Excerpt from bbc.comAstronomers have proved that they can accurately tell the age of a star from how fast it is spinning. We know that stars slow down over time, but until recently there was little data to support exact calculations. For ...
Tag: the journal Nature (page 2 of 2)
A jagged line etched on a fossil mussel shell may be the oldest evidence of geometric art.Photograph by Wim Lustenhouwer, VU University Amsterdam(Reuters) - It's a simple zigzag design scratched onto the surface of a freshwater mussel shell on t...
news.stanford.edu
By Chris Cesare
A new ultrathin multilayered material can cool buildings without air conditioning by radiating warmth from inside the buildings into space while also reflecting sunlight to reduce incoming heat.
Stanford engineers have invented a material designed to help cool buildings. The material reflects incoming sunlight, and it sends heat from inside the structure directly into space as infrared radiation (represented by reddish rays).A team led by electrical engineering Professor Shanhui Fan and research associate Aaswath Raman reported this energy-saving breakthrough in the journal Nature.
The heart of the invention is an ultrathin, multilayered material that deals with light, both invisible and visible, in a new way.
Invisible light in the form of infrared radiation is one of the ways that all objects and living things throw off heat. When we stand in front of a closed oven without touching it, the heat we feel is infrared light. This invisible, heat-bearing light is what the Stanford invention shunts away from buildings and sends into space.
Of course, sunshine also warms buildings. The new material, in addition dealing with infrared light, is also a stunningly efficient mirror that reflects virtually all of the incoming sunlight that strikes it.
The result is what the Stanford team calls photonic radiative cooling – a one-two punch that offloads infrared heat from within a building while also reflecting the sunlight that would otherwise warm it up. The result is cooler buildings that require less air conditioning.
"This is very novel and an extraordinarily simple idea," said Eli Yablonovitch, a professor of engineering at the University of California, Berkeley, and a pioneer of photonics who directs the Center for Energy Efficient Electronics Science. "As a result of professor Fan's work, we can now [use radiative cooling], not only at night but counter-intuitively in the daytime as well."
The researchers say they designed the material to be cost-effective for large-scale deployment on building rooftops. Though still a young technology, they believe it could one day reduce demand for electricity. As much as 15 percent of the energy used in buildings in the United States is spent powering air conditioning systems.
In practice the researchers think the coating might be sprayed on a more solid material to make it suitable for withstanding the elements.
"This team has shown how to passively cool structures by simply radiating heat into the cold darkness of space," said Nobel Prize-winning physicist Burton Richter, professor emeritus at Stanford and former director of the research facility now called the SLAC National Accelerator Laboratory.
A warming world needs cooling technologies that don't require power, according to Raman, lead author of the Nature paper.
"Across the developing world, photonic radiative cooling makes off-grid cooling a possibility in rural regions, in addition to meeting skyrocketing demand for air conditioning in urban areas," he said.
Using a window into space
The real breakthrough is how the Stanford material radiates heat away from buildings. |
Doctoral candidate Linxiao Zhu, Professor Shanhui Fan and research associate Aaswath Raman are members of the team that invented the breakthrough energy-saving material. |
As science students know, heat can be transferred in three ways: conduction, convection and radiation. Conduction transfers heat by touch. That's why you don't touch an oven pan without wearing a mitt. Convection transfers heat by movement of fluids or air. It's the warm rush of air when the oven is opened. Radiation transfers heat in the form of infrared light that emanates outward from objects, sight unseen.
The first part of the coating's one-two punch radiates heat-bearing infrared light directly into space. The ultrathin coating was carefully constructed to send this infrared light away from buildings at the precise frequency that allows it to pass through the atmosphere without warming the air, a key feature given the dangers of global warming."Think about it like having a window into space," said Fan.
Aiming the mirror
But transmitting heat into space is not enough on its own.This multilayered coating also acts as a highly efficient mirror, preventing 97 percent of sunlight from striking the building and heating it up.
"We've created something that's a radiator that also happens to be an excellent mirror," said Raman.
Together, the radiation and reflection make the photonic radiative cooler nearly 9 degrees Fahrenheit cooler than the surrounding air during the day.
From prototype to building panel
Making photonic radiative cooling practical requires solving at least two technical problems.
