Supercluster refers to the large-scale structure of the universeGalaxy clusterLarger structure.Observable universe There are about 10 million superclusters in.
someGalaxy clusterGathered together to form a higher levelsphere systems , also known as the secondary galaxy cluster.bookGalaxy clusterIt is the same as about 50 nearby galaxy clusters and galaxy clusters to form superclusters.GalaxyThe phenomenon of agglomeration and synthesis of superclusters is calledGalaxySuper or secondary clustering.SuperclusterQuality rangeIs 10fifteen～10seventeenSolar mass。[2]
Several galaxy clusters together form a higher levelsphere systems , also known as the secondary galaxy cluster.Local galaxy groupJust like 50 nearbyGalaxy clusterAnd galaxy clustersLocal supercluster。The phenomenon of galaxy agglomeration into super cluster is called super cluster or secondary cluster of galaxies.Usually, there are only 2-3 galaxy clusters in a supercluster.There are dozens ofMember galaxyThere are not many supercluster clusters.Superclusters tend to have a flat and long shape, with a length diameter range of 60 million to 100 million seconds, and an average ratio of length to diameter of about 4:1;This flat structure indicates that supercluster usually has rotation.Of a member galaxy cluster within a superclusterVelocity dispersionAbout 1000~3000 kilometers per secondGravitational interactionIt is much weaker than the gravitational interaction between the member galaxies in the cluster, so some people think that supercluster may be an unstable system.The existence of superclusters indicates that the distribution of matter in space is uneven at least on the scale of 100 million light-years.As for whether all galaxy clusters are members of superclusters of different sizes, due to the extremely insufficient observational data and difficulties in analytical methods, the issue is far from consensus.In addition, others believe that superclusters can be further clustered to form third-order galaxy clusters and even higher-level galaxy clusters.
Supercluster
Explanation of the existence of superclustersCosmic spaceAt least on the scale of hundreds of millions of light years, the material distribution is uneven.After the 1980s, astronomers found that there were few regions of galaxies with a diameter of hundreds of millions of light years in space, called void.Supercluster clusters and giant holes are intertwined to form the basic image of the large-scale structure of the universe.The supercluster where the local galaxy group is located is called the local supercluster.Closer supercluster includes Wuxian supercluster, Northern Corona superclusterpython-Virgo Supercluster Etc.
The existing superclusters show thatGalaxy distributionIs uneven;Most of them gather together to form groups and clusters, and the number of galaxies in each cluster ranges from 50 to thousands.These groups and groups and othersGalaxy formationThe larger isolated structures are called superclusters.
Once considered the largest structure in essence, supercluster is considered as the next level of a larger sheet or wall structure sometimes called "supercluster complex". They may span billions of light years, more thanVisible universe5%.Supercluster itself may span hundreds of millions of light years, and the typical speed of galaxies is about 1000 km/s.Hubble's law It suggests that the speed of these typical galaxies is about 30 million light-years at 1/H Hubble time, which is similar to that of the timeCosmic age。When expressed in human terms, these distances are much smaller than superclusters.In the expanding universe, aDistance of celestial bodiesdWhich is equivalent to his current speedvMultiply it by the time t it experiences, but the distance of the celestial body will be underestimated when the time is less than 1/H.The above calculation still needs to put forward some ideas to correct. How long it takes to form or dissipate these structures from galaxies in the normal process shows that they are older.When we observe superclusters and larger structures, we know what the universe was like when these superclusters were created.The direction of the rotation axis in the supercluster also gives us insight into the process of galaxy formation in early cosmic history [1].
No cluster composed of superclusters (extremely superclusters or superclusters) has been found, and whether there is a larger structure than superclusters is still under debate (see Galaxy Fiber, according to the data of cosmic microwave background radiation, the matter in the universelarge scaleThe following isuniform distributionIt seems that there is no structure larger than the "Galaxy Fiber".There are huge holes between superclusters, and only a few galaxies exist in space.Even if supercluster is confirmed to be the largest structure, the total number of supercluster still leaves the possibility of structure distribution. It is believed that the number of supercluster in the universe should be 10 million.)
Superclusters are often divided into small clusters called galactic clouds.
