Originally Broadcast May 17, 1997 Revised Dec. 9, 2001.
INFINITY #13: Some Problems With Galaxies.by Daniel H. Harris, Ph.D.
I. The Questions.
Do astronomers understand spiral galaxies? Is our Milky Way Galaxy about ten billion years old, as Big Bang theory says? What does the age of our own Milky Way Galaxy tell us about the age of the Earth? This INFINITY will answer these important questions.
II. Some Galaxy Basics.
A galaxy is an assortment of perhaps a hundred billion stars, more or less, many of which are like our sun, some being hotter and brighter, some being cooler and fainter than the Sun; the stars along with gas and dust are all presumably held together by gravity. The stars and all, appear to orbit a common center.
There are three main types of galaxies: 1) elliptical galaxies which look like spherical or flattened balls densly packed with stars; 2) spiral galaxies which are flat discs of stars and gas and dust, with a distinctive spiral pattern, and a central ball-like bulge; and 3) irregular galaxies, which often look like clumps of stars and gas and dust jumbled together.
III. Introducing Spiral Galaxies.
Many galaxies look like beautiful pinwheel spirals. In these spiral galaxies most stars, along with gas and dust, appear to participate in a common, nearly circular orbital motion. The stars, dust and gas, all go around the center of the spiral galaxy, like a dog chasing its tail, and seemingly gravity keeps everything together orbiting in place.
Most of the ordinary stars in a spiral galaxy are in the disc of the galaxy, these stars have orbits that are nearly circles, which are close to being on a flat surface. The disc of stars, gas and dust is thin compared to its diameter, like a coin. This disc of the galaxy also contains much of the mass of the galaxy. When a spiral galaxy is seen edge on, we see the edge of the disc of the galaxy, and generally we see a bulge of stars at the center of the galaxy called the nucleus. But when we look at a spiral galaxy edge on we can't see deep into the galaxy because our view is blocked by the abuandance of gas and dust in the disc of the galaxy. So seen edge on the spiral pattern isn't visible. When looking down onto the disc of a spiral galaxy, we see a spiral pattern made up of gas, dust and concentrations of bright mostly blue stars. These concentrations are called spiral arms. There are generally at least two spiral arms emerging from opposite sides of the nucleus of the galaxy. These spiral arms trace out the spiral pattern. Some spiral galaxies have closely spaced and tightly wound spiral arms, most of these have a large nuclear bulge. Other spirals have far appart and loosly wound spiral arms and a small nuclear buldge.
IV. Our Milky Way Galaxy.
Our own Milky Way galaxy is a spiral galaxy, more than one hundred thousand light years in diameter.* Our Sun lies slightly offset from the middle of a spiral arm, and the great gas and dust cloud in the constellation Orion is a prominent marker of that spiral arm. Our Sun is about 30,000 light years away from the center of our Milky Way galaxy, the center being in the direction of the southern constellation Sagittarius. But the great mass of stars making up the bulge at the center of the Milky Way is invisible to us because our view is blocked by intervening clouds of gas and dust in spiral arms closer to us.
* A light year is the distance that light travels in one year, about 5.9 trillion miles, or 9.4 trillion kilometers.
V. Galaxy Clusters and Superclusters.
Our Milky Way galaxy is also part of a local grouping of galaxies, not surprisingly, called the Local Group. Our Milky Way and the Andromeda galaxy are the two largest galaxies in our Local Group, with many smaller galaxies, including the Magellanic Clouds, which are companions to our galaxy. The Local Group is one of many groupings of galaxies, called galaxy clusters. The Local Group is also part of a much larger grouping, called the local super-cluster. This super-cluster is a great cluster made of many smaller galaxy clusters.
Galaxies are rarely seen without other galaxies nearby, a few are in close pairs, or in small groups, but most are in larger clusters of hundreds or thousands of galaxies. these larger clusters are generally dominated by a cental giant ellyptical galaxy. The portion of the universe we have sampled is dominated by groups of galaxies, galaxy clusters, and galaxy super-clusters. This hierarchy of clustering is seen all the way to the edge of the visible universe.
VI. Some Problems Revealed by Galaxies.
Most astronomers assert that all the galaxies we see, including our own Milky Way galaxy, are perhaps ten billion years old, having formed just a few billion years after the Big Bang.
Galaxies challenge astronomers for a number of reasons:
1) Galaxies show evidence that they are much younger than their supposed ten billion year ages.
