Atacama large millimeter wave/submillimeter wave array(English: Atacama Large Millimeter/submillimeter Array, ALMA)ChilenorthAtacama Desert, is byradio telescopeConstitutiveAstronomical interferometer。Because of the two excellent conditions of "high altitude" and "dry air", this is crucial to the observation of millimeter and submillimeter wavelengths. The array is finally located on the Chenanto Plateau at 5000 meters, near which there are Llano de Chajnantor Observatory andAtacama Pathfinder Experiment。The ALMA telescope array has 54 antennas with a diameter of 12 meters wide and 12 antennas with a diameter of 7 meters. A total of 66 antennas work together.Each antenna collects radiation from space individually and focuses the signal on the receiver on the antenna.Then, all antennas acquire signals via dedicated“Supercomputer”-- Correlator processing, and finally summarizing.66 ALMA antennas can be arranged into arrays in different configurations. The distance between antennas varies from 150 meters to 16 kilometers.If compared with the past telescope systems, ALMA can see darker objects in millimeter and submillimeter wave bands and obtain higher image resolution.
Chinese name
Atacama large millimeter wave/submillimeter wave array
Foreign name
Atacama Large Millimeter/submillimeter Array, ALMA
Atacama large millimeter wave/submillimeter wave array(English: Atacama Large Millimeter/submillimeter Array, ALMA)ChilenorthAtacama Desert, is byradio telescopeConstitutiveAstronomical interferometer。Because of the two excellent conditions of "high altitude" and "dry air", this is crucial to the observation of millimeter and submillimeter wavelengths. The array is finally located on the Chenanto Plateau at 5000 meters, near which there are Llano de Chajnantor Observatory andAtacama Pathfinder Experiment。The ALMA telescope array has 54 antennas with a diameter of 12 meters wide and 12 antennas with a diameter of 7 meters. A total of 66 antennas work together.Each antenna collects radiation from space individually and focuses the signal on the receiver on the antenna.Then, all antennas acquire signals via dedicated“Supercomputer”-- Correlator processing, and finally summarizing.66 ALMA antennas can be arranged into arrays in different configurations. The distance between antennas varies from 150 meters to 16 kilometers.If compared with the past telescope systems, ALMA can see darker objects in millimeter and submillimeter wave bands and obtain higher image resolution.
Called millimeter and submillimeter wave arraysALMA telescopeIn millimeter wave and submillimeter wavewavelengthThe observation band is 0.3mm to 9mm, and the resolution is up to 4 millisecondSpace telescopeSharp ten times.Due to the excellent site conditions of the station, together with ALMA's unprecedented detection sensitivity, angular resolution, spectral resolution and imaging quality, astronomers can carry out new research in a wider range of astronomy fields, which is expected to detect the origin of the earliest stars and galaxies, and even directly capture the images of the formation of planets.ALMA began its scientific observation in the second half of 2011, released its first image to the press on October 3, 2011, and began its full operation in March 2013.According to the latest results released by ALMA on March 31, 2016TW SerpentThe precision of the photo is known as the "best representative work in history" of telescope observation of protoplanetary disk.[1]
Overview
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It is composed of 66 high-precision antennas, with observation bands ranging from 0.3 to 9.6 mmwavelengthOfALMA array, sensitivity and analytical power are higher than those of existing submillimeter telescopes (such as James Clerk Maxwell Telescope with single mirror)Submillimeter wave array telescope（SMA，Submillimeter Array）、IRAM located in the Deboh Plateau.
Its concept is similar toU.S.ANew MexicoVery large antenna array（VLA）The antenna can move on the desert plateau from 150 meters to 16 kilometers, which makes the scaling function of ALMA powerful and the observation targets more diversified.When the array is composed of more telescopes, the sensitivity provided is also high.
The telescope array is composed of three different types of antennas: 25 in the United States, 25 in Europe, and 16 in Japan's ACA (Atacama Compact Array), including "4 large and 12 small" (the large aperture is 12 meters, and the small one is 7 meters).ACA arrays not only enhance the quality of astronomical images obtained by ALMA, but also expand the imaging field of view of ALMA.
history
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The concept of ALMA originated from the three astronomical projects that later merged into one - the "Micron Array" (MMA,Millimeter Array）、LSA (Large Southern Array) in Europe and LMA (Large Millimeter Wave Array) in Japan,Large Millimeter Array）。In order to further explore the universe, before and after the 1990s, three groups of astronomers were planning to build large observatories to observe millimeter waves: the United States had a "MMA array plan", Europeans wanted to build a southern sky array called "LSA" in the southern hemisphere, and the Japanese plan was the "LMSA submillimeter wave array plan".The first step taken by ALMA was in 1997 when NRAO, National Radio Astronomy Observatory andEuropean Southern Observatory(ESO) agreed to merge MMA and LSA into one, and the combined array should have both the frequency range of MMA and the sensitivity of LSA.ESO and NRAO joined two observatories in Canada and Spain (the latter later became a member of ESO) to define and organize a joint project in technology, science and management.
According to the resolution, in March 1999, the new array was named "Atacama Large Millimeter Array" or ALMA (Atacama Large Millimeter Array). "alma" means "soul" in Spanish and "knowledgeable" or "erudite" in Arabic.On February 25, 2003, North America and Europe signed an agreement.On November 6, 2003, ALMA held a groundbreaking ceremony, and a year and a half after the ALMA logo was first announced to the world, Japan also decided to join on September 14, 2005.National Astronomical Observatory of Japan(NAOJ, National Astronomical Observatory of Japan) will be responsible for the design and construction of Atacama Compact Array (ACA).The array was later named Morita Array in memory of the Japanese radio astronomer who contributed a lot to the ALMA telescope arrayMorita Genichiro。[1]
Scientific achievements
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In the summer of 2011, ALMA launched the first batch of published images of early scientific observation, which confirmed the great potential.One of the first observation targets is a pair of galaxies that are obviously distorted due to collision, calledTentacle galaxy。Although ALMA did not observe the merger of the whole galaxy, this image is the clearest image of the tentacle galaxy in the submillimeter wave band. It shows the formation of new stars from dense cold gas clouds, which is not visible in the visible light band.[1]
Interference
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interference(interference) InphysicsMiddle refers to two or more columnswavestayspaceOccurs when overlap occurs insuperpositionTo form a newwave formPhenomenon.
For example, usingBeam splitterPut a bunchmonochromelight beamAfter splitting into two bundles, let them overlap in an area in the space, and you will find thatlight intensityIt is not evenly distributed: its brightness varies with its position in space. The lightest place exceeds the sum of the original two light intensities, while the darkest place may have zero light intensity. This redistribution of light intensity is called "interference fringe".In history, the interference phenomenon andRelated experimentsIt's proof of lightVolatilityHowever, this interference property of light was not gradually discovered until the early 19th century, mainly because coherent light sources are not easily available.
In order to obtain the visible light interferenceCoherent light sourcePeople invented and manufactured various optical devices and interferometers that generated coherent light. These interferometers had very high measurement accuracy at that time:Albert MichelsonWith the help ofMichelson interferometerCompleted the famousMichelson Morey experiment, gotEther windThe zero result of the observation.Michelson also measured with this interferometerStandard meter gaugeAnd thus obtained the exact length ofThe nobel prize in physics。After the 1960s,laserThis invention of high-intensity coherent light source makesOptical interferometryThe technology has been widely used as never before, and can be seen in various precision measurementsLaser interferometerThe figure of.Now people know that two buncheselectromagnetic waveThe interference ofWave particle dualityThe interference of light is alsophotonSelfProbability amplitudeThe result of the stack.[2]
