Globular clusters are astronomynoun, becauseappearancesimilarsphericalIt gets its name.Globular clusters consist of thousands or even hundreds of thousandsfixed starThe composition is spherical in appearance, and the closer to the center, the denser the stars are.The average density of stars in globular clusters is higher than that around the sunStellar densityIt is ten times higher, and tens of thousands of times higher near its center.The stars in the same globular cluster have the same evolutionary process, with roughly the same direction and speed of motion, and they are likely to be formed at the same time.They areGalaxyThe first group of stars formed in China has a history of about 10 billion years.
Globular clusters have super dense star clusters (7200 light-years)[1]
Globular star clusters, spherical in appearance, orbit around the galactic core, much like satellitesfixed starGroup.Globular clusters are tightly bound by gravity, making them spherical in appearance and highly centered in stars.The globular clusters found are mostly in theGalactic haloWhich is far more than those found in the galactic diskOpen clusterHave more stars.
Globular clusters are common in galaxiesGalaxyAbout 150 of them are known, and perhaps 10-20 have not yet been found;Large galaxies will have more globular clusters, such asandromedaThere are as many as 500 galaxies, some giantElliptical galaxy, likeM87It may have as many as 1000 globular clusters.These globular clusters orbit the galaxy with a radius of 40000 seconds (about 131000 light-years) or more.
stayLocal galaxy groupGlobular clusters accompany every galaxy with enough mass, and almost every large galaxy that has ever been detected has also been found to have globular clusters.Sagittarius dwarf elliptical galaxyandCanis Major dwarf galaxyIt seems that globular clusters (likeParrome 12）Donate to the Milky Way.This shows how many globular clusters were acquired in the past.
Although the globular clusters in the galaxy seem to have the earliest stars in the galaxy, they areGalactic evolutionIt is still unclear what role it plays in the process of.He andDwarf ellipsoid galaxyThere are significant differences,Globular clusterIt seems that it should beParent galaxyThe place where the mid star is born, rather than an independent galaxy.
find
Announce
edit
Globular cluster
An ancient spherical cluster of stars in the orbit of a galaxy can contain up to one million stars.Globular clusters and open clusters (also called galactic clusters) are the two main clusters in the Milky Way.There are about 500 globular clusters in the Milky Way. The brightest globular cluster in the sky isCentaurω (NGC5139), its density is amazing. Millions of stars gather in the range of only tens of light years in diameter, and the stars in its center are only 0.1 light years away from each other on average.The nearest star to the solar system is 4 light years away.Northern halfcelestial sphereThe brightest globular cluster is M13.Centaur omega(NGC5139) and M13 were both discovered by British astronomer Halley.
Globular star clusters are spherically distributed in the Milky Way, belonging toHalo family。Globular clusters andSilver nucleusSimilarly, it is the most densely distributed place of stars in the Milky Way, where the average density of star distribution is about 50 times higher than that of stars near the sun, and the central density is about 1000 times higher.
Globular clusters are surrounded by huge elliptical orbits with large eccentricitySilver coreOperation, track plane andSilver plateIt has a large dip angle, and the cycle is generally about 300 million years.The members of the globular cluster are the first stars to form in the Milky Way, with an age of about 10 billion years.
The variable stars found in globular clusters are mainlyLyraRRVariable starThe rest are mostly Cepheid variables of family II, so the distance of some globular clusters can be calculated more accurately.Some globular clusters have been found outside the Milky Way, for example, NGC2419 is more thanLarge Magellanic CloudThe distance from the silver center is in interstellar space.In some places close to usExtragalactic galaxyGlobular clusters are also found in.[2]
A brief history of observation
Announce
edit
List of early discovered globular clusters
M22 is the first globular cluster discovered by German astronomer Abraham Ihle in 1665.However, due to the small aperture of telescopes in early years, the stars in the globular cluster could not be distinguished before Messier observed M4.The eight globular clusters first discovered are listed in the table, and then NGC 104, NGC 4833, M15, M69 and NGC 6397 are listed in Abb é Lacaille's table in 1751-52.The letter M in front of the number represents Messier, while NGC is Dreyer'sNew catalog of nebulae and clusters。
William Herschel In 1782, he made a survey of the sky. His large telescope was able to interpret the images of stars from 33 known globular clusters at that time. In addition, he found 37 new globular clusters.Published by Herschel in 1789deep space His second book, in the catalog, first used the word globular clusters to describe such objects.The number of globular clusters discovered is increasing, 83 in 1915, 93 in 1930 and 97 in 1947.Now, there are 151 globular clusters found in the Milky Way, and the total number is estimated to be 180 ± 20.In addition, the undiscovered globular clusters should be hidden behind the gas and dust in the Milky Way.
