The word "whale" may bring to mind the image of a blue whale, the largest animal ever to have lived. But did you know that dolphins and porpoises are also specialized whales? Today, there about 80 species of living whales, or cetaceans. Among these marine mammals, there are two groups: baleen and toothed.

As observers of a meteor that crashed in Russia’s Chelyabinsk region today can attest, near-earth objects that enter the earth’s atmosphere can wreak destruction. But these objects, which also include comets and asteroids, also provide clues to the solar system’s origins and could someday serve as stepping-stones to space exploration. In this podcast, Manager of NASA’s Near-Earth Objects program, Donald Yeomans, discusses the ongoing quest to find near-earth objects before they find us.

Later today, an asteroid designated 2012 DA14 will pass just 17,200 miles over Earth’s surface. Although this 150-foot space rock will slip harmlessly by, researchers estimate there are nearly 500,000 near-Earth asteroids. So far, they’ve tracked the orbit of 9,600. How do researchers track asteroids, anyway? A Science Bulletins video explains more about the process, and more about the odds of an asteroid collision with Earth.

What's the difference between a meteor, a meteorite, and an asteroid? In the Museum's Arthur Ross Hall of Meteorites, curated by Denton S. Ebel, chair of the Division of Physical Sciences (Earth and Planetary Sciences), the differences are clearly explained.

Talk about an eventful Friday night! Tomorrow night, a small asteroid will travel nearer Earth than any astronomers have identified beforehand. “It’s the closest that we’ve seen ahead of time,” says Denton S. Ebel, curator in the Division of Physical Sciences (Earth and Planetary Sciences).

For more about the asteroid flyby, participate in a live Twitter chat with Ebel, this Friday, February 15, at noon ET. Post your questions here or use hashtag #asteroidchat on Twitter.