volcano, Phlegethon Catena is a region exhibiting a high density of tectonic grabens, which are blocks of terrain that have dropped relative to their surroundings as a result of a geological extension of the crust.
In the colour image, this swarm of grabens trends roughly north-east to south-west, with individual widths ranging from approximately one half to ten kilometres.
The series of closely spaced depressions that exhibit a similar orientation to the grabens is described by the term ‘catena’.
These depressions are rimless, circular to elliptical and range from roughly 0.3 to 2.3 kilometres across.
Oblique perspective view taken by the High Resolution
Stereo Camera (HRSC) on board ESA’s Mars Express
spacecraft. (ESA/ DLR/ FU Berlin - G. Neukum)
The grabens may have formed as the result of stresses associated with the formation of Alba Patera, which rises three to four kilometres above the surrounding plains, or the Tharsis rise to the south, which reaches up to ten kilometres high.
It is unclear what process is responsible for the chain of depressions.
One possibility is the collapse of the surface due to the removal of subsurface materials, while other suggestions include that tension cracks may have formed in the subsurface and caused subsequent collapse.
The colour scenes have been derived from the three HRSC-colour channels and the nadir channel.
The perspective views have been calculated from the digital terrain model derived from the stereo channels.
The 3D anaglyph image was calculated from the nadir and one stereo channel. Image resolution has been decreased for use on the internet.
European Space Agency - http://www.esa.int
|Uganda Draining Lake Victoria |
Lake Victoria, the world's second largest
New Scientist News Release
By Fred Pearce
February 8, 2006 - East Africa's Lake Victoria, the world's second largest freshwater lake, is being secretly drained to keep the lights on in Uganda. A report published this week says Uganda is flouting a 50-year-old international agreement designed to protect the lake's waters.
Covering nearly 70,000 square kilometres, Lake Victoria takes a big bite out of surrounding Uganda, Kenya and Tanzania. An estimated 30 million people depend on it for their livelihoods. Since 2003, however, the lake has lost 75 cubic kilometres of water, about 3 per cent of its volume,leaving international ferries stranded far from their jetties, fishing boats mired in mud, and towns running low on water.
The only outlet for Lake Victoria, which is ringed by mountains, is at Jinja in Uganda, where it forms the Victoria Nile. Until 1954, the lake emptied into the Nile over a natural rock weir, but that year British colonial engineers blasted out the weir and replaced it with the Owens Falls dam, now renamed the Nalubaale dam, which effectively transformed the lake into a giant hydroelectric reservoir.
At the time, engineers agreed that the amount of water flowing through the dam's turbines should mimic the old natural flow over the weir. The formula -- known as the "agreed curve" -- set a maximum flow of between 300 and 1700 cubic metres per second, depending on the water level in the lake. The agreed curve remains in force today under a treaty with Egypt, the ultimate user of most of the Nile's water.
In 2002, Uganda finished building a second hydropower complex close to the first one. Soon after its completion people began to notice the water level falling, and today the lake is at an 80-year low. In recent weeks, the operator of the two dams, the Uganda Electricity Generating Company, has blamed disruption of electricity supplies on low lake levels, ostensibly caused by the 10 to 15 per cent decline in rainfall across the lake's catchment area during the past two years.
However, it now seems that the dams themselves are as much to blame as the recent drought. Daniel Kull, a hydrologist with the UN's International Strategy for Disaster Reduction in Nairobi, Kenya, calculates that if the dams had been operated according to the agreed curve during the past two years, the drought would have caused only half the water loss actually seen.
Lake Victoria (BBC)
"Today's lake levels would be around 45 centimetres higher," he writes in a report released this week by the California-based environmental lobby group, International Rivers Network.
Kull estimates that in the past two years, the Ugandan dams have released water at an average of almost 1250 cubic metres per second. That is 55 per cent more than the flow permitted for the relevant water levels.
While Uganda does not routinely publish figures on the dams' operations, Kull says sporadic official reports show that releases were nearly twice the permitted rates in both March and November 2005 -- supporting his conclusion.
"This dam complex is pulling the plug on Lake Victoria," says Frank Muramuzi of Uganda's National Association of Professional Environmentalists.
