CHAPTER 22 and 26 ASTRONOMY Chapters 22 The Milky way 1 How do we know that there is gas and dust in interstellar space The dust in space is what prevents us from seeing more clearly into our galactic plane When you look at the night sky there appears to be areas that are void of stars this is because gas and dust are dense enough to hide the light of some stars To put it simply if there WASN T gas and dust in interstellar space we d be able to clearly see everything in space 2 What is the shape form structure and various parts of the Milky Way The milky way is comprised of about 300 billion stars It is disc shaped with a central elliptic bulge which is like 12 000 lightyears in diameter It s surrounded by a flat disk with 6 spiral arms made up of stars which runs through the elliptic bulge The diameter of the milky way is about 100 000 lightyears 3 Where is our sun located in the Milky Way Our sun is situated in one of the smaller arms of the disk surrounding the milky way It is about 27 000 light years from the center of the galaxy 4 Why do astronomers think that much of the Milky Way consists of dark matter Scientists believe that 90 of our galaxy s mass consists of dark matter meaning that all of the luminous matter what we can see with the naked eye telescopes makes up less than 10 of the mass of the Milky Way The heavier the galaxy the faster they should be orbiting So if the galaxy was made up only of the matter that we can see then the rotation rate would be significantly less than what we observe So the rest of that mass must be made up of mass we can t see or dark matter 5 Why does the galaxy have spiral arms the arms of galaxies are density waves passing through the galaxy which have stars clumped within them Stars accelerate towards density waves the same way a crowd of people would swarm towards a big scene happening on the sidewalk 6 Is there a massive black hole at the center of the galaxy Most large galaxies have a supermassive black hole at the center The center of our galaxy is called Sagittarius A and it s a massive source of radio waves which scientists believe to be a black hole 7 What is an HII region and how does it evolve HII region is a term for singly ionized hydrogen The gas around a star is neutral and then ionizes one hydrogen atom this doesn t make sense to me but that s what google said 8 What is the origin of the 21 cm line and how do we utilize it in astronomy This line is created by a change in the energy state of hydrogen atoms Using the line in radio astronomy u can calculate the speed of an arm in a galaxy the rotation curve of our galaxy use the plot of the rotation curve the velocity to determine the distance to a specific point in a galaxy 9 What are the various types of nebulae in the Milky Way remnants of exploded stars clouds of gas and dust nurseries where new stars are forming out of clouds of gas and dust orion nebula Chapters 26 10 What does Hubble s law tell us about the beginning of the universe The further you are the faster you are moving velocity increases as distance increases The universe will keep expanding 11 How can we tell how old the universe is Knowing the current distances and speeds to galaxies along with the rate that the universe is accelerating we can calculate how long it took to get to their current location and trace it back to about 14 billion years 12 Can space itself be curved Space itself is most likely curved 13 What does that mean Light moves through space s curve According to einstein s theory of relativity massive objects warp the space time around them The effect the warp has is gravity 14 What important events happened early in the history of the universe After the big bang spacetime rapidly expanded over a short period of time due to hubble s law 15 What is the recombination period The epoch in which charged electrons and protons first became bound to form electrically neutral hydrogen atoms I think this is the point where the universe became transparent and started expanding rapidly but idk 16 What is the so called cosmic microwave background radiation CMBR and how it was discovered CMBR is supposedly left over heat faint light from the big bang that exists in the universe The big bang theory implies it 17 What is the meaning of anisotropies in the angular distribution of the CMBR Anisotropies are directionally dependent The CMBR temperature is dependent amongst angles in the universe and whatnot 18 What will the future of the universe be like and how the various scenarios depend on the curvature of spacetime The universe may eventually cease to exist the same way it came to be with a big bang But that would be so far ahead from now that the universe might as well exist infinitely Until then the universe should continue to expand
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