The first is how to conduct the heat inside the building to this exterior coating. Once it gets there, the coating can direct the heat into space, but engineers must first figure out how to efficiently deliver the building heat to the coating.
The second problem is production. Right now the Stanford team's prototype is the size of a personal pizza. Cooling buildings will require large panels. The researchers say there exist large-area fabrication facilities that can make their panels at the scales needed.
The cosmic fridge
More broadly, the team sees this project as a first step toward using the cold of space as a resource. In the same way that sunlight provides a renewable source of solar energy, the cold universe supplies a nearly unlimited expanse to dump heat."Every object that produces heat has to dump that heat into a heat sink," Fan said. "What we've done is to create a way that should allow us to use the coldness of the universe as a heat sink during the day."
In addition to Fan, Raman and Zhu, this paper has two additional co-authors: Marc Abou Anoma, a master's student in mechanical engineering who has graduated; and Eden Rephaeli, a doctoral student in applied physics who has graduated.
Excerpt frombelfasttelegraph.co.ukA US team discovered the barrier, some 7,200 miles above the Earth's surface, that blocks high energy electrons threatening astronauts and satellites.Scientists identified an "extremely sharp" boundary within the Van...
Excerpt from sciencedaily.comNew findings by a Johns Hopkins University-led team reveal long unknown details about carbon deep beneath Earth's surface and suggest ways this subterranean carbon might have influenced the history of life on the planet....
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| An artist's rendition of the amphibious Cartorhynchus lenticarpus. (Stefano Broccoli) |
My absolute favorite moment of the study though had to be the team's conclusion that the foot and a half long green amphibian "probably had a happy life". I could see now a room full of white lab coats concurring with one another. "Yes yes, happy indeed. I concur." A young lab technician then sheepishly speaks up. "I must disagree sirs. My research shows its not easy being green." "Oh yes, yes," the group of senior scientists now concede. "Indeed, it's not easy being green."
Motani's statement that his team now hopes to find the preceding evolutionary ancestor to Cartorhynchus lenticarpus as their next major breakthrough is the part of this report that I can't get out of my mind. What would the odds be that this small group of researchers not only find one crucial missing link, but will also discover the very next missing piece of the long evolutionary puzzle chain, evidence countless archeologists, scientists and researchers have been, for centuries, turning over stones in search of. Something smells fishy here, and it isn't the great, great, great grandfather of Kermit the Frog.
Greg Giles
Excerpts from the washingtonpost.com article by Rachel Feltman:
Researchers report that they've found the missing link between an ancient aquatic predator and its ancestors on land. Ichthyosaurs, the dolphin-like reptiles that lived in the sea during the time of the dinosaurs, evolved from terrestrial creatures that made their way back into the water over time.
But the fossil record for the lineage has been spotty, without a clear link between land-based reptiles and the aquatic ichthyosaurs scientists know came after. Now, researchers report in Nature that they've found that link — an amphibious ancestor of the swimming ichthyosaurs named Cartorhynchus lenticarpus.
"Many creationists have tried to portray ichthyosaurs as being contrary to evolution," said lead author Ryosuke Motani, a professor of earth and planetary sciences at the University of California Davis. "We knew based on their bone structure that they were reptiles, and that their ancestors lived on land at some time, but they were fully adapted to life in the water. So creationists would say, well, they couldn't have evolved from those reptiles, because where's the link?"
Now the gap has been filled, he said.
The creature is about a foot and a half long and lived 248 million years ago.
"Initially I was really puzzled by this fossil," Motani said. "I could tell it was related [to ichthyosaurs], but I didn't know how to place it. It took me about a year before I was sure I had no doubts."
One of the most important differences between this new ichthyosaur and its supposed descendants comes down to being big boned: When other vertebrates have evolved from land to sea living, they've gone through stages where they're amphibious and heavy. Their thick bones probably allowed them to fight the power of strong coastal waves and stay grounded in shallow waters. Sure enough, this new fossil has much thicker bones than previously examined ichthyosaurs.
"This animal probably had a happy life. It was in the tropics, and it was probably a bottom feeder that fed on soft-bodied things like squid and animals like shrimp," Motani said. "And for a predator like that to exist, there has to be plenty of prey. This was probably one of the first predators to appear after that extinction."
