“The heavens proclaim the glory of God. The skies display his craftsmanship. Day after day they continue to speak; night after night they make him known. They speak without a sound or word; their voice is never heard. Yet their message has gone throughout the earth and their words to all the world. God has made a home in the heavens for the sun.” (Psa 19:1-4 New Living Translation)
“The Milky Way is a barred spiral galaxy some 100,000–120,000 light-years in diameter which contains 100–400 billion stars. It may contain at least as many planets as well. The Solar System is located within the disk, about 27,000 light-years away from the Galactic Center, on the inner edge of a spiral-shaped concentration of gas and dust called the Orion–Cygnus Arm. The stars in the inner 10,000 light-years form a bulge and one or more bars that radiate from the bulge. The very center is marked by an intense radio source named Sagittarius A which is likely to be a supermassive black hole.”
“Determining the structure of our own Galaxy (and where exactly we reside in it) has been a longstanding problem for astronomers because we are inside it. In order to map the Milky Way, scientists need to accurately measure the distances to objects within the Galaxy. Measuring cosmic distances, however, also has been a difficult task, leading to large uncertainties. The result is that, while astronomers agree that our Galaxy has a spiral structure, there are disagreements on how many arms it has and on their specific locations.”
At one time it was believed that our Sun was located about halfway between the center of the galaxy and its edge located within a small, partial arm that is known as the Orion Arm, or Orion Spur, nestled between the Perseus Arm and the Sagittarius Arm, however new studies find that it is a little closer to the center of the galaxy than previously thought, and that what was once thought to be but a spur may indeed be a more prominent feature of the Milky Way perhaps even a major structure or branch of the Perseus Arm itself that or possibly an independent arm segment.
The diagrams above show the position of the sun in relation to the various spiral arms of our Milky Way galaxy, as seen from above the galactic “north pole.” Each hatch mark along the side of the first diagram represents 5 kilo-parsecs, or 16,300 light-years.
“A team of astronomers has taken an important step toward mapping the Milky Way by accurately measuring the distance to the star-forming region W3OH in the Perseus spiral arm, the nearest arm to us. This long strand of stars streaks out of the Milky Way’s disk in the same manner as others seen in galaxies across the universe.
Until now scientists had difficulties figuring just how far away spiral arms are, and various measurements and techniques had discrepancies ranging by a factor of two. The new results are from a telescope nearly the size of Earth. The astronomers used the Very Long Baseline Array, taking observations from several telescopes stretching from Hawaii to the Virgin Islands, to create the resolution of a telescope nearly 5,000 miles (8,000 kilometers) in diameter.
“We have established that the radio telescope we used, the Very Long Baseline Array, can measure distances with unprecedented accuracy — nearly a factor of 100 times better than previously accomplished,” (Mark Reid of the Harvard-Smithsonian Center for Astrophysics)
In doing so, they determined that W3OH is 1.95 ± 0.04 kilo-parsecs away. That’s about 36,000,000,000,000,000 miles.”
Location is Everything
”The Sun and our Solar System have been located in a stable orbit within our galaxy for the last 4.5 billion years. This orbit lies far from the center of our galaxy and between the spiral arms (of Perseus and Sagittarius). The stability of our position is possible because the sun is one of the rare stars that lie within the “galactic co-rotation radius (Likewise referred to as the GHZ or “Galactic Habitable Zone”).” Just as there are habitable zones located in solar systems so too with respects to galaxies. Typically, the stars in our galaxy orbit the center of the galaxy at a rate that differs from the rate of the trailing spiral arms. Thus, most stars located between spiral arms do not remain there for long, but would eventually be swept inside a spiral arm. Only at a certain precise distance from the galaxy’s center, the “co-rotation radius,” can a star remain in its place between two spirals arms, orbiting at precisely the same rate as the galaxy arms rotate around the core. (Mishurov, Y.N. and L. A. Zenina. 1999. Yes, the Sun is Located near the Co-rotation Circle. Astronomy & Astrophysics 341: 81-85.).
“The estimated Galactic habitable zone ranges between 23,000 to 29,000 light years from the Galactic center. Interestingly, our Earth lies exactly in the center of the Galactic habitable zone. Although this is a distinct possibility viz. the idea of a “Galactic habitable zone” it would seem unlikely that this “habitable zone” would extend within the spirals themselves as there would be far too many stars in close proximity one with another in these areas, nevertheless in the areas located between the spirals there could possibly be billions of stars encompassing this habitable zone with billions of future habitable worlds awaiting development.
Why is it important that we are not in one of the spiral arms?
First of all our location outside the spiral arms puts us in the safest location in the galaxy. We are far removed from the more densely occupied areas, where stellar interactions, (gravitational forces between stars) can lead to disruptions in planetary orbits. Located within these spiral arms of various gases and dust are the birthing grounds of many young blue stars. If our planetary system had been located near one of these stars we might not have lasted as long as we have.
“An example of a blue star is the familiar Rigel, the brightest star in the constellation Orion and the 6th brightest star in the sky. Astronomers calculate that Rigel is approximately 700 to 900 light-years away, and yet it appears almost as bright as a star like Sirius which is only 8.3 light-years away. The temperature of Rigel is approximately 11,000 Kelvin; it’s this high temperature that accounts for Rigel’s color. Rigel puts out about 40,000 times the energy of the Sun.
