From the Hubble Space Telescope
NASA's Hubble Space Telescope has captured the unveiling of the Stingray nebula (Hen-1357), the youngest known planetary nebula. Twenty years ago, the nebulous gas entombing the dying star was not hot enough to glow. The Stingray nebula is so named because its shape resembles a stingray fish. Only within the past 20 years did its central star rapidly heat up enough to make the nebula start to glow. It is extraordinary to catch a star in this exceedingly brief phase of its evolution. The nebula is one-tenth the size of most planetary nebulae and is 18,000 light-years away in the direction of the southern constellation Ara (the Altar). Because of its small size, no details of the Stingray nebula were visible before Hubble observations were carried out.
A planetary nebula forms after an aging, low-mass star swells to become a "red giant" and blows off some of its outer layers of material. As the nebula expands away from the star, the star's remaining core gets hotter and heats the gas until it glows. A fast wind - material propelled outward from the hot central star -- compresses the gas and pushes the gas bubble outward. While stars typically last for billions of years, the transition to a visible planetary nebula takes only about 100 years -- the blink of an eye compared to a star's lifetime. It is therefore not surprising that no younger planetary nebula has ever been identified.
The creation of twin bubbles of gas, which shape so many planetary nebulae, has always been a mystery to astronomers. The jets of gas revealed in the Hubble images are of great interest to astronomers because many types of astronomical objects - from young stars to active galaxies - produce similar, opposing flows of gas. The images how a ring of gas surrounding the central star, with bubbles of gas above and below the ring. The wind emanating from the central star has created enough pressure to blow open holes in the ends of the bubbles, allowing gas to escape. The bubbles act like nozzles that direct the escaping gas into two opposing streams. The images also show bright gas that is heated by a "shock" caused when the central star's wind hits the walls of the bubbles. A further discovery is a second star within the nebula, indicating that the Stingray's central star is part of a binary star system. This second star is important because astronomers have theorized that a companion might be necessary for the formation of the ring, bubbles, and columns of
Image Title: Hubble Reveals Details Of A Newly Born Planetary Nebula
based on press release for PHOTO NO.: STScI-PR98-15
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Last Modified On: Tuesday, December 19, 2000