A Constellation is a region of the sky

A Constellation is… … a region of the sky, within official borders set in 1928 by the IAU. • Often recognizable by a pattern or grouping of stars. • Some patterns, like the Winter Triangle, span several constellations. © 2004 Pearson Education Inc. , publishing as Addison-Wesley

Asterisms l These are familiar shapes but not official constellations The summer triangle © 2004 Pearson Education Inc. , publishing as Addison-Wesley

More asterisms l The big dipper l Actually part of Ursa Major Image from: The Big Bear http: //www. physics. csbsju. edu/astro/constellations/ursa_major_l. html Or Big Raccoon? l l © 2004 Pearson Education Inc. , publishing as Addison-Wesley

Cygnus “a real constellation” © 2004 Pearson Education Inc. , publishing as Addison-Wesley

Lyra—another real constellation © 2004 Pearson Education Inc. , publishing as Addison-Wesley

Prominent Constellations -Sagittarius. © 2004 Pearson Education Inc. , publishing as Addison-Wesley

Scorpius © 2004 Pearson Education Inc. , publishing as Addison-Wesley

Orion l Betelguese l © 2004 Pearson Education Inc. , publishing as Addison-Wesley Orion Nebula

l Betelguese Not what it appears! Radius of Earths orbit about sun! © 2004 Pearson Education Inc. , publishing as Addison-Wesley

Orion Nebula © 2004 Pearson Education Inc. , publishing as Addison-Wesley Planetary systems forming within!

The view from here: Celestial Astrononomy Even though we know the Earth goes around the sun and not vice versa. . l Don’t we? l 1/5 adults in USA don’t! l Its useful to think about a sphere of celestial objects surrounding the Earth l The signs of the zodiac are the constelltions that are along the sun’s path —the ecliptic! l © 2004 Pearson Education Inc. , publishing as Addison-Wesley

The Celestial Sphere The sky above looks like a dome…a hemisphere. . l If we imagine the sky around the entire Earth, we have the celestial sphere. l This a 2 -dimensional representation of the sky ¥ Because it represents our view from Earth, we place the Earth in the center of this sphere. l © 2004 Pearson Education Inc. , publishing as Addison-Wesley

The Celestial Sphere North & South celestial poles the points in the sky directly above the Earth’s North and South poles celestial equator the extension of the Earth’s equator onto the celestial sphere ecliptic the annual path of the Sun through the celestial sphere, which is a projection of ecliptic plane © 2004 Pearson Education Inc. , publishing as Addison-Wesley

Finding the North Celestial Pole l Image from younge Observers Merak Dubhe Polaris © 2004 Pearson Education Inc. , publishing as Addison-Wesley

The Daily Motion daily circles --- CCW looking north, CW looking south © 2004 Pearson Education Inc. , publishing as Addison-Wesley

Star Trails in two hemispheres Southen Hemisphere Northen Hemisphere Which direction How long was the shutter open? © 2004 Pearson Education Inc. , publishing as Addison-Wesley do the stars move? Images from NASA/APOD