Pictures: Hubble Spies Oddly "Perfect" Celestial Spiral

Cat's Eye Nebula

Image courtesy NASA/ESA

Unlike LL Pegasi, which is just starting to lose its outer layers of gassy material, the star that made the famed Cat's Eye nebula is further along in its demise: A white dwarf, the dense core of the dying star that formed the planetary nebula, is clearly visible in this 2004 Hubble picture.

(See another view of the Cat's Eye taken from California.)

The Hubble shot reveals a set of at least 11 faint rings around the white dwarf. These rings could have been made as the star ejected its matter in a series of pulses—or they could be evidence the dead star was once part of a binary system like LL Pegasi.

"Right now we see a single star, but that doesn't necessarily mean that it has always been a single star," JPL's Sahai said. "There are theories suggesting that a companion has been swallowed up by the main star."

Published September 9, 2010

Planetary Nebula NGC 2440

Image courtesy NASA/ESA

Not all dying stars leave such geometrically perfect remains, as evidenced by the uneven lobes of the planetary nebula NGC 2440, seen above in a 2007 Hubble picture.

The lone star that formed this nebula likely shed its mass unevenly during periodic outbursts that blasted gas and dust in many directions. Today its white dwarf—the hottest known—is giving off intense ultraviolet light that makes the surrounding stellar debris glow.

In about five billion years our sun will also end its life and give rise to a planetary nebula. (See "Red Giant Sun May Not Destroy Earth.")

Published September 9, 2010

Einstein Rings

Image courtesy NASA/ESA

Dying stars had nothing to do with this "bull's eye" in space. Instead, the double rings seen in a 2008 Hubble picture were created by a phenomenon called gravitational lensing.

Known as Einstein rings, the perfect circles of light come from two galaxies 11 billion and 6 billion light-years away. A massive third galaxy—the bright center of the bull's eye—sits directly in front of the other two just three billion light-years from Earth.

Because of the way the three galaxies are lined up, gravity from the nearest galaxy warps and magnifies the light from the farther two, creating the ringed effect. Such visible evidence of gravity bending light in space may help scientists map otherwise invisible dark matter.

Published September 9, 2010