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Tuesday, September 27, 2011
Astronomy - 'Darkest' world enlightens astronomers about mysterious light-gobbling planet
Astronomers from Princeton University and the Harvard-Smithsonian Center for Astrophysics found that the distant exoplanet TrES-2b -- shownhere in an artist's conception -- likely absorbs 99.9 percent of the light that strikes it, making it the most light-thirsty object in the known universe. The findings may help astronomers better understand a mysterious characteristic of similar planets found outside our solar system. (Image by David A. Aguilar, Harvard-Smithsonian Center for Astrophysics)
A giant Jupiter-like gas planet has been revealed to be the most light-thirsty object in the known universe -- a finding that may help astronomers better understand a mysterious characteristic of similar planets found outside our solar system.
Recent analysis on a planet dubbed TrES-2b has found that it probably absorbs 99.9 percent of the light that strikes it, more than any other known cosmic entity, according to a report by Princeton University's David Spiegel, a postdoctoral researcher in the Department of Astrophysical Sciences, and lead author David Kipping, a postdoctoral researcher at the Harvard-Smithsonian Center for Astrophysics.
Recently published in the journal Monthly Notices of the Royal Astronomical Society, the paper not only identifies the planet as the "darkest" world yet observed, but also sets a new standard in determining just how much light "hot Jupiter" planets -- scorching balls of hydrogen and helium already known for being non-reflective -- can keep to themselves.
TrES-2b, which was discovered in 2006, is one of roughly 150 hot Jupiter planets known to exist outside our solar system. Astronomers are working to better understand the sometimes mysterious properties of these "dark" planets, from their mass to their orbital patterns to their atmospheric makeup.
In the case of TrES-2b and other cosmic objects, "darkness" refers not to the absence of light, but rather the amount of visible light it absorbs, explained Spiegel. By that standard, TrES-2b is exceptionally "darker" than any substance found on Earth. Coal, among the darkest substances on Earth, absorbs 95 percent of the visible light that strikes it, reflecting only 5 percent of the visible light; TrES-2b absorbs all but 0.1 percent of the light that heads its way. However, TrES-2b orbits so close to its star that it is extremely hot and glows thermally -- despite its "darkness," if the planet was in Earth's solar system it would appear 3,000 times brighter than Venus, the solar system's brightest planet.
Spiegel, who focuses his research on the habitability and atmospheric and interior conditions of exoplanets -- those found outside our solar system -- noted that his and Kipping's work is among the first to find visible light emerging from an exoplanet in addition to the infrared light more typically observed.
Finding evidence of a puzzling component
What little light TrES-2b emits, relative to the amount it absorbs, is comparable to that from a burner on an electric stove, Spiegel said. The planet gives off a reddish glow of visible light while 95 percent of light coming from the planet is emitted as heat. This is an unusually high level of light obscuration, even among hot Jupiters, which are famously opaque. TrES-2b's dimness suggests that the planet is strongly influenced by a still-mysterious atmospheric component characteristic of hot Jupiter planets that absorbs an extraordinary amount of visible light, but had not been previously identified in TrES-2b, Spiegel said.
"We found evidence suggesting that something that seems to be present and absorb light in other planets hasn't been accounted for in basic models of TrES-2b," Spiegel said. "It looks like there's something missing from our list of 'ingredients' that make up the atmosphere of this planet. It is absorbing a lot of the optical light that hits this planet, but we're not sure what that extra ingredient is."
Kipping and Spiegel's finding adds another layer to the complex personality of hot Jupiter planets, said Gaspar Bakos, a Princeton assistant professor of astrophysical sciences noted for his work detecting exoplanets. First observed nearly 15 years ago, hot Jupiter planets can be readily detected with current observational instruments due to their size and orbital motion, and reveal new information about distant stars and solar systems.
"Hot Jupiters keep bringing us surprises," Bakos said. "First, some of them were found to be too big and too light compared to most theories. Then some turned out to be super-massive and compact. Some of them are 'well-mannered' and orbit their stars in the same direction as the star spins. Yet some are 'ill-mannered' with a retrograde orbit. Some orbit the stars on close to circular orbits, but others were found to follow wildly eccentric (elongated) orbits. The fact that TrES-2b is so 'dark' is yet another surprise."
TrES-2b has been a popular observation target for astronomers, particularly after the 2009 launch of NASA's Kepler satellite telescope brought the planet into clearer view, Spiegel said. In 2010, he and Princeton astrophysical sciences professor Adam Burrows published an analysis in The Astrophysical Journal of atmospheric data of TrES-2b and two other planets in Kepler's view. Because of that work, Kipping approached Spiegel with his own observations of TrES-2b as it orbited its sun.
Via the Kepler satellite, Kipping had, over several months, captured the planet as it passed in front of the star it orbits, TrES-2; took on full illumination as it started to duck behind the star; and finally fell into TrES-2's shadow. This cycle presented the planet at its brightest and dimmest -- and Kipping noted that the difference between the two was unexpectedly slight, suggesting that TrES-2b was retaining much of the light that hit it. Spiegel checked Kipping's observations against dozens of atmospheric models to find those that best explained the planet's lack of reflectivity.
The most applicable models factored in high levels of the enigmatic, light-absorbing compound thought to be in the atmosphere of other "dark" hot Jupiters, Spiegel said. Should that mystery element be behind TrES-2b's massive light absorption, then Spiegel and Kipping's research also reveals that whatever the compound is, it has the ability to soak up much more visible light than had previously been calculated, Spiegel said.
"This is not the first reporting of the mystery element," Spiegel said. "But it is the first identification of how non-reflective it can make a planet."
