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Constellations pg. 617-620. 1. # of stars? 2. Maps of sky Declination Right Ascension Earth’s spin 3. Constellations Define Names of key ones Asterisms. There are about 6000 named, visible stars in the sky. Astronomy: the oldest science !. Aristotelian view Has the earth and

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Constellations pg. 617-620

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Constellations pg 617 620

Constellations pg. 617-620

1. # of stars?

2. Maps of sky


Right Ascension

Earth’s spin

3. Constellations


Names of key ones


Constellations pg 617 620

There are about 6000 named, visible stars in the sky.

Astronomy the oldest science

Astronomy: the oldest science!

Aristotelian view

Has the earth and

sky on fixed spheres

  • The ancients imagined that the Earth was surrounded by a canopy of stars

The celestial sphere a globe of the sky

The Celestial Sphere:a globe of the sky!

An imaginary bubble that surrounds Earth onto which all the stars are positioned.

Like Earth, the Celestial sphere has a “North Pole”, a “South Pole”, and an equator.

To locate a place on the surface of the earth we use coordinates what is the location of chicago

To locate a place on the surface of the earth we use coordinates.What is the location of Chicago?

Shuffle the deck and have sum fun

Constellations pg 617 620

Stars, constellations, planets, can be found using the coordinates of declination and right ascension on the celestial sphere.

Locate Cygnus the Swan (looks like a cross)

Constellations pg 617 620

DEC (declination)

DEC is measured from the celestial equator in degrees (similar to __________).

Measurement to the

NORTH is positive. The celestial North Pole is at +90 degrees DEC.

Measurement to the

South is negative.

The South Celestial Pole is

at _______degrees DEC

Constellations pg 617 620

RA(right ascension) is similar to _______ is measured in hours, minutes, and seconds, as if we were measuring time instead of position!

0-24 hrs

RA reads to the EAST.

Astronomers decided to begin RA at the point where the path of the ecliptic crosses the celestial equator: the first day of SPRING.

(vernal equinox)

Constellations pg 617 620

We see a “flat” image of the stars in the constellations, but the stars are actually located at varying distances from earth.

Is the celestial sphere tipped over

Is the Celestial Sphere tipped over?

Is the celestial sphere tipped over1

Is the Celestial sphere tipped over?

It is actually Earth that is at an angle (tipped over at an angle of 23.5°

Ecliptic: the path of the sunthrough the sky

Circumpolar constellations

Circumpolar Constellations

Why did the north star change precession

Why did the North Star Change? Precession

  • The Earth is not a perfect circle so it does not have a perfect rotational spin. It “wobbles” like a top.

  • So, Polaris has not always been the “North” Star.

Constellations pg 617 620

Has Polaris always been our North Star?

Celestial portraits

Celestial Portraits

  • Human brains naturally create patterns.

  • What do you see when you look at the clouds?

  • The ancients did the same when they looked up at the sky.



  • A name given to a group of stars

  • 88 in all

  • What do you notice about the constellations that follow?

Zodiac constellations

Zodiac Constellations

The 12 constellations that move through during the year.

Constellations pg 617 620

Do you see a pattern in these stars?



Corona borealis

Corona Borealis

The Northern Crown

Constellations pg 617 620

Draco the Dragon

Ursa minor little dipper

Ursa Minor: Little Dipper

The last star in the handle of the Little Dipper is the North Star: Polaris: The North Star

The big bear

The Big Bear

Can you find the stars of the Big Dipper in the constellation?



  • A named group of stars that are part of a larger constellation

  • Example

    • The Big Dipper is part of

      the larger constellation

      Ursa Major

Constellations pg 617 620

The “tea pot” asterism in the constellation Sagittarius

You probably noticed constellations tell a story

You probably noticed Constellations Tell a story

  • Orion was a mythical hero and hunter, and in his amorous pursuit of the Pleiades (the 7 daughters of the giant Atlas), the Gods placed them in the sky. And Orion chases after them in the sky for all eternity.

Your turn

Your Turn!

  • Look for a pattern, picture, figure, of an object, person, by connecting the stars.

  • Outline the figure.

  • Name the constellation

  • Create a mythological story to go with your constellation

Constellations pg 714

Constellations pg. 714

  • 88 constellations in all

  • We still use 48 of the ancient ones and have added 40 new ones

  • 28 are in the northern sky, 48 are in the southern,

  • 12 are the zodiac constellations

  • In the Northern Hemisphere their named for mythology

  • In the Southern Hemisphere they have modern names

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