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Tuesday, December 12, 2017

Black Hole in Globular Cluster

Black Hole in Globular Cluster

X-Ray Data Indicates Black Hole Centered in Globular Cluster

A team of astronomers at the center of astrophysics in Cambridge, Massachusetts, has found evidence for a massive black hole in the center of the globular cluster NGC – 6624, about 15,000 light-years away. The astronomers estimate the black hole’s mass is 1,000 times that of the sun.

Analyzing the x-ray data gathered by the Astronomical Netherlands Satellite launched in 1975, the researchers found that the center of the cluster emitted two very intense x-ray bursts in March and September of that year. The x-ray energy given off during the bursts was a million times greater than the total light generated by the sun.

Present theories suggest that x-rays are produced in a close binary system in which one member is either a neutron star or a black hole. When the “normal” star swells into a red giant, some of its material escapes and spirals down onto its invisible companion. The already hot material gains more energy as it spirals, eventually becoming hot enough to emit x-rays before disappearing into the black hole.

Black Hole. Author: Alain r.

Globular clusters are very densely packed groups of up to a million stars each, situated around the outskirts of the galaxy. Probably as old as the Milky Way, they lack interstellar dust of gas; both have long since been incorporated into stars. The centers of globular clusters are so packed with stars that astronomers cannot distinguish individual stars.

Since globular clusters are so old, and very massive stars that originally were present would have long since completed their evolution to neutron stars of black holes. Over the cons, they would capture and fuse any field stars that approached too closely. A supermassive black hole might be built up in this way.

Missing Gas Clouds Found Between Galaxies

Missing Gas Clouds Found Between Galaxies


One of the tests of the modern technological view that the universe will expand forever – the big bang theory – is the amount of matter in the universe. Measurements of the universe’s mass. Derived from the relative motions of galaxies, indicate there is not enough matter to halt and reverse the general expansion of the universe. However, two astronomers presented evidence of large clouds of gas existing in the previously-believed empty spaces between galaxies. The overlooked quantity of matter might be enough to produce gravitational forces to overcome the universe’s expansion.

Robert E, Williams and Ray J. Weymann discovered the intergalactic gas clouds while studying the nature of quasars and the clouds of matter supposedly associated with them. The scientists found that the gas clouds are linked with clusters of galaxies containing quasars, furnishing clues on the evolutionary scheme of galactic clusters.

Molecular cloud which spans for 2 light-years. Image in public domain by Nasa.gov

Although surrounding clouds of gas are not visible on photographs of quasars, spectral studies reveal their presence. Absorption lines in quasar spectra indicate clouds of matter lying between quasars and us absorb a portion of their light. Scientists were led to believe that these gaseous clouds were associated with quasars.

Some clouds, however, appeared to be moving toward their host, although most were moving away from quasars. Reasoning that the mass of a quasar might be determined from an approaching cloud, William and Weymann began their studies.

Using the 90 each Steward Observatory telescope at Kitt Peak, the two researchers established that the light from the quasar (PHL 1222) was passing through several clouds; one of the clouds was moving toward the quasar. The approaching cloud, William said, “is composed of atoms having low ionisation or small positive electric charge(s). Since any matter near a quasar would be highly ionized, the cloud must be at a great distance from the quasar.” He estimated its distance from its host to be “at least 1,000,000 light-years”.

The gas cloud was found to be moving at 1,500 m.p.h. toward the quasars. The gravitation attraction of a quasar is not strong enough to account for the cloud’s speed at these distances. Only the largest clusters of galaxies, William observed, have large enough masses to account for the necessary attracting forces.

“The evidence indicates that the cloud which is moving toward PHL 1222 is not attracted by the quasar or even directly associated with it,” Williams said. “Rather, it is moving under the influence of a cluster of galaxies which contains the quasar.

The existence of such gas clouds suggests there is a substantial amount of matter present between galaxies. It might account for a good portion of the “missing” matter that steady state theorists believe exists. Current estimates of the average density of matter show there is far too little matter present to halt the observed expansion.

Old Astronomy News

Old Astronomy News

Briefs


More x-ray burst sources have been discovered by the SAS-3 and ANS astronomical satellites. First discovered in December 1975 in the region of a globular cluster in the constellation Sagittarius, two more have been located near the galactic core and two have been found in the constellation Scorpius. One of the bursters, as they are sometimes called, has a burst strength about equal to that of the Crab nebula.