In addition to their observations, Kipping and Spiegel's research emphasizes the benefit of publicly available data from satellites such as Kepler, said Princeton's Bakos.
"This paper presents a thorough analysis of high-quality, publicly available Kepler spacecraft data and combines it with cutting-edge theoretical interpretation," Bakos said, noting the availability of this data to the scientific community allows for creative work to be done in analyzing findings made outside our solar system.
Source: PhysOrg.com
Astronomy - Astronomers discover new way to measure Universe
Every galaxy has a supermassive black hole at its heart, millions to billions of times the mass of the Sun. When these dark hearts of galaxies actively accrete matter they become incredibly bright. These are quasars, and they outshine everything else in the universe.
Astronomers at Copenhagen's Niels Bohr Institute have found a new way to measure distances. This may not sound like much, but working out how far away something is, is one of the toughest fundamental problems in astrophysics and is central to cosmology as it allows scientists to work out the age of the Universe and what it’s fundamental properties are. Because their new method uses quasars, some of the brightest objects known, scientists say they will be able to determine distances much further than achieved to date, paving the way to a better understanding of dark energy.
Finding new ways to measure cosmic distances has a strong pedigree incosmology. In the 1990s a way was discovered to use supernovae, the explosions of massive stars, to measure distances. From that finding stemmed the discovery of the acceleration of the Universe in 1998, which showed that 70% of the Universe was made up of dark energy.
Now, Dr. Darach Watson and colleagues have discovered a way to find accurate distances using quasars. Quasars are powered by the supermassive black holes at the hearts of galaxies, and are so luminous that they can vastly outshine all the stars in their host galaxy combined. Due to their extreme luminosity, scientists have been searching for ways to use them to measure distances since they were discovered in the 1960s. After more than four decades, those attempts have finally been successful.
“It was a discovery waiting to happen,” says Dr. Kelly Denney, a member of the team. It has been known for some time that the size of the gas cloud falling into the supermassive black hole is related to the luminosity of the quasar. Watson and colleagues realised that new data on the sizes of gas clouds that were being measured for other reasons were now accurate enough to allow them to predict the luminosities of the quasars. Knowing how bright the quasars appeared from earth, they could easily determine how far away they were.
Quasars can be detected to very large distances, much farther than supernovae, which are currently the best measure of distance. “That’s what makes quasars so exciting,” says Watson, “seeing farther away means seeing farther back in time, and knowing how the universe expanded with time is the key to understanding dark energy.” Being able to measure the universe accurately at great distances will have profound implications for scientists’ future understanding of dark energy and the ultimate fate of the cosmos.
Niels Bohr Institute
Source: PhysOrg.com
Astronomy - A magnified supernova
Galaxy Cluster Abell 1689
Supernovae are among astronomers most important tools for exploring the history of the universe. Their frequency allows us to examine how active star formation was, how heavy elements have developed, and the distance to galaxies across vast distances. Yet even these titanic explosions are only so bright, and there’s an effective limit on how far we can detect them with the current generation of telescopes. However, this limit can be extended with a little help from gravity.
One of the consequences of Einstein’s theory of general relativity is that massive objects can distort space, allowing them to act as a lens. While first postulated in 1924, and proposed for galaxies by Fritz Zwicky in 1937, the effect wasn’t observed until 1979 when a distant quasar, an energetic core of a distant galaxy, was split in two by the gravitational disturbances of an intervening cluster of galaxies.
While lensing can distort images, it also provides the possibility that it may magnify a distant object, increasing the amount of light we receive. This would allow astronomers to probe even more distant regions with supernovae as their tool. But in doing so, astronomers must look for these events in a different manner than most supernova searches. These searches are generally limited to the visible portion of the spectrum, the portion we see with our eyes, but due to the expansion of the universe, the light from these objects is stretched into the near-infrared portion of the spectrum where few surveys to search for supernovae exist.
But one team, led by Rahman Amanullah at Stockholm University in Sweden, has conducted a survey using the Very Large Telescope array in Chile, to search for supernovae lensed by the massive galaxy cluster Abell 1689. This cluster is well known as a source of gravitationally lensed objects, making visible some galaxiesthat formed shortly after the Big Bang.
In 2009, the team discovered one supernova that was magnified by this cluster that originated 5-6 billion lightyears away. In a new paper, the team reveals details about an even more distant supernova, nearly 10 billion lightyears distant. This event was magnified by a factor of 4 from the effects of the foreground cluster. From the distribution of energy in different portions of the spectrum, the team concludes that the supernova was an implosion of a massive star leading to a core-collapse type of supernova. The distance of this event puts it among the most distant supernovae yet observed. Others at this distance have required extensive time using the Hubble telescope or other large telescopes.
Source: PhysOrg.com
Astronomy - Homeless supernovae
NGC 1058, the nearest galaxy to a potentially escaped supernova. Image credit: Bob Ferguson and Richard Desruisseau/Adam Block/NOAO/AURA/NSF
In a post earlier this month, we looked at a team of astronomers searching for stars that were on ejected from their birthplaces in clusters. These stars could receive the needed kick from a gravitational swing by the core of the cluster to achieve a velocity of a few tens of km/sec. But a similar mechanism can function in the cores of galaxies giving stars a speed of roughly 1,000 km/sec, enough to leave their parent galaxies. A new studyasks whether we have ever witnessed any of these stellar cast offs explode as supernovae.
The team, led by Peter-Christian Zinn at Ruhr University in Bochum, Germany, searched through roughly 6,000 supernovae listed in the Sternbarg Astronomical Institute Supernova Catalog, for which no host galaxy was apparent, yet weren’t too distant from any known galaxy. The latter criteria was added because, even at the high velocities, stars still couldn’t get too far before they reached the end of their fuses. The team imposed a rough inner cut off of around 10 kiloparsecs (roughly 1/3 of the width of the disk of the Milky Way). They expected stars should be at least this distance from the cores of the parent galaxy.
