The red wisps represent molecular hydrogen gas glowing in infrared wavelengths around NGC 7027.
			The beginning of a dying star’s end
			Hubble Telescope captures brief phase in stellar evolution

 

		By Alan Boyle MSNBC

 

March 19 — Using a camera that can see what the naked eye could never discern, the Hubble Space Telescope has captured a key moment in the death of a star like our sun — when it begins to light up the surrounding region of cool gas.

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	Mario Livio of the Space Telescope Science Institute explains the formation of planetary nebulae with the help of an animation.		THE PICTURES follow up on a jaw-dropping series of images released in December by the Baltimore-based Space Telescope Science Institute.         Like the previous batch, the images released Thursday record the final stages of a medium-size star’s life, when it blasts away the outer layers of stellar gas and dust in a colorful display. But these new images record the very start of the fireworks show in infrared wavelengths not visible to the naked eye.        “This is very much like what will happen to the sun,” Caltech astronomer William Latter told the Reuter news service. However, our sun is about 4.5 billion years away from the phase recorded in Thursday’s images.        This brief period in the stellar death process — its transition to a planetary nebula — lasts about 1,000 Earth years, a mere blink in cosmological time.        When a star starts to die, the nuclear fuel at its heart runs out and a very dense, cool shell of hydrogen gas is deposited around the star. This molecular shell cannot be seen in visible light but was detected by Hubble’s Near Infrared Camera and Multi-Object Spectrometer.        One nebula, known as NGC 7027 and located 3,000 light-years away in the direction of the constellation Cygnus, is seen in the new pictures as a glowing white ball surrounded by red wisps of the dissipating molecular shell.
	This image combines views of NGC 7027 in visible and infrared light to show the layers of gas surrounding the central star: a hot white bubble, a medium layer of glowing red and pink gas, and an even cooler outer region of molecular gas and dust, seen as a blue haze.		“What’s new about these images is we’re able to see a very thin transition between the ionized region and the formerly invisible atmosphere on the star,” Latter said.        Also Thursday, Hubble astronomers released images of two other dying stars that look like butterflies emerging from their cocoons.        The central stars of the Cotton Candy nebula and the Silkworm nebula are surrounded by thin “cocoons” of gas, which show up on the images as faint concentric circles. Colorful, butterfly-like “wings” of glowing gas and dust are seen breaking through the cooler gas cocoon.        Still other stars are surrounded by outer shells of cool gas, which contain fast-expanding bubbles of hotter material thrown off by the stars.        The stars and their surrounding clouds of glowing gas are known as planetary nebulae not because they have anything to do with actual planets, but because they have a disklike appearance similar to celestial planets when they are viewed through small telescopes.        Astronomers say detailed observations of such nebulae lead to a deeper understanding of stellar evolution. What’s more, dying stars hurl off some of the elements that are the building blocks for life on Earth, such as carbon. Thus, a study of stellar death throes may eventually shed new light on the origins of planets and life as well.          Reuter contributed to this story.

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