Galaxy. Artwork by Marc Paternostro

Walter Lewin, head of the Massachusetts Institute of Technology team that first discovered the sources, believes the bursters are binaries with a neutron star component. Because the collapsed star has a strong magnetic field, material flowing from the normal star toward its companion builds up until the field non longer can contain it. Matter that pours through and rapidly heats up, emitting bursts of x-rays.

The Ring Nebula. Photograph by NASA. Image of public domain


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The validity of the inverse square law at laboratory distances for gravity has been questioned by an Eastern Washington State College scientist. In a recent issue of Nature, D. R. Long stated that accurate determinations of the gravitational constant (G) suggests that the value of G increases as the separation between attracting masses increases. He found a discrepancy of 0.37 percent in the value of G.

The Planet Venus. Source of the photograph: Space.com

The inverse-square law has been verified by astronomers for planetary motions, although one researcher demonstrated that a slight modification in the law’s form could explain slight anomalies in Mercury’s motion. Long said, however, that what might be true at astronomical distances might not be true at laboratory distances.

The Crab Nebula. Photograph by NASA. Image of public domain

Long said his experimental results are consistent with past laboratory measurements of G. Convincing fellow scientists may not be so easy. The scientists stressed, however, that the important thing is to get someone to duplicate the experiment to see if his results are reliable.

The Rings of Saturn. Source of the photograph: lupuvictor.blogspot.com

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A recent cosmological theory states that galaxies, in addition to being gathered into groups and clusters, are also bound together in huge super-galaxies. Those who support this theory cite the apparent distribution of galaxies along a “super-galactic equator” – somewhat similar to the arrangement of nearby stars into the band of the Milky Way – and consider this apparent clustering as evidence of a huge “spiral arm” type of arrangement. The theory`s opponent state that this arrangement is an illusion produced by the presence of the stars and dust of the Milky Way, which blocks galaxies behind it from our sight. The diagram at right shows the arrangement of galaxies out to about 50 million light-years; the super-galactic equator by the red line.

Jupiter’s Cloud Belts Source of the photograph: cnn.com

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Galaxies more distant than 50 million light-years. The theory of the super-galaxy states that the apparent clustering of galaxy clusters shows that they are arranged in large flattened systems analogous to normal spiral galaxies. One of the largest groups is the Coma Virgo cluster, one of the largest clusters of galaxies known. Most of the theory`s proponents state that there are a large number of these super-galaxies: some take the apparent evidence still further and hypothesize a universe of galaxies arranged in one enormous system that contains our entire universe. Those who accept the big bang theory of the universe’s origins sometimes offer it as explanation for the apparent cosmic order.

(Old News, History of Astronomy. Astronomy Magazine, August 1976)

Clavius and Tycho Source of the photograph: sfutcher.co.uk


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We reproduce these fine photographs here as a source of inspiration for all who aspire to excellence in astrophtograhy.

Open Cluster M 11 or the Wild Duck Cluster photographed on amateur astrophotography equipment. Source of the photograph: Rawastrodata commons.wikimedia.org/wiki/File:The_Wild_Duck_Cluster_M11.jpg

Galaxy NGC 253 or Sculptor Galaxy. Source of the photograph: eso.org/public/images/eso1025a Emerson/Vista

The Orion Nebula. This image is in the public domain. Source: http://hubblesite.org/newscenter/newsdesk/archive/releases/2006/01

The Horsehead Nebula. Horsehead Galaxy. To the famous question – Where in the present universe did the Big Bang occur? – the answer is clearly, everywhere (quotations from Megan Jorgensen). Source of the photograph: Ken Crawford imagingdeepsky.com/Nebulae/Horsehead/Horsehead.htm

The Omega Nebula. Source of the photograph: eso.org/public/images/eso0925a

Super-galaxy

Super-galaxy

Clusters of Galaxy Clusters – Stellar Frontiers

Our galaxy, the Milky Way, is basically a large cluster of a few hundred billion stars lying in a disk-shaped region of space (typical of spiral galaxies) and containing many clusters and associations of stars.

Recent investigations into the phenomenon of clustering show that it does not occur on any preferred basis. Instead, clustering occurs on all scales, from a single galaxy to possible the entire observable universe. At the other extreme – that of particles such as atoms – clustering also seems to occur. Protons might be clusters of still smaller particles (various types of quarks). In fact, we might even think of our solar system as a cluster containing one star, nine planets, several dozen moons, and plentiful smaller bodies.The clustering phenomenon continues when we examine nearby galaxies: They form groups whose members are associated with one another. Our Milky Way is located in such a group called, simply, the Local group. The best counts indicate that the Local group contains about 27 member galaxies. Many of these are small, inconspicuous objects. But the Local group also includes some of the better known galaxies, such as M-31 in Andromeda, M-33 in Triangulum, and the Magellanic Clouds of the southern clouds.