In early 1914,Harlow Shapley Started a series of research on globular clusters and published about 40 scientific papers.He observed Cepheid variables in the cluster and estimated the distance using their cycle light relationship.In ourGalaxyMost of the globular clusters in the Milky Way are found near the galactic core, and most of the positions on the celestial sphere lie in the sky around the galactic core.
In 1918, Harlow Sharpley used this strong asymmetry to predict the overall size of galaxies.He assumed that globular clusters were roughly distributed near the galactic core, and estimated the distance between the sun and the galactic core through the position of the globular clusters.Although his estimate of the distance at that time was extremely wrong, it still showed that the size of the galaxy was larger than earlier cognition.His mistake was due to the fact that the dust in the Milky Way galaxy reduced the luminosity of a considerable number of globular clusters reaching the Earth, thus making the distance appear farther.However, the value estimated by Shapley is within the same order of magnitude, still within the current acceptable value.
Shapley's measurement also pointed out that the sun is far away from the center of the Milky Way, which is against the results derived from the uniform distribution of ordinary stars earlier.In fact, ordinary stars scattered on the galactic disk are often darkened by the shielding of gas and dust, while globular clusters are distributed outside the galactic disk and can still be seen even at a greater distance.Sharpley continues to work withHenrietta ScropandHelen Battles Sawyer(Hogg later) studies globular clusters.In 1927-29, Shapley and Helen Sawyer began to edit the catalog of star clusters, and took the degree of concentration toward the center as the basis for classification.The most concentrated group is classified as I, and then gradually reduced into XII.This is what we know nowSharpley Sawyer concentration classification(Often replaced by the number [Class 1 – 12]Roman numerals）。
Cluster composition
Announce
edit
brief introduction
Globular cluster
Globular clusters are usually composed of hundreds of thousands of lowMetal contentThese stars in globular clusters are associated withscrewThe globular nucleus of the galaxy is similar to the stars, but its volume is limited to only a fewCubic second gapWithin.There is no gas or dust in them, because it is assumed that they have condensed into stars long ago.
Since globular clusters are high density regions of stars, they are considered to be unfavourablePlanetary systemDevelopment area.planetThe orbits of planets are dynamically unstable due to the perturbations of other stars in the regions with dense stars.In the core area of 47 Rhododendron, a planet 1 astronomical unit away from the star can only exist for 108 years (order of magnitude).However, at least one planetary system circling pulsar (PSR B1620? 26) has been found in globular cluster M4.
Except for a few famous exceptions, each globular cluster has a definite age, that is, most stars in the cluster have similar ages in the stage of star evolution, suggesting that they are almost formed at the same time.All globular clusters seem inactiveStar formationThis is consistent with the view that globular clusters are the old members of galaxies, and they are the first stars to form.
There are some globular clusters, such as Omega Centauri in our Milky Way Galaxy and G 1 in M31, which have an unusually large mass (millions of solar masses). The members include a variety of star families.These two can be considered asDwarf galaxyThe evidence of being swallowed by large galaxies shows that the overweight globular clusters are the core of the remnant of dwarf galaxies.Some globular clusters (such as M15) have extremely massive cores, which may containblack hole, although the simulated model suggests focusing on the centralneutron star, GiantWhite dwarfOr small black holes.
