Cleopatra’s Eye (NGC 1535)

NGC 1535
NGC 1535: Image taken with the Hubble Space Telescope. © ESA/Hubble & NASA [477]

History

This planetary nebula was discovered on 1 February 1785 by William Herschel, observing with his large his 18.7 inch reflecting telescope of 20 feet focal length, located in Slough, England. He cataloged it as IV 26 and noted: «Very bright, perfectly round or very little elliptical, planetary but ill defined disk. 2nd observation. resolvable on the borders, and is probably a very compressed cluster of stars at an immense distance.» [463]

Herschels son John cataloged this nebula as h 2618, but did not include it in his Slough catalogue published in 1833. [466] In his «General Catalogue» of 1864 he listed it under the designation GC 826 and classified as globular cluster with the comments: «Very bright, small, round pretty suddenly very suddenly brighter in the middle, resolvable.» [467] In Dreyer's «New General Catalogue» appeared in 1888 the object is listed as NGC 1535 and classified as planetary nebula. [313]

Physical Properties

The planetary nebula NGC 1535 shows an unusual structure that is similar to the better-known Eskimo Nebula (NGC 2392). The nebula consists of a bright inner annular ring of diameter 20×17 arcseconds with the major axis oriented approximately at position angle 35°. It is surrounded by a attached, much fainter outer oval disc of 48×42 arcseconds size. The kinematics of NGC 1535 can be explained by assuming the inner shell to be of a spherical form but constricted by a torus of dens material. It expands with 21 km/s. The faint outer shell is spheroidal in form and expans slower with just 7.5 km/s. [478] Observations indicate that this PN is part of a gravitationally bound binary star system. [477]

The PN is located at a high galactic latitude. Measured distances are ranging from 1.2 kpc to 2.3 kpc. [145] Also the visual magnitudes found vary from 9.6 mag [149, 277] to 12.8 mag [145], probably confusing the brightness of the nebula with that of the central star.

«Strasbourg-ESO Catalogue of Galactic Planetary Nebulae» Acker et al., 1992 [141]
DesignationsPN G206.4-40.5: NGC 1535, PK 206-40.1, ARO 22, VV 19, VV' 25
Right Ascension (J2000.0)04h 14m 17s
Declination (J2000.0)-12° 44' 11"
Dimensions 21." (optical)
Distance 2.1 kpc
Radial Velocity-3.2 km/s ± 1.4 km/s
Expansion Velocity 20. km/s (O-III)
C-Star DesignationsAG82 29, BD -13 842, GCRV 2426, HD 26847, TD1 31084
C-Star Magnitude12.19 mag (B filter), 12.18 mag (V filter)
C-Star Spectral TypeO5, O(H)
DiscovererHERSCHEL 1785

Finder Chart

The planetary nebula NGC 1535 can be found in the constellation Eridanus, which is west of Orion and snakes southwards. The best observing time are the months October through March.

Chart Cleopatra’s Eye (NGC 1535)
Cleopatra’s Eye (NGC 1535) in constellation Eridanus. Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]

Visual Observation

320 mm aperture: The PN is easy to find and appears as a bright, fuzzy disk even at low magnification. With increasing magnification, darker structures appear in the nebula and the central star becomes visible. One also believes to see the few small stars in the disk of the PN, which led Herschel to believe that this is an unresolved globular cluster. A very beautiful planetary nebula! — 5 February 2022, Ibergeregg, Stefans 320 mm f/5 Dobsonian, 5 mm Baader Hyperion eyepiece, waxing crescent moon, -6 °C, a little bright, hazy sky plus stupid outdoor lighting of the restaurant, Bernd Nies

More Objects Nearby (±25°)

References

141Strasbourg-ESO Catalogue of Galactic Planetary Nebulae; A. Acker, F. Ochsenbein, B. Stenholm, R. Tylenda, J. Marcout, C. Schohn; European Southern Observatory; ISBN 3-923524-41-2 (1992); cdsarc.unistra.fr/viz-bin/cat/V/84 (2021-02-18)
145SIMBAD astronomical database; simbad.u-strasbg.fr/simbad
149SkySafari 6 Pro, Simulation Curriculum; skysafariastronomy.com
160The STScI Digitized Sky Survey; archive.stsci.edu/cgi-bin/dss_form
277«Historische Deep-Sky Kataloge» von Dr. Wolfgang Steinicke; klima-luft.de/steinicke (2021-02-17)
313«A New General Catalogue of Nebulae and Clusters of Stars, being the Catalogue of the late Sir John F.W. Herschel, Bart., revised, corrected, and enlarged» Dreyer, J. L. E. (1888); Memoirs of the Royal Astronomical Society. 49: 1–237; Bibcode:1888MmRAS..49....1D
463«Catalogue of one thousand new nebulae and clusters of stars» William Herschel, Philosophical Transactions of the Royal Society of London, 1 January 1786; DOI:10.1098/rstl.1786.0027
466«Observations of nebulæ and clusters of stars, made at Slough, with a twenty-feet reflector, between the years 1825 and 1833» John Frederick William Herschel, Philosophical Transactions of the Royal Society of London, 1 January 1833, Pages: 359-505; DOI:10.1098/rstl.1833.0021
467«Catalogue of nebulae and clusters of stars» John Frederick William Herschel, Philosophical Transactions of the Royal Society of London, 1 January 1864; DOI:10.1098/rstl.1864.0001
477Hubble Spies Eye in the Sky; nasa.gov/image-feature/goddard/2021/hubble-spies-eye-in-the-sky (2022-01-31)
478«A spatio-kinematic model for the multiple shell planetary nebula NGC 1535» Banerjee, D. P. K.; Anandarao, B. G.; Astronomy and Astrophysics, Vol. 250, p. 165, October 1991; Bibcode:1991A&A...250..165B