by Ann » Thu Sep 24, 2015 1:06 am
sallyseaver wrote:
Where does the original angular momentum come from? My understanding is that the original matter started like the big nebulae we see in other parts of the cosmos, like The Great Nebula (APOD Jan 19, 2015) or Gamma Cygni Nebula (APOD April 22, 2015) or the Carina Nebula.
No, the original matter did not start as a big nebula. Everything that exists in the universe was originally created in the Big Bang. The Big Bang was the sudden appearance and the immediate, violent expansion of the universe. From the beginning the universe was incredibly tiny, hot and dense. In the beginning it was far too hot and dense for matter and energy to be separate at all. When the universe had expanded and cooled to a certain degree, matter and energy could "decouple". That is when hydrogen first came into existence, the simplest form of ordinary matter. Helium, too, the second element, was created in the Big Bang, and also some lithium. This matter existed as a hot, dense, but expanding "soup".
The universe was certainly at least 400,000 years old, and possibly many million years old, before the first stars appeared. The first stars probably emerged out of nebulas, but the first nebulas were certainly very different from the typical nebulas of today. For one thing, the original nebulas contained no dust at all. Dust is made of elements more complex than hydrogen and helium (and lithium), but all such elements are created inside stars as rest products of their fusion of hydrogen and helium. Before the stars existed, there was no dust.
Where does the angular momentum come from? I'm not the correct person to answer that at all, but you must remember that the universe has always been teeming with energy, motion and outward expansion. Remember that the universe was always a place were outward expansion and inward-pressing gravity fought with one another. The distribution of matter and energy was always very slightly "uneven", encouraging the flow of matter away from more rarefied locations into more densely packed parts. Why should there not be angular momentum in such a dynamic place? What force could actually stop the angular momentum in the universe?
In any case, stars appears when a nebula shrinks and condenses under the influence of its own gravity. In other words, the nebula becomes smaller (or at least the part of the nebula that gives rise to the star becomes smaller). If the nebula is not perfectly "still", but contains some inherent rotation at all, this rotation will become much more pronounced as the nebula shrinks. Compared this with what figure skaters do to rotate, and to rotate faster. When they spin, they have to create their own initial rotation, but then they speed their rotation up by making themselves "smaller", by holding their arms and legs close to their "axis of rotation":
Click to play embedded YouTube video.
IF there is a dust prominence in the absence of interacting with a different galaxy, then it could mean that the dust is primarily iron (an abundant element)
Iron is not particularly abundant at all, compared with many other elements in the universe like oxygen, carbon and silicon. You can be sure that the dust in the universe is mostly made up of other elements than iron.
Ann
[quote]sallyseaver wrote:
Where does the original angular momentum come from? My understanding is that the original matter started like the big nebulae we see in other parts of the cosmos, like The Great Nebula (APOD Jan 19, 2015) or Gamma Cygni Nebula (APOD April 22, 2015) or the Carina Nebula.[/quote]
No, the original matter did not start as a big nebula. Everything that exists in the universe was originally created in the Big Bang. The Big Bang was the sudden appearance and the immediate, violent expansion of the universe. From the beginning the universe was incredibly tiny, hot and dense. In the beginning it was far too hot and dense for matter and energy to be separate at all. When the universe had expanded and cooled to a certain degree, matter and energy could "decouple". That is when hydrogen first came into existence, the simplest form of ordinary matter. Helium, too, the second element, was created in the Big Bang, and also some lithium. This matter existed as a hot, dense, but expanding "soup".
The universe was certainly at least 400,000 years old, and possibly many million years old, before the first stars appeared. The first stars probably emerged out of nebulas, but the first nebulas were certainly very different from the typical nebulas of today. For one thing, the original nebulas contained no dust at all. Dust is made of elements more complex than hydrogen and helium (and lithium), but all such elements are created inside stars as rest products of their fusion of hydrogen and helium. Before the stars existed, there was no dust.
Where does the angular momentum come from? I'm not the correct person to answer that at all, but you must remember that the universe has always been teeming with energy, motion and outward expansion. Remember that the universe was always a place were outward expansion and inward-pressing gravity fought with one another. The distribution of matter and energy was always very slightly "uneven", encouraging the flow of matter away from more rarefied locations into more densely packed parts. Why should there not be angular momentum in such a dynamic place? What force could actually stop the angular momentum in the universe?
In any case, stars appears when a nebula shrinks and condenses under the influence of its own gravity. In other words, the nebula becomes smaller (or at least the part of the nebula that gives rise to the star becomes smaller). If the nebula is not perfectly "still", but contains some inherent rotation at all, this rotation will become much more pronounced as the nebula shrinks. Compared this with what figure skaters do to rotate, and to rotate faster. When they spin, they have to create their own initial rotation, but then they speed their rotation up by making themselves "smaller", by holding their arms and legs close to their "axis of rotation":
[youtube]https://www.youtube.com/watch?v=l2VuosSk9zU[/youtube]
[quote]IF there is a dust prominence in the absence of interacting with a different galaxy, then it could mean that the dust is primarily iron (an abundant element) [/quote]
Iron is not particularly abundant at all, compared with many other elements in the universe like oxygen, carbon and silicon. You can be sure that the dust in the universe is mostly made up of other elements than iron.
Ann