End of life one star shines especially in the ultraviolet.
This radiation illuminates then once the gas expelled by ionizing radiation, and thus forms a planetary nebula, the circular aspect, such as the Helix Nebula.
Planetary nebulae are the representation of the death of a star like our sun. When these stars die, they expel into space their outer gaseous layers.
The Helix Nebula is a star cosmic often photographed by amateur astronomers for its vivid colors and its resemblance to a giant eye, open to the cosmos.
Discovery in the 18th century, it is located about 650 light-years away in the constellation Aquarius.
The Helix Nebula has spent his life turning hydrogen into helium in a runaway nuclear fusion reactions that took place in his heart.
It is this process of fusion which provided all the light and heat of the star during its lifetime.
Our Sun follows the same process but it will die in 5 billion years when the hydrogen fuel is exhausted.
The fusion of helium begins to turn into carbon and carbon nitrogen and nitrogen oxygen.
The star will be really dead, blowing off its outer gaseous layers.
The little heart hot and dense is called a white dwarf that has the size of the Earth, but with a mass close to that of the original star.
Light of this planetary nebula is particularly intriguing because it seems strikingly similar in a wide band spectrum from ultraviolet to infrared.
The Helix Nebula is recognizable regardless of the observed wavelength, but the combination of an image taken in ultraviolet light with an image taken in the infrared spectrum, as here, highlights some subtle differences. The intense ultraviolet radiation from the white dwarf heats the expelled gas layers, which shine brightly in the infrared.
GALEX chose ultraviolet to observe this nebula is visible in blue, while the Spitzer Space Telescope has used the infrared signature of dust and gas in yellow on the image. Part of the field beyond the nebula has not been observed by Spitzer, but Survey Explorer (WISE) in the infrared.
The white dwarf at the center of the image is hardly visible. Most brilliant purple circle in the center is a dust disk surrounding the white dwarf photographed in the ultraviolet combined to the infrared.
These are probably the remnants dust expelled from comets that survived the death of their star.
Before the star dies, planets and comets were ordered. When the star ran out of hydrogen and blew its outer layers, the icy bodies and outer planets would have been tossed, lifting the cloud of cosmic dust.
All the inner planets of the system have disappeared in the fire of their dying star.
nota: Helix Nebula or NGC 7293 a strange resemblance to the human eye, this earned him the nickname "God's eye".
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Image: The Helix Nebula or NGC 7293 as seen by the Spitzer Space Telescope. The hydrogen atoms emit red light, while the oxygen emits green light. The tiny white dot in the center of the photograph is the white dwarf star immersed in a surprisingly bright infrared glow. The red color in the middle of the eye represents the final layers of gas blown out when the star died. The bright red circle in the center is the glow of a dusty disk surrounding the white dwarf. Credit: image: NASA / JPL-Caltech combined to Spitzer Space Telescope NASA's and Galaxy Evolution Explorer (GALEX).