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------------------------------ Stars orbiting the Blackhole at the center of our galaxy
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---------------------- 2273 - The Diversity of Stars
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- The smaller stars 140% the mass of the Sun and less, all end up as White Dwarfs or Brown Dwarfs. Diversity of outcomes is all about the fight between mass and gravity. Let’s start with some spectacular examples:
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- “Magnetars” are spinning Neutron Stars that twist expansive magnetic fields that are 1,000,000,000’s times stronger than the strongest magnets we can create here on Earth.
As these Magnetars rotate they send out jets of X-rays and Gamma Rays.
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- In March, 1979, nine spacecraft measured a single event that released more radiation than the Sun will release over 1,000 years. ( Supernova remnant N49).
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- “Pulsars” are spinning Neutron Stars. The radiation pulses that occur are caused by star quakes, analogous to Earthquakes, on the surface. The cracks in the surface emit a burst of X-rays and Gamma Rays. Astronomers have measured these bursts of radiation and have found that the time to wait for the next quake is directly proportional to the size of the last quake.
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- What happens when two Neutron Stars collide? When a star collapses into a Neutron Star it is compressed with a mass greater than the Sun’s into a ball only 10 to 13 miles in diameter. Actually, the more mass the neutron star has the smaller its diameter.
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- This ball of neutrons is so dense that a cubic centimeter, a teaspoon full, or the size of a sugar cube, would weigh 1,000,000,000’s tons on Earth. Two Neutron Stars did collide in 2005 so astronomers could measure the burst of radiation. The collision occurred between the two Neutron Stars that were traveling 10,000 miles / second. The Gamma Ray burst released in the explosion amounted to as much radiation as released by 100,000,000,000,000 Sun’s.
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- A supernova explosion can send out shockwaves traveling 22,000,000 miles per hour. The last time one of these supernova shockwaves was witnessed in our Milky Way Galaxy was in 1604. It is known as Johannes Kepler’s supernova.
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- A few other supernova were witnessed before the telescope was invented. These exploding stars, brilliant new stars in the night sky, lasted for months in the years 1006, 1054, 1572, and 1604. Today with our telescopes and spacecraft astronomers observe supernova explosions in other galaxies almost daily. The closest one was supernova 1987A in the Large Magellanic Cloud Galaxy. The 1054 Supernova in our galaxy is now viewed as the Crab Nebula in the Constellation Taurus the Bull.
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- All of these star events are the result of the fight between mass and gravity. The bigger the mass the more spectacular the explosion and the quicker it happens, the bigger stars lifetimes being only a few million years before collapsing into Blackholes. Smaller stars live longer and collapse into Neutron Stars. The smallest stars live the longest, billion of years, and collapse into White Dwarfs or Brown Dwarfs.
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- Starting with the smaller mass stars and their fight with gravity, what prevents gravity from totally collapsing these stars. Living stars are burning fuel and the radiation from the thermal nuclear fusion at their cores expand with an outward pressure that balances against the collapsing pressure of gravity. The sunlight coming to us expanding out of the Sun is what keeps the Sun from collapsing.
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- When the fuel in a star runs out gravity wins and begins the collapse again until some kind of pressure can balance against it. The balance occurs in White Dwarf Stars that are about the size of our Sun before collapsing into a ball about 10 miles in diameter. What is preventing the collapse from going further is the pressure of the electrons resisting their collapse into each atomic nucleus. This is called electron degenerative pressure.
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- If the mass of the star is greater than 140% that of our Sun, the greater mass will mean even greater pressure to collapse. The electron degenerative pressure eventually gives way and the electrons get pushed into the nucleus to combine with protons and become neutrons. The entire star becomes a ball of neutrons, creating the Neutron Star.
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- If the mass of the star is still greater the pressure of gravity will collapse even the neutrons. When this happens the ball is crushed into a plasma of the neutron’s fundamental particles of quarks and gluons. This star, the Quark Star has not been found for sure but exists in theory. The next step for gravity gets into even more mystery. Greater mass and greater gravity will collapse the quark plasma of the star into a Blackhole.
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- The mass gravity fight does not even stop at Blackholes. Blackholes exist with mass inside and the influence of gravity being the exact same as any other mass that size. Astronomers do not know what is inside the Blackhole but theory assumes that mass is reduced to only the fundamental particles crunched into a singularity, a single particle.
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- At the edge of the Blackhole, called the Event Horizon, the fundamental particles can escape back into space with quantum fluctuations of particle - anti-particle pairs. When one particle is swallowed from the edge the other is flung back into space. This is called Hawking Radiation after Steven Hawking who developed the theory. It represents an evaporation of a Blackhole and therefore a limited lifetime for even this enormous mass.
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- Stars definitely have a wide range of diversity. Astronomers studying them have uncovered many new theories in physics needed to explain their behavior. Studying giants in the Universe has gotten down to the smallest fundamental subatomic particles.
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- Astronomers have learned to study stars beyond the wavelengths of visible light. Today they use measurements seeing with the entire electromagnetic spectrum. New discoveries keep coming and astronomers are still only working on the 4% of the Universe that is Ordinary Matter.
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- 95% of the Universe is Dark Matter and Dark Energy that we have yet to discover. Physics and Astronomy are fertile fields for new students if they can only get enough math and science in schools so they can get started.
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- What is the biggest star in the Universe? We will never know. The Universe is too big and we can only observe a small part of it. But, what is the biggest star we can “observe” in the Universe?
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- Our most observed star is our Sun. It is 870,000 miles across. By mass the Sun is 99.9 % of our entire Solar System. By volume you could fit 1,300,000 Earths inside the Sun.
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-------------------------------- volume = 4/3* pi* r^3
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------------------------------- Sun’s radius = 6.9599*10^8 meters
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------------------------------ Earth’s radius = 6.378*10^6 meters, Sun’s radius is 100 times larger.
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------------------------------ Ratio = 1.3*10^6, 1,300,000 times
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----------------------------- The Solar Radius is 432,000 miles
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----------------------------- The Solar Mass is 2*10^30 kilograms,
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----------------------------- 2,000,000,000,000,000,000,000,000,000,000 kg.
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- Eta Carinae is a monster star in our galaxy just 7,500 lightyears away. It is 100 times the Solar Mass. and it is 4,000,000 times brighter than our Sun. Its solar wind casts off 500 times the Earth mass every year. Its radius is 400 times Solar Radius. Astronomers are certain Eta Carinae is about ready to explode as a supernova. It is extremely hot, 25,000 Kelvin at its surface. Our Sun is 6,000 Kelvin.
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- But, Eta Carinae is not the biggest star we have found in our galaxy. VY Canis Majoris is 5,000 lightyears away and it is 2,100 time Solar Radius. It takes light 8 hours to go across it. It takes light only 8 minutes to reach us from the Sun.
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- There are likely more massive stars in our Milky Way Galaxy but we can not see them because they are hidden by intergalactic gas and dust. The largest stars are the coolest stars, that are still stars. VY Canis Majoris is only 3,500 Kelvin. Physics calculations are that the largest possible star is 3,000 Kelvin and 2,600 times Solar Radius.
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- If a star is less than 3,000 Kelvin it not a star, it is too cool to have nuclear fusion and to shine. There could be something bigger out there that does not shine. We have not found it unless you count Black Holes. Black Holes have been found that are 1,000,000,000’s times Solar Mass. And, they don’t shine.
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- February 14, 2019 949 907
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-------------------------- Thursday, February 14, 2019 --------------------------
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