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Supercluster
Supercluster including local galaxy cluster. In 1937, Holmberg analyzedDouble galaxyAnd multipleDistribution of galaxiesLater, it was believed that there was a "total galaxy cloud" with a scale range of 100 million seconds, which was the original concept of this superclusterIn the 1950s, Wokuler re proposed the concept of this supercluster, which was confirmed by later research. Wokuler believed that the length of this supercluster was 30 million to 75 million seconds, and it was a collection of many galaxy clouds and clusters, including the local galaxy cluster,Virgo Galaxy Cluster, the Great Bear Cluster and about 50 smaller groups and clustersTogether, they form a huge flat shapesphere systems Among them, bright galaxies brighter than 13.5 are concentrated on a large circle in the sky, which is called the supercellar equatorpolar coordinatesstayInternational Astronomical UnionGalactic coordinate systemMiddle isSilver meridian47°.37,Silver weft+6 °. 32. The center of this supercluster isvirgo cluster Nearby silver longitude 283 ° silver latitude+75 °For galaxies along the equator of the super galaxyApparent velocityOur analysis shows that this supercluster may be rotating and expandingRevolution periodAbout 100 billion years
It is composed of two petal shaped clusters. Usually, the whole cluster is regarded as a supercluster. Sometimes, individual parts of the whole cluster are called the Serpentine supercluster Centaur supercluster
There are at least two galaxy clustersRXJ 0848.9+4452(z=1.26) andRXJ 0848.6+4453(z=1.27)
Astronomical discovery
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Supercluster
Not long ago, American astronomers discovered a huge "supercluster".This has attracted people's attention.As you know,solar systemIn addition, there are two or three hundred billion stars“Galaxy”(Galaxy, short for 湦);There are thousands of "external galaxies" outside the Milky Way.These galaxies are often distributed in the universe in groups of three or five. Astronomers call them "galaxy groups".There is also a group larger than a galaxy cluster - a dozen or even thousands of galaxies together, called "galaxy clusters".If several galaxy clusters form another system, it is called "supercluster".The general supercluster has only two or three galaxy clusters, rarely more than dozens of galaxy clusters;The space range is about tens to hundreds of millions of light years.
NASA dispatches a U-2 aircraftNorthern HemisphereIn the process of measuring the cosmic microwave background radiation at high altitude, a giant supercluster was found, extending to 2 billion light years of space.Compared with the space depth of 10 billion light years that we can observe, this supercluster occupies a large part.An astronomer sighed: The universe still has a certain structure in such a huge range, which is really amazing!
You see, the distribution of cosmic matter, from the solar systemGalaxyFrom galaxy clusters (clusters) to supercluster clusters, it seems that they form one "ladder" after another.Some people speculate that there can be "super" super clusters and "super" super clusters on top of super clusters... However, today, due to the limitations of observation methods, writers have not been able to verify this.
Measuring cosmic microwave background radiation can be used to testcosmologyIn“Primitive fireball”Theory.According to this theory, the universe was formed in a big explosion by an ultra dense and overpressure "primitive fireball" 120 billion years ago.Extra largeSuperclusterThe discovery ofCosmologistAs envisaged, according to the uniformIsotropyIt is carried out in an uneven and non isotropic manner.
Galaxy distribution
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The numerical density of LSC galaxies isVirgo Galaxy ClusterThe relationship between the center and the square of the distance dropped, indicating that this galaxy group was not randomly selected.In short, bright galaxies（Absolute magnitudeMore than 13) are mostly concentrated in a few galaxy clouds (groups of galaxy clusters), and 98% of bright galaxies are found in 11 clouds (decreasing in the number of bright nebulaeSequential arrangement）：Hound galaxyCluster, Virgo Galaxy Cluster, Virgo II (extending southward)lionII、Virgo III, Jujue（NGC3672), Lion I, Little Lion（NGC 2841）, Tianlong（NGC 5907）, cylinder（NGC 2997）And NGC 5643.Among the bright galaxies on the disk, one third belong to the Virgo Galaxy Cluster, the rest belong to the Hound Galaxy Cluster and Virgo II Cloud, and some may belong to NGC 5643.Bright galaxies in the halo are also concentrated in a few galaxy clouds (94% are distributed in seven clouds).This distribution shows that "most areas of the supercluster disk are huge holes".It can be compared with the observed phenomenonSoap bubbleStructure of.Slightly flat galaxy clusters and supercluster clusters can be found at the intersection of bubbles. They are huge bubbles, which are nearly spherical (the order of magnitude of the diameter is 20-60 million seconds) in space.The filamentary structure of field fiber seems to be dominant.One example is the serpent centaur supercluster, the supercluster closest to the LSC, which extends from about 30 million seconds to 60 million seconds.