This single fossil hasn't revealed all of the ichthyosaurs' secrets. Motani hopes to find the preceding evolutionary ancestor next — one that was also amphibious, but spent slightly more of its time on land. "We're looking for that one now," Motani said.
Excerpt from
uncovermichigan.com
Astronomers have revealed that their efforts to spot earth-like planets, also called as exo-planets, could be undermined by space dust and grit from asteroid collisions in addition to comet remnants. According to them, exozodiacal light, which is a light reflected from dust and grime of asteroids, could hide exo-planets and their alien suns.
The researchers put the Very Large Telescope Interferometer (VLTI) located in Chile into use to detect the exozodical light from far away galaxies. Researchers compared the results with the data available from previous studies to produce a clearer, more complete picture. Habitable areas in nine alien star systems were probably surrounded by these light formations.
Zodiacal light can be seen from earth as a white glow in areas with completely dark skies. It seems to be emanating from the horizon around the sun. The best time to spot zodiacal light is usually before sunrise or right after sunset. According to experts, the white glow appears to be triangular in shape and it seems to emanate directly from the sun itself.
Sunlight reflecting off gas and dust surrounding the sun lead to creation of zodiacal light seen on earth’s skies. However, it was certainly the first time when the exozodiacal light was witnessed on alien solar systems, thanks to the VLTI telescope.
Details of the study have been published online this week in the journal Nature Physics.
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This artist’s impression shows exocomets orbiting Beta Pictoris. Image credit: ESO / L. Calçada. |
sci-news.com
French astronomers using the HARPS instrument on the ESO 3.6-m telescope at the La Silla Observatory in Chile have discovered nearly 500 comets around the nearby star Beta Pictoris and have found that they belong to two distinct families: old comets that have made multiple passages near the star, and younger comets that probably came from the recent breakup of one or more larger objects.
For almost three decades, astronomers have seen subtle changes in the light from this star that were thought to be caused by the passage of comets in front of the star itself.
The analysis revealed the presence of two distinct families of exocomets: one family of old exocomets whose orbits are controlled by a massive planet, and another family, probably arising from the recent breakdown of one or a few bigger objects. Different families of comets also exist in our Solar System.
“For the first time a statistical study has determined the physics and orbits for a large number of exocomets. This work provides a remarkable look at the mechanisms that were at work in the Solar System just after its formation 4.5 billion years ago,” concluded Dr Kiefer, who is the first author of the paper published in the journal Nature.
By Nola Taylor Redd, Space.com Contributor
A Neptune-size planet beyond the solar system has telltale traces of water vapor in its atmosphere, making it the smallest exoplanet known to have the wet stuff yet, scientists say.
Several massive Jupiter-size giants have had the components of their atmosphere examined, but until now, the atmospheres of smaller planets have proved more elusive. In this new study, scientists discovered traces of water on the alien planet HAT-P-11b, which orbits a star 124 light-years from Earth in the constellation Cygnus.
"Water is the most cosmically abundant molecule that we can directly observe in exoplanets, and we expect it to be prevalent in the upper atmospheres of planets at these temperatures," lead author Jonathan Fraine said in an email interview. Fraine, a graduate student at the University of Maryland, worked with a team lead by Drake Deming, also of the University of Maryland.
"Detecting it is both a confirmation of our theories and revealing for the bulk of the spectrum that we can observe," Fraine told Space.com.
This artist’s illustration depicts the alien planet HAT-P-11b, which shows signs of water in its atmosphere, as the exoplanet crosses in front of its parent star. As starlight passes through the puffed-up atmosphere surrounding the planet, shown here in orange, scientists can detect its composition.
Credit: NASA/JPL-Caltech
Credit: NASA/JPL-Caltech
Detecting alien planet atmospheres
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This image from the Hubble Space Telescope shows the star HAT-P-11 (center), which has a Neptune-size planet that is the smallest yet known to have water in its atmosphere. The planet, HAT-P-11b, is not visible in this image. The other bright object seen here is another star. Credit: NASA, ESA, J. Fraine |
As a planet passes, or transits, between Earth and its sun, it blocks light from the star. The dip in light is how many exoplanets are first found. But these transits also allow astronomers to study the atmospheres of exoplanets. By observing the spectrum of light that passes through an exoplanet’s atmosphere, scientists can determine what it is made up of.