The initial list contained five candidate stars, dating back as far as 1969. The first step the team used to determine if the supernova was truly in a galaxy or not, was to take long exposure images of the immediate area, to draw out potential low surface brightness hosts. The team also used archival data in the far ultraviolet as well as the x-ray spectrum to determine whether or not the nearby galaxies from which the supernovae could potentially be ejected had an extended disk, invisible in the visible portion of the spectrum that would have allowed the progenitor star to form in the outskirts of the galaxy. These wavelengths are tracers of ongoing star formation which are sites in which high mass stars that would lead to core-collapse supernovae, would likely be found.
The oldest candidate, SN 1969L, was located near the flocculent spiral NGC 1058. While the deep exposures did not show a host galaxy, the x-ray and UV images both showed some extended structure of the parent galaxy at the distance of the supernova. This led to the conclusion that this supernova, while far removed from its host galaxy, was still gravitationally tied to it.
With the second candidate, SN 1970L, the team again failed to find any faint host galaxy. However, the supernova was situated between two galaxies, NGC 2968 and a faint elliptical, NGC 2970. A 1994 study had revealed a faint bridge of matter connecting the two, implying that they had had an interaction in the past. This interaction would likely have pulled off gas and stars, of which SN 1970L could have been one.
SN 1997C was the third candidate and also lacked a discernible host galaxy, even with long exposures. This one also did not have an indication of an extended disk of which the supernova could have been part. Given the characteristics of the supernova, the team estimated that it had an original mass of 15 times that of the Sun. Given its projected distance and the lifetime of such stars, the team noted that this would correspond to a velocity of some 3,000 km/sec, which is several times the speed of the highest confirmed hypervelocity star. As such, the team expected that this star would have to be ejected in a similar manner to SN 1970L, using an interaction between galaxies. Given that the host galaxy is known to be one in a small cluster and the disk shows some signs of perturbation, they suggested this was likely.
The fourth candidate, SN 2005nc, the team selected because there was no nearby galaxy they could assign as a possible parent. They suggested this was due to an extremely distant host galaxy, too faint to resolve with previous studies. The basis for this assertion was that the supernova came with a gamma ray burst that indicated an origin some 5-6 billion light years distant. Due to the associated GRB, the Hubble telescope swung in to take a look. These archival pictures failed to reveal any objects that could readily be identified as host galaxies leaving the team to presume the host was simply too far away to resolve.
The last candidate was SN 2006bx located near the galaxy UGC 5434. This supernova did not appear to be in a faint background galaxy and did not have hints of being formed in an extended disk. The estimated velocity from the projected distance was ~850 km/sec which placed it in the realm of plausible speeds for stars ejected by gravitational assists from the supermassive black hole at the center of galaxies.
Astronomy - Astronomers crack the Fried Egg Nebula
Using the European Southern Observatory's Very Large Telescope (VLT), teams from The University of Manchester, among others, took the new picture showing for the first time a huge dusty double shell surrounding the central hypergiant.
The star and its shells resemble an egg white around a yolky centre, leading theastronomers to nickname the object the Fried Egg Nebula. The international team's results are published in the journal Astronomy & Astrophysics.
The monster star, known to astronomers as IRAS 17163-3907, has a diameter about a thousand times bigger than our Sun. At a distance of about 13 000 light-years from Earth, it is the closest yellow hypergiant found to date and new observations show it shines some 500 000 times more brightly than the Sun.
The observations of the star and the discovery of its surrounding shells were made using the VISIR infrared camera on the VLT. The pictures are the first of this object to clearly show the material around it and reveal two almost perfectly spherical shells.
If the Fried Egg Nebula were placed in the centre of the Solar System, the Earth would lie deep within the star itself and the planet Jupiter would be orbiting just above its surface.
The much larger surrounding nebula would engulf all the planets and dwarf planets and even some of the comets that orbit far beyond the orbit of Neptune. The outer shell has a radius of 10 000 times the distance from the Earth to the Sun.
"This object was known to glow brightly in the infrared but, surprisingly, nobody had identified it as a yellow hypergiant before," said Eric Lagadec (European Southern Observatory), who led the team that produced the new discovery.
Yellow hypergiants are in an extremely volatile phase of their evolution, undergoing a series of explosive events — this star has ejected four times the mass of the Sun in just a few hundred years. The material flung out during these bursts has formed the extensive double shell of the nebula, which is made of dust rich in silicates and surrounded by gas.
Professor Albert Zijlstra, from The University of Manchester, said: "It is amazing that one of the brightest stars in the infrared sky had previously gone unnoticed. We are seeing a very rare event, when a star is beginning to blow off its outer layers, as a prelude to its final explosion as a supernova."
This activity also shows that the star is likely to soon die an explosive death — it will be one of the next supernova explosions in our galaxy. Supernovae provide much-needed chemicals to the surrounding interstellar environment and the resulting shock waves can kick start the formation of new stars.
The Very Large Telescope mid-IR instrument, VISIR, captured this delicious image of the Fried Egg Nebula through three mid-infrared filters that are here coloured blue, green and red.
More information: “A double detached shell around a post-Red Supergiant: IRAS 17163-3907, the Fried Egg nebula“ by E. Lagadec et al., Astronomy & Astrophysics.
