The ancient Greeks saw the five visible planets and called them “wandering stars” because they moved randomly across the sky instead of staying in fixed positions like the stars. The word “planet” comes from the Greek word for “wanderer.”
We have known for many centuries that the planets are not stars. They appear to wander because they orbit the Sun, just like our planet Earth. They orbit at different speeds, making them appear to wander in the sky. For astronomers to classify a celestial body as a planet, it must meet three requirements:
It must have enough mass for gravity to cause it to become spherical, unlike an asteroid.
It must not have enough mass to cause thermonuclear fusion, which would make it a star.
It must have cleared the area of debris known as planetesimals.
We have five planets that are visible without the aid of telescopes or even binoculars. Two of the visible planets are called inferior planets, not because of importance but because their orbit is inside Earth’s orbit. They are Mercury and Venus. The other three are known as the superior planets since they are beyond Earth’s orbit. They are Mars, Jupiter, and Saturn.
There is one essential thing the ancient Greeks did not understand about the solar system. They did not know that it is orderly. The Greeks saw a pantheon of gods controlling various aspects of the Earth and skies. Each of their gods had all of the bad traits of humans struggling with each other. It was the Judeo-Christian concept of one almighty and wise creator God who created an orderly system that led to the scientific understanding of the cosmos.
Above is a photo of the Sun. If you look closely, you will see a small dot in the upper half near the right side. That is the planet Mercury, the closest planet to our Sun. Mercury made what astronomers call a “transit” of the Sun on Monday morning, November 11, 2019. In our area of the country, the sky was overcast, and it was snowing. However, Bill Ingalls of NASA took this photograph from his location in Arlington, Virginia. I find it interesting to consider what the Mercury Transit tells us.
What’s so special about Mercury passing in front of the Sun? For one thing, it doesn’t happen very often. Although the last time was only three years ago, the next time will be in 2032, but it won’t be visible from North America. The next Mercury transit visible in North America will be in 2049. Since Mercury is closer to the Sun, it passes between the Sun and us every 116 days. However, most of the time, it is either above or below the Sun from our view, and Earth’s atmosphere makes it invisible in the daylight.
Scientists used precision telescopes and equipment to study the transit. They can learn more about the atmosphere of Mercury as it is silhouetted against the Sun. Historically Sir Edmund Halley (1656-1742) watched a transit of Mercury and realized that it could be used to measure the distance between the Earth and the Sun. It occurred to him that a transiting planet would appear in different positions to viewers in different locations on Earth. Measuring the apparent shift between two distant Earth locations at the same time and applying a little math, one could calculate the distance to the Sun. In 1769, after Halley’s death, astronomers used a transit of Venus to calculate the Earth-Sun distance.
The solar system record for the largest number of moons has just been taken over by Saturn. Previously Jupiter was the record holder with 79. Now the moon record in the solar system goes to Saturn with 82!
Astronomers used some of the world’s largest telescopes, including the Subaru Telescope in Hawaii to make the recent discoveries. The same team led by Scott Sheppard of the Carnegie Institution for Science in Washington, D.C., discovered 12 previously unknown moons around Jupiter last year. Now they have helped Saturn pull ahead of the competition.
Here we are living on a planet with only one Moon. Should we feel disadvantaged? Not at all! Imagine how confusing it would be to live on a planet with 82 moons. Seriously, one is enough. That is especially true when we have one Moon that is just right. We have pointed out before how precisely well-designed and well-placed our lone Moon is. Here are a few reminders with links to get more information:
Science has made significant progress in understanding many things about the universe and our planet and the life on it. However, there are many, many things that we have not yet begun to understand. There are also many things we think we understand, but we are still working on better understandings. One question involves how the elements were created.
At the time of the cosmic creation event (widely called the “big bang”), there were atoms with one proton and one electron and some with twice that many. We call simplest element hydrogen, and two hydrogen atoms combine to form helium in the process of nuclear fusion. More and more fusion took place and still is happening in our Sun and other stars. The process requires intense heat and pressure to fuse the atomic nuclei into a heavier atom.
