INTRODUCTION

For 65 years they have been working their way through theory after theory. Model after model has vanished into history, some theories are still just that, not having the dignity of being a fact. There is no consensus as yet. But new ideas are showing more promise than previous ones. Beatrice Tinsley in 1968 changed the game on Galactic evolution by herground breaking publications. At age 14, having moved from war torn England to New Zealand. She changed her ambition to be a musician having played in the New Zealand National Orchestra for 2 years to become an astrophysicist. She got a degree in physics 1961 at age 20, attended the First Texas Symposium on Relativistic Astrophysics. Every famous living man from all over the world attended. It did not take her long to find her place among all those luminaries and take issue with most of them. She got a Phd from the University at Austin in 1966, in just two years, her extraordinary ability was  evident. Her classic paper on THE EVOLUTION OF GALAXIES AND ITS             SIGNIFICANCE FOR COSMOLOGY was published in 1968. In 1972 she enlarged on her work and published 11 papers that year. Her main paper was in November and it was in print within ten days.  Her work made giant strides, it was good  timing as radio astronomy was coming into its own and galaxies were a favorite subject. The rest is history. She is one of the great cosmologists and changed things drastically. (Mitton pp. 140-145)

EVOLUTION OF OUR MILKY WAY

Our Galaxy , the Milky Way, is just one of the Cosmos’ grandest spiral Galaxies—one that astronomers are only now coming to fully understand. (Dorminey p. 22) And why not, we are in the middle of our galaxy.  Immanuel Kant, perhaps the most important European Philosopher of modern times and a deep thinker, first asserted about 1755 our haze of stars in which we are imbedded was an island universe, a galaxy. (Honderich p. 435) if he had lived longer he would have had more to say in his unfinished Opus Postumum. It would take another one hundred and seventy five years before accumulation of guesses and corroboration that astronomers came to recognize the Milky Way was a spiral galaxy. But only one of billions.  It would be Joseph Smith publishing in 1844, after his death, that would really define the reality of the immensity of the universe filled with finite Big Bangs and 10⁶²  worlds and the same amount, of suns and moons, let alone the rest of the stars and features, all of which  are considered only a beginning!; ”and thy curtains are stretched out still…” (Moses 7:30)  (see COSMOS 1 of this series)

SOME HIGHLIGHTS

In 1919 Shapley claimed the globular star clusters lay in a great cloud about the center of our galaxy.  He called the dense band of stars seen across the sky a metagalaxy and invisioned it as a swarm of lesser systems. Between 1923 and 1925 the new telescope available to Hubble permitted him to identify our spiral nebulae as an “island universe,” with many more like it out there. (Hubble pp. 1-10)  In 1927 the rotation of the Milky Way about the star clouds of the constellation Sagittarius,  was demonstrated, pinpointing the center of our Galaxy. In 1926-7 The Dutch astronomers Linblad and Oort provided conclusive proof of the galactic rotation. (Bok pp. 152-153) The sun, 8.500 parsecs [a parsec is  3.262 llght- years], is about 27,727 light years from the center of the galaxy, , and the great majority of the stars in our vicinity move about the center in roughly circular orbits with speeds on the order of 220 kilometers per second, orbiting the galaxy center about once in 2.5 billion years. By 1940 few astronomers doubted that ours was a whirling spiral galaxy. (Whitney p. 165; Bok p. 153)

THE ADVENT OF RADIO ASTRONOMY

During WW11 a young Dutch astronomer suggested using hydrogen emissions of radio signals to map the spiral arms. The radio signals from hydrogen is a pure note like the sound of a tuning fork whose doppler shift could reveal the velocity of the radio radiation. These signals were first detected in America and Holland in 1951.  Suddenly the map of the Milky Way was filled with details. The first members of spiral galaxies are the stars, followed by clouds of gas and dust. Walter Baade and others  found the stars to be two major types,  Population 1,  young blue stars of various sizes, and Population 11, old red stars,  also of various sizes, and then variations in between.

