-
-
-----------------------------1908 - Stars to Blackholes
-
- Looking up at the sky on a starry night we perceive we are looking at great distances to the stars. We are. But, we are also looking backwards in time. That shining star might not be there today. It may have gone supernova and now only reside as a dark cinder.
-
- Information and perception travel at the speed of light, 671,000,000 miles per hour. Even our star, our Sun, is viewed 8 minutes backward in time. And, so is gravity that is traveling at the same speed as light. The more distant star in the night sky could be 10 lightyears away from us. It takes 10 years for its light to reach us. To us it is alive, but, that star could be a “ stellar ghost” today. There is such a star at the center of the Crab Nebula, 6,523 lightyears away
- Our largest stars die as Neutron Stars or, as Blackholes. A star’s life is balanced by radioactive fusion and its own gravitational contraction, which depends on its size. It lives in equilibrium surviving by the balancing act between these two forces. The star is born fusing hydrogen into helium. When the hydrogen at the core is used up helium begins to condense at the core. The star shrinks, its core density increases, its core temperature rises. The star the size of our Sun fuses elements heavier than helium, up to the element carbon. Gravity created by the Sun-size stars is not strong enough to fuse elements heavier than carbon. Fusion stops. The star’s radiation dies. It becomes a stellar ghost.
-
- However, for stars 7 times larger than our Sun the fusion to heavier elements continues under the stronger pressure of gravity. Past carbon and oxygen, past silicon, past heavier elements until fusion reaches the element iron. Iron absorbs compression energy. It does not release energy radiation to reach the next heavier element like the lighter elements do. Without excess radiation energy to hold it up the star it collapses under gravity. The inward free fall of layers of elements meet at the center and rebound outward as an exploding supernova.
-
- The outward explosion is so intense in temperature that the elements heavier than iron are created fusing all the way to the heaviest, Uranium. All these new elements are blasted into the Cosmos as gas and dust to become seeds for new star formation.
-
- What happens next all depends on how much mass is left at the core of the supernova. If it ends up as a ball of degenerative neutrons it becomes a Neutron Star, so dense a teaspoon would weight 10 million tons. So concentrated in gravity pull the escape velocity required would be 40 % the speed of light. If it is spinning at incredible velocities it is called a : Pulsar” with beams of radiation emitting from its poles.
-
- The spinning Neutron star generates an enormous magnetic field. Electrons are accelerated into the magnetic poles. These accelerating electric charges generate radio waves, X-rays, Gamma Rays. If the magnetic pole is offset from the rotational pole the rotating beam of escaping charged particles becomes a light house sweeping around many times per second. What astronomers see as a beam sweeping by our region of the sky, it is a “pulsar”.
-
- If the star’s core has a still greater mass it does not stop at a Neutron Star; it continues to be crushed into a Blackhole where the escape velocity becomes over 100% the speed of light. Light can not escape. Its gravity warps space-time back onto itself. It condenses to a point of infinite density.
-
- These massive stars are larger than 18 times Solar Mass. Inside the Event Horizon that surrounds the Blackhole no information escapes. It is even beyond the laws of physics. We really don’t know what happens beyond the Event Horizon inside the Blackhole.
-
- The supernova that blasted elements away from the core forms molecular clouds in space to become stellar nurseries to form new stars, new planetary formations. The accretion disks of rotating dust and gas around a newly formed star coalesce into planets, asteroids, and comets.
-
- The debris of the exploding star is what our world, our life, is made of. The “ stellar ghosts” are our ancestors. They exist within us. Thoughts to ponder when staring into the starry night sky.
-
- But, what happens to the Blackholes? We are learning that there are massive Blackholes at the center of most every large galaxy. There is a massive Blackhole at the center of our Milky Way Galaxy. We obviously can not see it, but, we can see stars that are orbiting some large center of mass. A particular star orbiting with a period of 15.2 years, 11.18 billion miles radius, about a center mass must be held by a mass of 4.1 million Solar Mass, 9.04 * 10^33 tons. The radius of the center mass must be less than 120 Astronomical Units (AU) in diameter, otherwise this star would crash into it.
-
- Similar massive Blackholes have been calculated to be at the centers of the Andromeda Galaxy ( M31), the elliptical galaxy ( M32), the spiral galaxy ( NGC4395). Likely these super massive Blackholes are at the heart of all the large galaxies?
-
- Could these massive gravity pits be the result of merging smaller, stellar Blackholes? Or, could these massive objects have formed in the primordial Big Bang era? Or, are these giants remnants of several massive stars exploding and concentrating as accretion matter at galactic centers? We don’t know.
-
- Besides rotating stars about galactic centers there are accretion disks of gas and dust gradually feeding these center gravity pits. The compression, collision, and speed of rotating, in falling, material reaches temperatures of millions of degrees Kelvin, generating bright radiation in electromagnetic energy. These dynamos create powerful magnetic jets above and below the Blackhole reaching relativistic speeds extending out hundreds of thousands of lightyears. These are called “ Quasars”.
-
- Super massive Blackholes have lower average density because their volume is directly proportional to the cube of their radius:
-
------------------------------- V = 4/3 pi r^3
-
- And, the minimum density is inversely proportional to the square of the mass:
-
--------------------------- Density = mass / Volume
-
- The result being the tidal forces in the vicinity of the Event Horizon are significantly weaker for massive Blackholes.
-
- The diameter, or rather the radius, of the Event Horizon is 3 times the mass of the Blackhole:
-
---------------------------- Radius = 3 * mass
-
- Gamma Ray bursts have been detected leaving the Event Horizon. One such burst was detected March 28, 2011, at the center of a galaxy 3.8 billion lightyears away. X-ray detections followed. The duration of the X-ray flares gave an indication of the size , or diameter, of the Blackhole accretion disk.
-
- Three X-ray flares had an average duration of 8 hours. The flares traveling at the speed of light would travel a distance of 8.6 billion kilometers.
-
-------------------------- Distance = speed * time
-
--------------------------- Distance = ( 300,000 kilometers / sec) * (8 hours) * ( 3,600 seconds / hour)
-
--------------------------- Distance = 8.6 billion kilometers
-
- The radius of the Blackhole is estimated to be 100 times smaller due to the measured “ beaming effect” of the flares. So, the Blackhole radius is 43 million kilometers.
-
--------------------------- Radius = 3 * mass
-
-------------------------- Mass of the Blackhole = 14 million Solar Mass
-
- This is about 3 times larger than the Blackhole measured at the center of the Milky Way Galaxy, which is 4.1 million Solar Mass.
-
- I have several other reviews on “ Blackholes” if you want to learn more.
-
- --------------------------------------------------------------------------------------
---- Comments appreciated and Pass it on to whomever is interested. ----
--- Some reviews are at: -------------- http://jdetrick.blogspot.com -----
-- email feedback, corrections, request for copies or Index of all reviews
- to: ------- jamesdetrick@comcast.net ------ “Jim Detrick” -----------
- https://plus.google.com/u/0/ -- www.facebook.com -- www.twitter.com
----- 707-536-3272 ---------------- Tuesday, December 13, 2016 -----
------------------------------------------------------------------------------------------
No comments:
Post a Comment