Units of scale

Metric System Review Basic Units: Meter (m)- length Kilogram (kg)- mass Second (s)- time

Conversions you should know: 1 km = 1000 m 1 AU= 149,600,000 km 1 Light year = 63,000 AU 1 m = 100 cm 1 cm = 10 mm 1 km=.625 mi 1 mi = 5,280 ft 1 ft = 12 in 1 in = 2.54 cm

Common misconception: A light year is a measure of time A light year is actually a measure of distance A light year (ly)= the distance light travels in 1 year 63,000 AU is one light year km (1 trillion km) Ex. The nearest star to the sun: Proxima Centauri- 4.2 light years away

Scientific Notation

one thousand1000= 10 3 one million1,000,000= 10 6 one billion1,000,000,000= 10 9 one trillion1,000,000,000,000= one thousandth0.001= 10 –3 one millionth = 10 –6 To express large numbers astronomers use scientific notation ●Also known as the power of 10 ●Example: 10 6 = 10x10x10x10x10x10 = 1,000,000

Putting numbers into scientific notation: step by step 1: Find your numbers 2: Move your decimal point until there is only one number to the left of the decimal 3: Count the number of times you move it 4: Drop the zeros and add x10 n (n= the number of times you moved it) 5: Check your work

Practice: 12,000 9,000,000,000 17,000,000 2, x x x x x x10 -3

Summer Triangle

Cygnus the Swan or Northern Cross

Aquila the Eagle

Lyra

Ursa Major

Ursa Minor

Bootes

Scorpius

The Celestial Sphere — A model of the sky Nadir: Point on the celestial sphere directly underneath (never visible!) Zenith: Point on the celestial sphere directly overhead Celestial equator: projection of Earth’s equator onto the c.s. North celestial pole: projection of Earth’s north pole onto the c.s.

[ More general view of the celestial sphere ] The ecliptic is shown crossing the celestial equator at an angle of 23.5°. *The ecliptic (the annual motion of the sun) always makes 23.5° with the celestial equator, while the horizon makes an angle that depends on the person’s latitude.

The Ecliptic The Ecliptic: The path the sun appears to take around the Earth Angled at 23.5° This explains the seasons

Apparent Motion of the Celestial Sphere

Horizon System The horizon system is a convenient system to use to locate stars and other celestial objects from one’s local vantage point. Altitude (“height”) is angular distance from the horizon. Azimuth (“direction”) locates the place on the horizon just below the star.

0º Position in Degrees Longitude – connecting the poles Latitude – parallel to the equator, 0 – 90 N and 0 – 90 S 0º 90º N 90º S Columbia, MO latitude 38.56ºN, longitude: 92.2ºW

Longitude lines Latitude lines

Equatorial Coordinate System Like the longitude and latitude on the earth, we have Right Ascension and Declination in the Equatorial system The equatorial coordinate system rotates with stars and galaxies

Equatorial System Right Ascension (RA) or α = projection of Earth’s longitude onto the celestial sphere. Declination (Dec) or δ = projection of latitude onto the celestial sphere.

Lines of right ascension (α) (In hours and minutes ) Starts at vernal equinox Lines of declination (δ) (In degrees)