This document provides an overview of astronomy and the solar system. It defines astronomy as the study of anything seen in the sky and beyond. It describes how astronomy uses observation and integration with other sciences due to the difficulty of conducting experiments. It then reviews the key components of the solar system, including the sun, terrestrial planets like Earth and Mars, gas giants like Jupiter and Saturn, and smaller objects. Finally, it discusses units for measuring astronomical distances and provides examples to demonstrate the immense sizes within the universe.

1. Astronomy

2. What is Astronomy?
 Astronomy is the study of anything we
see in the sky, and beyond
 Overlaps with physics, chemistry,
geology, and other sciences

3. The Scientific Method in
Astronomy
 Astronomy is one of the most difficult
sciences to do, because we can’t do very
many things in a lab
 We have to combine our observations with
our understanding of other sciences to make
good predictions
 Sometimes, our “lab” is a computer

4. Astrology
 Astrology - the belief that the stars and planets
affect your life
 Despite the –ology, it’s not a science!
 Gravity of other planets is not as strong as the
gravity of your obstetrician!
 Does not use the scientific method
 It’s complete poppycock

5. Observing the Universe
 Astronomy began with people observing
their surroundings
 What did the sky look like when herds
moved? When a season changed?
 When was it good to plant?
 Planets, sun, moon, and stars all seemed
to move independently

6. What have you Observed?
 An incomplete list:
 Moon
 Planets (Venus, Mercury, Mars, Jupiter, Saturn)
 Stars
 Meteors (shooting stars)
 Aurora
 Comets

7. What’s Out There, Anyway?
 Atmospheric phenomena
 Solar System
 Sun and planets; comets, asteroids, etc.
 Milky Way
 Our galaxy
 Extra-galactic
 Other galaxies
 Some objects like our galaxy
 Some completely different phenomena
 Things between galaxies

8. Atmospheric phenomena
 Auroras
 Meteor Showers

9. Solar System Objects and
Phenomena
 The Sun
 Eclipses
 Planets & Moons
 Asteroids
 Comets

10. Galactic Objects and
Phenomena
 Stars & star clusters
 Nebulas
 Supernova Remnants
 Dead Stars
 White Dwarfs
 Neutron Stars
 Black Holes
 Dark Matter

11. Extra-Galactic Objects and
Phenomena
 Other Galaxies
 Galaxy Clusters
 Super Clusters
 Dark Matter
 Dark Energy

13. Neighborhood Tour - Our Solar
System

14. The Solar System
• Condensed from Solar nebula about
five billion years ago
• Contains Sun, planets, asteroids,
comets, and dust

15. Terrestrial verses Jovian
Planets
 Terrestrial Planets Include:
 Mercury, Venus, Earth and Mars
 Jovian Planets Include:
 Jupiter, Saturn, Uranus & Neptune
 Also Interesting: Jovian moons
 Not sure what to do with them:
 Pluto/Charon
 Xena

16. Sol (our sun)
SOHO/Extreme Ultraviolet Imaging Telescope (EIT) consortium

17. The Solar System

18. Terrestrial Planets
Small and rocky, composed of Oxygen, Silicon, Aluminum,
Calcium, Iron, and Magnesium
1. Mercury
2. Venus
3. Earth
4. Mars

19. Mercury
 Mercury has
a lunar-like
geology.
Caloris Basin

20. Mercury
 Mercury is
almost tidally
locked, like
the Moon.

21. Venus
 Venus’
surface
has only
been
revealed
in the
past 10
years.

22. Venus
 The surface of Venus
is like the surface of
hell.

23. Venus
 Venus has a
young, basaltic
surface.

24. You Probably Know This One

27. Mars
 Mars has
the most
Earth-like
geology.

28. Mars
 Mars has a thin
atmosphere of
CO2.

29. Mars
 Familiar geologic
features/processes

30. Mars
 Familiar geologic
features/processes

31. Mars
 Mars’ geologic
history was
once warmer
and wetter than
now.

32. The Real Face of Mars

33. Mars from Pathfinder

34. Sojourner

35. Olympus Mons

36. Mars’ Polar Caps

37. Martian Meteorite

38. Martian Fossils ?

39. Deimos and Phobos

40. Jovian Planets
Large, gaseous, composed mainly of hydrogen and helium
1. Jupiter
2. Saturn
3. Uranus
4. Neptune

41. Jupiter
 Jupiter’s geologic
features are all
atmospheric.

44. Moons of Jupiter
 Io is the most active
body in the Solar
System.

45. Moons of Jupiter
 “All these worlds are
yours except
Europa…”

46. Moons of Jupiter
 Ganymede and
Callisto are two of
the larger bodies in
the Solar System.

47. Saturn
 Saturn is the
furthest out of
the historical
planets.

48. Saturn’s moons

49. First ever color
picture of
Titan’s surface
Water and
hydrocarbon ice
January 14, 2005
ESA/NASA/Univ. of Arizona

50. Uranus & moons
 Uranus orbits the
Sun on its side.

51. Neptune & moons

53. Pluto & Charon

55. Units for Measuring
Astronomical Distances
 Astronomical Units (AU)
 Defined as the distance from the Sun to the Earth
 About 1.496x1011 m (about 150 million km)
 Light-years
 Defined as the distance light travels in one year
 About 9.46x1015 m
 Parsecs
 Derived from the way stars appear to shift slightly
in the sky as the Earth orbits the Sun
 Equal to about 3.26 light-years

56. How Big Is It?
 Our Earth
 12,756 km across
 Earth to the Moon
 384,400 km
 Earth to the Sun
 150 million km
 = 1 AU
 = 500 light-seconds

57. How Big Is It?, cont.
 Sun to Jupiter
 5.2 AU
 Sun to Pluto
 Between 30 and 49 AU
 Oort Cloud
 Theoretical, unobserved edge of the Solar
System
 Out to about 50,000 AU (= 0.79 light-year)

58. How Big Is It?, cont.
 Nearest star
 4.2 light-years away
 Our Galaxy
 100,000 light-years across
 To the nearest large galaxy
 2.5 million light-years away

59. How Big Is It?, cont.
 Virgo Cluster of Galaxies
 Nearest cluster of galaxies to us
 About 50 million light-years (debated)
 Quasar 3C 273
 One of the nearest and brightest quasars
 About 2 billion light-years
 Edge of the observable Universe
 About 13.7 billion light-years away

60. Light travel times…
 Across earth: 0.04 seconds
 From moon: 1.3 seconds
 From sun: 8 minutes
 From Neptune: 4 hours

61. Light travel times…
 From nearest star: 4 years
 From galactic center: 25,000 years
 From Andromeda galaxy: 2 million years
 From hot early universe: 14 billion years