Metal content
Globular clusters usually have stars of the second star family. Compared with stars of the first star family, such as the sun, the content of metals is less.(In astronomy, the metal isheliumHeavy elements, such as lithium and carbon.)
Pieter Oosterhoff, a Dutch astronomer, noticed that globular clusters have two different kinds of stars, which have been recognized as Oosterhoff groups.The second type is the RR Lyra variable star with a longer period.These two groups of stars have weak spectral lines of metal elements, but the spectral lines in the first type (OoI) are more obvious than those in the second type (OoII), because the first type is "rich in metal" and the second type is "poor in metal".
These two types of stars have been observed in many galaxies (especially massive elliptical galaxies), and they are both the same age (almost the same age as the universe)Metal contentDifference on.Many theories have tried to explain the causes of these two subgroups, including the violent merger of galaxies containing a lot of gasDwarf galaxyAnd star birth in multiple stages in a galaxy.In our galaxy,Metal poor clusterGather inSilver haloMedium, andMetal rich clusterThenBulbar nucleusMedium.
In the Milky Way, metal poor star clusters are found to be distributed in a straight line in the galactic plane and the peripheral silver halo, which supports that type II stars areSatellite galaxyInstead of the globular cluster system previously thought to exist in the Milky Way.The difference between the two clusters may be used to explain the difference in the time when the two galaxies formed their own cluster systems.
Strange Members
Globular clusters have very high star density, so the close proximity and collision between stars will often occur here.Because of these opportunities, some strange star types have emerged, such asBlue stragglers 、Millisecond pulsar, and low qualityX-ray binary, are common in globular clusters.The blue falling star is formed by the merger of two stars due to encounter. It may originally be a binary star. As a result, the temperature in the star cluster is higher than that of ordinary stars, but the luminosity is the same, different fromMain sequence starThe stars of.
stayGlobular cluster M15There is a black hole of about 4000 solar mass in the core of NASA image.Astronomers have been searching for black holes in globular clusters since the 1970s.This task is hard and difficult to achieve. It is estimated that onlyHubble Space TelescopeIt is possible, and he really confirmed the first discovery.In a separate project, the Hubble Space TelescopeM15 globular clusterOur observations show that there is a medium mass black hole in its core with a mass 4000 times that of the sun (simulation provides a possible target selection);stayandromedaThe globular cluster Meio II of the galaxy has a solar mass of 20000black hole。Of particular interest is the discovery for the first time of a medium mass black hole between a conventional stellar black hole and a supermassive black hole at the core of a galaxy.The proportion of such medium mass black holes in globular clusters is very high. As expected, they are found around galaxies where supermassive black holes exist.
There are many suspected controversies about intermediate mass black holes. The mass intensive part of globular clusters is expected to deviate from the core of the cluster due to the separation of many masses;It should be like globular clusters, full of white dwarfs and neutron stars, these old star groups.In two papers by Holger Baumgardt and his collaborators, it was pointed out that even if there is no black hole, the mass light ratio of M15 and Meio II should increase significantly when they are close to the center.
Magnitude diagram
Announce
edit
Herotu(Black chart) is a color index map made from a large number of star samples and their absolute magnitude. B? V is the difference between their magnitude in blue (B) and their apparent magnitude (V, yellow green);A large positive value indicates that the star is a red star with a lower surface temperature, while a negative value indicates a blue star with a higher surface temperature.
Globular cluster
When stars adjacent to the sun are depicted on the Herro diagram, the distribution of their mass, lifespan and composition can be shown.Most stars are located on an inclined curve, known as the main sequence belt, the hotter starsAbsolute magnitudeThe brighter, the bluer the color.But there are also some stars that have evolved to a later stage, and their positions are far away from the curve of the main sequence belt.
Because all the stars in the globular cluster are the same distance from us, the correction difference between the apparent magnitude and the absolute magnitude is the same.We believe thatMain sequence starIt will also be distributed in the main sequence belt like the stars near the sun.(The correctness of this hypothesis can observe the short period of the adjacent sunVariable star, for exampleRR Lyrae variable It is confirmed by comparing with Cepheid variable and the same variable in the cluster.)
