© Boardworks Ltd 2004 1 of 20 1 18 Astronomy Constellations.

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Astronomy

Constellations

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What are Constellations?

A constellation is a group of stars that make an imaginary shape in the night sky.

They are usually named after mythological characters, people, animals and objects.

Ancient farmers created imaginary images out of stars to keep track of the seasons and know when to plant and harvest crops.

There are 88 constellations.


The constellations that we see in the sky are not physical groupings held together by gravity.

In most cases the stars in constellations are each very different distances from us, and only appear to be grouped because they lie in approximately the same direction.

Constellations aren’t a true group of stars


The constellation Ursa Major contains the group of stars commonly called the Big Dipper. The handle of the Dipper is the Big Bear's tail and the Dipper's cup is the Bear's flank.

The Big Dipper is not a constellation itself, but an asterism, which is a distinctive group of stars.

Another famous asterism is the Little Dipper in the constellation Ursa Minor.

Ursa Major


The Little Dipper

STARS OF THE LITTLE DIPPER

Name Distance (ly)

Polaris 431

Kocab 126

Pherkad 480

Yildun 183

Pherkad Minor 389

Urodelus 346

Ahfa 376

Anwar 97

The stars in the Little Dipper appear to be near one another when viewed from Earth, but in actuality they are very far apart from each other.


Astronomy and Astrology are not the same!

Astronomy vs. Astrology

Astronomy is the scientific study of stars, planets, and other objects in outer space

Astrology is the study of how the positions of the stars have a supposed influence on events and on the lives of people.

What most people knowabout astrology is their"sign," which refers to one of the 12 constellations of the zodiac which they were “born under”


What’s wrong with “Your Sign”

The astrology and mythology of the constellations, especially those of the signs of the zodiac may be enjoyable, but the science behind it isn’t quite the same.

Precession: Due to the moon and sun’s pull of gravity, Earth wobbles as it spins. This wobbling is called precession and it's so slow that Earth takes 25,800 yrs for 1 wobble. The result is that most astrological signs are off by one or two constellations, unless you were born over two thousand years ago.


Another problem is that when the astrological sun sign system was set up more than two thousand years ago, the sun's path was divided into twelve equally spaced "signs," each 30 degrees wide.

Can you find the problem with this?



Another problem is that when the astrological sun sign system was set up more than two thousand years ago, the sun's path was divided into twelve equally spaced "signs," each 30 degrees wide.

The constellations are different sizes!

Cancer, for example, is a small constellation, and Pisces is huge, but both are accorded one twelfth of the sun's annual path.



Astronomers finally settled this nagging problem about 60 years ago when the international Astronomical Union published the constellation boundaries.

This redrawing of the boundaries added a constellation to the zodiac. According to the official modern constellation boundaries that all astronomers use, the sun passes through 13 constellations, not 12.

The "thirteenth constellation" of the zodiac is Ophiuchus the Serpent Bearer, and the sun is in front of its stars during the first half of December.



What is your true sign?

The True Constellations of the Zodiac

Constellation DatesNumberof Days

Sagittarius Dec 18 - Jan 18 32

Capricornus Jan 19 - Feb 15 28

Aquarius Feb 16 - Mar 11 24

Pisces Mar 12 - Apr 18 38

Aries Apr 19 - May 13 25

Taurus May 14 - Jun 19 37

Gemini Jun 20 - Jul 20 31

Cancer Jul 21 - Aug 9 20

Leo Aug 10 - Sep 15 37

Virgo Sep 16 - Oct 30 45

Libra Oct 31 - Nov 22 23

Scorpius Nov 23 - Nov 29 7

Ophiuchus Nov 30 - Dec 17 18


• Given: Date and time looking for a star– Put “ruler” on local meridian I will explain– Move the “ruler to the right for a time earlier

than 8pm!– Move the “ruler to the left for times later than

8 pm.


• Given a star and a time– Find the star– Put your ruler over the star – Move to the right if the time is later than 8 pm– And to the left if its earlier than 8 pm

© Boardworks Ltd 2004 1 of 20 1 18 Astronomy Constellations.

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