Helix Nebula

The Helix Nebula is the nearest planetary nebula to Earth, making it one of the largest in apparent angular size — spanning more than half a degree on the sky, larger than the full Moon. Its closeness makes it a prime target for detailed structural studies.

Often nicknamed the “Eye of God,” the Helix has a complex, layered structure that reveals multiple episodes of mass loss from the central star. The inner disk was ejected more recently than the outer halo, creating a nested shell appearance. High-resolution Hubble imaging shows thousands of cometary knots — compact, comet-shaped gas clouds — distributed throughout the inner ring, each roughly the size of the Solar System with heads pointing toward the central star and tails extending radially outward.

The blue-green inner region glows from doubly ionized oxygen at temperatures around 20,000 K, where the UV radiation from the central star is most intense. The outer red ring is dominated by cooler hydrogen and nitrogen at greater distances from the star.

The white dwarf at the center has a surface temperature of roughly 120,000 K — one of the hottest known. It will cool over billions of years to eventually become a dark, inert cinder.