The absolute magnitude of the main sequence stars in the globular cluster can be measured through the comparison of the Herot chart, which in turn can provide the distance estimation of the globular cluster, because the difference between the apparent magnitude and the absolute magnitude is the distance module, which can measure the distance.When the Herot diagram of a globular cluster is depicted, almost all the stars fall on the defined relative curve. Different from the Herot diagram of nearby solar stars, the stars in the cluster have the same origin and age. The curve shape of the globular cluster is the same time, the same material and composition, and only the typical curve formed by stars with different masses.Since each position on the Herro diagram corresponds to the lifetime of stars with different masses, the shape of the curve can measure the overall age of globular clusters.
The main sequence star with the largest mass in the globular cluster has the highest absolute magnitude, and will also be the first star to transform to the giant star stage.With the growth of age, low-quality stars will gradually evolve into the giant stage, so the age of globular clusters can be shifted from positive to giant stageHerotuThe position on the.The "bay curve" formed on the Herot chart will face to the right of the main sequence belt.Corresponding to the bendAbsolute magnitudeIt is the role of globular clusters as a whole, and the age range can be drawn from the axis parallel to the magnitude.On the other hand, white dwarfs with the lowest temperature in globular clusters can also be measured. The typical result is that the age of globular clusters is about 12.7 billion years old.This is compared with the open star cluster whose age is only tens of millions of years.
The age of globular clusters is almost the upper limit of the age of the universe, which is a major limitation of cosmology.In the early 1990s, astronomers encountered the dilemma that globular clusters were older than the cosmological model allowed.Fortunately, this problem has been solved through better sky surveys, such as the measurement of cosmological parameters by COBE satellite, and differentStellar evolutionModel.
The research on the evolution of globular clusters can also be used to measure the composition of gas and dust at the beginning of globular clusters, that is, because the abundance of heavy elements changes, the evolution path can be traced (heavy elements in astronomy refer toheliumHeavy elements).The data obtained from the study of globular clusters can be used to study the whole Milky Way.A few stars in globular clusters have been observed to be blue stragglers. The source of these stars is not very clear, but most models suggest that these stars are the result of mass transfer in multi star systems.
Cluster configuration
Announce
edit
overview
Ellipticity of sphere
Compared with open clusters, the main stars in most globular clusters are constrained by gravity field all their lives.(A possible exception is that other massive objectstideForce may cause star diffusion.)At present, the formation of globular clusters is still very limited.However, observations of globular clusters show that these stars were initially formed in regions with high star birth efficiency, and the local interstellar matter density is also higher than that of general star birth sites.Globular clusters are formed in the dominant starburst regions under the interaction of galaxies.
After their formation, stars in globular clusters will interact with each other gravitationally. As a result, the velocity vectors of all stars are stable and balanced, and all of them lose their original velocities in early history.The time for this characteristic to occur is called the relaxation period, and the length of this period is determined by the number and quality of stars in the cluster.The time required for each cluster is different, and the average time is 109 years.
Although the appearance of globular clusters is spherical, the ellipticity is the result of tidal forces.In the Milky Way andAndromeda Galaxy The typical shape of star clusters inLarge Magellanic GalaxyThe in is flatter.
radius
Globular cluster
Astronomers describe the shape of globular clusters through the standard radius, which are the radius of the core (rc), the radius of the halo (rh), and the radius of the tide (rt).The overall brightness decreases steadily from the core outwards. The core radius is the distance from the core where the surface luminosity decreases to half of the center. The amount used for comparison is the halo radius, or the radius where the total luminosity reaches half of the whole cluster area. Usually, this value is larger than the core radius.