From 1950 to 1981 there was a gradual progression from this two fold division of stars to a six fold classification of diverse stars in a minimum of three major subdivisions, representing the structure of the galaxy:  a highly flattened, an intermediate, and a roughly spherical component, In the complex continuous sequence of stars grouped by their physical and chemical characteristics and motions into separate subdivisions of the Galaxy. (Bok pp. 97-110) They werel gathering information to make a credible theory to explain everything.  By 1981, the estimate for the total mass of our galaxy, including the barred central bulge, with its massive black hole, the galactic disk, the  halo, and the corona,  was  2,000 billion solar masses and counting, assuming a radius to the galaxy of 100,000 parsecs,  or more than 300 thousand light years. (Bok pp. 170-171)

In recent years with the advent and proliferation of new technology and instruments of detection, they have shifted the theoretical and observational approach to study the vertical structure of the galaxy as it would appear edge on. (Dorminey p. 22)

THE DISK   

Our solar system as it travels around the galaxy is bobbing up and down in the galaxy’s thin disk. But we are far enough from the galactic center that we can look north and south of the galactic poles and see deep into the outer fringes, and observe the vertical structure. NASA’S Cosmic Background Explorer  satellite first recorded  this glow in detail, more recently NASA’S Wilkinson Microwave Anisotropy Probe and the European Space Agency’s,  (ESA) Plank satellite has  added immense detail, providing images of the foreground dust and a good edge on view of our galaxy. Some of which has been discussed in earlier entries in this series.

In the past decade, the main observational tool for studying “…the milky Way’s vertical structure has been the Sloan Digital Sky Survey (SDSS).” (Dorminey p. 23) SDSS has been discussed in this series earlier, it continues to make contributions in multiple areas. The astronomers are busy measuring the ages of the stars, their chemical composition and movement through the galaxy. There have been a lot of surprises.  Wide field ground based surveys and SDSS astronomers have been forced to “reshuffle their decks” to work out the more complicated picture of the galactic disk that is emerging.  Population 1 stars lurk in the  disk of the galaxy where the sun and we, reside. Most of these stars are young, blue, enriched in metals, having elements heavier than hydrogen and helium.. Matter there is unorganized, so it can be used to generate earths which require most of the 92 elements found on this earth. The prospects for finding earths in such areas are good, and that is where they are concentrating their observations to find Exoplanets. Population 11 stars are much older, reddish in color, metal poor and generally reside in the halo of the Galaxy. Very old populations are characterized by their yellow color and relatively smooth distribution. (Wray  p. vi.)

THE REVISED MODEL 

The whole Cosmos community are now waiting for the results of ESA’s GAIA SATELLITE which is targeting more than a billion stars and will surly complicate the interpretation of the galaxy and the universe at large. One can sketch the model now being developed into which the new data will be inserted and modifications of the theories will be made as they integrate all the data from the large array of star types and regions they occupy. Hans Walter Fix of Germany at Max Planck Institute of Astronomy in Heidelberg believes: “That wherever the stars  happened to form they have remained in either the galaxy’s disk or bulge.” (Dorminey p. 23) The GAIA Mission is now taking a census of the Milky Way from six dimensions providing direct distances to more than a billion stars. It will provide information on the dark matter component of the galaxy, and on the formation, history, and evolution. But much of the data will not be fully gathered     until 2017 when more information on the distances, positions, and motions will become available. The project will continue until well into 2020. (Ibid p. 27)

THE MAKE UP OF THE DISK

So, when we look into the disk,  edge  on, of the galaxy we see a thick disk of mostly older stars 3000 light years in height or thickness. Inside this disk is an old thin disk about 1,000 light years in height or thickness and inside that disk is the  young thin disk of molecular gas clouds and new stars. This is a very thin disk about 300 light years in height or thickness, host to the star forming regions containing the visually stunning molecular clouds that produce new stars.  These three disks are contained in a disk of less dense gas clouds and stars that, at the distance we are from the center bulge, 27,000 light years, is about 10,000 light years thick. As one looks toward the central bulge the three disks along with the diffuse envelope disk turn into the central bar which contains the nucleus of the galaxy with its black hole and surroundings. (Dorminey pp. 22-23)  There are four spiral arms, that need further confirmation, that start at the end of the bar. (See the image of the galaxy front on in an earlier entry.   

