• As early as 5000 years ago, people
began naming patterns of stars, called
constellations, in the honor of
mythological characters or great heroes.
• Today, 88 constellations are recognized.
• They divide the sky into disjoint units.
• Every star in the sky is in one of these
constellations.
• Astronomers label stars
within a constellation
based on their apparent
brightness,
– brightest = alpha a,
– second brightest = beta b,
–…
• Some of the brightest
stars have actual
names, like Rigel &
Betelgeuse (both in the
constellation Orion)
Ursa Major
Ursa Major, the Great
Bear, is visible in the
Northern Hemisphere
all year long.
Ursa Major
Circumpolar Constellation
How to find Pole Star
Ursa Minor
• Ursa Minor, the Little Bear,
is visible in the Northern
Hemisphere all year long.
• Ursa Minor is mostly
known for Polaris, the
North Star, which may be
found at the end of the
handle.
Ursa Minor
Circumpolar Constellation
Saharan Starry Night
Views of Orion from
Tasmania (Australia) and Iran (Asia)
Cepheus
• The story behind it:
– Cepheus was the King of Ethiopia. He married Cassiopeia and they
had a daughter Andromeda. Cassiopeia was incredibly beautiful but
immensely vain. She was also proud of her daughter's beauty. In fact
she continually boasted that the two of them were more beautiful than
any of the fifty sea nymphs who attended Poseidon's court.
– These nymphs (the Nereids) complained to Poseidon, who felt he had
to defend his own reputation. So he sent a flood to devastate Cepheus'
kingdom. The oracles told Cepheus that in order to save his people he
must sacrifice his daughter to a great sea monster: Andromeda was
tied to a rock along the coastline, dressed only in her jewelry. The
monster would be along in due time to take his prize.
– At that moment Perseus came flying by. He had just killed the Gorgon
Medusa and was carrying the severed head back to Athene. To make a
long story short, he saved her then turned everyone into stone by
showing them the severed head.
– Poseidon then put the stone frozen Cepheus and Cassiopeia into the
heavens, but with a twist: he made the vain Cassiopeia spin around on
her chair, spending half the year upside down. As for Cepheus,
Poseidon gave him a number of medium sized stars that go to make his
square face with a pointed crown.
Cepheus
Circumpolar Constellation
Cassiopeia
Circumpolar Constellation
Draco
• Draco, the Dragon, used
to hold special
significance as the
location of the pole star,
but due to the Earth's
precession, the pole has
shifted to Polaris in Ursa
Minor.
Circumpolar Constellations
Circumpolar Constellations
Circumpolar Constellations
Circumpolar Constellations
Circumpolar Constellations
Circumpolar
Constellations
Orion
• Orion is the master of the winter skies. He lords over
the heavens from late fall to early spring, with his
hunting dog Sirius trailing at his feet.
• The story behind it: (Orion holding an animal)
– Orion was known as the "dweller of the mountain",
and was famous for his prowess both as a hunter and
as a lover. But when he boasted that he would
eventually rid the earth of all the wild animals, his
doom may have been sealed. The Earth Goddess
sent the deadly scorpion to Orion to kill him. Orion
engaged the scorpion in battle but quickly realized its
armour was impervious to any mortal's attack. Orion
then jumped into the sea and died. In his eternal
hunting, Orion is careful to keep well ahead of the
scorpion. Orion disappears over the horizon by the
time Scorpio rises in the east, as it becomes his turn
to rule the evening sky.
Orion
Not a circumpolar constellation, but a seasonal constellation
Betelgeuse, the right arm of Orion (or "armpit" as the name suggests), glows with a
dull red.
Rigel, in the opposite corner of the constellation, is blue and much brighter.
• Orion
•On the left: The Hunter - Orion
•In the middle: Name: The Bull - Taurus
•On the right: Name: The Greater Dog - Canis Major
• On the left: The Lion - Leo
• In the middle: The Herdsman - Böötes
• On the right: The Virgin - Virgo
• On the left: The Crab - Cancer
• In the middle: The Scorpion - Scorpio
• On the right: The Archer - Sagittarius
• On the left and in the middle: Andromeda
– The Andromeda constellation is famous for containing the
Andromeda Nebula, the closest galaxy to our Milky Way.
• On the right: The Fishes, Pisces
Ecliptic Constellations & Zodiac Signs
• A band of 12 constellations around the sky
entered on the ecliptic (apparent path of
the sun on the earth as the earth revolves
around it).
• Aries, Leo, Sagittarius, Taurus, Virgo,
Capricorn, Gemini, Libra, Aquarius,
Cancer, Scorpio, and Pisces.
Ecliptic Constellations
Hindu Calendar Rashi
The Constellations, using H. A. Rey's Scheme
Andromeda
Antlia
Apus
Aquarius
Aquila
Ara
Aries
Auriga
Boötes
Caelum
Camelopardalis
Cancer
Canes Venatici
Canis Major
Canis Minor
Capricornus
Carina
Cassiopeia
Centaurus
Cepheus
Cetus
Chamaeleon
Circinus
Columba
Coma Berenices
Corona Australis
Corona Borealis
Corvus
Crater
Crux
Cygnus
Delphinus
Dorado
Draco
Equuleus
Eridanus
Fornax
Gemini
Grus
Hercules
Horologium
Hydra
Hydrus
Indus
Lacerta
Leo
Leo Minor
Lepus
Libra
Lupus
Lynx
Lyra
Mensa
Microscopium
Monoceros
Musca
Norma
Octans
Ophiuchus
Orion
Pavo
Pegasus
Perseus
Phoenix
Pictor
Pisces
Piscis Austrinus
Puppis
Pyxis
Reticulum
Sagitta
Sagittarius
Scorpius
Sculptor
Scutum
Serpens
Sextans
Taurus
Telescopium
Triangulum
Triangulum Australe
Tucana
Ursa Major
Ursa Minor
Vela
Virgo
Volans
Vulpecula
Brightest Stars
and Their Constellations
http://www.enchantedlearning.com/subjects/astronomy/stars/br
http://www.astro.wisc.edu/~dolan/constellations/extra/brighte
The Dome of the Sky:
Definitions in your local sky
To Polaris
Angular size of moon ~ ½ o
Angular distance between the “pointer stars” ~ 5o
Latitude and
Longitude
Beavercreek, OH
Latitude: 39.73 N,
Longitude: 84.06
W
Different sets of constellations are visible in
northern and southern skies.
The Altitude of the celestial pole (Polaris) = your latitude
Counter-Clockwise
Rotation
Northern Hemisphere
The
Clockwise Rotation
Southern Hemisphere
Altitude of the celestial pole (Polaris) = your
Right Ascension and Declination
• Right Ascension (RA): Analogous to
longitude, but on the celestial sphere.
– It is the east-west angle between the
vernal equinox and a location on the
celestial sphere.
• Declination (dec): Analogous to
latitude, but on the celestial sphere.
– It is the north-south angle between the
celestial equator and a location on the
celestial sphere.
Units of R.A.
360o = 24h
 15o/h
Azimuth and Altitude are observer centric.