New Scientist - http://www.newscientist.com
|The Man in the Moon |
Ohio State University News Release
COLUMBUS OHIO February 9, 2006 – Ohio State University planetary scientists have found the remains of ancient lunar impacts that may have helped create the surface feature commonly called the "man in the moon."
Their study suggests that a large object hit the far side of the moon and sent a shock wave through the moon's core and all the way to the Earth-facing side. The crust recoiled -- and the moon bears the scars from that encounter even today.
The finding holds implications for lunar prospecting, and may solve a mystery about how past impacts on Earth affect it's geology today.
The early Apollo missions revealed that the moon isn't perfectly spherical. Its surface is warped in two spots; an earth-facing bulge on the near side is complemented by a large depression on the Moon's far side. Scientists have long wondered whether these surface features were caused by Earth's gravity tugging on the moon early in its existence, when its surface was still molten and malleable.
According to Laramie Potts and Ralph von Frese, a postdoctoral researcher and professor of geological sciences respectively at Ohio State , these features are instead remnants from ancient impacts.
Potts and von Frese came to this conclusion after they used gravity fluctuations measured by NASA's Clementine and Lunar Prospector satellites to map the moon's interior. They reported the results in a recent issue of the journal Physics of the Earth and Planetary Interiors.
They expected to see defects beneath the moon's crust that corresponded to craters on the surface. Old impacts, they thought, would have left marks only down to the mantle, the thick rocky layer between the moon's metallic core and its thin outer crust. And that's exactly what they saw, at first.
Potts pointed to a cross-sectional image of the moon that the scientists created using the Clementine data. On the far side of the moon, the crust looks as though it was depressed and then recoiled from a giant impact, he said. Beneath the depression, the mantle dips down as he and von Frese would expect it to do if it had absorbed a shock.
Evidence of the ancient catastrophe should have ended there. But some 700 miles directly below the point of impact, a piece of the mantle still juts into the moon's core today.
That was surprising enough. "People don't think of impacts as things that reach all the way to the planet's core," von Frese said.
The man in the moon (purple)
But what they saw from the core all the way to the surface on the near side of the moon was even more surprising. The core bulges, as if core material was pushed in on the far side and pulled out into the mantle on the near side. Above that, an outward-facing bulge in the mantle, and above that -- on the Earth-facing side of the moon -- sits a bulge on the surface.
To the Ohio State scientists, the way these features line up suggests that a large object such as an asteroid hit the far side of the moon and sent a shock wave through the core that emerged on the near side.
The scientists believe that a similar, but earlier impact occurred on the near side.
Potts and von Frese suspect that these events happened about four billion years ago, during a period when the moon was geologically active -- with its core and mantle still molten and magma flowing.
Back then, the moon was much closer to the Earth than it is today, Potts explained, so the gravitational interactions between the two were stronger.
When magma was freed from the Moon's deep interior by the impacts, Earth's gravity took hold of it and wouldn't let go.
So the warped surfaces on the near and far sides of the moon and the interior features that connect them are all essentially signs of injuries that never healed.
"This research shows that even after the collisions happened, the Earth had a profound effect on the moon," Potts said.
The impacts may have created conditions that led to a prominent lunar feature.
The "man in the moon" is a collection of dark plains on the Earth-facing side of the moon, where magma from the moon's mantle once flowed out onto the surface and flooded lunar craters. The moon has long since cooled, von Frese explained, but the dark plains are a remnant of that early active time -- "a frozen magma ocean."
How that magma made it to the surface is a mystery, but if he and Potts are right, giant impacts could have created a geologic "hot spot" on the moon – a site where magma bubbles to the surface. Some time between when the impacts occurred and when the moon solidified, some magma escaped the mantle through cracks in the crust and flooded the nearside surface and formed a lunar “hot spot”.
A hot spot on Earth forms the volcanoes that make the Hawaiian island chain. The Ohio State scientists wondered: could similar ancient impacts have penetrated the Earth, and caused the hot spots that exist here today? von Frese thinks that it's possible.
"Surely Earth was peppered with impacts, too," he said. "Evidence of impacts here is obscured, but there are hot spots like Hawaii . Some hot spots have corresponding hot spots on the opposite side of the Earth. That could be a consequence of this effect."