The inner central region, 15 light years across, is a circumnuclear disk of shocked molecular gas in which is embedded, in the center and about 5 light years across is an area  of an array of filaments, fast moving stars, winds. and SAGITTARIUS A * [A STAR];  the black hole. (Melia pp. 24-25) Most of the galaxy’s stars reside in the 1000 light years thick,  old thin disk. Mergers with small galaxies should have wrecked this thin disk. All big spiral galaxies seem to have extended old thin disks. So this question is on the agenda of things to learn.

THE GALACTIC HALO

A galactic halo envelopes the inner part of the galaxy. The oldest metal poor stars reside in this region which does not rotate. The vast outer halo extending to more than a radius of 300,000 light years holds more than 100 small satellite galaxies including, in the southern sky, the Megellanic clouds, the larger cloud is being shredded by this merger into the greater galaxy. Other small galaxies are becoming destroyed by the tidal influence of the gravity of our big galaxy. Creating long debris streams that are being mapped.  (Dorminey p. 24) 

“Hovering beyond this galactic structure is a huge halo of dark matter, still a mysterious form of matter that intersects with other material only through gravity. This approximately spherical dark matter halo remains concealed except for its gravitational influence. It spans some 600,000 light years or some four times the diameter of the visible Milky Way, and holds about a billion solar masses of material.” (Dorminey p. 26)

The astronomers had come up with a model for the formation of the galaxy in which the galaxy began as a big blob of protogalactic gas that settled down and stared to form stars. Steve Majewski, astronomer at the University of Virginia is the chief investigator for the Apache Point Observatory Galaxy Evolution Experiment, (APOGEE). The model couldn’t explain stars revolving around the galaxy in the opposite direction from the sun. How can you produce that from a collapsing cloud in which everything is spinning in the same direction? You can’t!

APOGEE  is the only on-going comprehensive spaced based survey to make an analysis and  observations of distant and fainter regions The survey started taking spectra observations in the near-infrared wavelengths in the spring of 2011 using the 2.5 meter wide field Sloan Telescope at Apache Point, New Mexico. In 2016 the survey has been extended to include the 2.5 meter Irenee du Pont Telescope at Las Campanas Observatory in Chile. They hope to wrap up the survey by 2020 or when they complete 500,000 stars. APOGEE will permit the direct measurement of stellar ages and the vertical distribution of stars and the change through time.  (Dorminey p. 26)

The first measurements of APOGEE showed  that the  stellar  populations formed less than 8 billion years ago and do not have a constant thickness, but become thicker the farther they are from the galactic center, showing these stars do not remain at the same distance from the center but migrate over large distances with enough time. The bright red stars or red giants that have consumed their  hydrogen and are now burning  helium  are perfect targets for determinIng the largest distance at any apparent magnitude and therefore quite useful. (Ibid p. 26)

The APOGEE team, before observations, took a milling machine drill and drilled  holes in nine 40 inch wide,  aluminum plates in order to match exactly the holes with the position of 300 stars in each patch of sky they would survey. In each hole they put fiber optic plugs with fiber optic cables to channel the light to take their individual spectrums. By doing this they have made the first ever large scale map of the relative chemical composition of stars all the way from the middle of the galaxy to the edge of the disk both north and south. (Ibid pp. 26-27)

THE THEORISTS      

Theorists now think the galaxy formed through continual mergers with dwarf galaxies and dark matter filaments and halos. Primordial gas clouds that had already existed in the local Group environment probably accreted and merged with one another, thinks Denilso Camargo, an astronomer at the Brazilian Ministry of Defense Military College in Porto Alegra. Majewski agrees. “We now believe galaxies form from the inside out and that as we accrete more stuff, the disk of the Milky Way grows outward.” If so, the Milky Way should be bombarded by tiny satellite galaxies, at least more than it is now. So there are fundamental problems with this approach that may not be solved until new equipment is operational.

