ISP205 Section 2
Lecture#1: Tuesday, January 9

Handouts:

Topics:

  1. Course Introduction

  2. A tour through the Universe

  3. The sky - Introduction

  4. Scientific notation

  1. Course Introduction:

    1. Syllabus

    2. Website: http://www.nscl.msu.edu/~schatz/isp205_2.html

    3. Schedule

    4. Homework with CAPA

    5. Textbook: Voyages Through the Universe, by Fraknoi, Morrison, Wolff
      Textbook Website: http://www.harcourtcollege.com/astro/fraknoi/

    6. Recommended: Redshift College Edition from Maris Multimedia

  2. A tour through the Universe

    1. Objects in the Universe: Stars, Planets, Moons, Nebulae, Galaxies, Galaxy Cluster
      Galaxies contain lots of stars: ~200 Billion in ours

    2. Stars generate their own light; Planets and Moons reflect starlight

    3. The solar system: 9 Planets (including earth) orbiting around the Sun (a star)
      and around themselves.
      (Redshift Demo)

    4. Sizes of objects in solar system vary a lot ! (see figure P.7 in book)
      Diameter: Earth: 13000km, Pluto: roughly half, Jupiter X11, Sun X110

    5. Rotation roughly within one plane - except for Pluto
      (Redshift Demo)

  3. A short break: Distances in Astronomy
    The Universe is so big that one needs several length scales to describe it.

    1. Average distance from Earth to Sun: 150,000,000 km (=1 astronomical unit AU)

    2. Size of the solar system (planets only): ~80AU (Pluto is ~40AU away from sun)

    3. Distance to the nearest star (not counting the sun): Proxima Centauri: 269,000 AU

    4. 1 light year (1ly) = distance light travels in 1 year
      Speed of light: 300,000 km/s - 
      so 1ly = 9,500,000,000,000 (9.5e12 km)

      light travels

      • around the world in 0.1s

      • to the moon in 1.3s

      • to the sun in 8 min

      • to Proxima Centauri in 4.3 years.

      Proxima Centauri is therefore 4.3 ly away.

       

  4. Continue Tour of the Universe:

    1. Other things than stars in our Galaxy. Example:
      See image of Eagle nebula taken from Hubble Space Telescope
      A cloud of hydrogen gas and dust that forms into stars.

    2. Size of our galaxy: 100,000 ly

    3. Distance to next galaxy (Andromeda) ~2,200,000 ly

    4. Size of the Universe: 14,000,000,000 ly (14 billion light years)
      more about this later in the term

    5. There are some 100 billion galaxies in the universe
      See Hubble Deep Field image - example how new observatories changed view of cosmos

    6. Because of finite speed of light looking at far away objects is like looking back in time
      (if  Proxima Centauri explodes we will see this 4.3 y. In other words: we see Proxima Centauri as it looked 4.3 years ago)

  5. Observing the sky - Introduction

    1. Most things we know about the universe we know from observing the sky. Only the moon
      and most of the planets (except Pluto) have been "visited" by spacecraft.

    2. We can see around 6000 stars by the unaided eye

    3. Night sky tonight: Constellations. In early days mystic component - today we use the
      names of constellations to mark zones on the sky for orientation.
      (Redshift Demo)

    4. Example Orion and Betelgeuze. (Redshift Demo)
      We will hear more about Betelgeuze - size 3AU !

    5. Stars move during the night because of earths rotation (but the relative distances
      constellations remain the same) (Redshift Demo)

    6. The earth takes 23h and 56min to rotate once. Then stars at the same position
      (Redshift Demo). (It will be explained later why it is not exactly 24 hours)
      But: some objects still move because they are so close that their motion is noticable:
      Greeks called them Planets (=wanderers). Today we
      exclude Sun and Moons and call the heavy bodies orbiting the sun "planets"
      Which planet can we see tonight ? Why ?

  6. Scientific Notation

    1. A common notation for numbers that avoids huge numbers of digits for very
      small or very large numbers is called scientific notation

    2. Examples:
      100 = 1x102
      1000 = 1x103
      0.01 = 1/100 = 1x10-2
       250,000,000,000 m = 2.5x1011 m
      1ly = 9,500,000,000,000,000 m = 9.5x1015 m

    3. Computers use E instead of x10.
      Example:132 = 1.32x102  is written as 1.32E+2

  7. Significant figures

    1. Many numbers are only known to a certain precision.

    2. Example: If I measure the temperature with a thermometer, but have only a quick look
      I can say that it is 70F. It could be anything between 65 and 74F so 70 has only
      one significant figure.If I look more careful I might find 72F, which has 2 significant
      figures and is more precise (between 71.5 and 72.4 - I cant tell for example because
      of the scale on the thermometer). To do a better measurement and to get to know
      more (significant) figures I need a better Thermometer (a digital thermometer might yield
      71.9 F - 3 significant figures).

    3. If the temperature would be exactly 70 (between 79.5 and 70.4) one writes 70.

    4. Rules: trailing zeroes with decimal point count as significant figures
                trailing zeroes without decimal point do not count as significant figures
                in scientific notation, all figures before the x10 are significant

    5. Examples
      100 - 1sf
      100. - 3sf
      100.000 - 6sf
      234 - 3sf
      0.002 - 1sf
      1.20x1022 - 3sf (the scientific notation part does not count)