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 Carina Nebula contains two smaller nebulae â the Homunculus Nebula and the Keyhole Nebula. The Keyhole Nebula â a small, dark cloud of dust and with bright filaments of fluorescent gas, was named by John Herschel in the 19th century.