Tuesday, June 30, 2009

The Godly Eye...

This is coil-shaped Helix Nebula is one of the largest and most detailed celestial images ever made. This is a seamless blend of ultra-sharp images from NASA's Hubble Space Telescope combined with the wide view of the Mosaic Camera on the National Science Foundation's 0.9-meter telescope at Kitt Peak National Observatory near Tucson, Ariz. The image shows a fine web of filamentary "bicycle-spoke" features embedded in the colorful red and blue ring of gas. At 650 light-years away, the Helix is one of the nearest planetary nebulae to Earth. A planetary nebula is the glowing gas around a dying, Sun-like star.

The Helix appears to be round because we are looking at one end of the nebula. It is actually a trillion-mile-long tunnel of glowing gases.

These features are a forest of thousands of comet-like tentacles that are embedded along the inner rim of the nebula. The tentacles point toward the central star, which is a small but super-hot white dwarf [white dot in center of nebula] that seems to float in a sea of blue gas. These tentacles formed when a hot "stellar wind" of gas plowed into colder shells of dust and gas ejected previously by the doomed star. These comet-like tentacles have been observed from ground-based telescopes for decades, but never have they been seen in such detail. They may actually lie in a disk encircling the hot star, like an animal's collar.

The Helix Nebula is one of the closest of all planetary nebulae, lying at a distance of about 400 light years from Earth.

To find the nebula, start from Fomalhaut (Alpha Piscis Austrinus) and move your telescope 11 degrees northwest to 5th-magnitude 47 Aquarii. From this star slide two degrees east to Upsilon Aquarii, and you're almost there.

The Helix Nebula is just one degree west of this star.The planetary appears bright at magnitude 7.3, and a huge 12.8 arcminutes across. This is about half the size of the Full Moon! However, despite its large size the nebula is faint and has a low surface brightness, making it hard to pick out from the sky background.

Small scopes show NGC 7293 as a circular misty patch, and a 150-mm telescope reveals that the center is dark and contains a 13th-magnitude star.

If observed from a dark location the Helix is visible even with binoculars, that show the object as a large circular hazy spot. Rich-field instruments with wide-angle eyepieces are ideal for picking up objects like this on the night sky.

1 comment:

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