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Posted: 27 Feb 2015 05:25 AM PST
New research by the University of Texas (UT) at Dallas astrophysicist provides revelations about the most energetic event in the universe — the merging of two spinning, orbiting black holes into a much larger black hole. The work by Dr. Michael Kesden, assistant professor of physics at UT Dallas, and his colleagues provides for the first time solutions to decades-old equations that describe conditions as two black holes in a binary system orbit each other and spiral in toward a collision. The research is available online and in the Feb. 27 issue of the journalPhysical Review Letters.
Kesden said the solutions should significantly impact not only the study of black holes, but also the search for gravitational waves in the cosmos. Albert Einstein’s general theory of relativity predicts that two massive objects orbiting in a binary system should move closer together as the system emits a type of radiation called gravitational waves.
“An accelerating charge, like an electron, produces electromagnetic radiation, including visible light waves. Similarly, any time you have an accelerating mass, you can produce gravitational waves,” Kesden said. “The energy lost to gravitational waves causes the black holes to spiral closer and closer together until they merge, which is the most energetic event in the universe,” he said. “That energy, rather than going out as visible light, which is easy to see, goes out as gravitational waves, which are very weak and much more difficult to detect.” While Einstein’s theories predict the existence of gravitational waves, they have not been directly detected. But the ability to “see” gravitational waves would open up a new window to view and study the universe. Optical telescopes can capture photos of visible objects, such as stars and planets, and radio and infrared telescopes can reveal additional information about invisible energetic events. Gravitational waves would provide yet another medium through which to examine astrophysical phenomena, Kesden said. “Using gravitational waves as an observational tool, you could learn about the characteristics of the black holes that were emitting those waves billions of years ago, information such as their masses and mass ratios,” he said. “That’s important data for more fully understanding the evolution and nature of the universe.” This year, a large-scale physics experiment called the Laser Interferometer Gravitational-Wave Observatory(LIGO) aims to be the first to directly detect gravitational waves. LIGO is one of the largest projects funded by the National Science Foundation. “The equations that we solved will help predict the characteristics of the gravitational waves that LIGO would expect to see from binary black hole mergers,” Kesden said. “We’re looking forward to comparing our solutions to the data that LIGO collects.” The equations Kesden solved deal specifically with the spin angular momentum of binary black holes and a phenomenon called precession. Angular momentum is a measure of the amount of rotation a spinning object has. Spin angular momentum includes the rotation’s speed and the direction in which that spin points. For a simple object like a spinning figure skater, the direction of angular momentum would point up. Another type of angular momentum, called orbital angular momentum, applies to a system in which objects are in orbit about one another. Orbital angular momentum also has a magnitude and a direction. In an astrophysical setting like a binary black hole system, the directions of the individual types of angular momenta change, or precess, over time. “In these systems, you have three angular momenta, all changing direction with respect to the plane of the orbit — the two spin angular momenta and the one orbital angular momentum,” Kesden said. “The solutions that we now have describe the orientations of the precessing black hole spins.” In addition to solving existing equations, Kesden also derived equations that will allow scientists to statistically track spin precession from black hole formation to merger far more efficiently and quickly. “We can do it millions of times faster than was previously possible,” he said. “With these solutions, we can create computer simulations that follow black hole evolution over billions of years. A simulation that previously would have taken years can now be done in seconds. But it’s not just faster. There are things that we can learn from these simulations that we just couldn’t learn any other way.” Researchers from the University of Cambridge, the Rochester Institute of Technology and the University of Mississippi also contributed to the Physical Review Letters paper. The researchers were supported in part by the National Science Foundation and UT Dallas. Credit: utdallas.edu  | ||
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Posted: 26 Feb 2015 01:53 PM PST
Scientists have discovered the brightest quasar in the early universe, powered by the most massive black hole yet known at that time. The international team led by astronomers from Peking University in China and from the University of Arizona (UA) announce their findings in the scientific journal Nature on Thursday. The discovery of this quasar, named SDSS J0100+2802, marks an important step in understanding how quasars, the most powerful objects in the universe, have evolved from the earliest epoch, only 900 million years after the Big Bang, which is thought to have happened 13.7 billion years ago. The quasar, with its central black hole mass of 12 billion solar masses and the luminosity of 420 trillion suns, is at a distance of 12.8 billion light-years from Earth. The discovery of this ultraluminous quasar also presents a major puzzle to the theory of black hole growth at early universe, according to Xiaohui Fan, Regents' Professor of Astronomy at the UA's Steward Observatory, who co-authored the study. "How can a quasar so luminous, and a black hole so massive, form so early in the history of the universe, at an era soon after the earliest stars and galaxies have just emerged?" Fan said. "And what is the relationship between this monster black hole and its surrounding environment, including its host galaxy?