It should be noted that the stars included in the halo radius include the stars outside the cluster in the direction of line of sight, so in theory, the half mass radius (rm) - will also be used, and the distance of half mass of the cluster will be included by the center log.If the half mass radius is less than half of the cluster radius, the core of the cluster is high-density. For example, M3 has an overall apparent diameter of 18 angular seconds, but the half mass radius is only 1.12 angular seconds.
The final tidal radius is the distance from the core to the periphery of the cluster that is more affected by the galaxy than the cluster itself. At this distance, the individual stars originally belonging to the cluster will be pulled out by the gravity of the galaxy.The tidal radius of M3 is about 38 ″.
Mass isolation and photometry
Globular cluster
When measuring the function between the core distance of a specific globular cluster and the luminosity curve, the luminosity of most globular clusters in the Milky Way will steadily decrease with the increase of distance, and then the luminosity will show a level.The typical distance is 1-2 seconds away from the core.However, 20% of globular clusters have experienced the so-called "core collapse" process. In this type of cluster, the luminosity has been steadily increased to the core area.An example of a globular cluster with a collapsed core is M15.
Rhododendron 47 – the second brightest globular cluster in the Milky Way after Omega Centauri.The core collapse is considered to be the situation that occurs when the heavier star in the globular cluster encounters its lighter companion. As a result, the heavier star loses kinetic energy and falls towards the core.After a long time, the massive stars are concentrated near the core.
Hubble Space TelescopeIt is used to collect and observe the process and procedure of massive stars concentrating towards the center.Zhongxing stars cluster in the crowded core due to deceleration, while light stars spend a long time around the periphery due to acceleration.Globular clusterRhododendron47 There are about one million stars, which is one of the most dense globular clusters of stars in the southern hemisphere. An intensive photographic observation was carried out on this cluster, enabling astronomers to track the movement of stars in it, and almost 15000 stars' accurate movement speed was obtained.
The overall luminosity of globular clusters in the Milky Way and M31 can shape the Gaussian curve through brightness Mv and variable σ 2.The luminosity distribution of globular clusters is called the globular cluster luminosity function (GCLF). In the Milky Way, Mv=7.20 ± 0.13, σ=1.1 ± 0.1 magnitude.GCLF can also be the mostStandard candleTo measure the distance of other galaxies, just assume that globular clusters in other galaxies also follow the rules in the Milky Way.
Multibody simulation
To calculate the interaction between stars in globular clusters, we must solve the multi-body problemPolynomial functionIn other words, each star in the globular cluster interacts with N1 stars, where N is the total number of stars in the cluster.General computers are in the dynamic simulationCPUThe utilization rate increases at the rate of N3, so to make such calculations, computers need to have amazing potential to accurately simulate.
An effective way to study the multi-body dynamics in globular clusters mathematically is to divide the whole cluster into smaller volumes according to the speed range for simulation, and describe the position of stars with probability.In this way, the motion of stars can be described by Fokker Planck equation, which can be solved in a simplified form, or processed by Monte Carlo simulation using random numbers.However, it is very difficult to simulate the effect of binary stars and other external gravity (such as the gravity from the Milky Way).
The results of multi-body simulation show that the moving path of stars in globular clusters is very unusual, some will form a cycle, and some will fall straight into the core, and then rotate around the center of mass alone.On the other hand, because the interaction with other stars will increase the speed, some stars will get enough energy to leave the cluster. After a long time period, the cluster will collapse, which is called evaporation process.The typical evaporation time scale of globular clusters is 10 billion years (1010 years).
The number of conjoined stars in the galaxy is extremely large, and almost half of the stars are conjoined.Numerical simulations of globular clusters show that,Conjoint starIt may hinder or change the process of core collapse of globular clusters.When a star in a cluster encounters a conjoined star by gravity, one possible result is that the conjoined star becomes more compact, and the kinetic energy is transferred (added) to this single star.When a massive star is accelerated in this process, it will reduce the core shrinkage, or even terminate the core collapse.
Intermediate form
The classification of globular clusters is always unclear, and some will be found in other categories.For example, BH 176 has bothOpen clusterAnd globular clusters.
