- We live just 26,000 short lightyears away from a massive Blackhole. The size of the Blackhole is 4,000,000 times the mass of the Sun. With the staggering amount of gravity that comes with that immense mass stars orbiting close to the center are moving very fast. The force of gravity is:
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------------------------ F = G * M*m / r^2
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- The force is directly proportional to the masses ( M*m ) and inversely proportional to their distance of separation ( r ). Suns ( stars ) orbiting close to the center of the Milky Way Galaxy have been clocked at 3,000 miles per second, that’s 10,800,000 miles per hour. If the Earth was in orbit with that velocity it would circle the Sun in 3 days. The orbital velocity is:
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--------------------- v^2 = M * G / r
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- Orbital velocity is directly proportional to the total mass inside the orbit radius ( M ) and inversely proportional to the radius ( r ). The bigger the mass the faster the orbit velocity. The smaller the distance from the mass the faster the orbital velocity.
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- G is the constant of proportionality . In the units we use it is 6.674215*10^-11 meters^3 ( kilogram * seconds^2). 10^-11 is very small. Gravity is a very weak force unless the mass is very, very big.
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- One of these stars was clocked orbiting just 17 lighthours form the center. (hours not lightyears). That distance is equivalent to 3 times the distance from Pluto to our Sun.
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- Other galaxies have had similar measurements made on their central orbiting stars. M87 is an elliptical galaxy that has a 3,000,000 Solar Mass Blackhole. Andromeda Galaxy next door to us has a 140,000,000 Solar Mass Blackhole, 35 times bigger than our Milky Way Blackhole.
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- “ Light” waves can not make these measurements for our galaxy because our center is crowded with opaque gas and dust. However, radio waves and infrared waves can penetrate the dust and “ see” the stars orbiting the center. The shell of dust is rotating counter-clockwise around the center, the opposite of the Galaxy’s rotation.
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- Over a dozen stars have had their orbits calculated over the past 10 years ( labeled S2 through S20 ). S2 is the one the loops within 17 lighthours closest to the center. It completes an orbit in 15 years. The elliptical orbit extends from 17 lighthours to 240 lighthours, or 10 light days at its farthest point.
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- Tracking these stars is no small achievement. It is like aiming a gun sight at a basketball that is 1,000 miles away. But, spectroscopy measurements have been made and S2 was found to be a main-sequences star of 15 Solar Mass. This size star has a lifetime of about 10,000,000 years. Measurements tell astronomers that these stars likely formed between 3 and 6 million years ago, which is a very young star. Our star is 4.6 billion years old.
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- One theory to explain these young stars it that they could be the cores of older stars that have collided and merged together.
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- A second theory to explain such young star is that the actually formed somewhere else and migrated to the Blackhole to be captured by its gravity.
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- A third theory is that the stars formed in the Blackhole’s spiral arms and spiraled down to within a few lightyears of the center in less than 10 million years. To do these descending orbits stars would have to loose angular momentum . However, this could happen if stars were colliding. If not collisions between suns, which is unlikely, maybe it as collision between gas clouds and suns.?
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- A forth theory has two binary Blackholes at the center with the second smaller Blackhole dragging the young stars closer to the bigger Blackhole at the center.
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- Bursts of infrared light have been measured and timed suggesting that the Blackhole is spinning with a period of 17 minutes.
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- The center around the Blackhole has been likened to a pin ball machine. With stars colliding or passing near each other perturbing each other’s orbits. Stars could even be totally knocked out of the galactic halo if they attained enough escape velocity in their exchange of angular momentum. A few of the “ hyper velocity” stars have been found. If a star escapes once every100,000 years then 100,000 stars could have been flung outside of the Galaxy by the central Blackhole by now.
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- There are a lot of mysteries to be solved at the center of our Galaxy. Radio astronomers are working with 1 millimeter wavelengths to get more precise measurement data. If nothing else it a chance to study some dynamic astronomy. A lot is happening at the center pin ball machine. An announcement will be made shortly , stay tuned.
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707-536-3272, Wednesday, December 12, 2012
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