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.
Nebulae are often star-forming regions, such as in the Pillars of Creation in the Eagle Nebula. In these regions the formations of gas, dust, and other materials clump together to form larger masses, which attract further matter, and eventually will become massive enough to form stars.mission nebulae, such as the Eagle Nebula, are vast, glowing clouds of ionised hydrogen and dust where stars are born. Others, such as planetary nebulae, are the bright shells of gas shed by dying stars. Despite their name, planetary nebulae have nothing to do with planets.