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------------------ 2169 - UNIVERSE - the one we live in
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- The Universe is 13.8 billion years old. Our sun is 5 billion years old. Our sun must be a second or third generation star. It is composed of the residue of 2 or 3 earlier supernovae explosions from earlier stars that died spreading their elements all over the cosmos.
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- The more we learn about our sun the more we will know about the other stars in the Universe. One thing for sure our sun still has many secrets. Just 20 years ago we learned that the upper most layer of the sun rotates slower than the rest of the sun’s interior.
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- It was previously known that the sun rotates faster at its equator than it does at its poles. This is what drives the sun’s 11-year sunspot cycle. But, we do not know what causes this difference in rotation.
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- A new theory proposed is that the light generated at the sun’s surface has a braking effect on the surface layers. The solar radiation is braking the sun’s rotation because Special Relativity is gradually slowing the rotation down, starting at the surface.
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- Photons carry the electromagnetic force and that light carries a tiny amount of momentum with it Calculations are that a 5 billion year lifetime allows the surface to slow down the upper most 5% of the sun. The drag caused by the photon’s leaving the surface of the sun have created this measurable effect.
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- The new measurements use helioseismology which measures seismic waves traveling through the sun. This is very similar to the measurements of seismic waves created by earthquakes here on Earth. The waves travel differently in different material creating a picture of the underground that we cannot see.
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- The sun has the same effect below its surface but the sun isn’t a solid body like the Earth’ s rock and metal. The sun is made of a dense plasma of gas. Helioseismology can still measure waves creating oscillations at the surface.
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- Studying these waves astronomers hope to learn how the sun’s magnetic field affects its interior. And, just how much magnetic drag , caused by Einstein’s Special Relativity, has slowed rotation of the sun’s surface.
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- Even a tiny effect can result in significant change over 5 billion years. We are using our sun as a laboratory to study all the stars and stellar evolution throughout the cosmos. We already know that the sun’s magnetism causes “space weather” that triggers solar flares and coronal mass ejections. These events interfere with Earth’s satellites and power grids. Something we need to learn a lot more about.
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- We know our sun has had a mother star that was born a few tens of billions of years before it. The star died in a supernova explosion that seeded space with heavy elements and radioactive elements. Some of these elements were collected in the makeup of our sun.
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- The sun was born in a cloud of dust and gas. This material collected by the force of gravity until the core condensed enough to ignite nuclear fusion. When the sun was still young the dust in orbit was collecting into asteroids and planetary bodies. The Earth was born soon after the sun was born, , within 38 million and 120 million years after. Then less than 1 billion years after that, life was born on our new planet.
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- Five billion years later here we are. And, five billion years from now the sun will end its life. Its fuel will be gone and its outer gas layers will expand into a planetary nebula. The center core will condense into a white dwarf star The Earth and the inner planets will be engulfed in this nebula and all life here as we know it will be gone.
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- Bye for now.
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- Footnote: How did we learn about the ages of stars and planets?
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- Astronomers reconstruct this history using meteorites that are remnants of these early stars. They compare the amounts of the various isotopes of the radioactive material. The different abundance of radioactive material diminish over specific time scales.
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- For example, aluminum 26 isotope has a half-life of 730,000 years. It is found in meteorites dating to the earliest birth of our solar system. Estimates are that this radioactive aluminum 26 formed in a supermassive star 30 times the mass of our sun. Supermassive stars have a short life and explode as supernova after only a few million years.
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- Heavy metals , such as gold, silver, and platinum, found in meteorites arriving on Earth some 100 million years before the birth of the sun. Evidence from these meteorites suggests that solid matter condensed to form these asteroids within 1 million years after the sun was born. Mars formed 2 million years after the sun was born. Earth formed between 38 million and 120 million years after the sun did.
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- 70,000 years ago modern humans were spreading out of Africa. Humans have been studying the sun ever since. We know it is the source for all life on Earth. It is not only a truth about our little corner of the cosmos, but, it is also a window into the many stars we can only see and admire in the night sky and beyond.
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- November 23, 2018
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-------------------------- Friday, November 23, 2018 --------------------------
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