june 2012

planetary nebula
The planetary nebula Sharpless 2-71, as imaged by the Gemini Multi-Object Spectrograph on Gemini North in Hawaii. The long-assumed central star is the brightest star near the center, but some astronomers wonder if the dimmer and bluer star (just to the right and down a bit) might be the parent of this beautiful object. (Photo: Gemini Observatory/AURA)

A Mysterious Nebula, Captured Glowing Bright

The staff at Space.com reports that a telescope in Hawaii has captured a spectacular new view on a distant nebula, revealing a glowing swirl of gas that is at the center of an unsolved mystery surrounding the nebula's birth.

The photo above, from the Gemini North telescope in Hawaii, shows the complex planetary nebula Sharpless 2-71, which is located about 3,260 light-years from Earth in the constellation Aquila (The Eagle).

Planetary nebulas form when a star like our sun exhausts its hydrogen fuel. The star's outer layers expand and cool, creating a huge envelope of dust and gas. Radiation flowing from the dying star ionizes this envelope, causing it to glow.

Despite their name, planetary nebulas have nothing to do with planets. Rather, the term refers to their superficial resemblance to giant planets, when observed through early telescopes.

For decades, astronomers assumed that Sharpless 2-71 (Sh2-71 for short) formed from the death throes of an obvious bright star near the planetary nebula's center, which is prominent in the new photo. But now some researchers aren't so sure.

cosmic rose
This infrared image from NASA's WISE space telescope shows a cosmic rosebud blossoming with new stars, including the Berkeley 59 cluster and a supernova remnant. Photo: NASA/JPL-Caltech/UCLA

New observations have suggested that a dimmer, bluer star--visible just to the right and down from the bright central star--might actually be the nebula's "birth parent," researchers said.

The brighter central star--which is actually part of a binary system--doesn't appear to radiate enough high-energy ultraviolet light to account for the nebula's intense glow, the reasoning goes, whereas the bluer star likely does.

"At the assumed distance to the nebula, the faint star has about the right brightness to be the fading remnant of the nebula's progenitor star," said David Frew, of Macquarie University in Sydney, Australia, in a statement. Frew is part of a team of researchers studying the dim blue star to better understand its nature.

On the other hand, researchers said, the central star's binary nature would help explain the nebula's asymmetrical shape. It's not yet known if the central star's unseen companion is hot enough to cause the nebula's bright glow, or if the bluer star is part of a binary system.

rosetta nebula
A new image taken by NASA's Wide-field Infrared Survey Explorer (WISE) shows the Rosette nebula located within the constellation Monoceros (the Unicorn). This flower-shaped nebula is a huge star-forming cloud of dust and gas in our Milky Way galaxy, about 4,500-5,000 light-years away. Photo: NASA/JPL-Caltech/UCLA

It's possible, Frew added, that the central binary and the dimmer star could all have played a role in the nebula's evolution.

"So there could be at least three stars in this system," he said.

The strange and beautiful Sh2-71 has already attracted a fair bit of scientific attention, but more work needs to be done before researchers get a good handle on the mysterious object's history.

"The chaotic morphology of Sh2-71 implies that very complex processes have been involved in its formation," said Luis Miranda of Spain's Instituto de Astrofísica de Andalucía, who has studied the planetary nebula extensively.

ghost nebula
Ghost-Like Nebula Revealed in Haunting Space Photo: The ghost-like nebula, IRAS 05437+2502, includes a small star-forming region filled with dark dust that was first noted in images taken by the IRAS satellite in infrared light in 1983. This recently released image from the Hubble Space Telescope shows many new details, but has not uncovered a clear cause of the bright sharp arc. (Photo: NASA, ESA, Hubble, R. Sahai [JPL])

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