Students' hands gather in a circle in Tanya Streicher's class at Gilpin Montessori School in Denver. Courtesy of Tanya Streicher hide caption

An artist's concept shows the WISE spacecraft in its orbit around Earth. NASA/JPL-Caltech hide caption

While Presidents Day is a time to think of America's commanders in chief, it is also a time when many stores have mattress sales. Patrick Fallon/Bloomberg via Getty Images hide caption

Windy City is Alison Krauss' first solo album in 18 years. Courtesy of the artist hide caption

Kim Jong Nam, the estranged half-brother of North Korean leader Kim Jong Un seen here in a May 2001 file photo, was alleged assassinated at the Kuala Lumpur airport last week. Shizuo Kambayashi/AP hide caption

Facebook claims to have 1.23 billion daily users globally. Mark Zuckerberg recently announced that he wants that number to grow and for users to conduct their digital lives only on his platform. bombuscreative/iStock hide caption

Susan Gallagher, chief naturalist at the Carbon County Environmental Education Center in Pennsylvania, examines the eagle that died from lead poisoning. Kevin Spotts hide caption