They summarize that the early galaxy was a an accreting mass of  accumulating  small galaxies and dark matter with some of the dark matter belonging to protogalaxies and some just flowing along dark matter filaments, which quickly formed the early  halo stars and soon after generating a  large turbulent disk with lots of gas and star formation. About 3.8 billion years after the Big Bang, and 10 billion years ago, a satellite with as much mass as the Large Magellanic Cloud was swept into the mass, creating the Galaxy’s thick disk. Star forming regions then settled into a large disk about 300 light–years thick. Subsequently about 8 billion years ago, this disk grew thicker as stars diffused out leaving a thickness of about 1,000 light years. Small galaxies, high velocity clouds of gas continue falling into the halo, including the Sagittarius Dwarf Spheroidal Galaxy along with the Smith Cloud and clouds of ordinary gas. The dark matter halo formed first and gas then aggregates into the dark matter and cools into a gas disk. Parts of this gas disk then become unstable and collapse and eventually form stars.  Most stars are in the thin disk which is embedded in the thick disk, but the thick disk gets up to higher altitudes above the galactic plane and those stars all seem to be 8 to 9 billion years old. ‘The process of galaxy building has now been in progress for nearly five billion years. The 10 billion old stars were born in a thick layer of gas, the gas gradually becomes thinner, new born stars thin out and the thinner distribution continues until we now have the very thin gas layer. The gas mass that made up the thick disk only had a mass a tenth of the Milky Way. The Sagittarius Dwarf Spheroidal Galaxy made stars all through its life but only started to become shredded by the gravity of the Milky Way in the last 3 billion years. Older stellar streams have been pulled apart so they are barely visible. One stream of stars is passing near are location in space.

FINE TUNING

Now to fine tune all of this they need multidimensional data of the stellar populations:  precise locations, chemical composition of elements in the star’s atmosphere, and motion throughout the Milky Way, the disks and spiral arms. By chemically tagging a stellar population it will not only tell where a star is but what other stars are associated with it and how they are moving and where they are going.  A daunting task. (Dorminey pp. 25-26) But the astronomers have to have something to do.

STAR CLUSTERS

A Brazilian led team has made a breakthrough using data from NASA’S Wide field Infrared Survey Explorer space craft tracking some 400 embedded star CLUSTERS most of which lie in the Perseus spiral arm at distances roughly 30,000 light-years from the galaxy’s center. These clusters have not had enough time to move far from their birth place so they can be used to map spiral patterns of the four spiral arm structures now considered to be present in the galaxy. They have also found two star clusters at high galactic latitudes where they were not expected to form  stars, so there is more star forming matter out there than realized.. 

The Australian National University SkyMapper Telescope  has detected the Milky Way’s oldest Population 11 stars in the galaxy’s central bulge, formed about  300 million years after the Big Bang and more than  13 billion years ago.  They predate the Milky Way. They are extremely metal poor have compositions just barely enriched by an even earlier supernova. The stars have no detectable carbon and an iron abundance lower than our sun has. (Ibid p. 27) As the plasma after the Big Bang began to cool so matter could form, it is slowly beginning to reveal its secrets by such observations. It even might require the age of the Big Bang to be lengthened to accommodate the findings. Data on an earlier age is embedded in the TC and Mormon teachings. 

Louise Howes, a postdoctoral researcher at Sweden’s Lund University says: “The stars we observed are {red} giants with masses about .8 times that of the Sun.” These stars are metal poor Population 11 stars formed from the Cosmos’ very first so-called Population 111  stars. They were in one of the largest protogalactic clouds when they exploded as supernova.  Of 14,000 stars they observed some 300 are very metal poor and likely extremely old. Howes and her colleaguesidentified 23 stars as the most ancient with ages of about 13.5 billion years. (Ibid p. 27)

Dwarf galaxy AGC 198691 has justbeen  given a title as the most metal-poor galaxy known. The Cosmos has accumulated its metals from generations of stars fusing elements during their lives and explosive deaths, a metal-poor galaxy is a good field test of how the early universe looked and behaved.  Astronomers used the galaxy’s spectrums, or chemical fingerprint, to identify and measure the elements present in the faint galaxy 30 million light-years away in in the constellation Leo containing only a few million stars. The system has been nicknamed Leoncine, or “Little Lion” after Ricardo Giovanelli, an Italian born astronomer who first identified it. (Astronomy September 2016 p. 15)

Now that we have a general picture of the galaxy we can plug data into it as it comes from the observers. There is a great deal more to learn and great changes ahead. Perhaps the change that will be most destructive will be the merger of the Andromeda Galaxy with our own, sometime between 2 and 4 billion years from now.  Before the two great galaxies merge their spiral arms patterns will be totally shredded. That would make an interesting 4th of July fireworks show?

