A remarkable latest image from NASA’s Hubble Space Telescope highlights a striking mixture of brightness and shadow contained in the Egg Nebula. This dramatic scene has been shaped by clouds of dust recently expelled by a dying star. About 1,000 light years away within the constellation Cygnus, the nebula surrounds a hidden central star buried inside a thick blanket of dust, resembling a glowing “yolk” inside a dark “egg white.” Hubble’s exceptional resolution reveals advantageous structures that help scientists understand how this unusual object is taking shape.
The Egg Nebula holds a special distinction. It’s the primary, youngest, and closest pre-planetary nebula ever identified. (A pre-planetary nebula is a precursor stage of a planetary nebula, which is a structure of gas and dirt formed from the ejected layers of a dying, Sun-like star. The term is a misnomer, as planetary nebulae will not be related to planets.)
A Rare Glimpse of Stellar Evolution
Since it is in such an early phase, the Egg Nebula offers astronomers a precious probability to check what happens as Sun-like stars approach the tip of their lives. At this stage, the nebula shines by reflecting light from its central star. That light escapes through a polar opening, or “eye,” in the encircling dust. The glow comes from a dusty disk that the star expelled only a couple of hundred years ago.
Two vibrant beams stream outward from the star, lighting up fast-moving polar lobes that punch through older, slower rings of fabric arranged in concentric arcs. The structure and motion of those features point to possible gravitational effects from a number of unseen companion stars, which remain concealed throughout the dense disk of dust.
From Dying Star to Planetary Nebula
Stars much like our Sun eventually run out of hydrogen and helium fuel and start shedding their outer layers. As the new core becomes exposed, it emits intense radiation that energizes the encircling gas, producing the glowing shells seen in planetary nebulae comparable to the Helix, Stingray, and Butterfly nebulae. The Egg Nebula, nevertheless, has not yet reached that fully developed stage. It stays in a short-lived transitional period often known as the pre-planetary stage, which lasts only a couple of thousand years. Observing it now allows scientists to look at the ejection process while the evidence continues to be fresh.
The patterns visible in Hubble’s image are highly symmetrical, ruling out a chaotic explosion like a supernova. As an alternative, the arcs, lobes, and central dust cloud likely formed through a coordinated series of sputtering outbursts deep throughout the carbon-rich core of the aging star. Stars at this stage manufacture and release large amounts of dust, material that may later turn out to be part of recent star systems. Our own solar system, including Earth and the opposite rocky planets, formed from such recycled material about 4.5 billion years ago.
Hubble’s Continuing Observations
Hubble has studied the Egg Nebula multiple times through the years. An early visible light image from WFPC2 (Wide Field and Planetary Camera 2) was followed in 1997 by a near infrared view from NICMOS (Near Infrared Camera and Multi-Object Spectrometer), offering a more in-depth take a look at the nebula’s glow. In 2003, the ACS (Advanced Camera for Surveys) revealed the complete sweep of dusty ripples surrounding the article. Observations from WFC3 (Wide Field Camera 3) in 2012 zoomed in on the dense central cloud and powerful gas outflows. The latest image combines data from the 2012 program with additional observations, providing the clearest and most detailed portrait yet of this intricate cosmic egg.
For greater than 30 years, the Hubble Space Telescope has continued to deliver discoveries that reshape our understanding of the cosmos. The mission is a partnership between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland oversees telescope and mission operations, with additional operational support from Lockheed Martin Space in Denver. The Space Telescope Science Institute in Baltimore, operated by the Association of Universities for Research in Astronomy, manages Hubble’s science operations for NASA.