Source: PhysOrg.com
Space Exploration - Venus weather not boring after all, study shows
This is an ultraviolet image of Venus' clouds as seen by the Pioneer Venus Orbiter (Feb. 26, 1979). Credit: NASA
At first glance, a weather forecaster for Venus would have either a really easy or a really boring job, depending on your point of view. The climate on Venus is widely known to be unpleasant -- at the surface, the planet roasts at more than 800 degrees Fahrenheit under a suffocating blanket of sulfuric acid clouds and a crushing atmosphere more than 90 times the pressure of Earth's. Intrepid future explorers should abandon any hope for better days, however, because it won't change much.
"Any variability in the weather on Venus is noteworthy, because the planet has so many features to keep atmospheric conditions the same," says Dr. Tim Livengood, a researcher with the National Center for Earth and Space Science Education, Capitol Heights, Md., and now with the University of Maryland, College Park, Md.
"Earth has seasons because its rotation axis is tilted by about 23 degrees, which changes the intensity of sunlight and the length of the day in each hemisphere throughout the year. However, Venus has been tilted so much, it's almost completely upside down, leaving it with a net tilt of less than three degrees from the sun, so the seasonal effect is negligible," explains Livengood, who is stationed at NASA's Goddard Space Flight Center in Greenbelt, Md. "Also, its orbit is even more circular than Earth's, which prevents it from getting significantly hotter or cooler by moving closer to or further away from the sun. And while you might expect things to cool down at night -- especially since Venus rotates so slowly that its night lasts almost two Earth months -- the thick atmosphere and sulfuric acid clouds act like a blanket while winds move heat around, keeping temperatures pretty even. Finally, almost all the planet's water has escaped to space, so you don't get any storms or precipitation like on Earth where water evaporates and condenses as clouds."
However, higher up, the weather gets more interesting, according to a new study of old data by NASA and international scientists. The team detected strange things going on in data from telescopic observations of Venus in infrared light at about 68 miles (110 kilometers) above the planet's surface, in cold, clear air above the acid clouds, in two layers called the mesosphere and the thermosphere.
"Although the air over the polar regions in these upper atmospheric layers on Venus was colder than the air over the equator in most measurements, occasionally it appeared to be warmer," said Dr. Theodor Kostiuk of NASA Goddard. "In Earth's atmosphere, a circulation pattern called a 'Hadley cell' occurs when warm air rises over the equator and flows toward the poles, where it cools and sinks. Since the atmosphere is denser closer to the surface, the descending air gets compressed and warms the upper atmosphere over Earth's poles. We saw the opposite on Venus. In addition, although the surface temperature is fairly even, we've seen substantial changes – up to 54 degrees Fahrenheit (about 30 K change) – within a few Earth days in the mesosphere – thermosphere layers over low latitudes on Venus. The poles appeared to be more stable, but we still saw changes up to 27 degrees Fahrenheit (about 15 K change)."
Kostiuk and Livengood are co-authors of a paper about these observations that appeared July 23 in the online edition of the journal Icarus.
"The mesosphere and thermosphere of Venus are dynamically active," said lead author Dr. Guido Sonnabend of the University of Cologne, Germany. "Wind patterns resulting from solar heating and east to west zonal winds compete, possibly resulting in altered local temperatures and their variability over time."
This upper atmospheric variability could have many possible causes, according to the team. Turbulence from global air currents at different altitudes flowing at more than 200 miles per hour in opposite directions could exchange hot air from below with cold air from above to force changes in the upper atmosphere. Also, giant vortexes swirl around each pole. They, too, could generate turbulence and change the pressure, causing the temperature to vary.
Since the atmospheric layers the team observed are above the cloud blanket, they may be affected by changes in sunlight intensity as day transitions to night, or as latitude increases toward the poles. These layers are high enough that they could even be affected by solar activity (the solar cycle), such as solar explosions called flares and eruptions of solar material called coronal mass ejections.
Changes were seen over periods spanning days, to weeks, to a decade. Temperatures measured in 1990-91 are warmer than in 2009. Measurements obtained in 2007 using Goddard's Heterodyne Instrument for Planetary Wind and Composition (HIPWAC) observed warmer temperature in the equatorial region than in 2009. Having seen that the atmosphere can change, a lot more observations are needed to determine how so many phenomena can affect Venus' upper atmosphere over different intervals, according to the team.
"In addition to all these changes, we saw warmer temperatures than those predicted for this altitude by the leading accepted model, the Venus International Reference Atmosphere model," said Kostiuk. "This tells us that we have lots of work to do updating our upper atmospheric circulation model for Venus."
Although Venus is often referred to as Earth's twin, since they are almost the same size, it ended up with a climate very different from Earth. A deeper understanding of Venus' atmosphere will let researchers compare it to the evolution of Earth's atmosphere, giving insight as to why Earth now teems with life while Venus suffered a hellish fate.
The team measured temperature and wind speeds in Venus' upper atmosphere by observing an infrared glow emitted by carbon dioxide (CO2) molecules when they were energized by light from the sun. Infrared light is invisible to the human eye and is perceived by us as heat, but it can be detected by special instruments. In the research, it appeared as a line on a graph from a spectrometer, an instrument that separates light into its component colors, each of which corresponds to a specific frequency. The width of the line revealed the temperature, while shifts in its frequency gave the wind speed.
The researchers compared observations from 1990 and 1991 using Goddard's Infrared Heterodyne Spectrometer instrument at NASA's Infrared Telescope Facility on Mauna Kea, Hawaii, to observations from 2009 using the Cologne Tunable Heterodyne Infrared Spectrometer instrument at the National Optical Astronomy Observatory's McMath Telescope at Kitt Peak, Ariz.
Source: PhysOrg.com
Space Exploration - New hypothesis on crater debris
A team of researchers partnered with the NASA Lunar Science Institute (NLSI) has developed a new hypothesis for the origin of crater ejecta—debris that is launched out of a crater during meteorite impacts.
