Nebulous 'Spirograph' astounds Hubble astronomers
(CNN) -- A young nebula offers a brilliant display of textures and
colors, but its shape mystifies astronomers who have used the Hubble
Space Telescope to take clear pictures of the once sun-like star.
Hubble scientists snapped the picture of the Spirograph Nebula while
conducting a survey of planetary nebulas, a celestial census that could
shed light on the fate of our sun.
When ordinary stars like our sun enter their twilight years, they swell
into red giants and then cast off their outer layers, ghostly halos of
gas and matter. The death shrouds expand and glow, heated by
ultraviolet radiation from the hot core of the dying stars.
A nebula will expand for several millennia. Then, over billions of
years, the corpse of the interior star will gradually fade and cool into a white dwarf.
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Astronomers using ground-based telescopes thought that the nebula had
an elliptical shape, said Raghvendra Sahai, the lead Hubble researcher
studying the nebula. But the more powerful Hubble lens revealed that
it instead exhibited a more eccentric type of symmetry.
"The central symmetry is like an 'S' shape. A point has a corresponding
point on the opposite side, but not in a mirror image," said Sahai, a
physicist at NASA's Jet Propulsion Laboratory in Pasadena, California.
Sahai and others theorize that bipolar jets sprinkling out material
from dying stars are responsible for planetary nebulas, so called
because 18th century astronomers using small telescopes thought they
resembled distant planets.
In this example, 2,000 light years away in the direction of the
constellation Lepus, the jets seem to fire in one direction for awhile
and then change direction.
"We don't know why. It is a mystery," Sahai said.
Astronomers have enlisted Hubble to search the heavens for young
nebulae, at most thousands of years old, which display greater size and
shape diversity than their older brethren, Sahai said.
Hubble has spotted about 50 of them, and astronomers hope the orbiting telescope
can be enlisted to find hundreds more.
The cosmic catalog could offer clues about how nebulae form, offering
scientists a chance to compare theoretical models with a "mixed bag of
masses and sizes" from direct observations, Sahai said.
The Spirograph image, released last week, shows a color-enhanced
spectrum of heated elements. Red trace emissions from comparatively
cool ionized nitrogen, green from warmer hydrogen and blue from
super-hot ionized oxygen.
The sun is expected to experience a similarly nebulous fate, but not
for some 5 billion years.
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Space Telescope Science Institute
Spacelink - Hubble Space Telescope
Hubble images of young planetary nebulae
More planetary nebulae pictures obtained with Hubble
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