The vastness of the universe, explored and unexplored, presents possibilities for all of us to imagine new and different (and perhaps better) worlds, technological feats, and ourselves as active participants in the quest for knowledge beyond our own planet.

A good space book captures this melding of anticipation and discovery that lies at the heart of space exploration.

Space books generally touch on one or both of two major themes. First, there are books that feature astronomy — the science-focused books — that explain our knowledge of the planets, stars, and the universe, of comets and nebulae and black holes and all sorts of fascinating, mind-bending deep space phenomena. Then there are those that foreground space exploration — the technology-focused books — that introduce the engineering innovations like telescopes, spacecraft, and rockets that give us better access to what’s beyond our atmosphere. Cutting across and anchoring these two themes are people — the scientists engaged in discovery, the engineers who produce the craft, and the astronauts who get to fly them — and the possibility that young readers, too, could take on any of those roles.

Astronomy is first and foremost a visual field. Humans and machines have only physically been to a few extraterrestrial sites, so focusing on images is integral to the practice of astronomy. A good astronomy book puts visuals front and center. From old-school naked-eye stargazing to the latest in imaging technology, what we see is the data on which the field of astronomy rests. It’s hard to resist the beauty of the orangy-red planet Mars, a close-up of the sharp edge of a ring of Saturn, or the swirling stripes and whorls of the storm-produced clouds of Jupiter. The definitive images in this category belong to Seymour Simon, whose books on planetary bodies (Comets, Meteors, and Asteroids; Our Solar System; Venus; Destination: Space, etc.) set the bar so high that the many lower-quality solar system series books quite literally pale in comparison. Of course, others besides Simon have produced excellent image-centric books. Twenty years of distortion-free images from the Hubble Space Telescope, most recently covered brilliantly in Elaine Scott’s Space, Stars, and the Beginning of Time: What the Hubble Telescope Saw, have given researchers and the public alike access not just to better pictures of the planets but to invitingly mysterious nebulae clouds and distant clusters of star-peppered galaxies. First-rate images can also be found in Sally Ride and Tam O’Shaughnessy’s books (Mystery of Mars, Voyager: An Adventure to the Edge of the Solar System, and Exploring Our Solar System) — and who can beat learning planetary science from a physics PhD who also happens to be one of our most famous former astronauts?

A good astronomy book, however, doesn’t let readers just admire the pretty colors and move on. It also assists us in understanding the technical elements of image production, in a way, changing how we “see.” Some of the pictures in these books are not photographs in the sense we’re used to, but in fact number-crunched, color-enhanced renderings of a wider-than-visible spectrum of electromagnetic waves emitted from astronomical bodies. Others are artists’ conceptions that use scientific knowledge but take some liberties in imagining what such places as the surface of a distant planet or the inside of a future spacecraft might look like. Critical information accompanying the illustrations helps readers clearly delineate among what’s real, enhanced, or imagined.

Of course, we can’t forget that, prior to all sophisticated telescopes and satellite imaging equipment, there were centuries of astronomers just staring up at the sky. Historical accounts such as Peter Sís’s profile of Galileo in Starry Messenger and Boy, Were We Wrong about the Solar System! by Kathleen V. Kudlinski explain the impressive amount of astronomical knowledge determined before modern times.

They also introduce the social and historical contexts of scientific inquiry. Ideas are transformed over time not just with better access to data but with changes in prevailing thought and social conventions. Thinking about what lies beyond the earth, and how it got there, has meant significant conflicts with religious beliefs during periods of Western history in particular. These biographical and historical accounts help us understand the many factors affecting scientific practice.

Children begin with just their eyes, too, and are greatly assisted by Franklyn M. Branley’s classic contributions to the venerable Let’s-Read-and-Find-Out Science series (the originals are the best, such as The Moon Seems to Change and What Makes Day and Night?) and the still-in-print constellation guides produced by H. A. Rey (The Stars and Find the Constellations). These books are great because they start children where the astronomers started, learning to recognize the objects in the sky and to notice their patterns of movement. Branley’s books are the definitive example of how to explain space concepts in remarkably comprehensible language, and the match of concepts to target age is absolutely perfect. These books may not have the sleek photo images of the books described above, but the charm of Rey’s star charts, or the friendliness of the Let’s-Read illustrations, certainly do the trick. There are a few recent revisions to the Let’s-Read books, also found in lesser astronomy books, that take the whimsy a bit too far. Overly stylistic, mid-century retro cartoons that violate the scientific principles they’re illustrating are a no-no, and there should never, ever be an alien in a good astronomy book — unless we reach the time when scientists have found some.