These findings may help scientists target samples for extraction during future missions to asteroids and terrestrial bodies such as Mercury, Venus, the moon and Mars. The results are published in the Sept. 21, 2011, issue of the Elsevier journal, Earth and Planetary Science Letters.
The science team, led by professor Gordon Osinski at The University of Western Ontario, London, Ontario, compared observations of ejecta from all terrestrial planets. The observations showed that ejecta deposits all contained more than one layer.
"Understanding ejecta is critical for understanding the context of samples collected by humans and robots during previous missions and may aid in targeting future sample return missions to the moon, Mars and beyond," said Osinski.
Craters formed on the surfaces of planetary bodies, including the Earth, by high-speed impacts, are a basic landform on all the solid planets in the solar system. In prevailing models, a continuous sheet of ejected material forms during the excavation stage of cratering. Osinski and his team suggest that this stage is followed by a second major episode of ejecta emplacement during the final moments of crater formation – something that has not been taken into account in any previous models of crater formation. This second episode takes the form of flows of material molten by the impact event, which originates from deeper below the surface, potentially offering a unique window into planetary interiors. A more thorough understanding of the composition of planetary interiors reveals important insights into the history of how our solar system formed.
“It is rewarding to see that our international collaborations within the NASA Lunar Science Institute continue to make an impact on current theories and challenge fundamental principles in the field of lunar science,” said NLSI Director Yvonne Pendleton.
Source: PhysOrg.com
Stars Signal Existence of Dark-Matter Objects --"Primordial Black Holes"
Scientists may be able to spot evidence of elusive dark matter by detecting vibrations on the surfaces of stars that could indicate that a dark-matter object known as a primordial black hole has passed through the stars, according to the study. The ripples could thus provide observable proof of dark matter, which is thought to make up more than 80 percent of all matter in the universe but has thus far evaded direct detection.
"There's a larger question of what constitutes dark matter, and if a primordial black hole were found it would fit all the parameters," study co-author Shravan Hanasoge of Princeton University said in a statement. "Identifying one would have profound implications for our understanding of the early universe and dark matter."
The new study could help scientists get a better handle on what dark matter is, researchers said. They simulated what would happen if a primordial black hole passes through a star.
Primordial black holes are theoretical remnants of the Big Bang, the explosive event that created the universe. These odd objects, which have yet to be observed, are one of various cosmic structures that may be the source of dark matter, researchers said.
Primordial black holes are much smaller than "normal" black holes and thus would not swallow up a star and all of its light. Rather, their collisions with stars would cause noticeable vibrations on the stars' surfaces.
"If you imagine poking a water balloon and watching the water ripple inside, that's similar to how a star's surface appears," said lead author Michael Kesden of New York University. "By looking at how a star's surface moves, you can figure out what's going on inside. If a black hole goes through, you can see the surface vibrate."
"Now that we know primordial black holes can produce detectable vibrations in stars, we could try to look at a larger sample of stars than just our own sun," Kesden added. "The Milky Way has 100 billion stars, so about 10,000 detectable events should be happening every year in our galaxy if we just knew where to look."
Physical Review Letters & space.com
Source: The Daily Galaxy
Supernova Shockwave -The Death Ray of the Universe?
While there is, on average, only one supernova per galaxy per century, there is something on the order of 100 billion galaxies in the observable Universe. Taking 10 billion years for the age of the Universe (it's actually 13.7 billion, but stars didn't form for the first few hundred million), Dr. Richard Mushotzky of the NASA Goddard Space Flight Center, derived a figure of 1 billion supernovae per year, or 30 supernovae per second in the observable Universe!
Certain rare stars -real killers -type 11 stars, are core-collapse hypernova that generate deadly gamma ray bursts (GRBs). These long burst objects release 1000 times the non-neutrino energy release of an ordinary "core-collapse" supernova. Concrete proof of the core-collapse GRB model came in 2003.
It was made possible in part to a fortuitously "nearby" burst whose location was distributed to astronomers by the Gamma-ray Burst Coordinates Network (GCN). On March 29, 2003, a burst went off close enough that the follow-up observations were decisive in solving the gamma-ray burst mystery. The optical spectrum of the afterglow was nearly identical to that of supernova SN1998bw. In addition, observations from x-ray satellites showed the same characteristic signature of "shocked" and "heated" oxygen that's also present in supernovae. Thus, astronomers were able to determine the "afterglow" light of a relatively close gamma-ray burst (located "just" 2 billion light years away) resembled a supernova.
It isn't known if every hypernova is associated with a GRB. However, astronomers estimate only about one out of 100,000 supernovae produce a hypernova. This works out to about one gamma-ray burst per day, which is in fact what is observed.
What is almost certain is that the core of the star involved in a given hypernova is massive enough to collapse into a black hole (rather than a neutron star). So every GRB detected is also the "birth cry" of a new black hole.
The Daily Galaxy via NASAJPL materials. Hubble Image: The Kepler Supernova remnant was a supernova which occurred in the Milky Way, in the constellation Ophiuchus. It is the last supernova to have been unquestionably observed in our own galaxy, occurring no farther than 20,000 light-years from Earth.
Source: The Daily Galaxy
Astronomers Zoom in on a Dark Asteroid
Zooming in through forest-fire smoke with the 61-inch telescope on Mt. Bigelow north of Tucson, Carl Hergenrother observed the asteroid known as 1999 RQ36 on its 2011 Earth-approaching orbit early last June. The 1,900-foot diameter, blacker-than-coal asteroid is the destination asteroid for the U.S.' first asteroid-sample return mission, NASA's OSIRIS-REx. Hergenrother, of the Lunar and Planetary Laboratory at the University of Arizona, heads the OSIRIS-REx asteroid astronomy working group of more than three dozen scientists from the U.S., Canada and Europe.
