IC 4593

IC 4593, called the White-Eyed Pea Nebula, lies in the constellation Hercules. Astronomer Williamina Fleming spotted it in 1907. This planetary nebula spans about 0.96 light-years. At its heart sits a hot white dwarf, HD 145649, an O-type star classified as O7f, with a temperature between 30,000 and 40,000 K. A 2020 study revealed bubbles of extremely hot gas inside its inner cavities, where the gas reaches over a million degrees, created when stellar winds slammed into previously expelled gas.

The nebula is uniform and shapeless, showing little clumping compared to other planetary nebulae. Its central star is wrapped in an asymmetrical inner core roughly 10 arcseconds across. This core has a faint, fast gas flow exceeding 100 kilometers per second. A dense, ring-like structure encircles the star.

Bright, low-ionized knots extend from the core into the inner halo, most visible in nitrogen emission lines. The inner halo is partly enclosed by a shell, forming a visible arc or bulge near the northwest side. The outer halo is irregular and misaligned with the inner one, faint and broken into fragments.