IC 4593
A planetary nebula with a hot white dwarf and million-degree gas bubbles.
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.
- Discovery year
- 1907
- Discoverer
- Williamina Fleming
- Constellation
- Hercules
- Diameter light years
- 0.96
- Central star
- HD 145649
- Spectral type
- O7f
- Central star temperature k
- 30,000 to 40,000
Lore & Background
IC 4593 is homogeneous and amorphous, with little to no clustering compared to other planetary nebulae. The central star is surrounded by an asymmetrical inner core about 10 arcseconds across, which has a faint but fast gas flow reaching speeds over 100 kilometers per second. A dense ring-like structure encircles the star, and bright, low-ionized knots extend from the core into the inner halo, best seen in nitrogen emission lines. The inner halo is partially enclosed by a shell, creating a visible arc shape or bulge near the northwest part of the halo. The outer halo is irregular and unaligned with the inner halo, and is faint and fragmented.
Reader's Guide
IC 4593's significance lies in its structural complexity and the extreme conditions within it. A study published in 2020 found bubbles of extremely hot gas in its inner cavities, heated to over a million degrees, formed by stellar winds colliding with previously expelled gas. This makes it a valuable object for studying the dynamics of stellar winds and shock heating in planetary nebulae. The central white dwarf, HD 145649, is an O-type star with a spectral type of O7f and a temperature between 30,000 and 40,000 K, representing a late stage of stellar evolution. The nebula's asymmetrical inner core, fast gas flows, and low-ionized knots provide insights into the ejection and shaping processes of planetary nebulae. Its irregular outer halo further highlights the complex interactions between the central star and its surrounding environment.
Did You Know?
- IC 4593 is also called the White-Eyed Pea Nebula.
- It was discovered in 1907 by astronomer Williamina Fleming.
- The central star HD 145649 is an O-type star with spectral type O7f.
- Bubbles of gas in its inner cavities heat to over a million degrees.
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