--------- #1267 - Gamma Ray Bursts in Caught in Action?
- In recent months astronomers have used the newest space telescopes to catch Gamma Ray Bursts in action. They are beginning to confirm some theories as to what causes this enormous release of energy. This review does the math for two such events. The first burst occurred March 28, 2011.
- Attachments - none
- The Swift Gamma Burst Mission spacecraft first detected the Gamma Ray flash in the Constellation Draco the Dragon. (Sw1644+57). The source of the explosion was the center of a galaxy 3,800,000,000 lightyears away. The flash was of long duration, in fact, it is still occurring 2 ½ months later. Astronomers explain this as a star falling into a Blackhole that is a million times more massive. The star is spiraling into the Blackhole and is getting ripped apart as it descends. The Blackhole’s immense gravity puts tidal forces on the star that tear away clumps of gas. Intense radiation in the form of X-rays and Gamma Rays orbit the Blackhole and then escape out the rotational axis as high speed jets. These jets just happen to be pointed at us.
- If a Gamma Ray Burst is observed at an angle it is viewed as a “active galactic nuclei”. When the same event is viewed down the barrel of the jet it is called a “ Blazer.”
- Blackholes are at the core of most all galaxies, including our own Milky Way Galaxy. They can appear dormant until a star randomly wanders too close and gets shredded in the Blackhole’s Event Horizon. This could happen in our galaxy. Our Blackhole is relatively quiet, but, events can change.
- How do astronomers measure the size of the Blackhole, that they can not see?
- When the light curve is plotted the X-ray flares occur about 3 times in 24 hours. So the average flare duration is about 8 hours. If a flare starts in one region and then extends to another region in the Event Horizon the distance traveled can be calculated for the duration of the flare.
- A Blackhole with the mass of the Sun has an Event Horizon radius of about 3 kilometers ( less than 2 miles). The formula to calculate the radius of the Event Horizon is:
------------------------------- R = 2 * G * M / c^2
------------------------------- where: R is the radius in kilometers
------------------------- G is the Gravitational Constant = 6.67*10^-11 m^3/(kg*sec^2)
------------------------- c is the speed of light
------------------------- c^2 = 9 *10^16 meters^2 / second^2
-------------------------- M = the mass of the Blackhole in Solar Mass.
------------------------- Solar Mass = 1.99*10^30 kilograms
- Performing this calculation, the radius of the Event Horizon in kilometers is equal to 3 times the mass of the Blackhole in Solar Mass.
-------------------------- R = 3 * M
- The radius is estimated by the duration of the flare that is traveling at the speed of light across the Event Horizon. Distance = velocity * time. The velocity is the speed of light = 3 * 10^8 meters / second. The time duration is 8 hours. Therefore the distance traveled is 8.64 * 10^12 meters. This is about the distance of our Solar System, 58 Astronomical Units. One Astronomical Unit is the distance from the Earth to the Sun which is 1.5 * 10^8 kilometers. ( 93 million miles)
- The distance of 8.64 * 10^9 kilometers represents the diameter of the Event Horizon, so the radius is 4.32 * 10^9 kilometers.
-------------------- Mass = Radius / 3
-------------------- Mass = 1.44 * 10^9 Solar Mass
------------------- Mass of the Blackhole is 1,440,000,000 Solar Mass.
- This calculation is very rough. It only applies to a non-rotating Blackhole and it does not take into account the Theory of Relativity. As velocities approach the speed of light time slows and distances shrink. This math is above my pay grade, but, if it were done then we need to reduce our answer for the mass of the Blackhole by a factor of 100.
--------------- Mass of the Blackhole is 14,400,000 Solar Mass.
--------------- The Blackhole is 14 million times more massive than our Sun.
- The redshift of the X-ray light is 0.3534. This means that the galaxy is 3,800,000,000 lightyears away. So, the space expansion over that distance makes the galaxy appear to be traveling away from us at 35% the speed of light. That is how much the wavelengths of light have expanded or “redshifted”.
- Gamma Ray Bursts are so bright they can be seen with binoculars even though the galaxy is billions of lightyears away. It took that long for the light to get here. That is how old the event is when we see it. And, that is how far the light traveled to reach us.
- When astronomers measure the amount of energy in the radiation they know that it must be focused in a narrow beam. If it were a supernova explosion it would be radiating in a sphere in all directions. So, this scenario is ruled out. But, if the burst is channeled into a narrow beam exiting the rotating body at the poles then the calculations make more sense.
- There are two types of Gamma Ray Bursts, long duration and short duration bursts. A short duration burst could be a supernova that forms a Neutron Star. Or, a supernova that forms a Blackhole where even more matter crushes into an even smaller radius releasing many times more gravitational potential energy. Long duration Gamma Ray Bursts could come from the collision of two Neutron Stars, or one Neutron Star and a Blackhole. The two stars orbit each other and produce gravitational waves that radiate energy way from the system. This loss of energy causes the two stars to spiral in toward each other until they collide.
- There was a second X-ray flare that was recorded in the last few months that lasted 4 hours with the X-ray emissions increasing to over 10,000 times its normal brightness. This was a binary star system with one of the stars being a Neutron Star only 6 miles in diameter. The Neutron Star is so dense, totally collapsed atoms into packed neutrons, that it has an enormous gravitational field.
- A large clump of matter was pulled from the blue supergiant companion star. This huge bullet of gas hit the Neutron star releasing the X-ray flare that was recorded. The size of the clump of gas was calculate to be 10,000,000 miles across. Its volume was 100,000,000,000 the volume of our Moon. It’s total mass was only 1/1000 the mass of the Moon. But, when it hit the Neutron Star an enormous amount of energy was released.
- Gamma Ray Bursts occur somewhere in the sky on average once per day. There is some significant violence happening out there and we are just beginning to understand what causes it. An announcement will be made shortly. Stay tuned.
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707-536-3272, Monday, July 4, 2011
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