Using the Herschel Space Telescope, astronomers are set to obtain the first-ever images of asteroid 1999 RQ36 in far infrared light, a wavelength that the OSIRIS-REx spacecraft will not be able to see once it approaches the black chunk of rock floating in space.
Astronomers want to get as many observations of 1999 RQ36 as possible through spring 2012, before the asteroid heads away from Earth and beyond view for ground-based and space telescopes for the next six years. By which time, the OSIRIS-REx spacecraft will have launched. They plan observations with a network of telescopes in Arizona, the Canary Islands, Chile, Puerto Rico and space.
Observations will be challenging because the asteroid will pass no closer to Earth than 10.9 million miles (17.5 million kilometers) in early September, when it will be difficult to view against the angle of the sun. The asteroid appears 30 times dimmer in 2011 than it did in 2005, when it passed 3.1 million miles (5 million kilometers) from Earth and astronomers got a bonanza of data.
New observations will influence mission planning and development and also directly address some OSIRIS-REx mission key goals, said Dante Lauretta of the UA Lunar and Planetary Laboratory, OSIRIS-REx deputy principal investigator.
One goal is to compare results from ground-based and Earth-orbiting telescopes to results from cameras and other science instruments aboard the OSIRIS-REx spacecraft as it circles the asteroid, flying as close as four-tenths of a mile (0.7 kilometers), for about 500 days beginning October 2019.
This "ground truthing" of Earth-based telescopes empowers astronomers to interpret observations made from Earth more accurately and expand their science to other Earth-approaching asteroids and to the main belt between Mars and Jupiter, Lauretta said.
This year's first near-infrared observation of 1999 RQ36 was made about a month ago. Massachusetts Institute of Technology professor Richard Binzel and post-doctoral fellow Francesca DeMeo used one of the twin 6.5-meter Magellan telescopes at Las Campanas Observatory in Chile to view the asteroid at near-infrared wavelengths on July 26.
"The asteroid was extremely faint, an exceedingly difficult target, even with the Magellan telescope," Binzel said.
The new Magellan results are consistent with excellent data taken in 2005, which show the asteroid is composed of primitive material, he said.
This consistent result is gratifying because a core OSIRIS-REx mission goal is to bring back to Earth a good-sized, pristine sample of carbon-rich, primitive asteroid, a time capsule left over from solar system formation 4.5 billion years ago that could contain the building blocks of life.
"Even though these new data don't affect what we already know," Binzel said, "what is most important is that we are doggedly pursuing all opportunities to learn a little bit more about this object."
One highlight anticipated for September observations will be using the European Space Agency's Herschel space telescope to get first-ever views of the asteroid at far infrared wavelengths, Lauretta said. OSIRIS-REx will not see the asteroid at far infrared wavelengths.
Asteroid 1999 RQ36 will appear brighter in April and May 2012 than it does in September. Although it will be farther from Earth by next spring, it will have moved out of the glare of the sun and be positioned to reflect more light back to Earth, Lauretta and Hergenrother said.
This will give astronomers a better chance to do photometry, which measures how light brightens and dims over time. Prominent surface features cause dimming and brightening as the asteroid rotates, and astronomers can get a more precise rotation rate by watching the light changes.
To talk about 1999 RQ36 "brightness" is somewhat of a misnomer, Hergenrother noted, for the asteroid reflects only about 3 percent of the sunlight that hits it. Fresh asphalt is brighter.
Hergenrother in Arizona and colleagues in other parts of the world study how reflectivity changes during different asteroid phases.
Using the moon as an analogy, a full moon reflects far more light back to Earth than a crescent moon or a quarter moon does.
"Problem is, we never observe the asteroid at full phase from the ground," he said. "It's really difficult to do because the asteroid never lines up completely with the Earth and the sun."
By observing the asteroid at its different phases, astronomers can derive a function that tells them how bright it would be at full-phase. That gives them important information on albedo, which is how much total light the asteroid surface reflects.
Measuring albedo is important for mission planning and for helping astronomers constrain the size of asteroids they view with telescopes, Hergenrother said. It's also important for learning more about how sunlight heats an asteroid surface, possibly sending the asteroid into an orbit that eventually heads toward Earth.
University of Arizona
Source: The Daily Galaxy
Climate Temperature Fluctuations Triggered Human Evolution
By 1.5 million years ago we are left with a single human ancestor – Homo erectus. The key to the survival of Homo erectus appears to be its behavioural flexibility – it is the most geographically widespread species of the period, and endures for over one and a half million years. While other species may have specialized in environments that subsequently disappeared – causing their extinction – Homo erectus appears to have been a generalist, able to deal with many climatic and environmental contingencies.
Research at the University of Liverpool has found that periods of rapid fluctuation in temperature coincided with the emergence of the first distant relatives of human beings and the appearance and spread of stone tools.
Dr Matt Grove from the School of Archaeology, Classics and Egyptology reconstructed likely responses of human ancestors to the climate of the past five million years using genetic modelling techniques. When results were mapped against the timeline of human evolution, Dr Grove found that key events coincided with periods of high variability in recorded temperatures.
"The study confirmed that a major human adaptive radiation – a pattern whereby the number of coexisting species increases rapidly before crashing again to near previous levels - coincided with an extended period of climatic fluctuation." Grove said.
Following the onset of high climatic variability around 2.7 million years ago a number of new species appear in the fossil record, with most disappearing by 1.5 million years ago. The first stone tools appear at around 2.6 million years ago, and doubtless assisted some of these species in responding to the rapidly changing climatic conditions.
