Mapping the Celestial sphere

Locating stars and deep space objects

Important Terms Celestial: Anything

referring to the “heavens”, or space above us

Celestial Sphere: The night sky that looks like it is a painted dome above us

Terms Cont’d Celestial Poles: Points on

the celestial sphere directly above the North and South Pole

Celestial North Pole: Has the North Star, Polaris

Celestial South Pole: Has no Southern Star

Terms Cont’d

Celestial Equator: The line on the celestial sphere that is directly over the equator

Terms Cont’d Zenith: Imaginary

point on celestial sphere directly overhead (90°)

Nadir: Exact opposite of the Zenith You cannot

see it

Terms Cont’d Horizons: Place

where the earth and sky appear to meet Halfway between

zenith and nadir

2 terms we use to describe objects’ locations

1. Declination = Celestial Latitude Measured in Degrees

2. Right Ascension= Celestial Longitude Measured in time.

Location of a star Betelgeuse

RA: 5h 55m 10.2s east of vernal equinox

Dec: 7°24’26” north of celestial equator

HOW WE LOCATE STARS IN THE CELESTIAL SPHERE

3Ways: 1. Finding it relative to other markers (Celestial

equator/poles, zenith, horizon, etc…) 2. Finding it within a constellation (often in

terms of brightness) 3. Using Right Ascension and Declination

Constellations Constellations: A group of stars that appear to

form a pattern in the sky.

Starlight, Star Bright…. The 1st method of categorizing the brightness of stars: Magnitude

6 = barely seen with the unaided human eye. 5 = 2.5 times as bright as a 64 = 2.5 times as bright as a 53 = 2.5 times as bright as a 42 = 2.5 times as bright as a 31 = the brightest (then)

Apparent Magnitude Rating system has added numbers lower than 1 for VERY bright stars and numbers higher than 6 for objects only able to be seen by a telescope.

System of rating is dependent on how the star appears from Earth.

Bayer Designation System Naming stars within constellations

A Greek letter is given to each star in the constellation according to it brightness.

The brightest star is the “alpha star”, the next brightest is the “beta star”, and so forth.

Bayer Designation System & Apparent Magnitude

Star Bayer Designation Apparent Magnitude

Sirius Alpha Canis Majoris -1.46 Vega Alpha Lyrae 0.03 Rigel Beta Orionis 0.12 Betelgeuse Alpha Orionis 0.7 Antares Alpha Scorpii 0.96 Polaris Alpha Ursae Minoris 2.02

Constellation VisibilitySummer Winter

Earth Moves around the sun = different position

Constellations Changing Shape

Stars move at very fast speeds, from 3 to 122 km/s

Stars are so very far apart and so very far from us, they do not appear to change at all.

The constellations do change over very large time periods, however.