Overview
As long as I can remember, I have had a profound interest in the Universe. Even in my earliest years in school, the “let's pretend” games I liked best involved spaceships and flying around among the stars and planets. Of course, in my younger years I generally gave no thought to the Lord of the Cosmos; what little concept of spirituality I brought away from Sundays at the Episcopal Church never seemed to have any bearing on the vacuum of space or alien worlds. Most likely it was my own plain lack of interest. I'd have probably thought the same if my interests had lain in underwater basket weaving.
This page is my answer to that urge within me to understand the cosmos. Here, I will talk about planets, about stars and galaxies. I will mention nebulae, black holes and ideas about Little Green Men. I don't pretend to understand how they fit into the Greater Scheme of things such as life, death and salvation. Maybe someday we will all learn when God sets up His kingdom. But for now, I am simply satisfied that they are up there. For the heavens truly do declare the glory of God.
The Solar System
Even when I was a snot-nosed kid in kindergarten, I knew the names of the planets. Back then there were nine—nobody had yet come to realize that Pluto was merely one member of a belt of such objects orbiting out beyond Neptune. I even knew the names of many of the moons orbiting those worlds, although many that we now know of were still unknown at the time.
Much has taken place since then. We have sent probes past every planet in the solar system, and orbiters to five of them (Mercury, Venus, Mars, Jupiter and Saturn). We know things we never dreamed about when I was young. And we are still learning more. Admittedly, quite a bit of the exploration is motivated by the search for extraterrestrial life, something I highly doubt we will find in our own local family (see the final section on this page). Nevertheless, much science continues to be performed.
With the demotion of Pluto, the solar system has taken on an interesting symmetry. Here is a list of the planets and other objects, with links to individual pages that I have created for each one of them.
Here you can note the symmetry. First comes the sun, at the center of things. Then come the four small, terrestrial worlds; balls of rock like our own Earth. Then comes the asteroid belt. Beyond the asteroid belt come another four worlds, these being the gas giants; huge balls of hydrogen and other light elements that have little in common with our home world. Finally, another belt of small objects trails off into the depths of interstellar space.
Beyond the Solar System
As huge as our solar system may seem, it is infinitesimally tiny when compared with the rest of the universe. Light takes eight and a half minutes to get from the sun to the Earth. By contrast, it takes more than four hours to get all the way out to Neptune. On the other hand, it takes nearly four and a third years to get to the nearest star beyond our solar system. And it takes a hundred thousand years to travel across our galaxy. And more than two million years to get to the Andromeda galaxy, the nearest large spiral galaxy to our own. Altogether, we can see out beyond ten billion light years into the universe. And there is no evidence whatsoever that that is where it ends. Where that is, nobody knows…
Stars
Basic Facts
There are an estimated two hundred billion stars in our galaxy alone. Our Sun is an average one, a mid-sized yellow main sequence star with an expected total lifetime of around nine billion years on the main sequence, after which it will swell up into a red giant, eventually leaving behind nothing but a white dwarf, the cooling ember of its once furiously active core. The large majority of stars are red dwarfs; small, cool stars with a fraction of the Sun's luminosity, but which will live for trillions of years, long after the death of our home star. And there are a smaller number of bright suns which burn their hydrogen furiously, running out in mere millions of years, and if they are large enough, ending their lives in titanic explosions that we call supernovas, which can briefly outshine entire galaxies.
Stellar Structure
The first thing you might be thinking is that obviously, stars are spherical, like planets. After all, the Earth is a sphere. However, as it turns out, this is a simplification. Stars like our sun; yes they are spherical. The reason that they are spherical is because gravity (which holds them together) is the only significant force at work. Stars are gaseous, which means that they “flow” like any other fluid. Whatever is at a higher “elevation” is drawn down to a lower “elevation”, until the whole thing evens out. It is the same reason why you never see tilted lakes
However, for many stars, gravity is not the only force in play. Beginning with stars somewhat larger than our sun, they tend to have much faster rotation rates. This can result in the star being flattened, with a considerably shorter diameter between the poles than at the equator. A notable example is the star Altair, which is the brightest star in the constellation Aquila (The Eagle). In fact, it is so pronouncedly flattened that astronomers have been able to measure the difference in diameter by calculating the brightness contrast between the distended equator and flattened poles. Just to give you an idea of the difference in rotation speed between Altair and our Sun, our Sun rotates (at the equator) in around 25 days. Altair, on the other hand, completes one full rotation on its axis in just under 9 hours.