HOW MUCH DOES THE GALAXY WEIGH?

Calculations made by astronomers at McMaster University give an exact weight to the Milky Way Galaxy including both its dark and normal matter: it weighs 700 million times the mass of the sun. (Astronomy September 2016) Now you know!

DARK ENERGY UPDATE

Researchers using NASAS’S Chandra X-Ray Observatory’s, optical observatories, and the European Space Agency’s Planck satellite studied more than 300 galaxy CLUSTERS  and concluded that the amount of dark energy in the universe appears to be constant. (Monthly Notice of the Royal Astronomical Society April 11, 2016).The galaxy clusters from the universes younger days appear similar in X-ray observations to more nearby clusters, scaled down just as astronomers expected This implies not only that the current cosmological parameters are accurate but also that the universe’s dark energy supply has remained unchanged out to at least the 8.7 billion light years mark that defines the outmost limit of the cluster survey. (Astronomy September p. 13, 2016) Observations of many galaxies is making it clear that most star formation is galaxies is triggered by minor collisions where large galaxies consuming tiny ones rather than galaxies of near of equal size crashing together. (Astronomy  October 2016 p. 11) 

The model or theory of galactic development now needs to consider the findings of combining optical and X-ray data. Astronomers have now found evidence for black holes acting as seeds which form supermassive black holes from the direct collapse of gas, rather than from the buildup of smaller black holes born out of our of supernova explosions.  (Astronomy, September 2016 p. 13)

PARDON MY BURP!

The object V404-Cygni, a nearby black hole in the Milky Way has been blasting out flashes of red light, indicating the black hole’s powerful jets are flickering off and on as it consumes nearby material.  (Astronomy, September  2016, THE U P. 11

THE UINIVERSE MIGHT BE GETTING OLDER

As astronomers keeping pushing the distance and time to the Big Bang they also  push the distant records for stars and galaxies. They used the Spitzer Space Telescope to pinpoint GN-z11, an object at a distance of 13.4 light years. At an age of 13.8 billion light years, and assumptions that it took the hot plasma 300 million years to cool enough for matter to form especially hydrogen, out of which everything else is created., that would leave only 100 million years to get matter evolved into such objects, perhaps not enough time, or the Big Bang is older than now calculated. (Astronomy. September 2016, p. 11)

FROM THE CENTER AREA OF OUR GALAXY

Using a new gamma ray observatory to trace powerful cosmic rays they have traced  powerful cosmic rays coming from  the inner 33 light-years  of the Milky Way. Soon they will find the sosurce.  (Ibid)

