Transcript Constellations

Introductions to
Constellations
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http://www.astro.umass.edu/~ngow/
http://www.chinapage.com/astronomy/chart/celestialchart.html
http://www.geocities.com/ResearchTriangle/System/8870/memory/
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What did the ancient people
use stars (patterns of stars)
for?
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Navigation – sailing, travel
Seasons – when to plant and harvest
Preserve myths, traditions, etc
Group the brighter stars into
patterns, - constellations
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Patterns of stars
Boundaries
http://www.astro.virginia.edu/class/oconnell/astr130/im/
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Constellation
• One of the 88 named Regions of sky
defined by the International
Astronomical Union (IAU)
• Identified with the officially
recognized Patterns of Stars that lie
within the boundaries of the region
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The Northern Hemisphere
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About Constellations
• Stars in a
constellation
usually NOT
physically
associated
with each
others
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About Constellations
• Some constellations have a lot of
bright stars (Orion), others mainly
contain dim stars.
• Symbolized figures, some patterns
don't look like the subjects
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What are the 88 Constellations?
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14 men and women
9 birds
19 land animals
2 insects
10 water creatures
2 centaurs
1 head of hair
1 serpent
1 dragon
1 flying horse
1 river
29 inanimate objects, include scientific instruments (Microscopium,
Telescopium)
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Asterism
• A generally recognized smaller/cuter
pattern of stars that is not one of
the officially recognized
constellations
• Whether or not a region of sky is
named after it – yes: constellation;
no: asterism
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Asterism
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The Big Dipper in Ursa Major
The Little Dipper in Ursa Minor
The “W” of Cassiopeia
Lozenge of Draco
House (Cepheus)
Sword of Orion, Belt of Orion
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History of Modern
Constellations
• (Uncertain) Origin: Nomad in
Mesopotamia named some northern
constellations more than 5,000 years
ago, including Leo and Taurus
• More constellations were added by
Babylonian, Egyptian and Greek
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History of modern
constellations
• Oldest
systematic
description of
constellations:
Phaenomena, in
270 B.C. by Greek
poet Aratus
http://www.wikipedia.org
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History of modern
constellations
• In 150 A.D., Ptolemy
published The Almagest
(The Great Book)
– A catalog of 1022 stars,
with estimates of their
brightness, arrange into
48 constellations. The 48
constellations formed the
basis for our modern
constellations
• 44 southern
constellations were
added after 16th
century
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http://www.wikipedia.org
History of modern
constellations
• IAU officially adopted the list of 88
constellations that we use today in 1922
• Definitive boundaries between
constellations were set in 1930 – 88
regions cover the ENTIRE sky
• For today’s astronomer, constellations
refer not so much to the patterns of the
stars, but to precisely defined areas of the
sky
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• Modern constellations
– Greek Constellations
– Latin Names
– Many stars have Arabic names
• Al-Sufin, one of the greatest Arabic
astronomers, translated Ptolemy’s book
into Arab in the 10th century
• Different cultures grouped stars and
named constellation differently
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Are constellations permanent?
• Are stars fixed?
• Stars all move relative to the
Sun, with speed of many
kilometers per seconds
• Stars are far away, and stars
in the constellations are at
different distances
• Stars will move, shapes of
constellations will change, but
it takes thousands of years to
see the change
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What are circumpolar
Constellations?
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Star Trail
• Earth rotates about
an axis that is pointed
very close to the star
Polaris
• Stars rise in the east
and set in the west
everyday
Anglo Australian Observatory
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Circumpolar Constellations
• A Constellation that NEVER rises or sets
as seen at a certain latitude
• Six circumpolar constellations seen in
Amherst (42º N, 72º W)
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Ursa Major – Larger Bear
Ursa Minor – Smaller bear
Cassiopeia – Queen
Cepheus – King
Draco – Dragon
Camelopardalis – The Giraffe
Circumpolar Constellations at
Amherst
Ursa Major
Cepheus
Cassiopeia
Ursa Minor
Draco
Camelopardalis
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www.acmecompany.com/
Questions
• Where on the earth can we see the
maximum number of circumpolar
constellations?
• - At the earth’s pole
• Where on the earth can we see the
minimum number of circumpolar
constellations?
• - At the earth’s equator
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Summary
• Definition of Constellation
– 88, patterns of stars, boundaries
• Asterisms
– Not official
– If there’s a region of sky named after it
• Stars in a Constellation usually do not have
physically connections
• Circumpolar constellations
– Never rise or set
– Remember the 6 circumpolar constellations
seen at Amherst
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Find the
big dipper
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How to find Polaris from the Big Dipper
and Cassiopeia
• From the Dipper, follow the two
stars at the end of its bowl toward
Cassiopeia. There, about five times
the separation of these two stars,
you'll find Polaris.
• Use the middle three stars of
Cassiopeia's "W" as an arrow to
point in the direction of the
Dipper. Halfway there you will
encounter Polaris.
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Do we see different constellations at
different seasons?
• Earth rotates about an axis that is pointed very
close to the star Polaris
• Stars rise in the east and set in the west
everyday
• It takes 4 minutes less for a star to come back
to the position yesterday
• If we observe the sky at the same time every
night, (say 9pm), the positions of constellations
will change night by night
• 4 minutes each day, is 24 hours for 365 days!
• At different seasons, we see different
constellations!
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Zodiac Constellations
• Constellations of stars
that lie along the
apparent path of the
Sun across the heavens
(the ecliptic)
• Aquarius, Pisces, Aries,
Taurus, Gemini, Cancer,
Leo, Virgo, Libra,
Scorpio, Sagittarius,
Capricorn
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