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.
One of the most famous emission nebulae is the Orion Nebula (M42) located just below Orionâs belt. Another common type of emission nebula is a planetary nebula. These objects consist of a central white dwarf star surrounded by clouds of gas released as the original star evolved to the white dwarf phase.