In this composite image, taken on July 2, 2011, Hubble's Wide Field Camera 3 captured the glow of hydrogen (blue), oxygen (green), and nitrogen (red).
Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
In this composite image, ionised hydrogen gas is shown in blue, oxygen gas in green, and nitrogen gas in red. The field stars appear mainly white, with a reddish tint, which is indicative of the older population stars that make up the disk of our Milky Way galaxy.
Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
MARYLAND: A newly discovered planetary nebula has been photographed by NASA's Hubble Space Telescope for the first time, revealing its dazzling ring shape.
The object, aptly named the Necklace Nebula, is the glowing remains of an ordinary, Sun-like star. The nebula consists of a bright ring, measuring 12 trillion kilometres wide, and dotted with dense, bright knots of glowing hydrogen and oxygen gas. Each knot also dons a small tail pointing away from the central star.
The Necklace Nebula is located 15,000 light-years away in the constellation Sagitta. Edge to edge, it is nearly nine light-years long, over twice the distance between our Sun and our nearest stellar companion, Proxima Centauri.
The work of binary stars
A pair of stars orbiting close together produced the nebula, also called PN G054.2-03.4. About 10,000 years ago one of the aging stars ballooned to the point where it engulfed its companion star. The smaller star continued orbiting inside its larger companion, increasing the giant’s rotation rate.
The bloated companion star spun so fast that a large part of its gaseous envelope expanded into space. Due to centrifugal force, most of the gas escaped along the star’s equator, producing a ring. The embedded bright knots are dense gas clumps in the ring.
The pair is so close, only a few million kilometres apart, they appear as one bright dot in the centre. The stars are furiously whirling around each other, completing an orbit in a little more than a day.
Evidence for the existence of the two-body system arises from the nebula's appearance of a half-light-year-wide equatorial ring of dense material near the inner portion of the nebula.
The clumpy appearance of the ring may have been caused by density fluctuations in the shared material of the binary stars prior to the explosion, or possibly by magnetic field lines present in the giant star as it began to expand and shed off its outer layers.
