Lemon Slice Nebula

IC 3568 is a planetary nebula that is 1.3 kiloparsecs (4500 ly) away from Earth in the constellation of Camelopardalis (just 7.5 degrees from Polaris). It is a relatively young nebula and has a core diameter of only about 0.4 light years. It was dubbed the Lemon Slice Nebula by Jim Kaler, due to its appearance in one false-colour image from the Hubble Space Telescope.^[3][4] The Lemon Slice Nebula is one of the most simple nebulae known, with an almost perfectly spherical morphology. The core of the nebula does not have a distinctly visible structure in formation and is mostly composed of ionized helium.^[5] A faint halo of interstellar dust surrounds the nebula.

IC 3568

Emission nebula
Planetary nebula
Image of IC 3568 based on HST data
Observation data: J2000 epoch
Right ascension	12h 33m 06s
Declination	+82° 34′ 00″
Distance	Roughly 4.5⋅103 ly
Apparent magnitude (V)	12.3
Constellation	Camelopardalis
Physical characteristics
Radius	Core: 0.2 ly
Designations	IC 3568, Perek-Kohoutek 123+34.1 (PK 123+34.1),[1] HD 109540 (central star)[2]
See also: Lists of nebulae

False-colour image of the bright central region of IC 3568. This is the image that gave the nebula its common name.

The central star of the planetary nebula is a magnitude 12.8 O-type star with a spectral type of O(H)3. It is estimated to have a mass less than the Sun, a temperature of over 50,000 K, and a bolometric luminosity of about 2,400 L_☉.^[6]

IC 3568 was discovered on August 31, 1900 by the American astronomer Robert Grant Aitken while using Lick Observatory's 12" Clark refractor to observe comet Borrelly-Brooks. He noticed that the "star" BD+83°357 in Camelopardalis was actually a small nebula. He used the observatory's 36" refractor the next night to confirm that this was a round nebula.^[7] IC 3568 was mistakenly classified as a compact galaxy in the Uppsala General Catalogue, as UGC 7731.^[8]

See also

• NGC 40 (the Bow-Tie Nebula in Cepheus)