ASTRONOMY 161 Introduction to Solar System Astronomy

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ASTRONOMY 161Introduction to Solar System
Astronomy
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• Autumn Quarter 2009
• MWF 100 p.m. SH0100
• Professor Krzysztof (Kris) Stanek
• Office 4003 McPherson Lab
• Office hours MWF 230 p.m. 400 p.m.
• Email stanek.32_at_osu.edu

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• TA Karen Mogren
• Office 4029 McPherson Lab
• Office hours Tue 430-600 p.m., Thu 130-300
  p.m.
• Email mogren.2_at_osu.edu
• Text 21st Century Astronomy (2nd Edition) by
  Hester et al.
• Midterms Oct 9, Oct 30, Nov 20
• Final Mon. Dec 7, 1130 a.m.
• Grade 60 Midterms, 40 Final

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Astronomy 161 The Web Page

• www.astronomy.ohio-state.edu/kstanek/A161/
• The Web page for course contains the syllabus,
• lecture notes (as the course progresses), and
• other information, including links to various WWW
• sites related to astronomy.

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What is astronomy?

• astron star
• nomos law
• Astronomy is the science of stars and clusters
  of stars, galaxies and clusters of galaxies,
  planets, dwarf planets and their satellites,
  asteroids and comets, interstellar gas and dust
  (and anything else in the Universe).

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Star The Sun

• 150 million kilometers away
• 1.4 million kilometers across

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Cluster of Stars The Pleiades

• 430 light-years away
• 15 light-years across

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Galaxy The Andromeda Galaxy

• 2,200,200 light-years away
• 80,000 light-years across

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Cluster of Galaxies The Coma

• 320 million light-years away
• 10 million light-years across

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Gas Dust The Lagoon Nebula

• 5000 light-years away
• 50 light-years across

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Solar System
Eris
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Planet The Earth

• 13,000 kilometers across

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Dwarf Planet Pluto

• 2,300 kilometers across

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Satellite The Moon

• 380,000 kilometers away
• 3,500 kilometers across

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Asteroid Eros

• 33 kilometers long

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Comet Comet Hale-Bopp

• nucleus 10 kilometers across
• tail 100 million kilometers
  long

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What is Science?

• The SYSTEMATIC study of the Universe
• Gather facts
• Modify hypothesis Guess an explanation
• (Guesshypothesis)
• Test hypothesis

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MAIN QUESTIONS

• 1) What have astronomers learned?
• 2) HOW HAVE THEY LEARNED IT?

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Practical matters

• Astronomers use powers-of-ten notation to write
  LARGE and SMALL numbers.

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Astronomers measure length in meters,
astronomical units, light-years
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Astronomers measure time in seconds years

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Astronomers measure mass in kilograms

• Note mass and weight are NOT the same thing.
• MASS amount of matter.
• WEIGHT force with which gravity tugs on matter.
• Mass 1 kilogram
• Weight 35 ounces on Earth
• 6 ounces on Moon
• 13 ounces on Mars.

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• Very important concept
• DENSITY
• density mass/volume

DENSITY - gm/cm3 weight relative to water Air
0.001Wood - Balsa 0.1, Pine 0.5, Oak
0.6-0.9Gasoline 0.7 Ice 0.92Water
1.00Sugar 1.59Major Minerals
2.6-3.0Aluminum 2.7Iron 7.9Copper 9Lead
11.4Mercury 13.6Uranium 19Gold
19.3Platinum 21.4Iridium 22.4 (densest
material on Earth)