Science-based Q&A

Browse the questions and answers below to deepen your knowledge of astronomy as a science. Learn the facts about the universe’s fascinating array of celestial bodies, from planets to stars to black holes. Discover the difference (and evidence for) dark energy and dark matter. And learn about worlds closer to home such as Venus and Saturn.

The Q&As presented here probe a variety of topics. When will Earth see its last total solar eclipse? How many stars are in the Milky Way galaxy? How do you calculate the density of a black hole? Read on to discover the answers, and ask your own astronomy questions by sending a note to

Low Sun, Long Shadows and Icy Atmospherics

What is the Winter Solstice?

The moment the Sun reaches its southernmost point in the sky marks the December solstice, the official beginning of winter in the Northern Hemisphere (where it is called the winter solstice) and a time of great celebration in many northern cultures.

High-Definition Space Telescope (HDST)

Kavli Foundation Q&A: Searching for Alien Life with a “Super-Hubble” Space Telescope

Watch a Q&A with two astronomers on the promise of Hubble's successor telescope, courtesy of The Kavli Foundation. Scientists have unveiled a bold proposal for a giant new space-based telescope that would be far more powerful than today's observatories. Called the High Definition Space Telescope (HDST), the instrument is essentially a supersized Hubble Space Telescope,…