The sky around vdB 7 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 7 is a reflection nebula in Cassiopeia, 213 light-years away
vdB 7 is a reflection nebula in the constellation Cassiopeia, 213 light-years away. spans 6.2′ of sky, about 0.4 light-years across. It is a telescope object, 6 inches or larger, and it is highest in the evening sky in December.
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 7 is vdB 7 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 HD 17138, A3V, magnitude 6.3. He rated it faint in brightness and moderately blue in color.
Finding vdB 7 from Segin
vdB 7 lies 8.0° northeast of Segin, the magnitude 3.4 star. A fist held at arm's length covers about 10°.
vdB 7 is highest in the evening in December
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 20°S, and never sets north of 20°N.
vdB 7 is 213 light-years away
The light seen from vdB 7 tonight left it about 213 years ago, around 1813 AD. It is the nearest of the Van den Bergh nebulae. Distance source: Gaia DR3 parallax of the illuminating star via AT-HYG v3.2 (65 pc).