In stars much more massive than our Sun, heavier elements up to iron can are being formed by fusing more and more atoms together. When you go beyond iron, and all the way up to uranium, even the biggest, brightest, and hottest stars can’t squeeze those atoms together. Scientists believe that the heavier elements are created in exploding stars known as supernovae. When they explode, the theory goes, ripples of turbulence form as the supernovae toss their stellar material into the void of the universe. The forces in that turbulence press more and more atoms together to make the heavier elements. As those atomic elements fly off into space, gravity pulls them into lumps which eventually become planets, such as the one on which we live.
A problem with that explanation is that when the atoms are blasted from the supernovae, they are all traveling in the same direction at perhaps the same speed. How can that produce enough force and heat to fuse them together? An alternate explanation is that the explosion within the supernova is not symmetrical, creating areas of greater density. Ultradense and ultrahot regions concentrated in small areas of the exploding mass perhaps give a better explanation of how the elements were created. (See a paper on that published in the Proceedings of the National Academy of Sciences of the United States.)
Carbon is the basic building block of all living cells. Nitrogen and oxygen, which are the next steps above carbon, bond with it along with other atoms to form living molecules. A little higher on the atomic scale are sodium, magnesium, phosphorus, and other elements which are essential to life. Iron, nickel, copper, and other metals are in molecules within our bodies, and we use them in pure form to build our homes, cars, and electronics. The heavier radioactive elements such as uranium deep within the Earth generate the heat that creates a molten iron core that generates a magnetic field which surrounds and protects us. This is a very simple explanation of a very complex system that makes it possible for us to be here.
Astronomers today use technology to examine areas of the cosmos far removed from our solar system. The fact that they are finding the other systems are very much different from ours should tell us something. In fact, the more we study those other systems, the more we learn about our solar system design and why it is the way it is.
One interesting fact about other systems is that even though some planets are very large and obviously gaseous, they can exist very close to their stars. Astronomers in the past explained the fact that the inner planets of our own solar system are rocky and hard by saying that the Sun burned off the gases and left the rocky material. That may be partially true, but in 2002 astronomers discovered a planet they named OGLE-TR-56b. It is about the same mass as Jupiter but over 30 percent larger. It has to be a gaseous planet to have such a low density.
The surprising thing is that OGLE-TR-56b orbits its star at an average distance of only 2 million miles (3.2 million km). Our innermost planet Mercury is 36 million miles (58 million km) from the Sun. The outer atmosphere of this planet must be around 3000°F (1650° C). It is evident that gaseous planets can exist very close to their stars, so our old explanation of the inner planets in our solar system design is vastly oversimplified.
Most of the planets we see around other stars are very large, which is not surprising since it is easier to see a big planet than a small one. One extra-solar planet is 17 times as massive as Jupiter. The strange thing is that many of the giant planets are closer to the Sun than Venus. Old theories of planet formation suggested that due to the large gravity values of stars, it was impossible for planets to form close to the stars. We now know that is not true.
Science programs on television have delighted in proposing that the cosmos is full of planets and that every galaxy has literally millions of planets. The hope is that if you have enough planets, the chance of having another Earth is improved. We now know that many galactic systems do not have planets at all. The composition and age of galactic systems obviously have a major impact on whether planets can exist, but claims of billions of Earth-like planets in the cosmos are highly exaggerated.
The type of star also has an impact on whether planetary systems can form. Most stars in the cosmos are binary systems containing more than one star. A planet can orbit the stars at a great distance, but shifting gravity fields make planets unlikely if the stars are close together, as most are. How much metal there is in a star system affects planet formation. Metal content varies within galaxies as well as between stars. A part of space dominated by gases like hydrogen and helium are not as likely to produce planets as areas where there are large amounts of iron, manganese, cobalt, and the like. Solar system design requires the right kind of star.