Magellanic clouds and super-galaxy. Magellanic clouds. The largest nearby high velocity cloud, called the Magellanic stream, forms a long tongue of gas many hundreds of thousands of light-years in extent that links the Milky Way to the Magellanic clouds. It is possible that the Magellanic clouds and the gas stream, with the clumpiness seen within it, all formed billions of years ago from a single cloud of matter. The Magellanic cloud grew dense enough to form stars while the rest of the gas continued to swirl about in space. If this picture is correct, these are the first observations of extended clouds of intergalactic matter. Credit of the photograph: ESO/S. Brunier

By definition, a group of galaxies (the Local group is a good example) is a clump of less than 10 to several dozen galaxies. A group that exists on a larger scale, with more members, is known as a cluster of galaxies. Clusters may contain up to 1,000 galaxies, all apparently born many millions of years ago from one gigantic cloud of gas. Members of these aggregations of galaxies seem to be bound together by gravitational force.

It has been suggested that the groups and clusters of galaxies closest to our own may combine to form sort of a super-galaxy. Astronomers have deduced the super-galaxy’s existence by examining the distribution of some of the nearer collections of galaxies (those within 50 million light-years from us). We find that that they lie predominantly along the equator of a hypothetical super-galaxy, just as the nearby stars in our nearby galaxy lie along the equator.

While not all the astronomers agree that the super-galaxy exists, there is some evidence (although circumstantial) attesting to its reality.

There is also evidence that distant clusters of galaxies also are collected in groups similar to the local super-galaxy. We might, therefore, imagine a whole universe full of super-galaxies. There is no way at present of telling whether or not there is organization on an even bigger scale.

Astronomers visualize the local super-galaxy as a flattened system with an estimated diameter of 100 to 200 million light-years and a thickness of about 20 million light-years. According to one estimate, our galaxy must move about the nominal center of this super-galaxy at approximately 300 miles per second, taking 100 billion years for a single round trip. Since this is a time much greater than the age of the entire universe, it’s hard to see how a super-galaxy could even have been formed and set in motion in the first place. Such motion, however, is extremely difficult to detect and might not be real.
The evidence that such a super-galaxy is a flattened system is somewhat similar to the appearance of a clear night sky that indicates we live in a flattened disk of stars called the Milky Way. We see our galaxy as a band of stars because we look along the disk of the galaxy into the long dimension. As a result we see many more stars than we do in directions at right angles to the galactic equator. A similar effect occurs when we look at distant galaxies. The apparent evidence that they, too, lie in a band (highly inclined to the Milky Way) is analogous to the distribution of stars in the day. The band of stars seems to to indicate the existence of a similarly flattened super-galaxy whose member objects are entire galaxies, not stars.

The center of the super-galaxy is believed to lie in the direction of the constellation Virgo. A huge cluster of galaxies containing perhaps 1,000 members is located here. It’s among the largest of the tens of thousands of galaxy clusters known. The total mass of the super-galaxy may be as great as a quadrillion 10 (15) star masses.

We can best appreciate the enormous scale of the super-galaxy by comparing it with that of our own galaxy and the surrounding area. The size of a typical star cluster in the Milky Way ranges from a few dozen to a few hundred light-years across: the galaxy itself is about 100,000 light-years in diameter. The Magellanic Clouds, our nearest neighbor galaxies are about 160,000 light-years away while M-31 is some two million light-years distant. The diameter of our Local group of galaxies is five to six million light-years. About 15 other groups of galaxies lie within 30 million light-years, another 40 groups or clusters are between 30 and million 50 million light-years away. These clusters lie roughly along the super-galactic equator, although there are of course exceptions. These groups of galaxies may have formed within an enormous primeval cloud of gas 15 billion years ago, much as star clusters formed in the spiral arms of our galaxy.