"This ultraluminous quasar with its supermassive black hole provides a unique laboratory to the study of the mass assembly and galaxy formation around the most massive black holes in the early universe."
Team member Dr Fuyan Bian, from the Research School of Astronomy and Astrophysics at the Australian National University (ANU), said the discovery challenges theories of how black holes form and grow in the early universe.
“Forming such a large black hole so quickly is hard to interpret with current theories,” he said.
The quasar dates from a time close to the end of an important cosmic event that astronomers referred to as the "epoch of reionization”: the cosmic dawn when light from the earliest generations of galaxies and quasars is thought to have ended the "cosmic dark ages" and transformed the universe into how we see it today.
“This quasar is a unique laboratory to study the way that a quasar’s black hole and host galaxy co-evolve,” said astronomer Yuri Beletsky of the Carnegie Institution for Science. “Our findings indicate that in the early Universe, quasar black holes probably grew faster than their host galaxies, although more research is needed to confirm this idea.”
Discovered in 1963, quasars are the most powerful objects beyond our Milky Way galaxy, beaming vast amounts of energy across space as the supermassive black hole in their center sucks in matter from its surroundings. Thanks to the new generation of digital sky surveys, astronomers have discovered more than 200,000 quasars, with ages ranging from 0.7 billion years after the Big Bang to today.
Shining with the equivalent of 420 trillion suns, the new quasar is seven times brighter than the most distant quasar known (which is 13 billion years away). It harbors a black hole with mass of 12 billion solar masses, proving it to be the most luminous quasar with the most massive black hole among all the known high redshift (very distant) quasars.
"By comparison, our own Milky Way galaxy has a black hole with a mass of only 4 million solar masses at its center; the black hole that powers this new quasar is 3,000 time heavier," Fan said.
Feige Wang, a doctoral student from Peking University who is supervised jointly by Fan and Xue-Bing Wu at Peking University, the study's lead author, initially spotted this quasar for further study.
"This quasar was first discovered by our 2.4-meter Lijiang Telescope in Yunnan, China, making it the only quasar ever discovered by a 2-meter telescope at such distance, and we're very proud of it," Wang said. "The ultraluminous nature of this quasar will allow us to make unprecedented measurements of the temperature, ionization state and metal content of the intergalactic medium at the epoch of reionization."
Following the initial discovery, two telescopes in southern Arizona did the heavy lifting in determining the distance and mass of the black hole: the 8.4-meter Large Binocular Telescope, or LBT, on Mount Graham and the 6.5-meter Multiple Mirror Telescope, or MMT, on Mount Hopkins. Additional observations with the 6.5-meter Magellan Telescope in Las Campanas Observatory, Chile, and the 8.2-meter Gemini North Telescope in Mauna Kea, Hawaii, confirmed the results.
"This quasar is very unique," said Xue-Bing Wu, a professor of the Department of Astronomy, School of Physics at Peking University and the associate director of the Kavli Institute of Astronomy and Astrophysics. "Just like the brightest lighthouse in the distant universe, its glowing light will help us to probe more about the early universe."
Wu leads a team that has developed a method to effectively select quasars in the distant universe based on optical and near-infrared photometric data, in particular using data from the Sloan Digital Sky Survey and NASA’s Wide-Field Infrared Explorer, or WISE, satellite.
"This is a great accomplishment for the LBT," said Fan, who chairs the LBT Scientific Advisory Committee and also discovered the previous record holders for the most massive black hole in the early universe, about a fourth of the size of the newly discovered object. "The especially sensitive optical and infrared spectrographs of the LBT provided the early assessment of both the distance of the quasars and the mass of the black hole at the quasar's center."
For Christian Veillet, director of the Large Binocular Telescope Observatory, or LBTO, this discovery demonstrates both the power of international collaborations and the benefit of using a variety of facilities spread throughout the world.
"This result is particularly gratifying for LBTO, which is well on its way to full nighttime operations," Veillet said. "While in this case the authors used two different instruments in series, one for visible light spectroscopy and one for near-infrared imaging, LBTO will soon offer a pair of instruments that can be used simultaneously, effectively doubling the number of observations possible in clear skies and ultimately creating even more exciting science."
To further unveil the nature of this remarkable quasar, and to shed light on the physical processes that led to the formation of the earliest supermassive black holes, the research team will carry out further investigations on this quasar with more international telescopes, including the Hubble Space Telescope and the Chandra X-ray Telescope.
Bian expects more surprising objects will be discovered during the Skymapper survey of the southern skies, currently being run by the ANU.
“Skymapper will find more of these exciting objects. Because they are so luminous we can see further back in time and can use them to explore the early universe,” Bian said.
