NGC 1535 is a planetary nebula in the equatorial constellation of Eridanus. It is known as Cleopatra's Eye, and is located around 5500-7500 light years away from Earth. This nebula was discovered by German-British astronomer William Herschel on February 1, 1785. The object is included in the Astronomical League's Herschel 400 Observing Program.
Characteristics It is very similar to the Eskimo Nebula in both color and structure. It has a round exhibiting moderate ellipticity. The dust distribution inside NGC 1535 is uniform and nearly round in shape. It displays a dust halo with a noticeable inner ring of increased intensity.R A Pignata, W A Weidmann, E O Schmidt, A Mudrik, D Mast, Dust distribution in planetary nebulae, Monthly Notices of the Royal Astronomical Society, Volume 528, Issue 1, February 2024, Pages 459–480, https://doi.org/10.1093/mnras/stad3568 Outside this ring is a faint oval disk, note quite symmetrical with the main nebula. This region shows faint traces of ring formation in the southeastern region. The nebula seems to have formed in a somewhat metal-poor region having undergone little or no enhancement of elements mixing with nuclear-processed material.
NGC 1536 is a bright, high-excitatory nebula.Louise, R. & Pascoli, G.. (1985). Study of three high excitation planetary nebulae in the Southern Hemisphere - NGC 1535, NGC 2440, NGC 2452. Astronomy and Astrophysics. 150. 285-297. Spectra of NGC 1535 from ROSAT reveal of “double hump” shape with approximately one-third of the photons are within the high energy range with more than 0.5 keV. These high energies could not simply have been produced by a stellar photosphere, even with the central star having a temperature of 250,000 Kelvin.
Observations by Leahy et al. using ROSAT reported X-ray emissions from NGC 3587 and NGC 1535. However comparisons between optical and X-ray images shows that these X-ray emissions coincide with a star that was outside the optical boundary of the nebula. This would make previous reports of X-ray emission from NGC 1535 likely false. Observations were taken using ROSAT High Resolution Imager which clearly confirms that the X-ray emissions contain three peaks that are point sources (RX J111447.9+550106, RX J111450.9+550208, and RX J111504.9+550141). Only the first of these sources are projected to be from the central star.
Central star At the center of NGC 1535, there is a O-type star with a spectral type of O(H)5. It is difficult to visually observe with a magnitude of 10. This star has a mass of 0.59☉ and a temperature of 66,000 Kelvin. The star produces stellar winds with a terminal velocity of about 200 km/sec. These stellar winds are suspected to be the dominant force, shaping the morphology of the nebula to a round shape.Adam, J. & Köppen, J.. (2017). Influence of the Stellar Wind on the Nebular Ionization in NGC 1535 and 4361. Symposium - International Astronomical Union. 103. 338-339. 10.1017/S0074180900093888.
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