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

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...

Fermi visualization of Milky Way bubbles

Q&A: Understanding the Fermi Bubbles

Sky & Telescope features a Q&A between The Kavli Foundation and three astrophysicists who discovered two enormous and unexpected structures radiating from the center of our galaxy. They discuss what these mysterious bubbles can tell us about the history of the Milky Way and how they could help in the search for dark matter.

Closed universe (top), open universe (middle), and flat universe (bottom). 

Is space flat or curved?

Locally, spacetime is curved by the presence of massive objects. The total mass and energy density of the universe also has an effect on the overall curvature of space.

The dark matter concentrations in the galaxy cluster Abell 1689 are tinted blue. Astronomers determined the location of those concentrations from gravitational lensing.
NASA, ESA, and D. Coe (NASA JPL/Caltech and STScI)

What is dark matter?

Dark matter is a mysterious type of matter that doesn't interact with any form of electromagnetic radiation, i.e., light. Although we’ve never detected dark matter directly, a large amount of evidence points to its existence.

Supermassive black hole, NASA/JPL-Caltech

How big is a black hole?

Black holes are singularities: points of infinitely small volume with infinite density. However, the amount of a mass concentrated in a black hole varies, and the mass determines how wide the black hole's sphere of influence is.