An Introduction to Solar System Astronomy
Prof. Richard Pogge, MTWThF 2:30
Lecture 3: The Starry Night
About 6000 stars are visible to the naked eye
Uses of Constellations
- Figures drawn in the sky by connecting stars
- 88 modern constellations
- Cultural and Religious Roles
- Navigational Aids
Note: This lecture uses a lot of graphics, unfortunately
many of them (the paintings and photos) are copyrighted, and
cannot be reproduced on these web pages. To get the full visual
effect, you have to come to lecture.
The Starry Night
From a dark site, about 6000 stars are visible to the naked eye on a
This represents only a tiny fraction of the nearly 200 Billion stars
that make up the Milky Way Galaxy in which we reside.
From time immemorial, people have seen patterns and drawn figures in the
sky by connecting the bright stars.
These starry figures are the Constellations
All peoples have populated the night sky with constellations.
Figures in the Sky
Most constellations are composed of bright stars that stand out from the
Many look like what they are named
Peoples greatly separated in distance and/or time often made the same
connections. A few common examples:
- Orion depicted as a male human
- Scorpius called a scorpion by most desert peoples
- Celestial Rivers and Snakes
[Look for Orion in the winter sky, it rises in the east/southeast around sunset
beginning in late December].
The Classical Constellations
The oldest known constellations (Leo, Taurus, Scorpius) appear in
cuneiform tables dating from 3000 BC, but may be older still.
The Greek constellations and associated star lore were described in
the Phaenomena of Eudoxus of Cnidos (c. 366 BC), and likely
derived from Babylonian (Assyrian?) lore of c. 1100 BC.
The Greek astronomer Ptolemy made a catalog of 48 "classical"
constellations in the 2nd century AD:
All of the classical constellations are those visible from the middle
latitudes of the northern hemisphere.
Populating the Sky
16th & 18th century travelers to the southern hemisphere filled in
the rest of the sky.
Map makers invented new constellations to add to the Classical 48 of
There are now 88 Modern Constellations with boundaries and figures
defined by the International Astronomical Union (IAU). This work was
completed in 1888.
- Mix of classical, biblical and modern themes have been used
- Up to 150 constellations at one time.
- Many defunct constellations (e.g., Felis the Cat)
Role of Constellations
Constellations have served many purposes among the
peoples that created them. A few of the major ones
As Story-telling Mnemonics
- Celestial "Cheat Sheets"
- Figures were often culture heroes or deities.
Religious and Ritual Uses
- Lakota Sioux Sacred Hoop ceremonial site.
- Celestial alignments of Egyptian and Mayan sacred structures
- The Inca laid out their empire as a reflection of the heavens.
- Ursa Minor (Little Dipper) as a mnemonic for finding the pole star
Polaris in middle-ages to present.
- The faint constellation of Hydra possibly used as an East-West arrow by
Minoan sailors c. 2400BC
- Polynesians used constellations to navigate across vast distances in
the Pacific Islands.
This "purpose" is purely aesthetic. Constellations and views of the
night sky have figured in the arts in all ages and cultures:
- Egyptian and Mayan "sky vaults" in buildings
- Ornate Renaissance decorative sky atlases
- Celestial Themes in modern art (van Gogh's Starry Night,
Miro's Constellation..., etc.)
The brightest stars visible to the naked eye have all been given proper
In the western tradition, these names are mostly Arabic & Greek,
revealing the chain of transmission of the western astronomical
Mesopotamia -> Classical Greece -> Roman Empire
-> Islam -> Renaissance Europe -> Today
Other cultures have also named some of the brightest stars, though these
names are not in common use today.
Common Names of Stars
The common names of stars in use today are mainly Arabic, but there is a
mix of Greek and Latin for a few famous stars
- Arabic: Rigel, Alberio, Deneb
- Greek: Sirius (bright "dog star"), Arcturus
- Latin: Polaris (Northern Pole Star), Spica
- Unknown: Betelgeuse (corrupted Arabic?)
Extra Info: Names of Stars
This is really a topic that becomes more relevant when we talk about
the stars themselves in Astronomy 162, but it fits in context. I've
added it here as extra information, but will not include it on the
Bayer (Greek Letter) Names
In 1601, German astronomy Johannes Bayer developed a system of naming
stars using lower-case Greek letters in approximate order of
brightness (though he didn't always get it right). A "Bayer Name" for
a star consists of two parts
- Greek letter to indicate brightness, in order
of brightest to faintest.
- Genitive (possessive) form of the constellation name
And so forth.
- Betelgeuse = Alpha Orionis (brightest star)
- Rigel = Beta Orionis (2nd brightest star)
- Bellatrix = Gamma Orionis (3rd brightest star) etc.
After you run out of Greek letters (there are 24 letters), stars are
given "Flamsteed Numbers" (e.g., 61 Cygni), taken from a great catalog
of naked-eye stars created by John Flamsteed in the 18th century.
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Updated: 2007 September 16
Copyright © Richard W. Pogge, All