Astronomy
Constellations
1 of
18 20
© Boardworks Ltd 2004
Contents
Constellations
What are Constellations?
Ursa Minor
Astronomy vs. Astrology
Summary activities
1
2 of 20
18
© Boardworks Ltd 2004
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.
1
3 of 20
18
© Boardworks Ltd 2004
Constellations aren’t a true group of stars
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.
1
4 of 20
18
© Boardworks Ltd 2004
Contents
Constellations
What are Constellations?
Ursa Minor
Astronomy vs. Astrology
Summary activities
1
5 of 20
18
© Boardworks Ltd 2004
Ursa Major
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.
1
6 of 20
18
© Boardworks Ltd 2004
The Little Dipper
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.
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
1
7 of 20
18
© Boardworks Ltd 2004
Contents
Constellations
What are Constellations?
Ursa Minor
Astronomy vs. Astrology
Summary activities
1
8 of 20
18
© Boardworks Ltd 2004
Astronomy vs. Astrology
Astronomy and Astrology are not the same!
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 know
about astrology is their
"sign," which refers to one
of the 12 constellations
of the zodiac which they
were “born under”
1
9 of 20
18
© Boardworks Ltd 2004
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.
1
10ofof20
18
© Boardworks Ltd 2004
What’s wrong with “Your Sign”
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?
1
11ofof20
18
© Boardworks Ltd 2004
What’s wrong with “Your Sign”
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.
1
12ofof20
18
© Boardworks Ltd 2004
What’s wrong with “Your Sign”
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.
1
13ofof20
18
© Boardworks Ltd 2004
The True Constellations of the Zodiac
What is your true sign?
Constellation
Dates
Number
of 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
1
14ofof20
18
© Boardworks Ltd 2004
Contents
Constellations
What are Constellations?
Ursa Minor
Astronomy vs. Astrology
Summary activities
1
15ofof20
18
© Boardworks Ltd 2004
Glossary
 Asterism - a distinctive group of stars.
 Astronomy - the scientific study of stars, planets, and other
objects in outer space
 Astrology – the study of how the positions of the stars have
a supposed influence on events and on the lives of people.
 Constellation - a group of stars that make an imaginary
shape in the night sky.
 Ophiuchus– the 13th constellation of the zodiac
 Precession – the wobbling of Earth; one wobble takes
25,800 years.
1
16ofof20
18
© Boardworks Ltd 2004
Questions
 What is are constellations and who created them?
 How many constellations are there?
 Why isn’t a constellation a true grouping of stars?
 Ursa Minor is a constellation and the Little Dipper is an
asterism. Explain the difference.
 What is the difference between astrology and
astronomy?
 How has precession changed the position of the
constellations overhead?
 What is the name of the 13th constellation of the zodiac
and why was it added?
1
17ofof20
18
© Boardworks Ltd 2004
Make your own constellation
Random Number Generator
1
18ofof20
18
© Boardworks Ltd 2004