Chapter 1 Charting the Heavens: The Foundations of Astronomy

Size of Our Universe

Sun, Earth, and Moon

Figure 1-3 Galaxy

Figure 1-4 Galaxy Cluster This photograph shows a typical cluster of galaxies, roughly a million light-years from Earth. Each galaxy contains hundreds of billions of stars, probably planets, and, possibly, living creatures.

Figure 1-9 Orion in 3-D

Two groups of circumpolar constellations… one we never see.one we always see. North circumpolar constellations lie between 49º N and 90ºN South circumpolar constellations lie between 41ºS and 90ºS

Figure 1-11 Celestial Sphere Vocab: Celestial Equator (CE): Projection of Earth’s equator onto the celestial sphere Celestial Meridian (CM): A circle running through the celestial poles. Right Ascension (RA): Measures longitude on the celestial sphere Declination (DEC): Measures latitude on the celestial sphere.

Figure 1-15 The Zodiac Zodiacal constellations lie along the ecliptic. The ecliptic is a region of space that the sun appears to move over one year when viewed from Earth. The stars we can’t see when the sun is up are “eclipsed” by the sun.

Constellations Near Orion The 88 constellations span the entire sky. A star is “in” a constellation the same way a city or town is in a state.

Figure 1-8 Constellation Orion The stars are connected to show the pattern visualized by the Greeks: the outline of a hunter. You can easily find this constellation in the winter sky by identifying the line of three bright stars in the hunter’s “belt”.

The motion of the earth in its orbit causes our view of the nighttime background stars to be constantly changing. We associate different constellations with the seasons: Gemini and Leo with spring Scorpio and Hercules with summer Cygnus and Lyra with fall Orion and Taurus with winter

Star Naming Johann Bayer designated the brighter stars in each constellation by a Greek letter. Stars lettered in order of brightness α usually being the brightest and Ω usually the faintest John Flamsteed numbered the stars visible to the naked eye from west to east across the constellation. His systematic method was to name a star by using a letter or number followed by the Latin name of the constellation.

When using star charts east and west directions are opposite in the sky. To the right is west of the sun To the left is east of the sun

Star Charts Find the meridian in the sky using the date and time. Draw a verticle line. Find the field of view. Draw a two lines for your field of view. These are the stars that you can see on this date. Note: Along the CE you will be able to see exactly 12 h of RA from horizon to horizon. 6h to the east of your meridian and 6h to the west.

Figure 1-18 Precession

Figure 1-19 Variations in the Solar Day

Figure 1-29 Triangulation

Figure 1-30 Geometric Scaling

Figure 1-31 Parallax

Figure 1-32 Parallax Geometry

Figure 1-33 Measuring Earth’s Radius

More Precisely 1-1 Angular Measure

More Precisely 1-2 Celestial Coordinates

More Precisely 1-3a Measuring Distances with Geometry

More Precisely 1-3b Measuring Distances with Geometry