Nuclear Fusion
You have no doubt heard that stars are gigantic nuclear furnaces. They generate their energy by means of hydrogen fusion, which is the same process used in hydrogen bombs. The difference is that an H-bomb is a single, uncontrolled explosion, whereas in a star, the reaction continues for as long as there is fuel, harnessed by the tremendous pressure in the core of the star.
Fusion does not take place throughout most of the star. Most of the star is merely hot gas, lacking the extreme temperature and pressure necessary to cause fusion. The nuclear reactions themselves take place only in the core of the star, where immense pressure and temperatures of tens of millions of degrees force hydrogen nuclei together to the point where they can interact and fuse into helium, giving off tremendous amounts of energy. This energy is radiated out into the stellar envelope, causing it to expand until it reaches an equilibrium with the star's gravity. In some layers of the star, heat is transmitted through radiation, while in other layers (closer to the surface) it is transmitted by convection, that is, vertical cells of gas that rise, carrying energy to the surface, where they cool and then sink back down. Similar processes take place in planetary atmospheres. On small planets such as Earth, convection is driven by the external heat of the Sun, while in gas giants such as Jupiter, it is driven by the planet's own internal heat, even though they are not massive enough to undergo nuclear fusion.
A star will continue to fuse hydrogen as long as it has hydrogen in its core. Eventually, there comes a point when the hydrogen is exhausted, and fusion ceases. What happens next depends on the mass of the star. High mass stars (which actually burn their hydrogen much more rapidly and are thus much brigher) can actually begin to burn helium into carbon, since the core will collapse somewhat and the pressure and temperature rise even higher. Stars even more massive than these can burn carbon and even heavier elements—until you get to iron. Up to iron, fusion releases more energy than it requires to initiate the reaction. But from iron on, the opposite is true. So no matter how massive the star, fusion ceases when you get to iron.
Again, depending on the mass of the star, when fusion ceases, a number of different things can happen. In the following section I describe various types of stellar remnants, the remains of dead stars that have ceased nuclear fusion.
Dead Stars
White dwarfs are the most common type of dead star, a star which no longer fuses hydrogen. They are believed to be the cores of their original stars, with the outer layers having been ejected as an expanding nebula, often called a “planetary nebula” (even though they have nothing to do with planets). White dwarf stars are about the same size as a typical small planet such as Earth, but have the mass of a star, resulting in a powerful surface gravity crushing its atmosphere into a thin but very dense layer.
If a star is massive enough, then when fusion ceases completely in its core, the core will collapse. This collapse releases immense amounts of energy that blow the rest of the star out into space. This is a supernova, and as mentioned above, can briefly outshine entire galaxies. The outer layers of the star will continue to expand in the form of a nebula. As for what's left of the core…
When the core collapses in a supernova explosion, the remnant is something even more exotic than a white dwarf. Most supernovae leave behind a neutron star, which is about the size of a typical city, but with a mass considerably greater than our sun. Gravity crushes these objects into such incredible density that a teaspoonful of neutron material—individual atomic nuclei no longer exist, having been crushed into a “neutron soup”—would weigh more than ten billion elephants. A “mountain” on a neutron star could rise no higher than an inch, yet to climb that “mountain” would require more energy than a human being could generate with his body in an entire lifetime. Neutron stars often rotate at incredible speeds, spinning on their axis several times per second. When their magnetic poles do not line up with their rotational poles, this can create a bright spot which whips past our field of vision repeatedly—if it happens to point at Earth—creating a pulsing effect. These objects are called pulsars.
As incredibly small and dense as a neutron star is—with gravity that would crush a man to a film of subatomic particles smeared across its surface—there is something even more extreme. When the mass of a collapsed object exceeds the point where the “pressure” of individual neutrons can maintain their identity as distinct particles, the stellar remnant is crushed into something so small that the gravity becomes so intense that even light cannot escape. These so-called “black holes” do not even have a material surface; their “surface” is defined as the point where escape velocity equals the speed of light. What lies inside this “event horizon” can only be theorized, since it is impossible for anything to ever escape and carry out information. Theories state that even the properties of time and space are interchanged inside the event horizon of a black hole; it becomes possible to go forward or backward in time, but you can only move inward in the radial direction.
When astronomers finally realized that stars were actually distant suns, speculation began about what planets might possibly orbit them. This speculation has stimulated both fiction and serious thought. Some theories of solar system formation said that planetary systems such as our own would be extremely rare, while others predicted that planets around other stars would be common.
