Figure 18-4: R I V U X G
A Dark Nebula When first discovered in the late 1700s, dark nebulae were thought to be “holes in the heavens” where very few stars are present. In fact, they are opaque regions that block out light from the stars beyond them. The few stars that appear to be within Barnard 86 lie between us and the nebula. Barnard 86 is in the constellation Sagittarius and has an angular diameter of 4 arcminutes, about 1/7 the angular diameter of the full moon.
A Dark Nebula When first discovered in the late 1700s, dark nebulae were thought to be “holes in the heavens” where very few stars are present. In fact, they are opaque regions that block out light from the stars beyond them. The few stars that appear to be within Barnard 86 lie between us and the nebula. Barnard 86 is in the constellation Sagittarius and has an angular diameter of 4 arcminutes, about 1/7 the angular diameter of the full moon.
(Australian Astronomical Observatory/David Malin Images)