In 2005, astronomersAndromeda galaxyA new type of cluster, very similar to globular clusters, has been found in.The newly discovered star cluster has tens of thousands of stars. The number of stars is less than that of globular clusters, but it has the properties of globular clusters in other aspects, such as star family and metal content.However, in other features, it is different from globular clusters - spanning hundreds of light-years - and has a star density hundreds of times lower, so the distance between stars in clusters is also farther than that in globular clusters.In terms of parameters, this cluster is between globular clusters (lacking dark matter) and dwarf galaxies (dominated by dark matter).
How such clusters are formed is not known, but may be related to globular clusters.WhyM31There are such star clusters, but the Milky Way does not, and the reason is not clear.It is also unknown whether other galaxies have such clusters, but only M31 has such a special cluster is also unlikely.
Tidal encounter
Announce
edit
When globular clusters approach massive objects, such as galactic corestideForce interaction.When the gravity of a massive object pulls the near and far ends of a globular cluster differently, tidal forces will result.Whenever a star cluster passes through the plane of the galaxy, "tidal shock" will occur.
As a result of the tidal shock, a series of stars will be pulled out of the halo of the cluster, and only the stars at the core of the cluster will remain in the cluster.These stars pulled out by tidal action can drag out several degrees of star arcs composed of stars behind the cluster.These star arcs are usually scattered around the cluster along the orbit. These tails may accumulate a lot of original characteristics of the cluster and form clusters with similar characteristics.For example, shortly after the globular star cluster Parrome 5 passed through the near galactic point in the orbit in the Milky Way, a series of stars stretched out along the front and back of its orbit, with a distance of 13000 light-years.The interaction of tides peels off a lot of mass from Parrome 5. When she crosses the core of the galaxy, the further interaction will transform it into surroundingSilver haloA long chain of stars.
The interaction of tides increases the kinetic energy of globular clusters, dramatically increasing the evaporation rate and shrinking the size of clusters.The tidal shock wave not only peels off the stars around the globular cluster, but also accelerates the collapse of the core due to the increased evaporation rate.The same physical mechanism can also be applied to dwarf ellipsoidal galaxies, such as SagittariusDwarf elliptical galaxyThe core of the Milky Way is torn apart by tidal forces because it is close to the core of the Milky Way.
Messier object
Announce
edit
Globular cluster M2
Globular cluster M2
M2 (NGC 7089) is a very dazzling globular cluster.It appears as a round nebulous light, bright but opaque, and the brighter it is toward the center.The diameter is about 6.8 arc minutes, 40000 light years away from the earth.
M2 is located in the constellation Aquarius below the south pole of the Milky Way, about 37500 light years away from the Earth, about 150 light years across, and composed of more than 100000 stars.It was first discovered by Maraldi on September 11, 1746, and was also discovered by Messier on September 11, 1760. Later, it was listed in its own catalog number.Its brightness is about 6.5, which needsBinocularsTo see it.
M2 and 200 other globular clusters are surrounded byGalaxyThe center runs, and they are all objects left over from the birth of the Milky Way.Studying the distance and age of globular clusters like M 2 can find the upper limit for the size and age of the universe.
Globular cluster M3
Globular cluster M3
Globular cluster M3It is one of the most prominent globular clusters located in the constellation Hound, about 33900 light-years away, and can be seen with the naked eye when the observation conditions are good.The diameter of the star cluster is about 200 light-years, and the diameter of the star dense center is about 22 light-years.On May 3, 1764, Messier discovered and numbered it.
It is a huge sphere composed of more than 500000 stars older than the sun, which is located above the plane of our Milky Way Galaxy and is wandering in the Milky WaySilver haloOne of 250 globular clusters.In its dense cluster core, it is difficult to distinguish individual stars.But the match isclusterIt is easy to distinguish the color of bright stars in the peripheral area.
