The sky around vdB 113 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 113 is a reflection nebula in Sagittarius, 5,200 light-years away
vdB 113 (LBN 40) is a reflection nebula in the constellation Sagittarius, 5,200 light-years away. spans 17′ of sky, about 26 light-years across. It is a telescope object, 6 inches or larger, and it is highest in the evening sky in August.
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 113 is vdB 113 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 165784, A2/3Iab, magnitude 6.4. He rated it faint in brightness and blue in color.
Finding vdB 113 from Kaus Borealis
vdB 113 lies 6.0° northwest of Kaus Borealis, the magnitude 2.8 star. Three fingers held at arm's length cover about 5°.
vdB 113 is highest in the evening in August
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 southern hemisphere and north to about 69°N, and never sets south of 69°S.
vdB 113 is 5,200 light-years away
The light seen from vdB 113 tonight left it about 5,200 years ago. It ranks 148 of 158 by distance among the Van den Bergh nebulae. Distance source: Gaia DR3 parallax of the illuminating star via AT-HYG v3.2 (1594 pc).