Variability selection suggests that evolution, when faced with rapid climatic fluctuation, should respond to the range of habitats encountered rather than to each individual habitat in turn; the timeline of variability selection established by Dr Grove suggests that Homo erectus could be a product of exactly this process.
"Though often discussed under the banner term of 'global warming'," oberserved Grove, "what we see in many areas of the world today is in fact an increased annual range of temperatures and conditions; this means in particular that third world human populations, many living in what are already marginal environments, will face ever more difficult situations. The current pattern of human-induced climate change is unlike anything we have seen before, and is disproportionately affecting areas whose inhabitants do not have the technology required to deal with it."
The research is published in The Journal of Human Evolution and The Journal of Archaeological Science.
University of Liverpool
Source: The Daily Galaxy
From the X-Files Dept - Will the Human Species Evolve a Quantum Consciousness?
Stephen Hawking has voiced concern about the dangers that he believes are posed by aliens who may arrive some day on Earth: "To my mathematical brain, the numbers alone make thinking about aliens perfectly rational. The real challenge is to work out what aliens might actually be like..."
According to Hawking aliens "would be only limited by how much power they could harness and control, and that could be far more than we might first imagine...Such advanced aliens would perhaps become nomads, looking to conquer and colonize whatever planets they can reach...I imagine they might exist in massive ships, having used up all the resources from their home planet...If aliens ever visit us, I think the outcome would be much as when Christopher Columbus first landed in America, which didn’t turn out very well for the Native Americans."
Life as we know it is based on chemistry but what, asks Randy D. Allen of the Department of Biochemistry and Molecular Biology, Oklahoma State University, if life elsewhere is based, not on chemistry but on quantum mechanics?
An alien life form that can manipulate subatomic particles like our cells manipulate chemical compounds. Humans have existed as a species for less than a million years and we are, as far as we know, the only species on Earth that has even the vaguest notion of physics. We only discovered the atom and learned to unleash its power, Allen observes, within the last century:
"Our understanding of quantum mechanics is rudimentary, at best, yet we are on the verge of developing practical quantum computers that promise virtually unlimited computational power," Allen observed. "It is conceivable that, in the billions of years since the Big Bang, other organisms evolved at some time and some place that have already mastered quantum mechanics.
"Let’s say that intelligent, social, organisms with chemically-based metabolism, fundamentally not unlike ourselves, evolved on a planet somewhere in the universe," Allen added. "Their unquenchable curiosity about the universe (or, like us, their unquenchable desire to exploit it) led them to develop efficient quantum computers. They realized that, with such computers, the whole of their existence could be computerized, all memories and life experiences, all emotions and motivations, could be transferred to a collective “quantum brain”. In effect, their “species”, though biologically extinct, could become immortal. No more inefficient metabolism requiring huge energy input, no chemically derived bodies to wear out, no reproduction, no death, no taxes. Just supermassively parallel collective consciousness with unlimited capabilities. Perhaps, through super symmetry or entanglement, they can “see” or “feel” the entire universe. Maybe, they’ve gained the ability to manipulate elementary particles and can control its evolution and its fate."
We can project that with no need to compete for resources, quantum beings would most likely be peaceful and only want the best for the Universe and its inhabitants. They could be aware of our existence, Allen says, but don’t care about us, much as we ignore most of the “lower” organisms that surround us. Alternatively, perhaps they have noted our biological, social and technological evolution and realize that we humans may well join their ranks someday and become quantum beings ourselves.
Several of the world's leading thinkers from believe that with the exponential increase in human knowledge that we are on track to have artificial intelligence exceed human potential by 2040 or sooner.
Vernor Vinge, Hugo Award-winning author of A Fire Upon the Deep and Rainbows End, argues that exponential growth in technology will reach a point beyond which we cannot even speculate. "We are on the edge of change comparable to the rise of human life on Earth. Within thirty years, we will have the technological means to create superhuman intelligence."
Source: The Daily Galaxy
[Image] The Pencil Nebula Supernova
At 500,000 kilometers per hour, a supernova shockwave known as the Pencil Nebula, or NGC 2736 races through interstellar space. This shockwave is part of the Vela supernova remnant, an expanding shell of a star that exploded about 11,000 years ago. Initially the shockwave was moving at millions of kilometers per hour, but the weight of all the gas it has swept up has slowed it considerably. Pictured above, the shockwave moves from left to right, as can be discerned by the lack of gas on the left. The above region spans nearly a light year across, a small part of the 100+ light-year span of the entire Vela supernova remnant. The Hubble Space Telscope ACS captured the above image last October.
Imgae Credit: Hubble Heritage Team (STScI/AURA), W. Blair (JHU) & D. Malin (David Malin Images)
NASA
Source: The Daily Galaxy
Quantum Physics - The quantum world writ large: Using short optical pulses to study macroscopic quantum behavior
Proposed design and fabrication procedure for high-finesse optomechanical microcavities: Using microcavities provides optomechanical coupling rates many orders of magnitude larger than current millimeter or centimeter length scale implementations of optomechanical Fabry-Pérot cavities and can provide sufficient radiation-pressure interaction to resolve the small scale quantum properties of the mechanical resonator. Cross-sectional view with a quarter of the device removed. Uppermost (colored green) is the mechanical resonator supported by auxiliary beams. The optical field is injected into the device from below through a transparent handle (colored blue) and the curved rigid input mirror (colored pink) and then resonates in the vacuum-gap between this and the mechanical device before being retroreflected. Image (c) PNAS, doi: 10.1073/pnas.1105098108
Einstein infamously dismissed quantum entanglement asspooky action at a distance and quantum uncertainty with his quip that God does not play dice with the universe. Aside from revealing his conceptual prejudices, Einstein’s rejection of these now-established hallmarks of quantum mechanics point to the field’s elusive nature: Coherent quantum mechanical phenomena, such as entanglement and superposition, are not apparent at macroscopic levels of scale. In fact, a common view is that on these scales quantum behavior is masked by decoherence, or even that quantum mechanics itself needs revision. Encouragingly, however, researchers at the Vienna Center for Quantum Science and Technology(VCQ), University of Vienna, have recently proposed an experimental design that would use a macroscopic mechanical resonator, short optical pulses and optical microcavities to realize quantum state tomography, squeezing, and state purification that could shed light on this elusive boundary between the quantum and classical worlds.
