Introduction to Constellations (01:08)
Constellations have intrigued man for centuries. The patterns that once guided mariners across the waters now guide astronomers to uncover the mysteries that lie within the constellations.
Celestial Coordinate System (02:12)
The coordinate system of constellations is a direct extension of Earth's latitude and longitude. Mariners used this grid for navigation. Today, satellites are used in place of sextants in fixing a ship's position.
Appearances are Deceiving (02:24)
Determining distances of stars is difficult. Celestial coordinates do not account for distances, much like a flat map does not account for elevation.
Gauging Distance of Stars (02:20)
Astronomers use reference stars to gauge distance. The term parallax refers to the change in position of an object when viewed from two different positions. The closer the star, the greater the parallax.
Familiar Guideposts (03:11)
Pulsation patterns of the Cepheid Variable stars are used to determine stars distances. Apparent magnitude is a measurement of flux or brightness. Supernovas are another standard candle used for distance calculation.
Constellation Orion (02:09)
In Orion, there are many different kinds of stars in various stages of development. Betelgeuse, Alnitak, Alnilam, Mintaka, Orion Nebula, and Rigel have captivated scientific curiosity for thousands of years.
Thuban: Pole Star of the Pyramid Builders (03:22)
Some Egyptologists believe Orion might have been used for aligning the Great Pyramids of Egypt. Thuban was the Pole Star at just the time the Egyptians were building pyramids.
Polar Star (02:55)
Polaris is located in the constellation Ursa Minor and is much brighter than the sun. The Earth's axis makes a complete circle every 26,000 years. Halfway through that cycle, Vega will become the polar star.
T-Tauri Stars (02:03)
Stars vary in size, density and brightness. Variable stars exhibit a pattern of brightening and dimming. Protostars that are starting to blow away the gas and dust surrounding them are called T-Tauri stars.
Zodiac Constellations (02:32)
The constellation Taurus lies on the ecliptic plane--a plane that Earth also travels. The space above and below is called the Zodiac. Zodiac constellations fall within this band of space.
Zodiac Signs and Star Names (00:58)
Zodiac signs and names of stars originate from Mesopotamia, and from Greek and Roman cultures. Arabic astronomers kept records of this information from the ancients. Ptolemy labeled more than 1,000 stars.
Forgotten Zodiac Constellation (01:06)
Instead of 12 Zodiac constellations, there are 13. Ophiuchus, "The Serpent Bearer," is the forgotten sign.
Massive Stars (01:21)
The only star that does not belong to a specific constellation is Earth's sun. Wolf-Rayet stars are very large, massive stars--about 20 times bigger than the sun--nearly at the end of their stellar lives.
Night Sky of the Southern Hemisphere (01:42)
The most dominant feature in the night sky in the southern hemisphere is the Milky Way. Crux, or the Southern Cross, is the smallest of the 88 constellations, but also among the brightest.
Number of Constellations (01:41)
In 1922, the International Astronomical Union (IAU) adopted the modern list of 88 constellations.
White Supergiants (02:05)
Deneb is a blue-white supergiant star that forms the tail of the swan in the constellation Cygnus. Deneb is also one of the most luminous nearby stars. Several thousand light-years away, near the "heart" of Cygnus two stars are locked in a gravitational embrace.
Calendar in the Sky (02:00)
Within each constellation stars are born while others are swallowed by black holes. Constellations brought people the "nightly news." The ancients saw order in the sky that was useful for them to anticipate what was happening on Earth.
Map of the Night Sky (01:39)
Constellations have not outlived their usefulness. Instead of telling humans about the earth, they help us make sense of the stars. Like countries, constellations divide the sky into territories.
Centaurus Constellation (02:22)
Alpha and Beta Centauri from the Centaurus constellation are the brightest stars in the night sky. Omega Centauri is a cluster of millions of stars. A constellation exists only in the mind's eye.
Portrait of the Night Sky (03:46)
The flat planes of the constellations are an illusion. Constellation stars are in constant motion. Constellations are a snapshot, a flattened portrait of the night sky.
Credits: Constellations (01:20)
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