Perhaps one of the most exciting lessons we have learned from other solar systems is that the shape of the orbits of planets in our solar system is very unusual. Most of them have very circular orbits meaning that their distance from the Sun does not vary a great deal. Venus has an orbit that is .007 with 0 being a perfect circle and 1 is a straight line. Pluto has the most elliptical orbit, but even Pluto is less than .3 on the 0-1 scale. Our solar system design is unusual.
Circular orbits like ours are very rare in other solar systems where .7 is a very common orbital value, and virtually all orbits exceed .3. If a planet swings far out from its star and then comes much closer, it should be obvious that temperature conditions are going to be extreme. Not only will such a planet have extreme conditions itself, but it will have a very negative effect on any planets that do have a circular orbit in the system. If Jupiter came closer to the Sun than Earth with each orbit, imagine the conditions on Earth as Jupiter went by us.
We now know that our gas giant planets (Jupiter, Saturn, Uranus, and Neptune) are essential to us because their gravitational fields sweep up any debris from outer space. Without those planets, comets and asteroids would pound Earth and life here would be difficult if not impossible. The fact that they are outside Earth’s orbit at a considerable distance and in a circular orbit allows us to exist in a stable condition for an extended time. The comets that do enter our system by avoiding the gas giants do not come in along the plane of the solar system called the ecliptic. Coming in from other directions, they have no chance of hitting Earth since they are not in the plane of Earth’s orbit around the Sun.
June 10, 2019, is an excellent time to observe the largest planet in our solar system. The reason is that Jupiter is in opposition to our Sun.
When astronomers say that Jupiter is in opposition, they mean that planet Earth is passing between the Sun and Jupiter. At this time, Jupiter will rise in the east as the Sun sets in the west, and it will set in the west as the Sun rises in the east. In other words, Jupiter will be visible all night long, and it will be at its highest point in the sky in the middle of the night.
The picture was taken by the JunoCam on NASA’s spacecraft Juno which is currently orbiting Jupiter. NASA posts the raw images online and encourages individuals to download and process them. Citizen scientist Kevin M. Gill enhanced this one. You can find access to the raw images and see the work of other citizen scientists by clicking HERE.
When you see Jupiter in the sky tonight, it will not look like this picture, but it will be the brightest object in the sky. Jupiter is not a rocky planet like Earth. It’s a gas giant which if were 80 times more massive, would be hot enough to set off nuclear reactions in its core. Then it would be a star giving off its own light instead of just reflecting the Sun’s light. However, if you could lump all the other planets in our solar system together (including Earth), Jupiter would be 2.5 times more massive than them all.
Why do we need such a huge gas giant in the outer solar system? As we have said in previous posts, Jupiter is a comet sweeper. With its massive size and gravity, Jupiter protects us from objects such as comets coming from outside our solar system. In the 1990s, NASA observed Jupiter pulling apart and destroying comet Shoemaker-Levy 9. You can read about that in our previous post HERE. Jupiter also affects Earth’s climate cycles, which you can read about HERE.
Jupiter is in opposition about every 13 months. Last year opposition occurred in May. Next year it will be on July 14. If you miss seeing Jupiter tonight because of cloudy weather or any other reason, don’t despair. Jupiter will be closest to Earth on June 12, and it will continue to be visible, but right now it’s visible all night long.
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.
One of the struggles we all have in dealing with the creation of the cosmos is understanding the vastness of space. When someone tries to give a naturalistic explanation for Earth and its abundance of life, they assume that the variables necessary for the creation of life and the conditions required for life to exist have just happened naturally. Because of the number of stars and planets, they assume that the creation can be a product of blind opportunistic chance.
In 1961 Frank Drake (a founder of SETI) presented what is known as the Drake equation. It involves multiplying seven variables that are necessary for creating a planet with intelligent life by the odds of each of those variables happening by chance alone. Let’s say the odds of having one of Drake’s seven variables are 1 in a million. Those promoting chance explanations of the creation would say that since there are 100 billion stars in the galaxy in which we live, the odds are reasonable for the creation to happen by chance.