2) Secondly, astronomers are intensively working on various naturl law aproaches in efforts to understand the formation of galaxies. But none of the various approaches has described the formation of galaxies in a way that actually agrees with the observed characteristics of real galaxies. None of the natural law approaches to galaxy formation has worked well enough to become a generally recognized theory.
3) Thirdly, the currently popular Big Bang theory of the origin of the universe has difficulty making galaxies, and an even greater difficulty making galaxy clusters, without the inclusion of mysterious invisible dark matter. And it is virtually impossible for the Big Bang Model to explain larger groupings of galaxies such as galaxy superclusters. Obviously we can't examine all of these problems with galaxies here. So, for the present discussion we will focus on the problem with galaxy ages. And perhaps elsewhere we will discuss other problems which arise in the study of galaxies and the universe.
VII. A Little Reported Mystery: The Missing Supernova Remnants.
Our Milky Way Galaxy presents us with a serious problem, the mystery of the missing supernova remnants. Radio telescope observations of our Milky Way Galaxy should show thousands of holes in the interstellar gas, holes blown by supernova explosions over past ages. But the thousands of supernova remnants aren't there!
A supernova explosion is a giant explosion of a star. During the initial outburst, when the star is near maximum brightness the star is putting out as much light as the combined light of all the stars of a typical galaxy. [Generally it takes one to three weeks to reach maximum, and the decline to invisiblity takes many months. Telescopic observations show supernova explosions at a rate of several per year among nearby galaxies [perhaps 200/yr out as far as we can see with largest telescopes]. And naked eye observations have shown several supernova events per millennium in our galaxy. In combination these observations permit astronomers to estimate that about twice each century there is a supernova explosion somewhere within our Milky Way Galaxy. Some ten percent of supernovae in our Milky Way galaxy are close enough to Earth to be seen [through the obscuring dust and gas] by naked eye observers. [Over the last 40 years astronomers estimates of the rate of supernovae in our galaxy have ranged widely, from about one supernova explosion per century, to about four per century.]
Each supernova explosion releases an energy close to 1044 Joules, or about 2 x 1028 Megatons of TNT equivalent. That's about one billion times a billion times a billion of hydrogen bombs. That's enough energy to accelerate a shell of gas with the mass of our Sun to a speed of 10,000 km/sec [6,000 mile/sec]. A significant portion of the supernoava's energy goes into the rapidly expanding shell of gas. This expanding shell of very hot gas blows a bubble in the already present gas between the stars. This bubble in the interstellar gas and dust is called a Supernova Remnant. The rapidly expanding gas collides so violently with the surrounding interstellar gas, that it making a shock wave, which heats the gas until it glows with visible light. These hollow shells of hot gas, stand out against the faint background of low temperature emission from the much cooler interstellar gas. With so many holes in the interstellar gas the interstallar gas should look like Swiss Cheese, when viewed with radio telescopes. [For more see http://www.creation.on.ca/cdp/snrart.html]
Since radio waves pass right through the gas and dust of our galaxy, radio astronomers can easily see the other side of the Milky Way [views with light are blocked by dense dust clouds.]
Over the years since World War II radio astronomers have used a variety of radio telescopes to carefully map our entire galaxy, looking for supernova remnants. After having done many thorough searches, radio astronomers have found only about 220 supernova remnants** (see ref. 1). At a rate of two supernova explosions per century in the Milky Way,*** that tells us that our galaxy has existed for only about a 110 centuries, or eleven thousand years. ** The number of supernova remnants in the galaxy is uncertain by perhpas as much as 30%. *** The rate of supernova events in the Milky Way is uncertain by perhaps a factor of two. If the Milky Way were 10 billion years old, as is commmonly supposed, based on Big Bang cosmology, then about 200,000,000 supernova events should have occurred in our Milky Way galaxy, and the gas between the stars should be so full of supernova remnants, that the gas between the stars has been processed through supernova shells many times, the remnant shells should overlap like craters on the Moon. But that eneourmous number of supernova remnants is missing!
There is absolutely no possibility that this number of supernova remanats could be missed. They just aren't there! Radio astronomers have made herculean efforts to find the missing supernova remnants. They aren't there. Even with the maximum uncertainty present in the measurements, the estimated age of the Milky Way is only uncertain by at most about a factor of about two or three. Thus the age of the Milky Way is somewhere between 5,000 and 22,000 years. In round numbers the supernova remnants tell us that our galaxy is about ten thousand years old.
