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《Flash Physics: LIGO resumes its search, sound moves magnetic domains, asteroid is tiny and bright》

  • 来源专题：水声领域信息监测
  • 编译者： ioalib
  • 发布时间：2016-12-12

  • The Laser Interferometer Gravitational-wave Observatory (LIGO) – a pair of gravitational-wave detectors in Hanford, Washington, and Livingston, Louisiana – have been turned back on following almost a year of upgrades. On 11 February, the LIGO collaboration announced the first-ever direct observation of gravitational waves, which were generated by the collision of two black holes 1.3 billion light-years away. This was followed by the announcement of a second gravitational-wave detection on 15 June, also from merging black holes. The detections were made during LIGO's first run from September 2015 to January 2016, and since then engineers have been making improvements to the facility's lasers, electronics and optics. The Livingston detector now has about a 25% improvement in sensitivity, allowing it to spot black-hole mergers at greater distances. The sensitivity of the Hanford detector, meanwhile, is similar to the first run, however the power of the laser has been increased and the detector is more stable, increasing the time that the detector is operational. "Already LIGO has exceeded our expectations, and, like most of the scientific world and beyond, I am excited to see what a more sensitive, upgraded LIGO will detect next," says National Science Foundation director France Córdova. The detectors are now expected to run for around six months before undergoing further maintenance and upgrades.

