The March 2020 issue of Scientific American (page 10-11) carried an interesting interview with well-known astronomer Dr. Mike Brown. One of the issues raised is the uniqueness of our solar system compared to other known planetary systems in the Milky Way galaxy. Astronomers have discovered thousands of extra-solar planets, and the evidence shows that our solar system design is not typical.
Dr. Brown points out that we are finding giant planets that are closer to their suns than our planet Mercury. We also find stars with eight very small planets that are also inside the orbital distance of Mercury. We don’t see a planet as small as Earth located as far from the parent star as we are anywhere else in the Milky Way. That makes the chances of having a planet in the “Goldilocks Zone” (where water could exist as a liquid) very low. It also means that the masses of the giant planets close to their parent stars must be enormous, and the speed of their orbits must be astronomical.
Proverbs 8 finds “Wisdom” speaking, and she says in verses 22-27, “The Lord possessed me in the beginning of His work before the Earth ever was … when he prepared the heavens, I was there.” The production of our planet was an incredible work of design, not an accident. That certainly urges us to care for what God has created.
In the long history of looking for life elsewhere in the cosmos, one of the exciting discoveries has been learning the things a planet needs to support life. In 1961, American astronomer Frank Drake proposed what is called the Drake Equation. He was looking for a way to calculate the number of inhabited planets in our galaxy with which communication might be possible. Drake’s equation lists seven parameters that would determine the answer to that question. They are:
1) The rate of formation of stars in our galaxy.
2) The fraction of those stars with planetary systems.
3) The number of planets per solar system with an environment suitable for life.
4) The fraction of suitable planets on which life actually appears.
5) The fraction of life-bearing planets on which intelligent life emerges.
6) The fraction of civilizations that develop a technology that releases detectable signs of their existence into space.
7) The length of time such civilizations release detectable signals into space.
If you knew each of these probabilities, you could calculate how many planets in our galaxy might be inhabited by intelligent beings with whom we could communicate. Drake gave each of these parameters a number or probability, but they were wild guesses. Once you have the numbers, all you need to do is multiply each of these variables by each other.
Let me explain. What are the odds of drawing the ace of spaces from a card deck twice in a row back to back? The odds of drawing one ace of spades out of a full deck is 1 out of 52 since there are 52 cards in a deck. To calculate the odds of doing that twice in a row would be 1 out of 52 times one out of 52. You multiply the individual probabilities, so the total probability would be one out of 2704. If you knew the likelihood of each parameter in the Drake equation, multiplying them together would give you the theoretical odds that we could receive radio communication from intelligent life on another planet in our galaxy.
Going back to the card analogy, if you drew one time out of a deck of 52 cards, the odds would be one out of 52. If you drew the ace of spades 52 times in a row, the number would be astronomical since you would multiply the result 52 times! The problem with the Drake equation is that the parameters are unknown and are probably unknowable.
There are also variables that the Drake equation didn’t include, such as the type of star. For example, a supermassive star will have a very short life expectancy. Researchers at Rice University reported in January of 2020 that many stars have extended magnetic fields which overlap the Goldilocks zones of most exoplanets. (As we have explained before, we say that a planet is in the Goldilocks zone when it can contain water in the liquid state). These strong magnetic fields will strip away any atmosphere the planet might have. Our Sun has a magnetic field, but it is not strong enough to strip electrons from atoms and molecules in the Goldilocks zone where Earth is located.
More variables regularly show up, and they tell us that our solar system and Sun have been carefully designed and formatted so that we can exist. Psalms 1:19 continues to take on new meaning with every discovery we make in space. “The heavens (do) declare the glory of God, and the firmament (does) show His handiwork.”
The more scientists study Earth and other objects that surround us in space, the more variables we realize must be carefully controlled for life to exist. Many times before, in our posts, our videos, our books, and our printed quarterly, we have discussed the growing list of parameters that must be carefully chosen. NASA posted a graphic of different kinds of stars in the cosmos and whether they could support life. This picture of stars and habitable zones adds to our understanding of the unique qualities of our Sun.
Water is essential for life. Science defines life as having properties such as moving, breathing, eating, reproducing, and responding to outside stimuli. We don’t discuss “rock people” or “gas people” because they don’t fit that definition. For that reason, scientists are interested in stars and habitable zones–the just-right “Goldilocks zone” surrounding a star where water can exist as a liquid.
In their daily posting on apod.nasa.gov for January 31, 2020, NASA gives the distribution of Goldilocks zones for G spectral stars like our Sun, which are yellow, K dwarf stars, which are orange, and M stars, which are red. The other spectral groupings, such as blue stars, are not considered because of their high radiation levels and activity, which would make life impossible.