Globular cluster M4
On July 10, 2003, a shining star cluster from an atmospheric planet about 13 billion years ago occupied the core of the globular cluster M4, and the sky was full of stars.Globular clusters cannot become planets because of the heavy mass of their constituent materials, but the appearance of this astronomical landscape means that the formation of planets in the early universe is a common phenomenon.
Globular cluster M5
Globular cluster M5
The equatorial coordinates of M5 (NGC5904) are: 15:18.5 right ascension, 2 ° 04 ′ declination, and 5.7 apparent magnitude;Angular diameter 22 ';It is 25000 light years away from the earth.Gottfried Kirch discovered it in 1702.The observation record of Messier on May 23, 1764 is as follows: located in the balance andSerpentIt is a beautiful nebula near Flamsteed5, a sixth magnitude star in the constellation Serpentius. It is round, and there is no star in the nebula. Under a good night sky background, a 30cm diameterRefracting telescopeIt will be very clear.He painted M5 in 1753 on page 40 of the Annals of the French Academy of Sciences published in 1774cometPicture.On September 5, 1780, January 10 and March 22, 1781, Messier observed M5 three times.
It is a very prominent globular cluster. It is very bright and large. The stars in the middle of the cluster are crowded. Some stars have brightness between 11 and 15 degrees.
Globular cluster M9
Globular cluster M9
Type: globular cluster
Constellation: Ophiuchus
Distance from the Earth: 258000 light years
Right ascension (h: m): 17:19.2
Declination (deg: m): - 18:31
Apparent magnitude: 7.7
NGC No.: NGC6333
M9 is a loose globular cluster, very small, and the brightest star is also about+14. It requires a 10 inch (25 cm) telescope to see part of it.
Globular cluster M15
Globular cluster M15
The globular cluster M15 (NGC7078) in Pegasus is an unusual globular cluster, which is the only one known to containPlanetary nebulaGlobular clusters.Its position is: 21:30 right ascension;Declination 12 ° 10 ′ (2000.0).
This star cluster was first discovered by French astronomer Jean Dominique Marardi of Italian origin on September 7, 1764, when he was looking for Comet de Chesso in the sky.He said that he found a nebulous star composed of many stars, which was slightly bright.Jean Dominique Marardi (1709-1788)Jacques Philip MalarThe nephew of No. (1665-1729) came to Paris from Italy in 1727 and became an academician of the French Academy of Sciences in 1731.He followed his uncle to engage in astrogeodesy. He used to observe the eclipse of Ganymede to determine the geographical longitude, which was measured by Marardigreenwich observatory The longitude difference with the Paris Observatory is 9 minutes and 23 seconds (the current measured value is 9 minutes and 20.93 seconds). He once observedMercury transitandVenus transit, also calculated in 1759cometHe also participated in the publication of 25 volumes of the French Astronomical Yearbook.The second year after the death of the French astronomer Lakay in 1762, Malardi published the Coelum Australe Stell ifernm, also known as the Lakay catalog.
Tencent Science News (Everett/Compilation) According to foreign media reports, astronomers accidentally discoveredStellar black hole, making scientists rethink the space environment of globular clusters containing hundreds of thousands of stars.The newly discovered black hole is located in the M22 globular cluster, which is about 10000 light-years away from the Earth. Scientists had hoped to find a rare medium mass black hole in the cluster. The mass of such a black hole is only about ten times greater than that of the sun, and is larger than that of the galaxy coreSupermassive black holeSmall.
Artist's drawing of black holes in globular clusters
According to Laura Chomiuk, a scientist at the University of Michigan and the National Radio Astronomy Observatory in the United States, "although we did not find the expected signal of a medium mass black hole, we found some other surprising events, that is, two black holes with smaller mass than the medium mass.The reason why this discovery surprises scientists is that most theorists believe that there is at most one black hole in the star cluster. "Black hole is a kind of strange celestial body in the universe. Its strong gravity makes it impossible for light to escape. It is formed by the explosion of super massive stars.
