ConstellationsConstellations

The rotation of the earth causes the apparent The rotation of the earth causes the apparent daily motion of stars.daily motion of stars.

Their daily paths, diurnal circles, are Their daily paths, diurnal circles, are centered on the celestial pole.centered on the celestial pole.

Stars rise in the Stars rise in the east, set in the east, set in the west.west.

Circumpolar stars Circumpolar stars never set.never set.

They circle the They circle the pole.pole.

All visible stars are in our galaxy.All visible stars are in our galaxy. Only about 1 in 4 stars is single.Only about 1 in 4 stars is single.

Most occur in groupsMost occur in groups of 2 (binary) or of 2 (binary) or moremore

Stars are “suns” but millions of times Stars are “suns” but millions of times further away.further away.

A few thousand stars are visible to the A few thousand stars are visible to the unaided eye.unaided eye.

What you see depends on the What you see depends on the brightness of the sky and the quality brightness of the sky and the quality of your vision of your vision

http://www.inhabitat.com/2006/08/19/light-pollution-the-continuing-spread/

Even far from city lights our eyes see Even far from city lights our eyes see only a fraction of the 100 billion stars only a fraction of the 100 billion stars in our galaxy.in our galaxy.

Star groups that form recognizable Star groups that form recognizable patterns are called constellations.patterns are called constellations.

Modern def refers to a region of the sky.

The 88 official constellations cover the celestial sphere.

Stars in a constellation appear close Stars in a constellation appear close together but have no relationship to each together but have no relationship to each other.other.

Asterisms are not Asterisms are not ConstellationsConstellations

Some commonly recognized patterns Some commonly recognized patterns of stars have names but are not of stars have names but are not constellationsconstellations

The Big Dipper is a prime example, being just The Big Dipper is a prime example, being just the rear end and tail of Ursa Major (the Great the rear end and tail of Ursa Major (the Great Bear)Bear)

Stars in a constellation are labeled Stars in a constellation are labeled according to brightness.according to brightness.

EX: Betelgeuse the brightest star in EX: Betelgeuse the brightest star in Orion, is labeled Alpha, Orion, is labeled Alpha,

Every star you see has dozens of Every star you see has dozens of namesnames The bright star The bright star VegaVega, is also, is also

Lyrae, HR 7001, 3 Lyrae, 2MASS Lyrae, HR 7001, 3 Lyrae, 2MASS J18365633+3847012, …J18365633+3847012, …

The brightest stars have classical The brightest stars have classical names, originating largely from the names, originating largely from the Arabic language.Arabic language.

Rigel (Rigel ( Ori) – The left leg of the giant Ori) – The left leg of the giant Sheliak (Sheliak ( Lyr) – The tortise Lyr) – The tortise Aldebaran (Aldebaran ( Tau) – The Follower (of the Tau) – The Follower (of the

Pleiades)Pleiades) Antares (Antares ( Sco) – The rival of Mars Sco) – The rival of Mars

As the earth orbits the sun different As the earth orbits the sun different constellations are visible at night.constellations are visible at night.

The stars are all moving relative to The stars are all moving relative to one anotherone another

These motions are perceptible to the eye only These motions are perceptible to the eye only over thousands of years.over thousands of years.

The constellations/asterisms known to us will The constellations/asterisms known to us will be obsolete 100,000 years from now.be obsolete 100,000 years from now.

Movie of the Changing Big Dipper