The most common type of star in our galaxy, making up 73% of all stars in the Milky Way, are M stars. These red stars have very active magnetic fields and massive radiation. Their Goldilocks zone would be minimal and very close to the star. Orange K stars make up 13% of the stars in the Milky Way. They have a modest Goldilocks zone but are fairly active with some radiation levels. Yellow G type stars like our Sun, make up only 6% of the stars in the Milky Way. These stars have very large Goldilocks zones, and they are very quiet compared to K stars.
As we consider stars and habitable zones, we must realize that the type of star is just the beginning of the variables necessary for a star system to support life. Other critical factors include the size of the star, the location of the planet relative to the star, and the shielding a planet has for protection from the radiation of the star. Also, the stability of the star’s location in the Milky Way is another factor that goes into a life-supporting planetary system.
Our existence is not a product of chance. The more we learn about the Earth, the Sun, and the stars and habitable zones within the Milky Way, the more we understand that the statement, “In the beginning, God created the heaven and the earth” is a massive understatement of what God did to make a place for us to exist.
Does it matter how far away the Sun is? Absolutely yes. The picture shows the order of the planets in our solar system, but not their distance from the Sun. So how far away is the Sun from Earth?
Any star that has planets orbiting it may potentially create a “habitable zone” where the light and heat are just right for the possibility of life to exist. Earth resides in the middle of the Sun’s habitable zone with Venus and Mars near the edge of the zone. Of course, there are many other factors required to support any kind of life, and it appears that Earth is the only planet in our solar system that has all of those factors. Earth has everything needed to support not just primitive life, but advanced life.
So what is the range of the habitable zone? That depends on the star. The size and brightness of the star are critical. Another essential factor is the type of radiation emitted by the star. Our Sun has the just-right radiation. Other stars may emit x-rays, gamma rays, or other deadly radiation in amounts that would destroy all life and prevent a habitable zone from existing.
Back in the eighteenth century, scientists determined the distance to the Sun by watching a transit of Venus across the Sun. Venus passes between the Earth and the Sun twice every hundred years or so. By measuring the time of the transit of Venus from two locations on Earth, scientists were able to use triangulation and simple math to calculate the distance to the Sun.
But the question was, how far away is the Sun? The Sun is about 93,000,000 miles (150,000,000 km) away from us. Since the speed of light is 186,000 miles (300,000 km) per second, it takes about eight and one-third minutes for the light from the Sun to reach the surface of the Earth. The energy the Sun delivers to our planet is just right to make life possible.
At a June 7 meeting of the American Astronomical Society, Benjamin Hoscheit presented information gained from studying 120,000 galaxies. The study agreed with earlier findings that our Milky Way galaxy is located in the largest cosmic void that we can observe. When scientists look one billion light-years out into the universe, they find that the cosmic density becomes much greater. The conclusion they have reached is that the Milky Way is in a relatively open area of space about two billion light-years across. We live in a quiet neighborhood.
The computer image from the Millennium Simulation Project illustrates the dense filaments of dark matter stretching through space. Galaxies are mostly clumped along the filaments. The Milky Way resides in one of the voids between those strands. What are the implications of that? Galaxies tend to be in clusters, and our cluster is called the Local Group. A typical galaxy cluster will have 10,000 galaxies close together. (Close by cosmic standards.) The Local Group has only forty galaxies, and all of them are dwarf galaxies except the Milky Way and Andromeda which are medium-sized. If there were large galaxies close to us, their gravity could distort the spiral structure of the Milky Way making advanced life on Earth impossible.
The Milky Way is a spiral galaxy—the only kind of galaxy capable of supporting advanced life. Star formation drives the spiral motion. Star formation requires the infusion of gas and dust which the small galaxies provide. Clusters of galaxies reside inside superclusters. Our Local Group cluster is on the outer fringe of the Virgo supercluster. If it were near the center of Virgo, the massive clusters there would absorb the Local Group and make life impossible.
Also, our solar system is located in the best position within our galaxy at about two-thirds of the distance from the center. In the center of the Milky Way (and most galaxies), there is a massive black hole that would swallow our solar system if we were anywhere near it. If we were farther out in the spiral, the solar system would be subject to massive instability, again making life impossible.
Of course, Earth is also located in the solar habitable zone where we are not too close or too far from the Sun. One final thing to note is that in this cosmic void and the position in our galaxy, we are at the optimum location for observing all of the things I mentioned. We have an excellent view of the universe. We are in more than a quiet neighborhood. We are in the “Goldilocks Zone” where everything is “just right.”