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Changing appearance of the sky and Constellations

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Presentation on theme: "Changing appearance of the sky and Constellations"— Presentation transcript:

1 Changing appearance of the sky and Constellations

2 Stars rise in the east and set in the west following diurnal circles.
Circumpolar stars circle the celestial pole all year, they never set. These apparent motions are caused by the rotation of the earth.

3 Stars move gradually westward in the sky over time
Stars move gradually westward in the sky over time. This apparent motion is caused by the revolution of the earth around the sun.

4 Stars have real motions. They are all moving relative to one another
These motions are perceptible to the eye only over thousands of years. The constellations/asterisms known to us will be obsolete 100,000 years from now.

5 All visible stars are in our galaxy.
Most occur in groups of 2 (binary) or more Only about 1 in 4 stars is single.

6 Stars are “suns” but millions of times further away.
A few thousand stars are visible to the naked eye. What you see depends on the brightness of the sky and the quality of your vision

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

8 In olden days star groups that formed recognizable patterns were called constellations.
Modern def refers to a region of the sky. The 88 official constellations cover the celestial sphere.

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

10 Asterisms are commonly recognized patterns of stars have names but are not official constellations
(The Big Dipper is an example, being just the rear end and tail of Ursa Major (the Great Bear)

11 Stars can have dozens of names
EX: Vega, is also  Lyrae, HR 7001, 3 Lyrae, 2MASS J Stars are labeled with Greek letters according to brightness. EX: Betelgeuse the brightest star in Orion, is labeled Alpha () Orionis. FYI: the brightest stars have classical names, originating largely from the Arabic language. Rigel ( Ori) – The left leg of the giant Sheliak ( Lyr) – The tortise Aldebaran ( Tau) – The Follower (of the Pleiades) Antares ( Sco) – The rival of Mars


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