Ask An Astronomer 

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• We answer all questions at out discretion.. We will do our best to answer all questions, particularly from school age children (pre-school through 12th grade), but there is no guarantee of a response. Please read why don't we answer all questions for more information.
• For questions from the general public, we answer selected questions and post the answers on our web site approximately bi-weekly. (Why don't we answer all questions?)
• Before asking a question, please read our FAQ
• Please check the following websites. They have answered many of our most common questions!

• Seeing Back in Time
• Spiral Galaxies and Interactions
• Extrasolar Gas Giants

Older Newsletters:

• Oct 17, 2003 answers: Planets with retrograde rotation, Distance from the Earth to the Sun, Looking Back in Time, Expansion of the Universe,
• July 18, 2003 answers: Gamma Ray Bursts, Rings around Planets, Virtual Particles and Dark Matter, Learning about Dark Matter through Gravitational Lensing, Gravity waves,
• February 9, 2003 answers: Rings around the Moon, Duplicate Earths, The Observable Universe, The Interstellar Medium, The Expansion of the Universe, Seeing the Big Bang, Comets and Asteroids,
• November 16, 2002 answers: The color of observatories, the Space Shuttle, Satellites, Gravitational Lensing with the Moon, The Big Bang, Distances to Nebulae, Additional Planets in the Solar System, Light from Saturn, Moons around Moons, the Moon's rotation, Collapsing Star Clusters
• February 1, 2002: Formation of comet tails, coronal mass ejections, purchasing stars, galaxy groups in an expanding universe, and Groundhog Day.
• November 21, 2001: Viewing aurorae, asteroids hitting ice, shape of the Milky Way, Earth's not the center, and big extrasolar planets
• October 29, 2001: Color-blindness and astronomers, new planets and the frequency of life, stars outside of galaxies, the Moon's rotation, sound in space, and asteroid threats
• October 10, 2001: Measuring stars' masses, colorful twinkling of stars, the "dark ages" of the Universe, Earth's magnetic field reversals, and why comets have two tails
• Feb 16, 2001: Photographing Star Trails, Jupiter's Great Red Spot, Mars Rocks!, Accretion Disks, Ring Around the Moon

or search our archives

Many archived answers include links to other web sites. We do not update the archived answers, and, with time, many links become invalid. We apologize for this, and if a link doesn't work, we suggest you use your favorite search engine to look for a similar page. Thanks!

BLUE MOON - What is a blue moon? When is the next blue moon? Read the answers to our most popular question! Also, read about the mistake which started the entire blue moon craze from Sky and Telescope Magazine

All About Astronomers -- A short description of what astronomers do, a good resource if you would like to interview an astronomer for a class project.

The Solar System - Learn about our solar system with this excellent page by the Students for the Exploration and Development of Space

Extrasolar Planets - This page is an up-to-date collection of information on many of the planets known outside our own solar system.

The Constellations Web Page - A web page with detailed information on constellations and stars therein.

The American Meteor Society - information on meteors, meteor showers, meteorites. Has a form for reporting fireballs (very bright meteors). Please report meteors to the AMS and not to us. Thanks!

Sky & Telescope Magazine - comet finder charts, eclipse info, telescope reviews, amateur astronomy clubs directory. Did you see a bright star or planet in the sky? Check out their weekly and monthly sky highlights!

How do I Become an Astronomer? - A description from the American Astronomical Society of the steps to becoming an astronomer.

Yahoo! Astronomy Links - one of the most powerful search engines on the Web with its own astronomy web site database.

Bay Area Astronomy Programs -- San Francisco Bay Area organizations that provide public observing sessions and other public astronomical resources