In globular clusters, with the end of the life cycle of massive black holes, many star black holes may have formed in the 12 billion year history of the birth of star clusters.By building models, scientists found that these relatively small black holes would gradually move towards the center of the cluster, and then start a horrible "gravitational dance" with each other. Due to the complexity of multi-body movement, most or all of these small black holes would be "thrown" out of the cluster under the complex gravity.
According to Jay Strader, a scientist at the Harvard Smithsonian Center for Astrophysics at the University of Michigan in the United States, "The black holes found in the observation are likely to be survivors, and the number is not the same, which indicates that there is another way out mechanism between the globular cluster and the current theory." Astronomers put forward some possible explanations for this,First of all, with the evolution of stars, black holes falling into the center of star clusters may usually make the center of star clusters bulge, and the density also drops. Therefore, the mechanism of black holes' multi-body movement popping out of star clusters depends on the "gravitational dance" formed between them, or the evolution of star clusters is not as previously thought.
In future observation missions, the Carl G. Youngsky Very Large Array will help us understand the final fate of black holes in globular clusters. The two black holes discovered this time are the first to find stellar black holes in our Milky Way Galaxy, and also the first to detect the existence of black holes through radio bands, not X-ray observations.The scientists involved in this study areuniversity of southampton Thomas Maccarone, Chomiuk and Strader;James Miller Jones, a scientist from the International Center for Radio Astronomy Research, Curtin University of Technology, Australia, and Anil Seth, a researcher from the University of Utah, published their research results in the journal Nature on October 4.[3]
Royal Astronomical SocietyA research result released on the 23rd said that not all the stars in the Milky Way are "indigenous", and about a quarter of the globular clusters may be "outsiders" entering the Milky Way during galaxy mergers.
The new issue of the Monthly Journal of the Royal Astronomical Society reports that Australian and Canadian researchers have used the data collected by the Hubble Space Telescope to build the largest database of globular clusters in the Milky Way to date.By analyzing the age and chemical properties of these clusters, they believe that about a quarter of the globular clusters in the Milky Way were not born in the Milky Way.
Globular clusters are groups of tens of thousands to millions of stars, which are spherical in appearance. They are the older star systems in the Milky Way.Astronomers have long believed that some globular clusters migrated into the Milky Way from other galaxies.
Duncan Forbes, a professor at Swinburne University of Technology in Australia, who participated in the research, said: "Using the latest database, we can analyze the origin information of these globular clusters. Therefore, we determined that about a quarter of the globular clusters in the Milky Way are 'alien', which means that tens of millions of stars in the Milky Way are alien." He believed that,These globular clusters may come from some small galaxies annexed by the Milky Way.Astronomers have confirmed that the Milky Way has absorbed two such small galaxies, but new research shows that six to eight small galaxies have been merged.The study of these globular clusters of annexed small galaxies is helpful to understand the history of the Milky Way.
[4]
Latest findings
Announce
edit
Scientists discover hidden medium mass black holes in globular clusters
According to the physics website, all black holes are divided into two types: small, stellar black holes, which are several times the mass of the sun;The supermassive black hole weighs millions to billions of times more than the sun.AstronomyAccording to experts,universeAt the same time, there is a medium mass black hole, whose weight is 100-10000 times that of the sun, but so far no conclusive evidence has been found for the existence of a medium mass black hole.At present, astronomers claim that the newly discovered medium mass black hole (IMBH), whose mass is 2200 times that of the sun, is hidden in the central region of the Rhododendron 47 globular cluster.
Brent Kiziltan, the research leader of the Harvard Smithsonian Center for Astrophysics (CfA), said: "We hope to find medium mass black holes because they are the missing link between stellar mass and supermassive black holes. They may be the original seeds, which gradually grow to supermassive black holes similar to the center of the Milky Way."
This latest research was published in the journal Nature on February 9. The Rhododendron 47 globular cluster is an ancient globular cluster 13000 light-years away from the Earth. It has a history of 12 billion years. It contains thousands of stars, forming a spherical structure about 120 light-years in diameter.At the same time, there are about 20 pulsars among them, so it is of great significance to study and analyze them.[5]