VI. The Problem of Spiral Arms Winding Up.
Perhaps the most profound difficulty with the present theory of galaxies is, that there is no adequate or generally acceptable explanation for the spiral arms of spiral galaxies.
A. Inner Stars, Gas, and Dust Gain Laps.
Using telescopes in combination with specroscopic equipment astronomers have measured the velocities of stars, gas, and dust, at various distances from the center of spiral galaxies. Such measures show that the matterial close to the center of a galaxy makes many revolutions in the same amount of time taken for just one revolution by the stars, gas, and dust far away from the center of the galaxy. Therefore, the matter near the center of the galalxy gains many laps on the matter farther out in the spiral pattern. As a consequence the spiral arms should wind up and vanish rapidly.
B. Computer Simulations Show Spiral Arms Winding Up.
Modern computer simulations of galaxies, which compute the detailed motions of stars, dust and gas; confirm that spiral arms should wind up and vanish very quickly; in just a few revolutions of the galaxy. As a consequence disc galaxies much of the time shouldn't show a spiral pattern at all. Instead disc galaxies should look like just a smooth disc of stars, gas and dust, without a spiral pattern. Thus the simulations don't fit what we see when we look at spiral glaxies.
C. Density Waves to the Rescue?
In the late 1960's through the 70's astronomers became excited about a new theory which many hoped would explain the spiral pattern found in so many galaxies. The idea, proposed by C.C. Lin and Frank Shu, was called the density wave theory. This theory supposed that spiral regions are concentrations of matter, having higher that average mass density. Furthermore they supposed that the spiral patterm rotates nearly like a solid disc with a speed less than that of the stars, gas, and dust. Lin and Shu supposed that there might be a self sustaining density wave, that, by the action of gravity, the concentration of matter in the spiral pattern might be able to produce and maintain a density wave in spiral arms. They imagined orbiting stars, gas, and dust, spending a little extra time in spiral shaped regions of high concentration; and so with the extra time spent the additional mass would add to the concentration of matter in the spiral pattern. And astronomers expected that such a spiral density wave would trigger star formation. It was also hoped that these processes might explain the characteristics of spiral arms and spiral galaxies.
D. Where Does the Density Wave Theory Work?
For the spiral pattern to remain unchanged the density wave pattern must rotate like a solid disc. The spiral pattern must take the same amount of time for one revolution near its center as it does near its edge. 9;But actual velocitiy measures show that the stars, gas and dust, follow a totally different pattern of motion. The inner stars, gas, and dust gain laps on the outer stars, gas, and dust. As a consequence, the spiral density wave theory only works reasonably well at just one very limited distance from the galaxy center, where the density wave pattern is moving just a little slower than the orbital speed of the stars, gas, and dust.
Close to the center of a spiral galaxy, the stars, gas, and dust, orbit much faster than theoretical spiral pattern speed, so the stars gas and dust rapidly pass through the density wave, and destroy the density concentration [instead of lingering in the density wave and adding their weight to the density concentration]. The fast motion of stars, gas and dust, near the center of spiral galaxies, tears apart and smears out any density concentrations, and so the theory doesn't work there. 9;At the outer edge of a spiral galaxy, the stars orbit much more slowly than theoretical speed of the density wave pattern, so the conditions needed for the density wave theory to work are not met near the outer edge of spiral galaxies either. So by elementary analysis it is clear that the density wave theory of Lin and Shu doesn't work for most of the volume of an ordinary spiral galaxy. Accordingly the spiral pattern should appear only at distances from the galactic center where the matter velocity is near the spiral pattern velocity.
E. Spiral Patterns Everywhere!
We now have good observations of spiral arms very close to, even right into the centers of galaxies. For example, a recent Hubble Telescope image shows spiral arms near the center of the Whirlpool Galaxy, M51. Other galaxies show spiral patterns near their centers, including the Andromeda galaxy, M31; M74 in Pisces, and M101 in Ursa Major. All these galaxies show clear spiral arms within the central 7% of the galaxy radius, (see ref. 2). And all spiral galaxies show spiral arms out to the very edge of their discs.
