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.
A nebula is a cloud of dust and gas in space. Some of the clouds block out the light from the stars behind. These are called dark nebulae. One of the best-known is the Horse â¦ head Nebula.Other dust clouds reflect the light from the stars and shine brightly.These are called bright nebulae. nebula is a cloud of dust and gas in space. Some of the clouds block out the light from the stars behind. These are called dark nebulae. One of the best-known is the Horse â¦ head Nebula.