The Hubble Space Telescope has captured incredible new imagery of the Egg Nebula, providing astronomers with rare and precise details on the late-stage evolution of its central star.
Named for its resemblance to an egg, the star at the center of the nebula is obscured by a sprawling dust cloud, which contributes a yellow central coloration to the otherwise white mass of dust.
While the James Webb Space Telescope has been making headlines since its launch in December 2021, beginning operations the following July, the new imagery shows that Hubble remains important, providing scientists with new secrets of the cosmos, which could improve astronomers’ understanding of stellar evolution.
The Egg Nebula
Situated in the Cygnus constellation, the Egg Nebula, designated as CRL 2688, is 1,000 light-years from Earth. It is a pre-planetary nebula, a term that may be confusing, as planetary nebulae are unrelated to planets. Instead, planetary nebulae are enormous structures of gas and dust created from the deaths of Sun-like stars. A pre-planetary nebula is, therefore, a late-stage star about to make the final transformation into a planetary nebula.
Notably, the Egg Nebula is the first pre-planetary nebula ever discovered, first described in 1975. It is also the closest and youngest known pre-planetary nebula. Observing the Egg Nebula provides astronomers with a natural laboratory to test stellar evolution theories, as it is so early in its development.
Light reflecting from the central star lights up the Egg Nebula, exiting through the dust cloud’s polar eye. A dusty disk expelled from the star only a few hundred years ago allows light to escape. From the motions and shapes spotted as two beams of light from the central star illuminate the fast-moving polar lobes, which pierce an older, slower-moving set of concentric arcs, astronomers discern gravitational hints of additional hidden stars obscured by the dusty disk.
Hubble Spies the Egg Nebula
As Sun-like stars reach the end of their lives, burning their hydrogen and helium fuel, they shed their outer layers, exposing their cores. When this occurs, a glowing shell of gas forms as the hot core ionizes nearby gas. Known planetary nebulae such as the Helix, Stingray, and Butterfly all display this glowing shell of gas. As the Egg Nebula is still in this stage, in the midst of a transition expected to last thousands of years, researchers have an exciting opportunity to study the process at work.
The Hubble observation presents an ordered system, lacking the chaos expected of a violent supernova explosion. However, that order remains poorly understood. Astronomers believe that the arcs, lobes, and central dust result from events surrounding the star’s demise, yet remain unclear on how these processes operate.
Our own star system owes its existence to the earlier demise of such carbon-rich stars. These stars create and push out dust that settles into planet-forming disks, like the one that spawned our planet 4.5 billion years ago.
Hubble Keeps an Eye Out
This is not the first image Hubble has taken of the Egg Nebula. The WFPC2 (Wide Field and Planetary Camera 2) and NICMOS (Near Infrared Camera and Multi-Object Spectrometer) instruments captured complementary observations back in 1997, 7 years into the Hubble mission. More detail was captured in 2003, when the Advanced Camera for Surveys (ACS) showcased the dust ripples surrounding the Egg Nebula.
Almost a decade later, WFC3 (Wide Field Camera 3) provided new insights into the central dust cloud and gas outflows, which were expanded upon with further observations to create the new image. The researchers plan to directly compare this new image with previous observations to determine how minor details of the dusty shell have evolved over the past few years. The ultimate goal is to produce more precise models of planetary nebulae, enabling researchers to better understand the end stages of stellar evolution.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.