"I began as an amateur, then I became a professional astronomer, and in retirement I am an amateur again."

– Dr. Bart Bok, leading expert of the 20th century on the Milky Way.

Astronomers are stargazers. Whether simply standing outside identifying a constellation for a child or employing the Hubble Space Telescope to search for the most distant objects in our universe, we all share the same universe. Unlike nuclear physics or molecular biology, astronomy is accessible to both amateurs and professionals. Sometimes, it's difficult to distinguish between them.

In "Science Educators Under the Stars: Amateur Astronomers Engaged in Education and Public Outreach," Marni Berendsen and Martin Storksdieck identified three sorts of amateurs:

The research level amateur astronomers have a long and valued relationship with the professionals. The AAVSO (American Association of Variable Star Observers) has collected data used by professionals for almost a century. More recently, amateurs have joined professionals in successful ground-based searches for transiting planets, which have been published as peer-reviewed papers in professional journals such as Astrophysical Journal. "Tooled-Up Amateurs Are Joining Forces with the Professionals" (Science, Oct. 12, 2007) describes these pro-am partnerships, and points to work being led by Rick Feinberg, editor of Sky and Telescope, to set up a registry for pro-am collaborations through the American Astronomical Society.

Astronomy enthusiasts are what I think of as armchair astronomers. Perhaps they own and use a telescope, but more likely they enjoy astronomy via books, magazines such as Sky and Telescope and Astronomy, and television and IMAX productions. Access to astronomy and space science has blossomed on the internet with Google Sky and Microsoft's yet-to-be-released World Wide Telescope project: Both aim to make astronomical discoveries more accessible to all of the public. I enjoy the Astronomy Picture of the Day, which delivers a tantalizing astronomical image each day. And, of course there's SPACE.com bringing daily astronomy and space science to the public plus blogs, and podcast science program such as the SETI Institute's weekly science program, "Are We Alone?" There's a veritable feast of astronomical information to graze on. Berendsen and Storksdieck estimate that there are 300,000 to 400,000 such enthusiasts in the US alone.

Observing amateur astronomers are out at night with their telescopes, enjoying and sharing the universe. There are about 750 amateur astronomy clubs with an estimated membership of 50,000. The American Astronomical Society, the major organization of professional astronomers, has a membership of about 7,350. The number of amateur astronomers far exceeds the ranks of the professionals. For most of the public, personal contact with an astronomer is very likely to be with an amateur astronomer.

NASA-JPL's Navigator Education and Public Outreach program and the Astronomical Society of the Pacific have partnered with the amateurs nationwide to form the Night Sky Network (NSN). Several NASA Missions – including the Kepler Mission that I work upon – have collaborated with the NSN to create kits of simple demonstrations to assist amateurs with outreach. Beginning in March 2004, the NSN has recruited amateur astronomy clubs that conduct outreach for the public. The NSN provides the kits of support materials to clubs, and the club members report on their outreach activities in return. Since 2004, the astronomy clubs in every state and Puerto Rico have reached out to more than 580,000 people to share the sky. This highly successful program continues to expand as more clubs join in.

Along with supporting outreach by amateurs, ASP has also worked with amateurs astronomers to understand the community, their needs, and their best practices. "Science Educators Under the Stars" (edited by Michael Gibbs, Berendsen and Storksdieck) captures the spark of excitement that amateur astronomers enjoy and share. This is an excellent handbook that describes the best practices and experiences of amateur and professional astronomers alike in conducting outreach.

I have my copy, and recommend it to anyone interested in learning more about sharing the sky.