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Posted: 26 Feb 2015 01:13 PM PST
Think of it as the ultimate hitchhiking opportunity: ESA is offering CubeSats a ride to a pair of asteroids in deep space. CubeSats are among the smallest types of satellites: formed in standard cubic units of 10 cm per side, they provide affordable access to space for small companies, research institutes and universities. One-, two- or three-unit CubeSats are already being flown. Teams of researchers and companies from any ESA Member State are free to compete. The selected CubeSats will become Europe’s first to travel beyond Earth orbit once the Asteroid Impact Mission (AIM) is launched in October 2020.
“AIM has room for a total of six CubeSat units,” explains Ian Carnelli, managing the mission for ESA. “So potentially that might mean six different one-unit CubeSats could fly, but in practice it might turn out that two three-unit CubeSats will be needed to produce meaningful scientific return.
“We’re looking for innovative ideas for CubeSat-hosted sensors that will boost and complement AIM’s own scientific return.
“We also intend to use these CubeSats, together with AIM itself and its asteroid lander, to test out intersatellite communications networking.
"ESA’s SysNova initiative will be applied to survey a comparatively large number of alternative solutions, this competition framework giving industry and universities the opportunity to work together on developing their scientific investigations in a field that is the technological cutting edge.”
Beginning its preliminary Phase-A/B design work next month, ESA’s AIM spacecraft will be humanity’s first mission to a binary system – the paired Didymos asteroids, which come a comparatively close 11 million km to Earth in 2022. The 800 m-diameter main body is orbited by a 170 m moon.
AIM will perform high-resolution visual, thermal and radar mapping of the moon. It will also put down a lander – ESA’s first touchdown on a small body since Rosetta’s Philae landed on a comet last November.
AIM also represents ESA’s contribution to a larger international effort, the Asteroid Impact & Deflection Assessment (AIDA) mission.
The NASA-led Double Asteroid Redirection Test (DART) probe will impact the smaller body, while AIM will perform detailed before-and-after mapping, including pinpointing any shift in the asteroid’s orbit.
“While it will return invaluable science,” adds Ian, “AIM is conceived as a technology demonstration mission, testing out various technologies and techniques needed for deep space expeditions in future.
“These include two-way high-bandwidth optical communications – with data being returned via laser beam to ESA’s station in Tenerife – as well as intersatellite links in deep space and low-gravity lander operations.
“Once demonstrated, these capabilities will be available to future deep-space endeavours, such as Lagrange-point observatories returning large amounts of data and sample return missions to Phobos – and ultimately Mars – as well as crewed missions far beyond Earth orbit.”
The chance to put forward CubeSats is being organised as a SysNova competition, an initiative by ESA’s General Studies Programme – which is running the AIM project – to compare innovative solutions to space mission challenges.
Interested teams can get more information from the published announcement of opportunity. As a next step, qualified teams can submit initial ‘challenge responses’ describing their proposed mission concepts and how they address the defined technical challenges associated with operating such small spacecraft close to an asteroid.
The winning submissions will then be funded by ESA for further study over the next seven months, following up with a final review at ESA's ESTEC technical centre in Noordwijk, the Netherlands. The victors will then work with ESA to elaborate their designs, including sessions at ESTEC's Concurrent Design Facility.
Credit: ESA
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Posted: 26 Feb 2015 11:35 AM PST
Most of the laws of nature treat particles and antiparticles equally, but stars and planets are made of particles, or matter, and not antiparticles, or antimatter. That asymmetry, which favors matter to a very small degree, has puzzled scientists for many years. New research by UCLA physicists, published in the journal Physical Review Letters, offers a possible solution to the mystery of the origin of matter in the universe. Alexander Kusenko, a professor of physics and astronomy in the UCLA College, and colleagues propose that the matter-antimatter asymmetry could be related to the Higgs boson particle, which was the subject of prominent news coverage when it was discovered at Switzerland’s Large Hadron Collider in 2012.
Specifically, the UCLA researchers write, the asymmetry may have been produced as a result of the motion of the Higgs field, which is associated with the Higgs boson, and which could have made the masses of particles and antiparticles in the universe temporarily unequal, allowing for a small excess of matter particles over antiparticles.
If a particle and an antiparticle meet, they disappear by emitting two photons or a pair of some other particles. In the “primordial soup” that existed after the Big Bang, there were almost equal amounts of particles of antiparticles, except for a tiny asymmetry: one particle per 10 billion. As the universe cooled, the particles and antiparticles annihilated each other in equal numbers, and only a tiny number of particles remained; this tiny amount is all the stars and planets, and gas in today’s universe, said Kusenko, who is also a senior scientist with the Kavli Institute for the Physics and Mathematics of the Universe.
The research also is highlighted by Physical Review Letters in a commentary in the current issue.
