NGC 1501 is a planetary nebula with a complex structure, located in the northern constellation of Camelopardalis. It has the proper names Camel's Eye Nebula and the Oyster Nebula.[3] The nebula was discovered on 27 August 1787 by the British-German astronomer William Herschel.[5][6] The central star of NGC 1501 is located at a distance of approximately 3,840 light-years (1.177 kpc) from the Sun, and is 29,280 light-years (8.978 kpc) from the Galactic Center.[2]
Properties
A TESSlight curve for CH Camelopardalis, adapted from Córsico et al., (2021)[7]
Designated CH Camelopardalis,
spectral type of [WC4], similar to that of a carbon-rich Wolf–Rayet star.[9] It is a pulsating star, meaning that its brightness varies regularly and periodically.[8] In the case of NGC 1501's progenitor star, this is incredibly fast, with the star's brightness changing significantly in just half an hour. An analysis of Gaia data suggests that the central star is a binary system.[10]
The overall shape of the nebula is close to a thin-shelled
major axis spans an angular size of 44″.[11] There are a large lobes along the axes, with smaller bumps scattered across the surface. The three dimensional form has been described as a "boiling, tetra-lobed shell".[12] Visible-light observations capture the glow of gases including hydrogen and nitrogen.[13] Density peaks have a particle densities of up to 1,400 cm−3. The temperature of the free electrons in the nebula measured at up to 11,500 K, and the nebula turbulence is 18 km/s.[12]
The total mass of the nebula is estimated to be around 0.22 M☉, most of which is ionized gas (0.21 M☉) and a small fraction (8.9×10−4M☉) is carbon-rich dust.[14] Expansion velocities range from 38 to 55 km/s.[12] The estimated mass of the central star prior to entering the asymptotic giant branch stage and shedding its outer layer was 0.80–0.88 M☉.[14]
Gallery
The location of NGC 1501 (circled in red)
NGC 1501 from the 0.8m Schulman Telescope at the Mount Lemmon SkyCenter
Bond, H. E.; et al. (December 1996). "Asteroseismological Observations of the Central Star of the Planetary Nebula NGC 1501". Astronomical Journal. 112: 2699.
The location of NGC 1501 (circled in red)
NGC 1501 from the 0.8m Schulman Telescope at the Mount Lemmon SkyCenter
Media related to NGC 1501 at Wikimedia Commons