An even more extreme example of a blue star is the blue supergiant Eta Carinae, located about 8,000 light-years away in the Carina constellation. Again, Eta Carinae is 10 times further away than Rigel, and yet from our perspective it’s only a little dimmer. The surface temperature of Eta Carinae is 40,000 Kelvin, and it shines with much of its radiation in the ultraviolet spectrum. Since this wavelength is invisible to our eyes, we perceive it as blue. All told, Eta Carinae is blasting out 1,000,000 times the energy of our Sun.
Blue stars burn through their fuel at a tremendous rate. With 150 times the mass of the Sun, Eta Carinae has only been around for a few million years and it’s expected to detonate as a supernova within the next 100,000 years. Our Sun, in comparison, has been around for 4.5 billion years and is expected to live another 7 billion years.”
It would not bode well for us to be even remotely close to a star going supernova (i.e. closer than eight parsecs, 26 light-years), at this distance the gamma rays from a supernova could penetrate the earth’s magnetic field and induce a chemical reaction in the upper atmosphere (the outer layer of the ionosphere also known as the magnetosphere), which would then strip away the upper atmosphere including the ozone layer to an extent that the surface of the earth would then be bombarded by harmful solar and cosmic radiation. So you can see the benefit of our having resided outside of the spiral arms. “The 4.5 billion year longevity of earth’s relative peaceful existence (the time needed to prepare the earth for the eventual arrival of man) would not have been possible in most other locations in our galaxy.”
And yet there is still another reason why our position outside the spiral arms is to our benefit, have you ever stood in the darkness while someone was shinning a bright light in your direction? How well were you able to perceive objects outside the glare of this blinding light? Now consider if our vantage point were that of one taken from within the spiral arms amongst the bright young stars (take Rigel for instance which shines with a luminosity 130,000 times the brightness of our sun), it might have been possible to see a small fraction of what was outside this glare, but for the most part our vision of the universe would have been greatly impaired, and of course this does not even take into consideration the stellar dust and various other nebula gases residing in the spiral arms obstructing our view. No our present position has not only allowed us to gain valuable insight into our own galaxy, but likewise to visualize the sheer immensity of the universe itself.
At one time many imagined even as they imagined at one time in regards to the earth that our galaxy was the center of the universe, but now from our unique perspective located outside the spiral arms and with the aid of modern instrumentality (specifically the Hubble Space Telescope) we have come to realize that our galaxy is but one of hundreds of billions of galaxies within the known universe. Now when we gaze into the heavens and witness this most wondrous sight we truly understand how, “The heavens declare the glory of God.”
The Importance of our Position in the Solar System
In the solar system, there likewise exists a special zone where life can exist, an area where water for the most part remains in its liquid state. This zone is called a Habitable Zone. If we calculate the range of the Habitable Zone in the solar system, it becomes 0.95 – 1.15 AU (Astronomical Unit: 1 AU = distance from Earth to Sun). Thus, if the location of the Earth was 5% closer to the Sun, all of the water on Earth would have boiled and if 15% further away from the Sun, all water would have frozen.
The green area in the diagram above shows the Habitable Zone and it is only 0.05% of the area of orbital plane occupied by planets. Amazingly, our Earth is located right in the center of the Habitable Zone. The circles outside of the Habitable Zone represent the orbits of Mars, Jupiter, Saturn, Uranus, and Neptune.
Another important factor for the Earth to remain in the Habitable Zone is that the Earth has to maintain a circular orbit around the sun. If the Earth had an elliptical orbit with an eccentricity larger than 0.1, all the water upon the earth would freeze at points A and C, and boil at points B and D. Luckily (?), the Earth has a very small eccentricity and rotates around the Sun in near perfect circular orbit.
Is it a coincidence or God’s design?
The Importance of the Size of our Sun
The size of the Sun is important for life on Earth. If we had a small Sun, the habitable zone also becomes small and the distance from Sun to the habitable zone would become much closer than the current one. However if the planet were too close to star (as for example, Mercury), tidal lock between the planet and star could occur with one side of the planet always facing the sun and extremely too hot for life, and the other side facing away to cold.
Now if we had a large Sun we would have had the advantage of a much larger habitable zone, with the possibility of life on one of our sister planets, however with this large sun comes possible disadvantages, for the lifetime of the star is inversely proportional to its size. If our Sun were much larger than the current one, it would consume most of its hydrogen gas in a relatively short period of time. If it ran out of hydrogen fuel, it would gradually expand and engulf the Earth.
Another condition needed is that Sun has to be a single star. Unlike our sun, more than 50% of stars are binary systems. If we had two Suns we would most likely have had a much smaller habitable zone, and of course very strange weather patterns. Luckily (?), we have only one Sun that is just right size and has an estimated (?) lifetime of another 7 billion years.
The Importance of our Moon and its Size
The Moon plays an important role for life on Earth because of its size. Compared to other planets, the Earth has exceptionally large moon (that is in relation to the size of the Earth). The radius of Earth’s moon is 1,740 km whereas that of the Mars’ moon is only about 10 km. Because of its large size the Moon helps stabilize the rotational axis of the Earth and maintains its tilt angle of 23.5 degrees all the time. If there were no Moon, the Earth’s rotational axis would be wobbling and causing unfavorable climate change.
Another important role for the Moon is in producing tides and helping to maintain Earth’s marine ecosystem. The tides mix nutrient-rich fresh water with sea water and provide nutrients to plankton which forms the basis of the marine food chain. If we didn’t have Moon, we couldn’t have ocean tides. Without the tides the sea might possibly be covered in red tide and eventually wipe out most marine life.
Coincidence or God’s design?
(Excerpts taken from “Creation or Evolution?” http://www.cv.nrao.edu/~dkim/earth_e.html)
Continued with next post.