Cosmology
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Large-scale dynamics
Since the 1980s, it has been obvious that not only the local galaxy group, but also 50 millionSecond gapAll other substances are heading at a speed of about 600 km/sNorma Cluster (Abell 3627) Exercise.When astronomers measured the motion relative to the cosmic microwave background radiation (CMB), Leyden Bell et al. (1988) speculated that“Giant source", but why its essence is still difficult to understand.
dark substance
The total mass of LSC M ≈ 10 trillion solar mass and the total optical brightness L ≈ 3 trillion solar luminosity.The mass light ratio thus produced is about 300 times that of the sun, which is consistent with the pattern of other superclusters.(For comparison,GalaxyThe mass light ratio is 2.7dark substanceA popular main argument.
Fenghuang.comScience and Technology News According to Science Daily, when Planck detects the microwave sky, he uses the Sanyeviv Zeldovich effect, which is a unique effect in the cosmic microwave backgroundCosmic spaceUnder the huge object environmentGalaxy clusterFirst photo of.ESAThe joint action between the XMM Newton of the mission and the subsequent Planck detection revealed the existence of an informed and unknown supercluster.
The matter in the universe is dispersed in a highly dense manner, and stars are gathered togetherGalaxyGalaxies gather together closely, forming a huge cluster in the vast open space.Galaxy clusters can support a thousand galaxies, which are full of hot gas shining with bright X rays;They are mostly composed of dark matter.
Planck's primary goal is to obtain pictures of the ancient universe, that is, the cosmic microwave background (CMB), so it has nine high-quality channels,Spectral rangeFrom 30 to 857GHz。Such a wide spectral range is not only conducive to removingPollution sourceTo captureEarly universeIt also makes Planck an excellent hunter of galaxy clusters.
In fact, these nine channels were carefully selected by Planck's team based on a special phenomenon called the Sanyeviv Zeldovich Effect (SZE).When the CMB photon moves towards us again, it encounters the change of energy experienced by the galaxy cluster, which is called the Sanyeviv Zeldovich effect.So even in galaxy clustersred shiftSZE is still a unique tool for detecting galaxy clusters.
"WhenBig BangOfMolecular fossilpass throughCosmic timeIt facilitates the interaction of the matter it encounters: for example, when it passes through a galaxy cluster, CMB neutrons will disperse thefree electron。”Orsay, Francespatial data Nabila of the Institute?Agannan said that he was investigating the SZE team and the second timeanisotropyA leading member of the Planck scientists."These collisions redistribute the frequency of photons in a special way, which enables us to separate the interference group in the CMB signal."
becauseThermionicIt is more energetic than CMB neutrons, so the interaction between the two causes the neutrons to disperse to higher energy.This means that whenGalaxy clusterWhen looking at CMB, people can see the shortage of relatively low energy neutrons and the surplus of high-energy molecules.This distinction is insufficient and redundantCritical frequencyIt is 217GHz.Planck channel detects the spectrum below and above this critical frequency, and the frequency between them is exactly 217GHz.
"With this unprecedented spectral range, Planck can detect the positive and negative signals of galaxy clusters, so Planck is a very useful tool to locate these clusters in the whole sky and measure their physical properties," said Jan Taber, a scientist of the Planck project.Planck's first pictures include some galaxy clusters that astronomers have been taking, such as comet hair, a very hot nearby galaxy cluster, and Albert 2319, a very close galaxy cluster.
Planck's design is specifically aimed at detecting SZE signals of galaxy clusters scattered in the sky, because it is not suitable for in-depth investigation, and its separation rate is too low to detect the details of these galaxy clusters, especially someNew findingsHigh redshift galaxies.
To determine their identity, scientists used ESA'sX-rayObserve - XMM Newton."Because of its high sensitivity, XMM Newton is the best tool to continue to complete the galaxy clusters detected by Planck," said Monique Arnold, who led Planck's team to use XMM Newton for subsequent research.It is between these two ESA tasksSynergyThis enabled astronomers to use XMM Newton to confirm that what Planck had detected earlier was indeed a galaxy cluster, and it also found that it was actually a larger structure: a supercluster!
"XMM Newton observation shows that one of the galaxy clusters is actually a supercluster composed of three independent giant galaxies, which Planck did not detect."
"The synergy between these two missions shows great success. XMM Newton will continue Planck's detection to determine what is the essence of this galaxy cluster?"XMM Newton project scientist Norbert said.
"This is the first time that SZE has detected the existence of superclusters, and this important discovery has opened a new window for the study of superclusters“
The SZ signal of this newly discovered supercluster comes from the sum of the signals of three independent clusters, among which there may be other filaments between clusters.This also gives large-scaleGas distributionIt provides an important clue, which is also crucial for tracking the distribution of dark matter.
Planck's first sky survey began in mid August 2009 and ended in June 2010.Planck will continue to receive data until the end of 2011, during which time it will complete all sky scans.