He and Potts are exploring the idea, by studying gravitational anomalies under the Chicxulub Crater on Mexico 's Yucatan Peninsula . A giant asteroid struck the spot some 65 million years ago, and is believed to have set off an environmental chain reaction that killed the dinosaurs.
NASA funded this research. The space agency has been charged with returning astronauts to the moon to prospect for valuable gases and minerals.
But even today, scientists don't entirely know what the moon is made of – not down to the core, anyway. They can calculate where certain minerals should be, given the conditions they believe existed when the moon formed. But impacts like the one Potts and von Frese discovered have since shuffled materials around. Gravity measurements, they said, will play a key role as scientists figure out what materials lie within the moon, and where.
"We don't fully understand the way these minerals settle out under temperature and pressure, so the exact composition of the moon is difficult to determine. We have to use gravity measurements to calculate the density of materials, and then use that information to extrapolate the likely composition," Potts said.
von Frese said a lunar base would be needed before scientists can more completely answer these questions.
Potts agreed. "Once we have more rock samples and soil samples, we will have a lot more to go on. Nothing is better than having a person on the ground," he said.
Ohio State University - http://researchnews.osu.edu
|Ancient Man: Love Not War! |
Templeton has shown that the African populations interbred
with the Eurasian populations — thus, making love, not war.
Washington University in St. Louis News Release
By Tony Fitzpatrick
February 2, 2006 — A new, more robust analysis of recently derived human gene trees by Alan R. Templeton, Ph.D, of Washington University in St Louis, shows three distinct major waves of human migration out of Africa instead of just two, and statistically refutes — strongly — the 'Out of Africa' replacement theory.
That theory holds that populations of Homo sapiens left Africa 100,000 years ago and wiped out existing populations of humans. Templeton has shown that the African populations interbred with the Eurasian populations — thus, making love, not war.
"The 'Out of Africa' replacement theory has always been a big controversy," Templeton said. "I set up a null hypothesis and the program rejected that hypothesis using the new data with a probability level of 10 to the minus 17th. In science, you don't get any more conclusive than that. It says that the hypothesis of no interbreeding is so grossly incompatible with the data, that you can reject it."
Templeton's analysis is considered to be the only definitive statistical test to refute the theory, dominant in human evolution science for more than two decades.
"Not only does the new analysis reject the theory, it demolishes it," Templeton said.
Templeton published his results in the Yearbook of Physical Anthropology, 2005.
A trellis, not a tree
He used a computer program called GEODIS, which he created in 1995 and later modified with the help of David Posada, Ph.D., and Keith Crandall, Ph.D. at Brigham Young University, to determine genetic relationships among and within populations based on an examination of specific haplotypes, clusters of genes that are inherited as a unit.
In 2002, Templeton analyzed ten different haplotype trees and performed phylogeographic analyses that reconstructed the history of the species through space and time.
Three years later, he had 25 regions to analyze and the data provided molecular evidence of a third migration, this one the oldest, back to 1.9 million years ago.
"This time frame corresponds extremely well with the fossil record, which shows Homo erectus expanding out of Africa then," Templeton said.
Another novel find is that populations of Homo erectus in Eurasia had recurrent genetic interchange with African populations 1.5 million years ago, much earlier than previously thought, and that these populations persisted instead of going extinct, which some human evolution researchers thought had occurred.
The new data confirm an expansion out of Africa to 700,000 years ago that was detected in the 2002 analysis.
"Both (the 1.9 million and 700,000 year) expansions coincide with recent paleoclimatic data that indicate periods of very high rainfall in eastern Africa, making what is now the Sahara Desert a savannah," Templeton said. "That makes the timing very amenable for movements of large populations through the area."
Templeton said that the fossil record indicates a significant change in brain size for modern humans at 700,000 years ago as well as the adaptation and expansion of a new stone tool culture first found in Africa and later at 700,000 years expanded throughout Eurasia.
"By the time you're done with this phase you can be 99 percent confident that there was recurrent genetic interchange between African and Eurasian populations," he said. "So the idea of pure, distinct races in humans does not exist. We humans don't have a tree relationship, rather a trellis. We're intertwined."
Washington University in St. Louis - http://www.wustl.edu