The van den Bergh Catalogue

vdB 20

vdB 20, also known as the Pleiades (Messier 45) or the Seven Sisters, are an open star cluster containing middle-aged, hot B-type stars located in the constellation of Taurus. The cluster is dominated by hot blue stars that have formed within the last 100 million years. A faint reflection nebulosity around the brightest stars is likely an unrelated foreground dust cloud in the interstellar medium, through which the stars are currently passing. Astronomers estimate that the cluster will survive for about another 250 million years, after which it will disperse due to gravitational interactions with its galactic neighborhood.

(Source: Wikipedia)

vdB 139

vdB 139, also known as NGC 7023 or the Iris Nebula, is a bright reflection nebula in the constellation Cepheus. NGC 7023 is actually the cluster within the nebula, LBN 487, and the nebula is lit by a magnitude +7 star, SAO 19158. It shines at magnitude +6.8. NGC 7023 lies 1,300 light years away and is six light years across. It was discovered in 1794 by Sir William Herschel.

(Source: Wikipedia)