- 3150 - STARS - big and strange? The diversity of star stretches from star mass ½ the size of our Sun to those 1,000 times bigger. The bigger stars all go supernova, their explosions leaving a core of either a Blackhole or a Neutron Star. The smaller stars 140% the mass of the Sun and less, all end up as White Dwarfs or Brown Dwarfs. Diversity is all about the fight between mass and gravity.
- ----------------------- 3150 - STARS - big and strange?
- For the first 100,000,000 years the Universe was totally dark. There were no stars, planets, galaxies, or starlight. The Universe was just hydrogen gas, and a little bit of helium gas.
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- The Universe expanded and cooled enough for the hydrogen nucleus proton and the electron to bind together with electromagnetic energy. Hydrogen gas clouds began to form and electromagnetic energy began to spread out into space.
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- Space was not entirely uniform and gravity pulled the denser clumps of gas together. These clumps collapsed enough to form the first stars. The near spherical cloud started with maybe 100,000 Solar Mass. Within it many stars would form with 30 to 500 Solar Mass.
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- Stars got bigger back then, maybe even up to 1,000 Solar Mass. But, the bigger stars were so hot that the hydrogen gas was mostly ionized. Ionized hydrogen, i.e. protons, do not emit many photons, or electromagnetic energy to allow them to cool efficiently.
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- Stars remained hot, and big, and bright, but, with short lifetimes of only a few million years of age. They relatively quickly burnt up all their hydrogen, and helium fuel and exploded into GIANT supernovae. It was in this explosion the fusion created the heavier elements and spread them into the interstellar medium for the next gas cloud to form.
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- It was another 900,000,000 years before the first galaxies began to form. Still the gas was predominately hydrogen and helium. But, the gas had cooled down from 1,000 Kelvin to 300 Kelvin.
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- This lower temperature allowed molecules to form and ordinary matter to contract into gravitationally bound clumps. 90% of the first galaxies contained Dark Matter as well. However, the Dark matter does not emit radiation, that is why it is “dark”. That is also why it would not have cooled down.
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- Dark Matter remained scattered in the primordial cloud around the galaxy. The denser clumps of ordinary matter that cooled within the cloud eventually condensed to form stars. When the first galaxies formed 90% of the mass was in the Dark Matter halo surrounding the galaxy.
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- The First Big Stars we exceptionally massive and bright. They could be 1,000 Solar Mass and lightyears across, but extremely short lifetimes of a few million years. Their surface temperatures were 100,000 Kelvin and their brightness was mostly ultraviolet light.
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- When they ran out of fuel and exploded into GIANT supernovae hydrogen and helium fused into the heavier elements spreading into space leaving a Blackhole behind at the core. These Big Star Blackholes later became the hearts of the first galaxies. These first galaxies were highly active and we can see them today as Quasars.
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- Today’s interstellar gas contains many of the heavier elements and molecules resulting from many supernovae explosions. Gas molecules and heavier elements are very efficient at emitting electromagnetic energy and thus cooling very quickly from 1,000 Kelvin to 10 Kelvin for today’s stars to form.
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- Molecular hydrogen by itself cannot cool the gas below 200 Kelvin. That is why the first stars had to be 300 Solar Mass or greater with surface temperatures of 100,000 Kelvin. (The Sun’s is 6,000 Kelvin). That also meant that the first stars were shining in ultraviolet wavelengths. The ultraviolet radiation from these first stars would again re-ionize the hydrogen gas in the interstellar medium creating darkness for a second time.
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- Since then the first stars and galaxies the Universe have expanded by 1,000 times and the interstellar medium has cooled to 3 Kelvin. The biggest stars that can form in today’s interstellar medium is 150 Solar Mass. Astronomers believe there are about 300 of these Big Stars in our galaxy today, but, only a few have been discovered. For every one Big Star there are 10,000 stars the size of our Sun.
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- In 2006 one Big Star was discovered 20,000 lightyears away and believed to be 116 Solar Mass. The mass is calculated by measuring the orbits of the other stars around the Big Star. The uncertainty of these measurements is put at 116 Solar Mass +or - 30 Solar Mass. That is the Big Star could be as big as 146 Solar Mass or and small as 86 Solar Mass and still be within the measurement errors. The second Big Star to be found was calculated to be 89 Solar Mass + or - 15 Solar Mass.
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- Another reason more Big Stars have not been found is that they have intense Solar Winds. The Solar Winds are so intense they equate to the star shedding one Solar Mass every 100,000 years. This solar wind creates a bright cloud of material around it so dense that it hides the bright star from view.
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- A third reason that many Big Stars are not found is the they live for only 2 to 3 million years, before they go supernova. The last supernova explosion witnessed in our Milky Way galaxy occurred 400 years ago, in 1604. It is known as the Johannes Kepler supernova.
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- Our Sun has a surface temperature of 6,000 Kelvin which puts it greenish yellow in color. When the sunlight enters our atmosphere the air scatters the blue light making the Sun appear yellow to us on the ground. The Sun is not big enough to go supernova. It will become a planetary nebula with a white dwarf neutron star at the core.
