Stars, Constellations, and Quasars Everything you ever wanted to know (and maybe more) Created for the sixth grade students of American Preparatory Academy (2007)

Movement of Stars Earth orbits the Sun in about 365¼ days. During this orbit Earth rotates like a spinning top with its axis always pointing in the same direction. On or around June 21 the north pole is most tilted toward the Sun. This point in Earth’s orbit is the northern hemisphere’s summer solstice. On that day the Sun is directly above the Tropic of Cancer (23½° north latitude).

Movement of Stars Six months later, around December 21, the north pole is tilted away from the Sun to its greatest extent. This is the northern hemisphere’s winter solstice, and the Sun is directly above the Tropic of Capricorn (23½° south latitude)

Movement of Stars Equinoxes occur midway between the two solstices. The autumnal equinox occurs around September 22, and the vernal (Latin for “spring”) equinox occurs around March 21. On the equinoxes, there are 12 hours of daylight and 12 hours of darkness at every location on Earth. This is because the Earth’s axis points neither toward nor away from the Sun. The Sun is directly overhead at the equator during equinoxes.

Movement of Stars RSolstices and equinoxes mark the beginnings of the seasons. RBecause the northern hemisphere is tilted away from the Sun when the southern hemisphere is tilted toward it (and vice versa), these hemispheres have opposite seasons. It is winter in the northern hemisphere when it is summer in the southern hemisphere, and it is spring in the northern hemisphere when it is fall in the southern hemisphere. RSolstices and equinoxes mark the beginnings of the seasons. RBecause the northern hemisphere is tilted away from the Sun when the southern hemisphere is tilted toward it (and vice versa), these hemispheres have opposite seasons. It is winter in the northern hemisphere when it is summer in the southern hemisphere, and it is spring in the northern hemisphere when it is fall in the southern hemisphere.

Movement of Stars Sidereal time (star time) is determined by the movement of stars across the upper meridian

Constellations RConstellations are visual groupings of stars RExamples: Big Dipper, Orion, Little Bear RConstellations are visual groupings of stars RExamples: Big Dipper, Orion, Little Bear

Constellations Virtually every ancient civilization observed and studied the nighttime sky, and archaeological evidence such as Stonehenge points to these early studies of astronomy. Ancient cultures also developed elaborate mythologies around stars and constellations and gave them names, some of which are still in use today.

Constellations RThere are about 6,000 stars visible to the unaided human eye. Because we see only half the sky, there are only about 3,000 stars visible at any one time. To help locate stars, astronomers use a star map that divides the sky into 88 sectors named for a constellation within each sector.

Constellations

Some constellations and stars are very familiar. These include Ursa Major (the Great Bear), which includes the Big Dipper, and Ursa Minor (the Little Bear), which includes the Little Dipper. Polaris, which is also known as the North Star or the Pole Star, is an important star in the handle of Ursa Minor. Polaris takes its name from the fact that Earth’s rotational axis (north pole) points toward that star.

Constellations Ursa Major (the Great Bear) including the Big Dipper

Constellations Ursa Minor (the Little Bear) including the Little Dipper and Polaris (the North Star)

Constellations Other constellations that are easy to identify are Canis Major; Canis Minor; Orion in the winter and spring; and Cygnus, Lyra, and Aquila in summer and fall. These constellations include the brightest stars in the sky.

Constellations Canis Major

Constellations Canis Minor

Constellations Orion Orion’s Belt Orion’s Belt

Constellations Can you find Cygnus, Lyra, and Aquila?

And my personal favorite - Camelopardalis

Quasars Artist's impression of quasar GB1508 with Chandra x-ray image from NASA

Quasars RQUASi-stellAR radio source Rextremely bright and distant active galactic nucleus Rcompact halo of matter surrounding the central supermassive black hole of a young galaxy RQUASi-stellAR radio source Rextremely bright and distant active galactic nucleus Rcompact halo of matter surrounding the central supermassive black hole of a young galaxy

Quasar as photographed by Hubble

Do you have any questions?

Have a beautiful day! Then, look at the stars tonight!

Bibliography Rhttp://imagine.gsfc.nasa.gov/Images/news/gb1508_xray_illustration.jpghttp://imagine.gsfc.nasa.gov/Images/news/gb1508_xray_illustration.jpg RCore Knowledge Sequence, p. 153, ISBN: Rhttps:// Rhttp://images.google.com/imgres?imgurl= map- large.gif&imgrefurl= QWD8oD_1ZoPM:&tbnh=135&tbnw=149&prev=/images%3Fq%3Dstar%2Bmap%26um%3D1 &start=1&sa=X&oi=images&ct=image&cd=1 Rwww.lindahall.org/.../websize/maps/ w.jpgwww.lindahall.org/.../websize/maps/ w.jpg Rhttp:// RGoogle Image Search: Ursa Major, Ursa Minor, Canis Major, Canis Minor, Orion, Cygnus, Lyra, Aquila Rhttp://imagine.gsfc.nasa.gov/Images/news/gb1508_xray_illustration.jpghttp://imagine.gsfc.nasa.gov/Images/news/gb1508_xray_illustration.jpg RCore Knowledge Sequence, p. 153, ISBN: Rhttps:// Rhttp://images.google.com/imgres?imgurl= map- large.gif&imgrefurl= QWD8oD_1ZoPM:&tbnh=135&tbnw=149&prev=/images%3Fq%3Dstar%2Bmap%26um%3D1 &start=1&sa=X&oi=images&ct=image&cd=1 Rwww.lindahall.org/.../websize/maps/ w.jpgwww.lindahall.org/.../websize/maps/ w.jpg Rhttp:// RGoogle Image Search: Ursa Major, Ursa Minor, Canis Major, Canis Minor, Orion, Cygnus, Lyra, Aquila