Telescopes and Horoscopes

1
Telescopes and Horoscopes

• Chapter 1

2
Our Place in Space

• Are we unique?
• Are we alone?
• How did we begin?
• The universe is the totality of all matter,
  energy, time and space.
• Astronomy is the study of this universe.
• How big is the universe? How do we measure such
  vast distances?

3
The Obvious View

• Watching our sky.. what can we observe?
• Stars 3000/6000 can be observed with naked eye
• Constellations (88) map our sky
• Not proximal only look to be close together
• Historical significance / Navigation (Polaris)
• Astrologers pseudoscientists?

4
(No Transcript)
5
Motion of the Sun and Stars

• 24-hour solar day how long it takes Earth to
  align back up with the Sun (set/rise/noon)
• Earth has 2 main motions
• Rotation about axis
• Revolution about Sun in an orbit
• These cause the sidereal day (according to the
  stars). It is 23 hours 56 minutes long.
• 0.986o additional angle to rotate through

6
Solar Day vs. Sidereal Day
7
Path of Sun (same time of day) throughout the
year
8
(No Transcript)
9
What causes the seasons?

10
Is it how far we are from the Sun?
11
Earth What causes the Seasons?
12
Seasonal Changes

• Ecliptic path the Sun follows on the celestial
  sphere over one year
• The ecliptic and the celestial equator are not
  the same because Earth is tilted 23.5 degrees
• Summer solstice June 21 (around or on)
• Winter solstice December 21
• Autumnal equinox September 21
• Vernal equinox March 21
• Tropical year 365.242 solar days

13
Summer Solstice

14
Winter Solstice

15
Sun Clocks
16
The Motion of the Moon

• Our Moon has a name... meet Luna!
• 8 Phases can you name them all?
• Sidereal month 27.3 days
• Synodic month 29.5 day (1 phase cycle)
• Causes eclipses both lunar and solar

17
The Eight Phases of the Moon
18
(No Transcript)
19
(No Transcript)
20
(No Transcript)
21
(No Transcript)
22
Whats wrong with this picture?
23
Sun/Moon Time of Day
24
(No Transcript)
25
Eclipses

• The Sun and Moon are in opposite directions
• There are two main types of eclipses
• Solar and lunar
• Eclipses can be partial or total

26
Freds Excellent Eclipse
27
Lunar Eclipses

• Earth is in the way and blocks the suns light
  from the moon.
• Most cases are a partial eclipse
• Lasts about 100 minutes total
• Can sometimes appear red

28
Solar Eclipses

• The Moon blocks out the Sun
• They have the same diameter as seen from Earth
• Can be total or partial

29
Solar Eclipses
30
Why doesnt it happen every month?
31
Effects of an Solar Eclipse

• Dark shadow on a section of Earth
• Umbra -- complete darkness
• Penumbra -- diffracted darkness

32
Summer/Winter Constellations

• Constellations change as Earth orbits the Sun
• Summer triangle Vega, Deneb and Altair
• Why am I a LeoI cant see it on my birthday?
• Zodiac Sun passes through 12 animal
  constellations throughout the year
• Time it takes for all 12 constellations to pass
  (from one point on Earth) is the sidereal year
  which is 365.256 days

33
(No Transcript)
34
(No Transcript)
35
Ecliptic and Zodiac
36
Long Term Changes

• The difference between the sidereal and tropical
  years is only 20 minutes!
• Why? The tropical year occurs 20 minutes sooner
  than the sidereal year because the Earth wobbles
  like a top as it spins about its axis.
• This additional movement is called precession.
• If you dont want summer to occur in the month we
  call February we have to use the tropical year
  to keep time/calendars.

37
Measurements in Space
38
Distances to the Stars

• Measuring distance in space could be accomplished
  by using miles and kilometers.
• Talk about huge numbers!!!
• The Sun is (take your pick)
• 93 million miles away
• 150 million kilometers away
• 1 Astronomical Unit (AU)
• 8 light-minutes away
• The Moon is the distance of 1 light-second from
  Earth.

39
Tools for Determining Distance
40
The Light-Year

• The distance that light travels in 1 year
• Light travels 300,000 km/sec
• Therefore the Moon is one light-second from Earth
• One light-year is almost 10 trillion kilometers!
• The l.y. is a rather small distance in the
  astronomical scale.
• 1 Parsec 3.26 light-years

Meet your neighbors
41
Parallax
2
3
1
5
6
8
4
7

• This is what enables you to hit a baseball with a
  bat
• Your two eyes and brain work together to
  interpret distances to things
• Deer doesnt have it neither do children under 9
• ? is the parallax angle, but what is THAT?
• This angle allows us to use a little geometry to
  determine distances to objects almost anywhere
• Index finger 3o
• Parallax (in space)

January
42
Cepheid Variable Stars

• Determining the brightness of a star is a science
  in itself
• Many methods
• But using a special kind of stars brightness
  variance helps us find distance
• Longer cycles are brighter
• Galaxies that contain Cepheid stars help us
  determine how far away the entire galaxy is.

43
Can you tell which is the Cepheid variable star?