Object of the Week December 11th, 2016 - NGC 1501 The Oyster Nebula


NGC1501
PK144+6.1

Camelopardalis

Planetary Nebula


RA 04 06 59.6
DEC 60 55 11

Mag: 11.5
CS Mag: 14.3

Size: 52.0"

Discovered on November 3rd, 1787 by William Herschel, NGC1501 lies approximately 5000 light years distant in the constellation Camelopardalis. Williams' notes about his discovery that night read "a pretty bright...round, of uniform light and pretty well defined... and a little elliptical."

Visually, NGC1501 can be spotted in scopes as small as 4 inches. Sue French, in her wonderful book, Deep-Sky Wonders, reports that NGC1501 appears as a "small, round and fairly bright" in her 105mm refractor. In larger scopes, NGC 1501, atleast to me, resembles IC418 in Lepus. The resemblance is only similar in structure and not in color, where NGC1501 has a bright gray/green glow in my 25" and IC418 is a beautiful and rare pink/reddish color. NGC1501 does have a very mottled appearance similar to IC418. Larger scopes reveal a subtle oval shape that is aligned northeast to southwest with an apparent central star that shines at 14.3 magnitude. Annularity can be seen in magnifications greater than 350x though don't expect anything like M57. Here, the donut effect is muchmore subtle.

On a more scientific note, NGC 1501 has been a subject of study for quite some time. As printed in the Proceedings of the 180th Symposium of the Astronomical Union under the entry title Asteroseismology of Planetary Nuclei, Bond et al reported that in November of 1991, 5 observatories from around the world were in search of low amplitude pulsations of central stars in 29 known planetary nebulae. Of those 29, 6 were confirmed to have pulsing central stars, NGC 1501 being one of them. NGC1501, whose central star is a Wolf-Rayet star, has a period of 20-30 minutes and a variation of approximately 0.1 magnitude, much to low for us to detect visually of course. But what the researchers found interesting was that this WR star, at the heart of a planetary nebula no less, was a variable; something that isn't known to be too common.

So if you're far enough north, be sure to take a look towards Camelopardalis this winter. NGC 1501 is a beautiful PN visible in all manners of scope, so please don't be shy.

And as always,

Give it a go and let us know!

NGC1501_ESA_HST.jpg
©Hubble/ESA/NASA

ngc1501_adamblock.jpg
©Adam Block