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- Bigger stars, 7 to 20 Solar Mass have much hotter surfaces temperatures up to 100,000 Kelvin making them blue-white in color. The luminosity they radiate every second is over 1,000,000 times that of our Sun‘s. Our Sun puts 1,300 watts of energy on every square meter of ground in every second of daylight. It has a lifetime of 10 billion years.
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- If a Big Star is 25 to 100 Solar Mass it has a life of only a few million years. During 90% of the Big Star’s lifetime it is burning hydrogen just like our Sun. When the hydrogen burns up at the core the temperatures get hot enough, over 100,000,000 Kelvin, to begin fusing helium into heavier elements. This star becomes a red supergiant with hydrogen still burning on its surface. This is what the star Betelgeuse in the Orion Constellation is today.
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- If a Big Star is greater than 35 Solar Mass it can enter an interim phase as a luminous Blue Variable star. This is what Eta Carinae is today. Either way when the star looses mass with its solar winds down to 7 to 20 Solar Mass helium is fusing into nitrogen and the surface temperature is 30,000 to 40,000 Kelvin.
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- Once nitrogen is gone the surface temperature reaches 100,000 Kelvin and fusion creates elements carbon and oxygen. During all these phases the Big Stars are casting off mass as a solar wind, 1 Solar Mass per 100,000 years. This all adds up so during the Big Stars total lifetime it is flinging half of its mass into space with the heavier elements being the raw material for new stars and planets.
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- Carbon dust can make up 15% of this solar wind. It is a mystery how dust can even exist at these high temperatures. Recent discoveries are indicating that 85% of the stars are multiple star systems. 50% being binary stars and 35% being 3 or more star systems. If the Big Star is in such a system than the dust could be formed in the solar wind collisions between the stars. These collisions create pinwheels of cooler winds the spew out dust like water from a garden sprayer.
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- One such binary star has been studied, Wolf-Rayet 140, WR140, is orbited by a type OB star every 7.94 years. A dusty pinwheel has been sighted in 1985, 1993, 2001, and another is expected in 2009. A second big star, WR104, has been observed in the infrared to have a dust trail spiraling every 241 days.
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- The Hubble Space Telescope has observed this star and found at least one other star in the system. The spiraling pinwheels are like comet tails away from the solar wind of the Big Star. But, because the Big Star is in an orbit with other stars the tail twists away in the shape of a giant spiral.
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- The closest Big Star to us is V444 Cygni which is 3,700 lightyears away. We do not know when it will go supernova. It will someday after its short 2 to 3 million year lifetime. Modern astronomy has yet to see a supernova explosion in our galaxy. The closest one occurred in 1987 and that was in another galaxy, the Large Megellanic Cloud galaxy, our neighbor that is 160,000 lightyears away.
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- Our Sun is 1 Solar Mass and only 4.7 light seconds across. One light second is 186,000 miles.
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- The diversity of star stretches from star mass ½ the size of our Sun to those 1,000 times bigger. The bigger stars all go supernova, their explosions leaving a core of either a Blackhole or a Neutron Star. The smaller stars 140% the mass of the Sun and less, all end up as White Dwarfs or Brown Dwarfs. Diversity is all about the fight between mass and gravity.
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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. 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 two Neutron Stars 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.
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- 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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- Let’s start with the smaller mass stars and their fight with gravity. What prevents gravity from collapsing 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 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.
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- 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!, what a 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. 95% of the Universe is Dark Matter and Dark Energy that we have yet to discover.
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- 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. Here are more reviews:
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- 3071 - STARS - neutron stars, magnetars and pulsars? Big stars have short lives and dramatic deaths. This review highlights the bigger supernovae explosions that create Gamma Ray Bursts, Magnetars, and Pulsars. It refers to a small satellite student project that hopes to contribute to our understanding of these cosmic wonders.
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- 3048 - SHOOTING STARS - Out of the Galaxy? If a star is traveling over 1,000,000 miles per hour it is referred to as a “hypervelocity star“. Some 16 or these hypervelocity stars have been discovered. The first one discovered in 2005 was traveling over 2,000,000 miles per hour. In 2006 and 2007 seven more hypervelocity stars were discovered.
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- 3035 - STARS - How many stars are in the sky? How many stars can you count on a clear night. I sure you would estimate several thousand. Astronomers have been fascinated with counting the stars for centuries. Over recent decades they have even developed a mathematical formula for calculating the number of stars you can see.
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- 2942 - STAR OF BETHLEHEM - December 21,2020. This Review covers the depths of science to the depths of religion. We need both faith and knowledge. Gravitational waves are our newest technology to explore the universe with science. The Star of Bethlehem is the story of the birth of Christ and the stars are again in alignment this year, 2020.
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- May 5, 2021 STARS - big and strange 949 947 3150
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--------------------- --- Wednesday, May 5, 2021 ---------------------------
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