In recent years, new techniques have moved so-called “extrasolar planets” from the realm of fiction into the realm of reality. Over thirty-eight hundred have already been confirmed, and more candidates await. Since this is a topic that deserves a page of its own, I will not go into any detail here. Just follow the link in the title of this sub-section to read about extrasolar planets.
Nebulae
A nebula (plural: nebulae) is essentially a cloud in space. But that is where the similarity ends. A typical nebula is considerably larger than our entire solar system, and is so tenuous that by terrestrial standards it would be considered a high vacuum. Common nebulae are simply masses of gas in space, such as the Orion Nebula, or the Horsehead Nebula. They stretch across light years. Some are dark, like the Coal Sack, because there are no nearby bright stars to illuminate them or to excite their atoms to glow with high energy radiation. Others shine brightly, often in many different colors, depending upon their composition.
Stars are believed to form from the collapse of nebulae. This collapse can be triggered by a shock wave from a supernova, collision with another nebula, or some other means. The Orion Nebula is an active star-forming region. Most visible gaseous nebulae, however, are not actively forming stars.
Some nebulae are more specialized. There are the aforementioned “planetary nebulae”, which are the outer layers of a typical sun-like star being ejected in the final stages of the star's active life (the part of a star's life where it undergoes nuclear fusion in its core, generating energy), before it turns into a white dwarf. Our sun will probably someday eject its outer layers in this manner. However, not to worry; it is not expected to happen for another 4 to 5 billion years!
Another special type of nebula is the supernova remnant. These are loosely related to planetary nebulae, in that they are the remnants of the outer layers of stars that have reached the end of their active lives. However, instead of being gently ejected, these nebulae are violently blown off in titanic explosions. The most famous example of a supernova remnant is the Crab Nebula.
Galaxies were once considered nebulae. Sometimes you will still hear them referred to as “spiral nebulae”. However, they are not nebulae; they are immense collections of stars. The following sub-section describes galaxies.
Galaxies
A galaxy is a vast collection of stars. Our own sun and solar system, as well as all of the visible stars in the sky, are part of a galaxy called the Milky Way. The Milky Way is a spiral galaxy, named because of its shape. Of course, we cannot actually see the shape of our own galaxy, because we are embedded within it, about 30,000 light years from its center, which our sun orbits the same way that the planets orbit the sun. However, we can see other galaxies, the most famous being the Andromeda Galaxy, which is a bit over two million light years away. (A light year is the distance light travels in one year.) The Andromeda Galaxy's spiral form is clearly visible. This galaxy, along with many other spiral galaxies visible out in the great beyond, told astronomers of their existence, and later on, observations of motions and distribution of stars in our own galaxy enabled them to determine that the Milky Way is also a spiral galaxy.
There is a sub-class of spiral galaxy called a barred spiral galaxy. These are similar to spiral galaxies, except that their inner spiral arms terminate in a straight bar that extends through the nucleus. Our Milky Way galaxy was recently determined to be a barred spiral galaxy.
Another common type of galaxy is the elliptical galaxy. Elliptical galaxies do not have any kind of spiral structure; they are giant ellipses of stars. Generally, elliptical galaxies have little or no free gas, whereas spiral galaxies are full of gas, in the form of nebulae of various kinds. There is little or no star formation going on in elliptical galaxies, and they generally contain older, redder stars than spiral galaxies. Some theories state that spiral galaxies will eventually turn into elliptical galaxies when they run out of gas to form new stars.
Still another type of galaxy is the irregular galaxy. These galaxies have no type of regular shape, but are merely “clouds” of stars in intergalactic space. Our Milky Way galaxy has two satellite galaxies, the Greater Magellanic Cloud and the Lesser Magellanic Cloud, which are irregular galaxies. In addition, there are still other galactic forms, such as rings and lenses. The variety is amazing.
And every galaxy is composed of anywhere from hundreds of thousands to up to a trillion stars. And most, if not all galaxies are believed to have a supermassive black hole—on the order of hundreds of thousands of times to millions of times the mass of our sun—at their center.
And beyond galaxies themselves are galactic clusters, which are structures on an even more gigantic scale, where the individual members are galaxies themselves.
The sheer scale of the Universe is staggering. How big must God be?
Quasars and Active Galaxies
Lastly, I will mention active galaxies and quasars. These are essentially variations of the same type of object. As stated in the previous section, most if not all galaxies have a supermassive black hole in their center. When the neighborhood of the black hole is relatively devoid of gas, there is little activity. However, a galaxy with a lot of gas in its central regions will display tremendous activity. Quasars are very distant galaxies with very active nuclei, where the nucleus is as bright or brighter than the rest of the galaxy combined. Recent models have shown that various types of observed quasars result from the orientation of the galaxy with respect to Earth.