So the galaxies show continuous spiral arms all the way from the center to the very edge, contrary to the best available theory. There is no theory which explains spiral galaxies as they are which keeps spiral arms for more than a few revolutions of the galaxy. After nearly seventy years of intense effort by some very brilliant mathematicians and astronomers, there is no working theory of spiral galaxies. The measured velocities of stars, gas, and dust in spiral galaxies show that spiral arms are winding up and should vanish in a few revolutions of the galaxy; that is, in less than a billion years. Therefore, since spiral galaxies still have spiral arms, we are force to recognize that the spiral galaxies are less than a billion years old.
VI. An Unexpected Pattern.
Another problem, which may indicate that galaxies are young, can be found much closer to home. Within a few hundred light years of our Sun, where star motions can be accurately measured, there is a most peculiar pattern. The motion of the nearby stars relative to the sun are not directed randomly in space, as astronomers would expect. #9;Long accepted theory says that most stars orbit in the general gravity of our Milky Way galaxy, and that most stars should follow similar, nearly circular orbits.
But another thing should be going on. As stars go around in their orbits, they should pass through the spiral arms twice. On going through a spiral arm some stars will pass near high density regions, such as star clusters and molecular cloud complexes. And other stars should go through less dense regions. The different gravity effects of passing near high density and low density regions should variously deflect the orbits of stars. These various gravity bumps should affect each stars motion differently. So kicks and bumps felt by each stars along its orbit should, after an orbit or two of the galaxy, produce a significant random velocity component added onto the general circular motion of the star. Thus after an orbit or two each star, having followed a different path to arrive at the same place, should have a significant component of random motion relative to neighboring stars and relative to the general circular motion.
But this is not what is seen when we study stars near the sun. Hot massive stars and cool low mass stars have significantly different systematic motions relative to the Sun (ref. 3). This suggests that the nearby stars have not yet orbited our Milky Way galaxy, and so they have not had their velocities affected. If the variety of nearby stars [which should have arrived hear from many different starting locations] have not yet orbited our galaxy, then they are at most a few hundred million years old. And this shows that our Milky Way Galaxy, is at most a few hundred million years old. If our Milky Way galaxy is young, then it is reasonable to suppose the the contents of the galaxy, including the Sun and the Earth, are also young. If the galaxy, the Sun, and the Earth are young, less that a few hundred million years old, then there has been not been sufficient time for natural law -- evolutionary processes to produce the galaxy, galaxy clusters, the solar system, the Earth or the many varieties of life we find on Earth. We are then forced to realize that creation is the only reasonable explanation for the universe which we see. And if the universe, the galaxy, the solar system and the Earth were all created, then there must be a creator.
But galaxies, galaxy clusters, and super-clusters must form quickly, right after the Big Bang, since we do see all of these structures, even the largest ones, all the way out to the edge of the visible universe. But large scale structures like super-clusters of galaxy clusters can't form quickly. This is because on large scales gravity acts slowly, since for larger structures gravity differences are weaker and matter must move greater distances. So large structures according to the Big Bang Model shouldn't have had time to form. Yet we do see large scale galaxy groupings all the way to the edge of the universe, where light supposedly orginated not long after the Big Bang.
The the Holy Bible in Jeremiah 51:15 says about the one true God, the God of Israel; "He hath made the earth by His power, He hath established the world by His wisdom, and hath stretched out the heaven by His understanding." So I invite you to put your trust in the one true God, the creator, who gave us His living word, the Bible.
Ref. 1. "The Catalog of Galactic Supernova Remnants" by D. A. Green, 1996, Mullard Radio Astronomy Observ., Cavendish Laboratory, Madingley Road, Cambridge, CB3 OHE, United Kingdom.
Internet ref. Http.//www.mrao.cam.a.c.uk/surveys/snrs
Lists 215 SNRS and some are questionable as distinctly separable.
See also "The Distribution of Supernova Remnants in the Galaxy" by Kieth Davies, p175-184 of "Proceedings of the Third International Conference on Creationism, July 18-23, 1994." ed. by Robert E. Walsh, Publ. by Creation Science Fellowship, Inc., Pittsburgh, PA, USA.
Ref. 2. "Galaxies" by Timothy Ferris, Harrison House, New York, 1987. For M31 see p69; for M101, see p82; for M74, see p102.
Spiral structure measured in the central region and compared to the maximum extent of the galaxy.
Ref. 3. "Solar Motion and the Velocity Distribution of Common Stars" by J. Delhaye, in "Galactic Structure", Ed. by Adriaan Blaauw and Martin Schmidt, U. of Chicago Press., 1965, p61.