Led by Michael R. Vanner in Prof. Markus Aspelmeyer’s Aspelmeyer Group for Quantum Foundation and Quantum Information at the Nano- and Microscale, the team – which also included I. Pikovski, G. D. Cole, M. S. Kim, Č. Brukner, K. Hammerer, and G. J. Milburn – faced a number of challenges in devising their optomechanical scheme to fully reconstruct quantum states of mechanical motion. One of the most fundamental is the attempt to observe quantum mechanical behavior of a macroscopic mechanical object, since any potential quantum features would exhibit themselves only on truly miniscule scales. “For the mechanical structures that we consider,” Vanner explains, “one needs to resolve position displacements of about a femtometer,” or one-trillionth of a millimeter. “This is a mind‐bogglingly small distance that is, in fact, smaller than even the diameter of a hydrogen nucleus.”
This then leads to additional challenges: In the attempt to measure an object’s position, the object moves and causes positional smearing by injecting uncertainty into the resulting position information, which is referred to as the Standard Quantum Limit (SQL). “The first challenge that we had to overcome was to find a method which circumvents the SQL,” Vanner continues. “The second was that making measurements of the position alone is insufficient to reconstruct aquantum state. This is because the quantum state contains all that is, at least in principle, knowable about the object. And so, one needs to also measure all the complementary properties of the state, such as its momentum, and to do so also in an equally precise manner.”
Since no existing microscopy technology is capable of resolving quantum-scale features, the team addressed these challenges with optical interferometry. “Perhaps where we benefited most,” Vanner reflects, “was from the work of V. B. Braginsky, who made several seminal contributions to the field of quantum measurement1. In particular he introduced a scheme using short pulses of light that can overcome the SQL.” A short pulsed interaction can achieve this because the mechanical object has very little time to move during the interaction, and thus smearing can be dramatically reduced. “Braginsky developed this technique to make sensitive force detectors with the goal of detecting gravitational waves,” notes Vanner. “We’ve utilized this technique to allow for very sensitive position measurements. What we introduce in our proposal is a protocol using these pulsed measurements to perform quantum state reconstruction, which was our primary interest, and also a protocol to prepare low entropy squeezed states.”
The state reconstruction scheme works in much the same way as many modern medical imaging techniques – that is, by taking images from many angles, as in X‐ray computed tomography, it is possible to determine the three-dimensional internal structure within the body. “Applying this analogy to our case,” Vanner continues, “the internal structure is the quantum state and the angles are its various properties: position, momentum, and their combinations. Our state reconstruction protocol uses appropriately timed pulses of light to access all these properties, thus providing a means to determine all the information in the quantum state.” An important point is that the team has analyzed the experimental feasibility and demonstrated that the scheme is realizable with current state‐of‐the‐art technology.
Vanner is optimistic about the development of additional innovations and extensions in pulse sequences and measurements based on their pulsed design. “As an example,” Vanner notes, “we’re currently trying to compliment our work reported in PNAS by developing pulsed approaches to quantum state preparation. Combining such results with our state reconstruction results provides a complete experimental framework.”
In terms of how their findings might enhance the future exploration of quantum mechanical phenomena on a macroscopic scale, Vanner points out that one important quantum mechanical phenomenon that is little explored in the laboratory is decoherence – the term given to the processes by which the environment surrounding a quantum object gains information about its state, often leading to the undesirable consequence of loss of quantum coherence between superposition components. “Decoherence is often regarded as one of the primary hindrances in efforts to construct a quantum computer. The quantum state tomography scheme that we have introduced can be used to observe and characterize decoherence, thus providing vital experimental data for the development of quantum mechanics based technology.”
Moreover, adds Vanner, “It is a fascinating prospect that quantum information can be encoded into the motion of a mechanical object. This may lead to a number of interesting possibilities, such as transduction between flying qubits – i.e., photons – and qubits in a solid state device or superconductor. A pulsed approach may indeed be a feasible route to achieving this goal.”
In addition to decoherence as discussed above, adds Vanner, “An attractive feature of the quantum state reconstruction scheme is that it can reconstruct and analyze any quantum state of motion. Thus, a large number of state‐dependent quantum effects can be studied. For example, one could utilize the fragility of a quantum superposition state as an extremely sensitive detector.”
For Vanner, one of the key prospects is to see their design actually realized. “We’re currently building an experiment to implement our quantum state reconstruction protocol,” he concludes. “I’m finding it very exciting to be able to physically implement our ideas and begin to experimentally see behavior that is predicted in our theoretical model.”
More information: Pulsed quantum optomechanics, PNAS, Published online before print September 7, 2011, doi: 10.1073/pnas.1105098108
1Related: Quantum nondemolition measurements: the route from toys to tools, V. B. Braginsky and F. Ya. Khalili, Reviews of Modern Physics 68, 1–11 (1996), doi: 10.1103/RevModPhys.68.1
Source: PhysOrg.com
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