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nIt means slow and gradual change. It usually refers to natural processes – not human-directed changes.
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nEvolution is most often discussed in regards to living things, because animals, plants, fungi, bacteria, and all other life forms on Earth are related – they all developed from earlier life forms, and if you far enough back, you discover that all Earth life evolved from teeny, relatively simple early living things.
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nBut it’s not just living things that evolve (slowly change). We also talk about the evolution of stars and galaxies (among other things).
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nToday’s birthday, born on this date in 1944, is known for her research on the evolution of galaxies. Sandra Faber is the University Professor of Astronomy and Astrophysics at UC Santa Cruz (in California), and she works at the Lick Observatory. She also helped develop the Keck telescopes in Hawaii.
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nSo…how do galaxies evolve?
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nSome galaxies get redder and redder, and fainter and fainter, as they get older and older, because the hottest, bluest stars evolve into red giants relatively quickly, and some relatively low-temperature red stars just fizzle out altogether and become brown dwarf stars. In this sort of evolution, the galaxy doesn’t change its shape, just its brightness and overall color.
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nOther galaxies get so close to one another that they interact and even (at times) merge. These interactions often cause new stars to form, so the overall galaxy gets bluer as hot young stars flare into existence. Sometimes mergers cause the shapes of the galaxies to change:
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nMergers of a spiral galaxy and dwarf galaxies may not disrupt the spiral shape – although of course the dwarf galaxies’ shapes are destroyed as they are gobbled up by the larger galaxy – but sometimes two spiral galaxies merge and become large, rather shapeless elliptical galaxies.
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nBack to Faber…
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nDr. Sandra Faber worked with other astronomers to learn more about galaxies and dark matter. She and a scientific partner discovered that the brightness of a galaxy is linked to the speed of the stars’ movements within the galaxy. Also, she found evidence that dark matter is likely slow moving particles that we have not yet discovered!
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nFaber received the National Medal of Science in 2013.
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nAlso on this date:
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nHoly Innocents’ Day in Mexico
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nAnniversary of the consecration of Westminster Abbey
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nAnniversary of chewing gum patent
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nIowa’s Statehood Celebration
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nnBirthday of President Woodrow Wilson
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nPlan ahead:
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Check out my Pinterest pages on:
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nHistorical anniversaries in December
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nJanuary birthdays
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