For HAT-P-11b, a planet roughly four times the radius of Earth, that makeup is 90 percent hydrogen, with traces of water vapor. The Neptune-size planet orbits its sun every five days, at a distance that is only one-twentieth of the Earth-sun distance (which is 93 million miles, or 150 million kilometers). As a result, the temperature climbs higher on HAT P-11b than it does on gas giants in the solar system, reaching a sizzling 1,120 degrees Fahrenheit (605 degrees Celsius).
Scientists have been studying the atmospheres of Jupiter-like planets for years, but smaller planets produce a smaller signal that is more challenging to observe. For the new study, researchers examined the atmospheres of four other smaller exoplanets — two roughly the size of Neptune and two smaller super-Earths — but the results were disappointingly featureless.
"We do indeed have the technology — the resolution — to observe Neptune-size exoplanets, and even super-Earths," Fraine said.
But the chemical compositions of the other four planets were blocked by a familiar phenomenon — clouds.
"We've just been seeing a whole lot of nothing," Eliza Kempton, of Grinnell College in Iowa. Kempton models planetary atmospheres but was not involved in the research.
This artist's illustration shows what the skies may look like on different alien planets. On the left is a cloudy planet, while on the right is a planet with clear skies that may resemble the sky of exoplanet HAT-P-11b, a Neptune-size world thought to have water in its atmosphere.
Credit: NASA
Credit: NASA
Kempton added that the flat, featureless signals observed for the other planets were attributed to clouds or hazes in the upper atmosphere. The high clouds blocked light from the star, keeping it from penetrating through to the observers' side of the planet and leaving scientists unable to characterize the chemicals in the atmosphere.
"It's not crazy to think that there should be clouds in these exoplanet atmospheres, because we see clouds in all the planetary atmospheres in our solar system," Kempton said.
Although the hot, Neptune-size planet lives in a different environment from the icy giants in the solar system, it is similar to one of the four smaller planets whose atmosphere had already been studied. Those planets are known as GJ436b, GJ1214b, HD97658b and GJ3470b.
HAT-P-11b is only slightly larger and warmer than the alien planet GJ436b, making them good to compare to one another because one has clouds and one does not, Fraine said.
"I like to consider them the bigger version of the Earth-Venus twin pair," Fraine said of the planets HAT-P-11b and GJ436b.
"They are basically the same mass, radius and temperature, but small changes in the formation, or even these bulk properties, may be causing vast changes in the atmospheric composition."
The research is detailed in the Sept. 25 issue of the journal Nature, along with a commentary article by Kempton.
A planet's upper atmosphere results from what happens both above and below it. The balancing act involves irradiation from its star and from cosmic rays on the outside, as well as the chemical and dynamical systems lower in the atmosphere, Fraine explained.
"If we know the input from above — the host star — and the upper atmosphere from our observations, then the missing piece of the puzzle is the interior composition," he said.
Although the interior of a planet is complex, Fraine called the newly characterized atmosphere "a great step forward in solving the puzzle."
The composition of the small planet's atmosphere also supports the core accretion model of planetary formation, where smaller particles combine to create larger and larger particles, eventually reaching planet-size proportions.
"Core accretion predicts that planets are built from the inside out," Fraine said.
"Measuring that HAT P-11b likely has a relatively hydrogen-poor atmosphere implies that it was formed from rocky material that later acquired a thick atmosphere above it, which is what the core-accretion model predicts."
Had the planet formed along the lines of the competing gravitational instability model, its composition and that of its atmosphere should bear a stronger similarity to its star than what was measured by scientists.
Because of its crucial role in the balancing act, the water vapor detected in the exoplanet's atmosphere played an important part in modeling its formation and evolution.
"In the long run, if we can detect water, methane, carbon monoxide, carbon dioxide, etc., in dozens to hundreds of exoplanet atmospheres of various bulk properties, then we will be able to paint a much clearer picture of how planets form, and, likewise, how Earth formed," Fraine said.
"This was just one of the beginning brush strokes to painting the full picture of how planets, as well as ourselves, were formed."
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