Today marks the birth of 18th-century astronomer Frederick William Herschel. Born November 15, 1738, Herschel made many discoveries during his lifetime. Most notable among his contributions to astronomy include determining the shape of the Milky Way, determining the rotation period of Saturn's rings, and sketching changes in Jupiter's atmosphere. Discoveries Mars and Jupiter show axial rotation Planet Uranus (1781) Uranus's two largest...

If you've followed my blogging, you know I love books. On Friday, November 2, I visited Linda Hall Library in Kansas City with Astronomy Editor David J. Eicher and contributing editor Raymond Shubinski. Linda Hall ranks as one of the world's finest science libraries, and it has a terrific collection of rare astronomy books. During the visit, we sat at a table and paged through a first edition of Isaac Newton's Principia — the book in which...

This month brings the 50th anniversary of two events that changed the world. The first, of course, needs little explanation: On October 4, 1957, the Space Age began with the Soviet Union's launch of the Sputnik 1 spacecraft. I want to talk about the event you probably aren't aware of. The October 1957 issue of Reviews of Modern Physics contains the article "Synthesis of the Elements in Stars" by Margaret Burbidge, Geoffrey Burbidge...

In this blog and my next, I'm going to try to demystify the magnitude system — the scale astronomers use to measure the brightness of a celestial object. Let me start with a little history. The first known observer to describe and catalog differences in star brightnesses was Greek astronomer Hipparchus (ca. 190–120 B.C.). He divided his catalog of roughly 850 visible stars into six brightness ranges, or magnitudes. He called the brightest 1st...

An interesting question hit my inbox this week. How far south can an aurora be seen? Specifically, are the “northern lights” ever visible from Timbuktu? A 2004 New York Times article about medieval Arabic manuscripts triggered the question. The city of Timbuktu, Mali, was one of Africa’s intellectual hubs when the Renaissance was barely a twinkle in Europeans’ eyes. The article focused on efforts to rescue the ancient manuscripts. One 16th-century...