The
Eskimo Nebula (NGC
2392): Clownface
Nebula or Caldwell 39
It
is a bipolar double-shell planetary nebula, surrounded by gas that
was once the outer layers of a Sun-like star. The inner filaments are
expelled by a strong wind made up of particles from the central star
while the outer disk contains unusual light-year-long filaments.
It
was discovered by astronomer William Herschel in 1787.
NGC
2392 lies more than 2,870 light-years away and is visible in the
constellation of Gemini.
The
Helix Nebula: The
Helix, NGC 7293
Large
planetary nebula is similar in appearance to the Cat's Eye Nebula and
the Ring Nebula, whose size, age, and physical characteristics are
similar to the Dumbbell Nebula. It only varies in its comparative
proximity and appearance from the equatorial viewing angle.The Helix
Nebula has sometimes been referred to as the "Eye of God",
as well as the "Eye of Sauron" based on the Lord of the
Rings series.
Discovered
by Karl Ludwig Harding in the 1800s, of all the bright planetary
nebulae it is one of the closest to the Earth. The estimated distance
is about 215 parsecs or 700 light-years.
It
is located in the constellation Aquarius.
Little
Ghost Nebula: NGC 6369
It
is located in the constellation Ophiuchus and was discovered by
William Herschel
Round
and planet-shaped, the nebula is also fairly faint. The former white
dwarf star, seen near the center in this photo, radiates strongly at
ultraviolet wavelengths and is what causes the nebula's glow. The
main ring structure is about a light-year across and the glow from
ionized oxygen, hydrogen, and nitrogen atoms are colored blue, green,
and red respectively.
The
Owl Nebula: Messier
Object 97 (M97)
and NGC 3587.
It
was discovered by French astronomer Pierre Méchain on February 16,
1781, though it wasn't until William Parsons, 3rd Earl of Rosse
observed the nebula in 1848, and his hand-drawn illustration
resembled an owl's head, that it was named the Owl Nebula.
It
is located approximately 2,030 light years away in the constellation
Ursa Major.
The
nebula is approximately 8,000 years old and is circular in
cross-section with a little visible internal structure. It is
arranged in three concentric shells, with the outermost shell being a
bit larger than the inner shell. The owl-like appearance of the
nebula comes from the inner shell that is not circularly symmetric,
but forms a barrel-like shape.
Its
outer radius is around 0.91ly (0.28pc) and it is still expanding.
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The nebula was imaged by the Hubble Space Telescope in the 1990s.
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Minkowski
2-9: M2-9,
Minkowski's Butterfly,
the Wings of a Butterfly Nebula
or just Butterfly Nebula,
and Twin Jet Nebula
Discovered
by Rudolph Minkowski in 1947 and is located about 2,100 light-years
away from Earth in the constellation Ophiuchus.
It
is a bipolar nebula which takes the peculiar form of twin lobes of
material that emanate from a central star. Astronomers have dubbed
this object as the Twin
Jet Nebula
because of the jets believed to cause the shape of the lobes. Its
form also resembles the wings of a butterfly. The primary component
of this nebula is the core of its star that has reached the end of
its main-sequence life cycle, ejecting most of its outer layers and
becoming a red giant, and is now in the process of contracting into a
white dwarf.
The
Cat's Eye Nebula:
NGC 6543
Relatively
bright planetary nebula in the northern constellation of Draco, and
was discovered by William Herschel on February 15, 1786. It was the
first planetary nebula whose spectrum was investigated by the English
astronomer William Huggins, demonstrating that planetary nebulae were
gaseous and not stellar in nature.
Its
small bright inner nebula covers an average of 16.1 arcsec, with the
outer prominent condensations about 25 arcsec. Deep images reveal an
extended halo about 300 arcsec across, that was most likely ejected
by the central star during its red giant phase.
The
Cat's Eye nebula, given in some sources, lies about three thousand
light-years from Earth.
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