The 2012 discovery of the Higgs boson particle was hailed as one of the great scientific accomplishments of recent decades. The Higgs boson was first postulated some 50 years ago as a crucial element of the modern theory of the forces of nature, and is, physicists say, what gives everything in the universe mass. Physicists at the LHC measured the particle’s mass and found its value to be peculiar; it is consistent with the possibility that the Higgs field in the first moments of the Big Bang was much larger than its “equilibrium value” observed today.
The Higgs field “had to descend to the equilibrium, in a process of ‘Higgs relaxation,’” said Kusenko, the lead author of the UCLA research.
Two of Kusenko’s graduate students, Louis Yang of UCLA and Lauren Pearce of the University of Minnesota, Minneapolis, were co-authors of the study. The research was supported by the U.S. Department of Energy (DE-SC0009937), the World Premier International Research Center Initiative in Japan and the National Science Foundation (PHYS-1066293).
Credit: ucla.edu
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Posted: 26 Feb 2015 11:10 AM PST
Russia's Khrunichev State Research and Production Space Center will finish assembling the new module for the International Space Station (ISS) in February 2016, the center's acting chief said Wednesday. "We will finish equipping the module in February 2016. Then the module will be transferred to [Russian rocket and space corporation] RSC Energia for final adjustments. After that, it will be ready to be launched and subsequently integrated into the international space station," Andrey Kalinovsky said.
The launch of module Nauka ("Science" in Russian) initially planned for 2007, has been repeatedly delayed.
Nauka will perform a range of functions including life-support, steering the ISS with an attached motor and docking with cargo vessels.
The modules of the ISS are canister- or sphere-shaped areas of the station where the astronauts live and work.
Currently, the ISS comprises more than a dozen modules, including five Russian modules, according to NASA.
Credit: sputniknews.com
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Posted: 26 Feb 2015 10:55 AM PST
NASA's Curiosity Mars rover used its drill on Tuesday, Feb. 24 to collect sample powder from inside a rock target called "Telegraph Peak." The target sits in the upper portion of "Pahrump Hills," an outcrop the mission has been investigating for five months. The Pahrump Hills campaign previously drilled at two other sites. The outcrop is an exposure of bedrock that forms the basal layer of Mount Sharp. Curiosity's extended mission, which began last year after a two-year prime mission, is examing layers of this mountain that are expected to hold records of how ancient wet environments on Mars evolved into drier environments.
The rover team is planning to drive Curiosity away from Pahrump Hills in coming days, exiting through a narrow valley called "Artist's Drive," which will lead the rover along a strategically planned route higher on the basal layer of Mount Sharp.
The Telegraph Peak site was selected after the team discussed the large set of physical and chemical measurements acquired throughout the campaign. In particular, measurements of the chemistry of the Telegraph Peak site, using the Alpha Particle X-ray Spectrometer (APXS) on the rover's arm, motivated selection of this target for drilling before the departure from Pahrump Hills.
Compared to the chemistry of rocks and soils that Curiosity assessed before reaching Mount Sharp, the rocks of Pahrump Hills are relatively enriched in the element silicon in proportion to the amounts of the elements aluminum and magnesium. The latest drilling site exhibits that characteristic even more strongly than the earlier two, which were lower in the outcrop.
"When you graph the ratios of silica to magnesium and silica to aluminum, 'Telegraph Peak' is toward the end of the range we've seen," said Curiosity co-investigator Doug Ming, of NASA Johnson Space Center, Houston. "It's what you would expect if there has been some acidic leaching. We want to see what minerals are present where we found this chemistry."
The rock-powder sample from Telegraph Peak goes to the rover's internal Chemistry and Mineralogy (CheMin) instrument for identification of the minerals. After that analysis, the team may also choose to deliver sample material to Curiosity's Sample Analysis at Mars (SAM) suite of laboratory instruments.
The sample-collection drilling at Telegraph Peak was the first in Curiosity's 30 months on Mars to be conducted without a preliminary "mini drill" test of the rock's suitability for drilling. The team judged full-depth drilling to be safe for the drill based on similarities of the target to the previous Pahrump Hills targets. The rover used a low-percussion-level drilling technique that it first used on the previous drilling target, "Mojave 2."
Curiosity reached the base of Mount Sharp after two years of examining other sites inside Gale Crater and driving toward the mountain at the crater's center.
NASA's Mars Science Laboratory Project is using Curiosity to assess ancient habitable environments and major changes in Martian environmental conditions. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, built the rover and manages the project for NASA's Science Mission Directorate in Washington. The rover's APXS was provided by the Canadian Space Agency. CheMin was developed by NASA Ames Research Center, Moffett Air Force Base, California, and SAM was developed by NASA Goddard Space Flight Center, Greenbelt, Maryland.
Credit: NASA
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2015년 2월 27일 금요일
Astro Watch
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