Pisces cluster, super-galaxy. An idea of the enormous scale of the universe can be had from this picture of a cluster of galaxies in Pisces, lying at the limit of the observable universe. At this distance, the Andromeda galaxy (M-31) would look no brighter than the brightest member of the Pisces cluster. Whether such clusters as these belong to a huge super-galaxy has yet to be determined. Hale Observatory photograph. Source de l’image : Astronomy Magazine

Remarkably, the majority of galaxies within the super-galaxy – including all common spiral galaxies – are themselves flattened, and generally the direction of their flattening seems to be the same as that of the super-galaxy. Perhaps some process involving rotation of the primeval gas cloud controlled the formation of the individual galaxies

How could the clusters or groups of galaxies that comprise the super-galaxy arise in the first place? If we accept the theory that most matter in the universe formed in the big bang, we must then give some thought to the chain of events that took place as the universe expanded. There must inevitable have been some slight irregularities within the universe as it expanded and cooled, and the pull between these random irregularities held some of them in regions that became separated from each other. In other words, clumps formed, which were later to be the birthplaces of the galaxy clusters. In turn, and on a smaller scale within the proto-galaxy cluster clouds, there were additional sub-units that became gravitationally tied together that formed the proto-galaxies themselves. These individual clouds eventually broke into sub-units that became clusters of stars.

Thus, according to this theory, we find a whole hierarchy of condensations occurring in the universe as far down as the formation of stars, with their accompanying planets and moons. But while our theories of star and planet formation seem to be fairly sound, the formation of the galaxies themselves is a much more complex and difficult problem to unravel – and the formation of clusters of galaxies, or the super-galaxy, is almost a complete mystery: we can only make reasonably intelligent guesses.
It’s tempting to draw analogies between the formation of various objects in their hierarchy, but such analogies tend to be misleading since they ignore essential differences between the vastly different scales of time and size.

Studies of unusual clouds of hydrogen gas that appear to be approaching our galaxy have provided totally unexpected new evidence supporting the existence of the local super-galaxy. Scientists have proposed several different explanations for these clouds (called high velocity clouds), including the suggestions that matter may be falling into the Milky Way from intergalactic space, or that matter may drift between the galaxies at distances similar to those of the Magellanic Clouds or M-31. Alternatively, the gas may be part of the spiral structure of our galaxy – that lying most distant from the nucleus. The high velocity clouds, however, apparently lie primarily near the equator of the super-galaxy. The may be stretched along it! Perhaps the clouds float between the galaxies – some of them between members of the Local Group and others between the components of more distant groups of galaxies. Possibly they represent the matter remaining after galaxy formation – matter that never was able to begin the process of star formation. Somewhat similar clouds of hydrogen have been detected near the galaxies M-31, M-33 and M-81, and the clouds are apparently directly associated with these galaxies.

Don’t try to find the local super-galaxy at your next observing station – it’s a phenomenon that is impossible to observe visually. Super-clustering is, after all, one of the most esoteric properties of the universe so far discovered by astronomers. If you want to imagine further groupings beyond that mentioned here, feel free. For example, might we speculate on groups of universes? How far can we take the hierarchical picture down into the microcosm? Such questions must today remain unanswered.

(Astronomy, August 1976, by Gerrit L. Verschuur)

Old News in Astronomy

Old News In Astronomy

Meteorite Falls In China

The 3,894 pound Kirin meteorite is shown with some of the fragments which broke off on impact. The fall, which took place around 4.p.m. on March 8, scattered fragments over a 200 square mile area. The Kirin meteorite broke the previous world’s record of 2,372 pounds which was attributed to a 1948 meteorite which fell in a cornfield in Norton County, Kansas.

Meteorite

X-Ray Nova Sources Growing in Number


X-ray novae are a new class of x-ray sources that must be added to the growing list of such objects. The first source, Cen X-2, was spotted in Centaurus in 1967. Last year a spectacular x-ray nova appeared in the constellation Monoceros and became the brightest x-ray source in the sky. In addition, during April 1975 an object near the Crab nebula, AO535 + 26, was observed to pulsate once every 104 seconds. The latter source faded in July, reappeared in August and faded again, and then reappeared in November 1975.

Two MIT scientists, Philip Morrison and Kenneth Brecher, have suggested that these new sources be divided into two groups. Sources like the brilliant one on Monoceros are “soft” x-ray objects that may generate radiation be ejected gases being excited by shock waves traveling through the nova. On the other hand, “hard” sources like AO535+26 may emit x-rays in the manner of neutron stars, by the excitation of matter falling onto a magnetized, rapidly rotating collapsed body.

(Astronomy Magazine, August 1976. History of Astronomy).