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The
Constellation
Orion
Ryukyu
Astronomy Club
28 March 2009
Discussion Topics
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Locating Orion
Mythology of Orion
Brightest Stars in Orion
Orion Nebula
Trapezoid Star Cluster
Horsehead Nebula
Double stars in Orion
Locating Orion
Orion is the key to
locating the constellations
of the Winter Sky
Locating Orion
Mythology of Orion
• In Greek mythology, Orion was a
great hunter who eventually
offended the gods, especially
Apollo. Apollo tricked Artemis, the
Goddess of the hunt, into shooting
Orion on a bet. When she
discovered that she had shot Orion,
she quickly lifted him to the heavens
and made him immortal, where he
now hunts eternally with his two
dogs, Canis Major and Canis Minor.
In front of him is his prey Taurus the
Bull.
Brightest Stars of Orion
And Deep Sky Objects
Meisaa
Betelgeuse
Bellatrix
Mintaka
Alnilam
Alnitak
Horsehead Nebula
Trapezium
M42 Orion Nebula
Saiph
Rigel
Brightest Stars of Orion
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Betelgeuse: "Alpha Orionis" is a massive red supergiant star nearing the end of its
life. It is the second brightest star in the Orion constellation and the twelfth
brightest star in the night sky.
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Rigel: "Beta Orionis" is a blue supergiant that is the seventh brightest star in the
night sky.
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Bellatrix: "Gamma Orionis“ is the twenty-second brightest star in the night sky.
Bellatrix is considered a blue giant, though it is too small to explode in a supernova.
Its luminosity is derived from its high temperature rather than its radius. Bellatrix
serves as Orion's "left shoulder.
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Mintaka: "Delta Orionis“ is the faintest of the three stars in Orion’s belt. It is a
multiple star system composed of a large blue giant and a more massive white star.
Mintaka is the westernmost of the three stars that constitute Orion's Belt.
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Alnilam: "Epsilon Orionis," is a blue supergiant, despite being nearly twice as far from
the Sun as Mintake and Alnitak, the other two belt stars.
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Alnitak: "Zeta Orionis" is the easternmost star in Orion's Belt. It is a triple star 800
light years distant, with the primary star being a hot blue supergiant.
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Saiph: "Kappa Orionis“ serves as Orion's right foot. It is of a similar distance and size
to Rigel, but appears much fainter, as its hot surface temperature (46,000°F or
26,000°C) causes it to emit most of its light in the ultraviolet region of the spectrum.
M42
The
Orion Nebula
- Interstellar cloud of hydrogen,
dust, and plasma.
- ~1300 light years away
- ~24 light years across
- Visible to naked eye
Trapezium
Star Cluster
- Over 1000 young stars
- Estimated 1M years old
- Most stars clouded from
view by dust
- Only 4-5 stars visible
with small scope
The Horsehead Nebula
Double Stars in Orion
Star
Magnitudes
Separation
Notes
Rigel (beta)
0.1, 6.8
9.5”
Difficult because of glare from primary.
Alnitak (zeta)
1.9, 4.0
2.3”
Test for 75mm telescope
Mintaka (delta)
2.2, 6.3
53”
Wide separation
Eta
3.8, 4.8
1.5”
Test for 100mm telescope
Sigma
3.7, 10, 7.5, 6, 8 11”, 13”,
42”, 30”
Quintuple star: all components visible to
small telescope
Theta_1
6.8, 7.0, 5.4, 6.3
The Trapezium (see earlier slide)
Iota
2.7, 6.9, 11
11”, 50”
747
4.7, 5.5
36”
Lambda
3.6, 5.5
4.4”
Rho
4.5, 8.3
7”
-
Wide separation; same field as Iota
Orion
Stars to
mag 7.0
Double
stars
indicated
by
Finally,
The Okinawan
Mythology
for Orion