New observations from a worldwide collection of Radio Telescopes aimed at bright objects that were such a mystery some time ago. They found the bright quasar 3C 273 to have a temperature of 10 trillion degrees. Cosmic radio waves had been discovered by Jansky and Reber as coming from our Milky Way.  With the advent of Radio Astronomy and using primitive equipment,  in 1946 James Hey while mapping the radio emissions from the Milky Way noticed a remarkable fluctuating radio signal from the constellation Cygnus.  The thinking then was that radio sources were all stars, but Hey’s discrete source was not even any star but from the space between them, and was not even in the Milky Way.  It was the first observation of a radio source entirely outside our galaxy.  It was called radio galaxy Cygnus A. By 1949, with new equipment, another source was found in the constellation Cassiopeia, called Cas A. Other astronomers got involved and the number of sources increased to five. With other equipment two of these were found to be remnants of super nova explosions.  The others were all outside our galaxy and were emitters of powerful radio signals, more than the whole of our galaxy. (Cygnus A was one of the most distant objects known at that time. Encouraged and with new radio telescopes they discovered more of these extragalactic radio sources.   So they started doing massive surveys. The first survey was at Cambridge in the 1950’s. The third survey resulted in so many that they set up a catalogue [3C] for what they were calling QUASI STELLER SOURCES-  QUASARS, and soon they had a list of 470 objects. Intensive search for optical counterparts led to the identification of every source listed. Next the work concentrated on getting diameters, shapes and structures if any, and other information, in this they were successful except for four of the objects because these four had diameters that were less than .5 arc second.  By the 1969’s three of these were considered to be at great distances because of their strange spectra, and were prodigiously powerful. (Graham-Smith p.91) All they needed were more instruments and equipment; and they are now or will be getting them. The doors were being opened to inaccessible depths. Among the new objects was 3C 273, so bright that even amateurs could see it. It is traveling away from us at one-sixth the speed of light. (Robinson Chapters 15 and 16) By 1965 Sandage and others had found a large number, hundreds, of objects like 3C 273, (Ibid pp. 92-93)) associated with a very active galactic nucleus, (AGN) they called Seyfert Galaxies because of the extremely powerful jets they were generating from what was later identified as massive black holes.  Our galaxy has a super-massive black hole, but the black holes in these strange galaxies are thousands of times more massive. (Ibid 93) Our Milky Way has a black hole of about 4 million solar masses. Cygnus X-1, the first to be discovered, has a black hole of 14.8 solar masses, Binary black hole systems have black holes with masses just 10-20 times of ours. Those  with an active galactic nucleus in the category of  3C 273 have black holes typically more than a million times more massive, and so far there have been no black holes  found between these two categories. (Ibid p. 94) It has taken nearly 65 years to get the temperature of 3C 273. It depends on the energy from the destruction of what is falling into it. Something massive or of vast quantities is becoming drawn into it and being devoured releasing huge quantities of energy. The black hole cannot radiate, but the accreting matter disintegrates and can become very hot and radiate X-rays, light, gravitational and other radiation as it is swallowed up. (Ibid p, 94) Rotation also effects the energy. Our sun has only a 1 % efficiency. Without rotation up to 6 % of the rest mass of the in falling material can be converted into energy. But rapid rotation, such as the objects we have been talking about have, they can by rapid rotation get a 42 % efficiency. This is the most efficient conversion of mass into energy anywhere in the Universe. The rotation of some of these objects is more the than 800 times per second. The energy efficiency will be immense, and it is. Rotation determines the direction of the jets, and the rotation also winds up the magnetic field into a straitjacket, which confines the jets as they leave the central engine or black hole. (Ibid p. 97) What did Abraham know about spin, energy, rotation and time, when he discussed the limits of duration and time allocated to man? (Abraham 5:13)  What is the medium by which Kolob and the other 14 governing planets that control everything of this earthly order? (Smith p. 34) We can only see the visible Light Universe, which is about 5 % of the Universe. 95 % of the Universe it accessible only by the plethora of instruments now created to “see” the rest.  “We expect to be able to describe the Universe in greater detail as a result of further observations [with new equipment] and advances in theoretical physics. (Mitton p. 387)

BIBLIOGRAPHY

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DORMINEY, Bruce, The Milky Way Through Thick and Thin, Astronomy, July 2016

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HUBBLE, Edwin, The Realm of the Nebulae, New Haven, Conn. 1936

MELIA, Fulvio, The Black Hole at the Center of Our Galaxy, Princeton University Press, Princeton and Oxford., 2003

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ROBINSON, Ivor, Alfred Schild &E. L. Schuckingk, Ed’s. Quasi-Stellar Sources and Gravitational Collapse The University of Chicago Presss, Chicago, 1965

SMITH, Joseph, Egyptain Alphabet & Grammer, Modern Microfilm Co., Salt Lake City, Utah 1966

WHITNEY. Charles A., The Discovery of Our Galaxy,  Alfred Knopf, New York, 1971

WRAY, James D., The Color Atlas of Galaxies, The Cambridge  University Press, New York, 1988