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--------- #1492 - New things we have learned about our galaxy
- At the center of our galaxy is a massive blackhole. It is 4,000,000 times more massive than our Sun. And, its size is about 15 times the size of our Sun, which is very, very small on galactic scales.
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- The Earth is 27,400 lightyears away from the center Blackhole. The Blackhole is called Sagittarius A Star. From our vantage point on Earth we can see where the A Star is located. Look to the southern night sky above the horizon at the Constellation Sagittarius. the Constellation is recognized as the outline of a teapot. Above the spout of the teapot is the location of the Blackhole.
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- We can not see much in visible light because the interstellar medium is filled with gas and dust that blocks our view. New telescopes in orbit above our atmosphere have new capabilities to view the full electromagnetic spectrum, from radio waves to Gamma rays. Astronomers have a new vision to learn much more about our Milky Way Galaxy.
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- Astronomers have found 24 smaller galaxies that are along side our giant Milky Way Galaxy.
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- Our galaxy is a spiral galaxy that appears similar to many spiral galaxies found throughout the cosmos. Our galaxy has a sphere-shaped “bulge” at the center surrounding the massive Blackhole. If the galaxy were a long playing phonograph record viewed edge-on this bulge would be the size of an orange at the center. The diameter of the bulge is 8,000 lightyears. That puts the bulge about 24,400 lightyears from us.
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- Running through the bulge is a “ bar” of stars and planets. The bar is a dense elongated concentration of stars in the shape of a cylinder. It could be represented by a thick straw punched through the center of the orange in the plane of the phonograph. The tube like clump of stars is rotating as a cylinder, like a toilet roll. At either end of the bar is a great stream of stars pouring off to create the pinwheel shape of the galaxy.
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- The galaxy is rotating stars and planets traveling at 559,250 miles per hour. Even at these break-neck speeds our Solar System takes 230,000,000 years to complete one rotation. We have completed the trip 22 times since the birth of the galaxy. However, our 2,000 years of human history have hardly moved at all by comparison.
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- The spiral arms look like water streams coming from a lawn sprinkler. However, a better analogy to explain the spiral arms is a “density wave”. More like a stream of cars on a 3-lane highway that is reduced to 2-lane and back to 3-lanes again. The spiral arms are those greater concentration, or density of stars.
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- The spiral density regions are rotating at half the speed of the rotating stars. Stars behind the region of greater density and gravity are pulled forward into the region and speed up. Stars leaving the spiral arm of greater gravity are pulled backward and slow down. Astronomers do not know what causes these density waves in spiral galaxies.
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- Astronomers are having problems getting physics to explain all the motions found in the bulge, the bar, and the spiral arms. The evidence suggests many galaxy collisions to create such diversity of motion. As if that were not challenging enough physics tells us that what we see is only 10% of what is there.
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- The physics that explains our solar system works perfectly. Planets orbiting a mass of our Sun are a balance between centripetal acceleration, (velocity)^2 / radius, and gravitational acceleration, Gravitational Constant * mass / radius^2.
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---------------------- v^2 / R = G * M / R^2
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- This equation works perfectly on our Solar System, but it does not work on galaxies. Solving for mass in this equation:
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---------------------------- M = v^2 * R / G
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- The equation tells us that mass should increase with radius, the distance from the center of the galaxy. However, the rotational velocities of the stars remain constant with distance. We should reach a point where the enclosed mass does not increase with distance. That would find the edge of the galaxy.
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- Beyond the edge the rotational velocities should decrease. The galaxy edge is not found in these measurements. The stars, dust, and gas in the disk , the stellar halo, all this can not explain the mass in the calculation. There must be additional mass that we cannot see. 90% of the mass must be “ Dark Matter”.
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- Could Dark Matter be explained with planets, Brown Dwarf stars, blackholes, neutrinos, or some exotic particles yet to be discovered? We do not know? We leave it as a puzzle for you to figure out. An announcement will be made shortly, stay tuned.
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707-536-3272, Monday, June 25, 2012
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