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  • 《With X-Ray Analysis, an Asteroid Provides a View into Our Solar System’s Past》
    • 来源专题：可再生能源
    • 编译者：武春亮
    • 发布时间：2024-07-01
    • Skip to main content Enter the terms you wish to search for. Search History Organization Chart Work with Us Newsroom Careers Energy.gov Offices National Labs Office of Science Main navigation Office of Science Home About Us About Us Leadership History Honors and Awards Diversity, Equity & Inclusion Energy.gov Home Initiatives Initiatives Advanced and Sustainable Energy Artificial Intelligence and Machine Learning Genomics High Performance Computing Large Scale Scientific Instrumentation Quantum Information Science Mission Mission Science Programs Field Mission Support Office of Project Assessment Science & Innovation Science & Innovation National Labs Universities User Facilities PuRe Data Resources Science Highlights DOE Explains... 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As the ALS is a Department of Energy (DOE) Office of Science user facility, the team that works there sees a lot of unusual items, from materials for solar cells to particles influenced by wildfires. But even for this crew, a sample from an asteroid was unusual. Fortunately, the innovative tools available at the ALS allowed them to support scientists digging into the history of these rocks delivered from space.Just like studying rocks on Earth can tell us about Earth’s early history, studying primitive small bodies such as asteroids, meteorites, and comets can tell us about our solar system’s history. Chondrites are a particularly useful type of meteorite. They are undifferentiated and chemically primitive. The rocks in them trace back to dust and small grains in the early solar system that came together to form a large parent body. A certain type of chondrites (called carbonaceous chondrites) preserve relatively abundant chemicals that are easily vaporized, including carbon and water. These are the building blocks of life on Earth. By studying these preserved materials, scientists can investigate one of humanity's fundamental questions: “Where did we come from?”  The team using the ALS examined a sample from the surface of a carbonaceous-type asteroid, Ryugu. They expected this asteroid to be similar to carbonaceous chondrite meteorites. Ryugu is relatively close to Earth, compared to asteroids in the main belt between Mars and Jupiter. Scientists hypothesize that Ryugu is a rubble-pile asteroid. They think that it formed when an object hit its parent body and then the rocks that were ejected re-coalesced into a new asteroid. After that process, the asteroid moved from the main belt to near-Earth orbit. The Japan Aerospace Exploration Agency (JAXA)’s spacecraft, Hayabusa2, collected samples from two locations on the surface of Ryugu in 2019 and returned them to Earth in 2020. The curatorial work at JAXA found a total of 5.4 g of sample. The agency allocated a small portion of the sample to the Hayabusa2 initial analysis team, consisting of about 400 scientists around the world. Hikaru Yabuta at Hiroshima University led one of six sub-teams of the initial analysis team. Ultrathin sections of the asteroid particles arrived at the ALS at DOE’s Lawrence Berkeley National Laboratory. The ALS allows scientists to precisely identify the elements and molecules inside materials. It uses a particle accelerator to produce extraordinarily bright X-ray beams. Like the X-rays at a doctor’s office, they reveal information about what is inside an object. But instead of just highlighting bones, these X-rays allow scientists to probe the chemical and structural properties of the matter itself. First, the team carefully scanned the sample in long horizontal rows—like text in a book—with X-rays. By measuring how the X-rays change as the scanning happens, scientists could identify individual grains of organic material in the asteroid sample. These grains were tiny – only 100 times bigger than a strand of DNA. Once the scientists identified grains of interest, they used X-rays to reveal the type of chemical bonds in the organic carbon grains. In this case, the researchers used the process to map out the various elements and functional groups (specific arrangements of atoms) in the sample. Based on this analysis, the scientists found four different types of carbon compounds as well as different types of structures. After identifying these materials, the scientists compared them to similar meteorites that they already knew the history of. Piecing together all of this data allowed them to outline a broad history of the asteroid during the early solar system, which formed about 4.6 billion years ago. The chemical compositions of the organic carbon in the samples indicated that Ryugu’s organic matter resulted from the precursors to that matter changing during a chemical reaction with liquid water on the asteroid’s parent body. The isotopes of carbon in the samples reflected that the organic precursors came from the extremely cold environment of space (about -200 °C). The team was the first to prove the direct link between organic matter in the carbonaceous asteroid and the similar organic matter in primitive carbonaceous chondrites (meteorites). There was one type of material notably missing – graphite. Graphite is a familiar form of carbon used in pencil leads. In asteroids, graphite or graphite-like material is a sign that the carbon was formed by radiogenic heating in parent bodies for several million years. The lack of it suggests that the sample collected from the asteroid was never exposed to heat above 390 °F (200 °C).Studying the material from Ryugu wasn’t the first or likely the last time that scientists will use the ALS to take a close look at rocks from space. Researchers used the ALS to analyze dust particles from the comet 81P/Wild 2 collected by NASA’s spacecraft Stardust in 2006. They found that the comet dust contained organic matter. This matter was composed of nitrogen- and oxygen-bearing chemical bonds as well as types of organic matter similar to that observed from the asteroid Ryugu and other chondritic meteorites.These studies demonstrated tools and techniques that have proven useful for analyzing samples like those from NASA’s OSIRIS-REx mission. This mission collected samples from the asteroid Bennu. In the fall of 2023, it returned them to Earth. The agency recently released a catalog of samples for scientists to study.  The ALS and other light sources allow us to draw lines from the earliest history of our solar system to today. Through shedding light on the objects in our current solar system, the DOE Office of Science scientists and user facilities may one day help us better understand how Earth became habitable. Shannon Brescher Shea Shannon Brescher Shea (shannon.shea@science.doe.gov) is the social media manager and senior writer/editor in the Office of Science’s Office of Communications and Public Affairs. more by this author Office of Science U.S. Department of Energy 1000 Independence Ave., SW Washington, DC 20585 (202) 586-5430 Sign Up for Email Updates Twitter Youtube Linkedin An office of About Office of Science Careers & Internships SC Home Contact Energy.gov Resources Budget & Performance Covid-19 Response Directives, Delegations & Requirements FOIA Inspector General Privacy Program Small Business Federal Government The White House USA.gov Vote.gov Web Policies Privacy No Fear Act Whistleblower Protection Notice of EEO Findings of Discrimination Information Quality Open Gov Accessibility Vulnerability Disclosure Program
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  • 《引力波天文台LIGO发起公民科学项目--”重力间谍”》
    • 来源专题：天文仪器与技术信息
    • 编译者：zwg@niaot.ac.cn
    • 发布时间：2016-10-24
    • LIGO最新的公民科学项目，”重力间谍”，将使世界各地的人帮助LIGO的科学家和LIGO电脑工程师更好，更快地寻找引力波的痕迹。 LIGO's newest Citizen Science Program, Gravity Spy, will enable anyone around the world to help LIGO scientists and LIGO computers become better and faster at finding the telltale traces of gravitational waves. As a "Gravity Spy" participant, you will look at real LIGO data in search of 'glitches', unwanted hiccups in the signal that can sometimes be confused for or mask out gravitational waves. Glitches make finding the real thing even more difficult than it already is! Nevertheless, they are an unfortunate fact of life for LIGO, so identifying the different kinds of glitches that appear in the interferometer data is crucial for LIGO scientists to be able to distinguish between annoying blips and signals from space! If you want to help LIGO continue to make scientific history, then Gravity Spy is the Citizen Science program for you! Click, SIGN ME UP FOR GRAVITY SPY! to get started today! If you still want a little more information, here's what the creators of Gravity Spy say about this exciting opportunity: "LIGO is the most sensitive and complicated gravitational experiment ever built. To detect gravitational waves even from the strongest events in the Universe, LIGO needs to be able to know when the length of its 4-kilometer arms change by a distance 10,000 times smaller than the diameter of a proton! This makes LIGO susceptible to a great deal of instrumental and environmental sources of noise. Of particular concern are transient, poorly modeled artifacts known by the LIGO community as glitches. Though the reason for having two detectors separated by thousands of miles is to isolate the detectors from common sources of noise, glitches happen frequently enough that they often can be coincident in the two detectors and can mimic astrophysical signals. Classifying and characterizing glitches is imperative in the effort to target and eliminate these artifacts, paving the way for more astrophysical signals to be detected. "Classifying glitches using computers has proven to be an exceedingly difficult task. A family of data analysis algorithms known as machine learning have made huge strides over the past decade in classification problems, though they usually require a large pre-classified dataset to operate effectively. However, human intuition has proven time and time again to be a useful tool in pattern recognition problems such as this. One of the innovations of this citizen science project is that citizen scientists and computer algorithms will work in a symbiotic relationship, helping one another to optimally classify and characterize glitches. The general workflow will be: 1：Citizen scientists will sift through the enormous amount of LIGO data to produce a robust "gold standard" glitch dataset that can be used to seed and train machine learning algorithms: 2：Machine learning algorithms will learn from this classified dataset to sort through more LIGO data, and choose the most interesting, abnormal glitches to be sent back to the citizen scientists 3：Citizen scientists will further classify and characterize these glitch morphologies, determining new glitch categories to be used in the training of the machine learning algorithms 4：Utilizing the strengths of both humans and computers, this project will keep LIGO data as clean as possible, and help to unlock more of the gravitational wave universe."
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