The reason that a galaxy with a lot of gas near its central black hole is active is because the gravitational force of the black hole literally sucks the gas into the black hole itself. As the gas falls into the immense gravity pit, it heats up due to the kinetic energy of infalling gas being transformed into radiated energy—light, gamma rays, etc.—as it is compressed when it gets close to the event horizon. Not all of the gas actually falls into the black hole; a lot of it is ejected along the magnetic poles, producing tremendous jets that are often longer than the size of the galaxy itself.
Active galaxies are places of tremendous energy and radiation. In all probability, life could not exist on any planet in an active galaxy. I have heard it said that the universe is “friendly to life”. This is erroneous. Earth is friendly to life, or at least, life as we know it here. The rest of the universe… not so much.
Life on other Planets
In my early years my imagination populated the heavens with myriads of alien races. Shows such as Buck Rogers and Star Trek served to fuel my visions; later, when I learned to read, I avidly devoured even more material and my ideas became more sophisticated. In the schoolyard, the jungle-gym transformed itself into a rocket ship, and the merry-go-round into a flying saucer. With the classmates that would join me, we went to Venus, Mars and beyond, visiting all of the exotic creatures that our overactive young minds envisioned were there.
By the time I was in sixth grade, reality had started to set in. Although I still hadn't grasped what scientists had already discovered about the planets, I somehow sensed that there really wasn't anything alive up there, at least not in our solar system. (That didn't stop me from writing a little tongue-in-cheek paper about “Little Blue Monkeys from Venus” when my sixth grade teacher asked us to write a page about what we believed about extraterrestrial life!)
When I was in high school, I had come to grips with the fact that Venus was really the next best thing to Hell itself, and I finally understood what a “gas giant” was. But I still hadn't completely given up on Mars. It was only when the Viking lander set down on the red planet and beamed back pictures of sand, pebbles and a red sky that I finally shrugged and admitted that it was dead. A part of me had been hoping to see cactus and desert rodents in those first views. Alas, nothing…
Eventually, I went to college, then to grad school. While I was in grad school, Voyager 1 went whizzing past Saturn and Titan. Up until then, the general idea of Titan was of a ball of ice and rock with a thin shroud of methane that barely served to lighten the sky from pitch black. I was quite surprised to learn that this moon of the ringed planet actually has a higher surface air pressure than does Earth, and that, like Earth, it is mostly nitrogen. Hopes soared again.
Finally, in January of 2005, the Huygens probe landed on Titan. I had still wondered if some kind of exotic life form that thrived at temperatures of minus 290° F and metabolized methane the way we breathe oxygen might possibly inhabit the place. But instead, pictures from the surface showed dead, eroded pebbles in a dry methane riverbed. No alien plants waving in the frigid breeze… No Titanian field mice trotting up to check out that hunk of metal that had fallen out of their dull orange sky…
So I was left to face the incontrovertible fact that, aside from Earth, our solar system is deader than a doornail and about as friendly as Saddam Hussein with an atom bomb. Yes, scientists are still desperately trying to find microbes buried under the Martian surface, or floating in the Venusian clouds, or living at the bottom of the Europan ocean, but since I don't believe that God does things in half-measures, I don't think they'll find anything.
And beyond our solar system? As I discuss in the section on extrasolar planets, astronomers have already found alien worlds running out their ears. The vast majority are clearly not the type where earthly life could exist. On the other hand, planets the size of ours are difficult to detect. There may indeed be huge numbers of Earth-sized worlds out there, orbiting their stars at the right distance to have liquid water on their surfaces, that we simply have not found yet. But do they have life?
With our present level of technology, it is impossible to tell. If you are an evolutionist, you may consider it to be inevitable. Nevertheless, without actual observation, it remains unproven. And if you believe in intelligent design, then it all depends on whether the Designer decided to put life on any other worlds besides our own. Again, unprovable short of actual observation.
An interesting idea that I have considered in recent years is the possibility that there are other forms of “matter” besides the one that we know that consists of electrons and quarks. There could be entirely different families of quanta, with entirely different properties. Astronomers estimate that 85% of the universe consists of what is called “dark matter”, i.e. something that has mass, but we cannot see. Its properties are unknown. If there are entirely different families of “building blocks” out there, then vast new realms of possibilities open up. (See the page on The World Around Us for more details.)
And in the end, only God really knows what is out there.
