Overview Of Astronomy1
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Transcript of Overview Of Astronomy1
![Page 1: Overview Of Astronomy1](https://reader035.fdocuments.us/reader035/viewer/2022062513/55509e17b4c9058b208b4aab/html5/thumbnails/1.jpg)
Objectives:Objectives:
Describe the importance/value/benefit of Astronomy
Clearly describe our place in the cosmos and the universe at various scales
Overview of AstronomyOverview of Astronomy
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1/ What is the value/benefit of Astronomy?1/ What is the value/benefit of Astronomy?
Scientific and TechnologicalPhysics Laws; Satellites and Rockets;
Materials, etc.
PracticalGeography; Time-keeping; Religious
Injunctions; etc.
PhilosophicalOur place in the Cosmos; Creation; etc.
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Astronomical distances and sizes are so Astronomical distances and sizes are so large that astronomers use special unitslarge that astronomers use special units
Astronomical Unit (AU) – applicable inside the solar system
= average distance between Sun and Earth
= 150,000,000 km = 1.5 x 108 km
Light-Year (ly) – applicable between stars and galaxies
= distance light travels in one year
= ~ 9 x 1012 km
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The Solar System:The Solar System: The Sun: Our nearby star, at 1 AU = 150
million km away, or just 8 minutes of light travel time, and 100 times the diameter of the Earth; the energy we use on Earth initially comes from nuclear reactions in its core.
• Four Small, Rocky Terrestrial Planets+ asteroids (belt)
• Four Large, Gaseous Jovian Planets + “Dwarf Planets”: Pluto + Eris + Sedna…
Scale of the Universe and Scale of the Universe and Overview of ContentsOverview of Contents
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Outskirts of the Solar System
• Comets: Icy objects, in elliptical orbits. They can enter the inner Solar System and sometimes hit planets.
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Stars and Other Things in the GalaxyStars and Other Things in the GalaxyStars: From dwarfs to supergiants; the nearest one is
Alpha Centauri, a triple star system at 4.34 ly = 40,000 billion km (~ 300,000 AU), visible from the Southern
Hemisphere (only).
Between stars: Nebulae (clouds) and interstellar matter.
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Do those stars have planets? So far, we've found more than 400, and we've just begun (since 1997).
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Our “country”: The Milky Way
100,000 light years across, contains ~ 200 billion stars.
A useful analogy: Universe and Earth Geography• City and Neighborhood• Country• Continents…
Our “city”: The Solar System
Downtown (Sun) and Neighborhoods (Planets).
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Other Galaxies and Other Galaxies and the Rest of the Universethe Rest of the Universe
Other Galaxies: Spiral, elliptical, or irregular. How many are there? About 100 billion in the visible
universe, arranged in clusters and superclusters and moving away from us.
Our neighbor countries: The Local Group (of ~ 20 galaxies), ~ 3 million light-years across.
The Andromeda Galaxy is our nearest neighbor, about 2 million light-years away.
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The Universe is also expanding, everywhere, in all directions, since the Big Bang, and the most recent observations seem to imply that it will probably expand forever…
• The Universe: A size of ~ 1023 km!
A “size” of the Universe can be determined from its age and from knowing how fast light travels from one region to another (speed of light = 300000 km/s). The most recent age of Universe (determined in January 2003) is 13.7 billion years...
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Graphical Summary of the scale levels of the Universe, from the Earth, to the Solar System, to the Galaxy, to the Universe as a whole!
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