Along with the brown bear, it is one of only two of the eight modern bear species not considered globally threatened with extinction by the IUCN. American black bears often mark trees using their teeth and claws as a form of communication with other bears, a behavior common to many species of bears.
Planetary nebulae are astronomical objects made up primarily of gaseous materials. They are extended in size and fuzzy in appearance, and generally show some degree of symmetry. The nebula is illuminated by a central star, which sometimes is too faint to be seen.
The first Planetary Nebula to be discovered was the Dumbbell Nebula (M27), but I think the Crab Nebula (M1) was discovered earlier-this is a supernova remnant.he Andromeda Galaxy was called the Andromeda Nebula before this. Back to the actual answer, the first nebulae were found and cataloged by Charles Messier in the 18th century.