The sky around vdB 23 at true scale, north up and east left, with stars to magnitude 8. The circles show the field of a low-power eyepiece and of 10×50 binoculars.
vdB 23 is a reflection nebula in Taurus, 440 light-years away
vdB 23 (Ced 19l) is a reflection nebula in the constellation Taurus, 440 light-years away. spans 27′ of sky, about 3.5 light-years across. It is a telescope object, 6 inches or larger, and it is highest in the evening sky in January.
Nebula: a cloud of gas and dust. Emission nebulae glow on their own, lit by ultraviolet light from hot young stars; reflection nebulae shine by starlight scattered from dust; dark nebulae block the light behind them.
vdB 23 is vdB 23 in the Van den Bergh catalog of reflection nebulae
Sidney van den Bergh listed it in his catalog of reflection nebulae (1966), drawn from the Palomar Sky Survey. He chose nebulae lit by a star bright enough to appear in the Bonner and Cordoba star catalogs. The star that lights it is Alcyone (Eta Tau), HD 23630, B7IIIe, magnitude 2.9. He rated it moderate in brightness and very blue in color.
Finding vdB 23 from ζ Per
vdB 23 lies 7.9° south of ζ Per, the magnitude 2.8 star. Three fingers held at arm's length cover about 5°.
vdB 23 is highest in the evening in January
The chart gives its height above the horizon at 9 pm through the year, from 60°N to 40°S. It can be seen from the whole northern hemisphere and south to about 66°S, and never sets north of 66°N.
vdB 23 is 440 light-years away
The light seen from vdB 23 tonight left it about 440 years ago, around 1586 AD. It ranks 8 of 158 by distance among the Van den Bergh nebulae. Distance source: Gaia DR3, Hunt and Reffert 2023 (Pleiades, M45).