There are many problems with this equation and the chosen variables. One statistical problem is that you can’t just have one variable which is isolated from all the other variables. If there are seven variables, then they all have to be accomplished at the same time in the same place. You can’t have variable one at one place at one time, and variable two at a different place and at a different time.
We don’t seem to comprehend the vastness of space, and how isolated stars are from one another. An excellent example of this is the asterism we call the Big Dipper. Seven stars make up the Big Dipper. When seen from Earth, they seem to be close together. The fact is that the stars are nowhere near each other. Mizar, the second star from the end of the handle is 78 light years away from Earth. (A light year is how far light goes in a year – roughly 588 quadrillion miles.) Dubhe, the star at the top edge of the bowl of the Big Dipper is 124 light years away. Merak which with Dubhe makes up the pointer stars of the Big Dipper is 79 light years away from Earth and 45 million light-years from Dubhe.
The size of the cosmos is incredible, but that size does not make chance explanations of the creation accurate. Having the right size planet going around a star that is a red giant would not support life. If you had the right size planet going around a spectral G-2 star (like our Sun), it would not support life if it were located at the core or in the equatorial plane of the galaxy. All variables have to work together at the same time and place, and that is unlikely considering the vastness of space.
When wisdom speaks in Proverbs 8:22-23 she says, “The Lord possessed me in the beginning of His way, before His works of old. I was set up from everlasting, from the beginning, before the Earth was.” The vastness of space isolates us from the destructive forces that exist throughout the cosmos. It also reinforces the statement of Romans 1:20 which says “we can know there is a God through the things He has made.”
Data is coming in from the Transiting Exoplanet Survey Satellite, known as TESS for short. It is the most powerful telescope ever deployed to look for planets orbiting other stars. Over two years, TESS can cover all 360 degrees of sky visible from Earth’s orbit. Our previous satellite called Kepler could only scan a small segment of the sky. Already Tess has identified over 300 probable exoplanets including one named HD 21749b which has the lowest known temperature for a planet orbiting a bright nearby star. (“Nearby” being 53 light-years away.)
The problem with this is that what astronomers consider “cool” is not cool from our standpoint. The surface temperature of HD 21749b is 150 degrees Celsius, which is way too hot for liquid water. (Water boils at 100 degrees Celsius.) A year on that planet equals 36 Earth days as it makes a complete orbit around its star. Most of the other exoplanets found at this time are vastly hotter than HD 21749b.
Astronomers have found other planetary systems, but they again have properties that would preclude any kind of life. Some of them have a planetary density equal to that of pure water. Some have orbits that are highly eccentric. Pi Mensae b, for example, has an orbit that varies widely. Its closest distance to its star approximately equals the distance from Earth to our Sun. The longest distance is similar to Jupiter’s distance from the Sun.
The picture shows a slice of a Martian meteorite. It landed in Morocco sometime in the past and was found there in 2011. On the edges, it shows evidence of the extreme heat of entry into Earth’s atmosphere.
How do we know that this piece of rock came from Mars? The Viking Landers analyzed the chemical composition of surface rocks on Mars, and the Mars Curiosity Rover examined the Martian atmosphere and argon level. Based on a chemical analysis of the element and isotope composition out of 61,000 meteorites found on Earth more than 130 give evidence of originating on the red planet. Their chemistry matches the Mars profile.
How did these meteorites get from Mars to Earth? They were dislodged by an impact of an asteroid on Mars which sent rocks flying out with enough force to escape the gravity of Mars. The surface gravity of Mars is only 38% of Earth’s gravity. After traveling through space, they were eventually pulled in by Earth’s gravity.
Some scientists have suggested that they detected evidence of organic (life) material in some Martian rocks. News media have been quick to attempt to say that this proves life existed on Mars in the past. Some even suggested that perhaps life came to Earth from another planet. However, further studies have disputed the organic origins or indicated that the organic evidence was actually picked up on Earth.