Though astronomy books are dominated by, well, astronomy, there are other scientific fields engaged in planetary exploration that when included enhance the quality of space books. Indeed, increasingly more important as we develop newer technologies and focus research efforts beyond just documentation and imaging is the cross-disciplinary potential of fields like planetary geology and exobiology. We have sensors that can remotely assess chemical compositions of rocks on the surface of a planet; we have actual samples from Mars and the moon; and researchers are actively exploring ways in which life might exist outside of the conditions we find normal. Exobiology, in particular, taps into that thrilling thought that there might be life other than us in the universe, and the science is cutting edge and complicated. Two notable profiles of scientists in search of life in outer space include Ellen Jackson’s Looking for Life in the Universe: The Search for Extraterrestrial Intelligence, which features Jill Tarter, director of the SETI (Search for Extra Terrestrial Intelligence) Institute, and Vicki Oransky Wittenstein’s Planet Hunter: Geoff Marcy and the Search for Other Earths. If there are aliens worthy of illustration in a children’s book, Marcy, Tarter, and their colleagues will be the ones to find them.

Or perhaps someday a space explorer will meet them. The fascination we have with actually going to outer space, and the massive technological (and financial) efforts exerted to put humans into space, make for some of the most compelling space books available. The recent fortieth anniversary of the Apollo 11 mission — the one where humans walked on the surface of the Moon for the very first time — was the impetus for some truly outstanding space books that capture the wide-open possibilities and space fervor of the 1960s. Andrew Chaikin’s Mission Control, This Is Apollo: The Story of the First Voyages to the Moon surveys all of the Apollo missions, personalized by the inclusion of astronaut Alan Bean’s impressionistic paintings and commentary, and effectively conveys the full scope of the Apollo program as it progressed from rocket building to flight testing to actual scientific missions. Moonshot: The Flight of Apollo 11 by Brian Floca is a masterful yet intimate telling of the Apollo 11 story, reflecting what it must have been like to be there for the mission, be it as an astronaut in the spacecraft or a spectator watching on TV. Readers can also get the astronaut perspective from Buzz Aldrin himself in Look to the Stars, and can very convincingly place themselves in a virtual mission by reading the second-person narration of Faith McNulty and Stephen Kellogg’s If You Decide to Go to the Moon, winner of the 2006 Boston Globe-Horn Book Award for Nonfiction.

Not all children have had equal opportunities to see themselves as space explorers, however, as the barriers faced by women and people of color attempting to enter the space program (at least in the United States) were not overcome until the late 1970s. Tanya Lee Stone’s noteworthy Almost Astronauts: 13 Women Who Dared to Dream presents an unvarnished history of the “Mercury 13” — the accomplished women who tried but failed to get into the American space program in the early 1960s — and the times in which they lived. A good space book like this one compels readers to discuss its implications, perhaps with their elders who lived through this era, to reflect on what still hasn’t changed about our expectations for women in space, and to appreciate what has.

What era are we living in today? Although we’ve had two more prominent space programs — the space shuttle and the International Space Station — there doesn’t seem to be similar enthusiasm in the book world to produce compelling stories about the last few decades of American efforts in piloted space missions. Do peacetime international cooperative agreements and an increased commercial outsourcing lack the frisson of the Cold War quest for space domination? With now hundreds of astronauts walking the Earth, do none stand out in our collective mind? Sure, there are plenty of lower quality books diagramming rocket parts or providing hero bios of various astronauts, but few are noteworthy. Two notable books about more recent space technologies (Floating in Space and The International Space Station) come, not surprisingly, from Franklyn M. Branley and the Let’s-Read series again, this time illustrated by True Kelley, but, published in 1998 and 2000, respectively, they’re starting to show their age.

Perhaps it is because the coolest missions going on right now are the human-free, computer-controlled ones. A series of trips to Mars in the past decade, fronted by the appealing Wall-E-like rovers, have been featured in superior books such as the latest in this category, Cars on Mars: Roving the Red Planet by Alexandra Siy. Hopefully the upcoming NASA missions, even sans humans, will spark additional interest. Or perhaps it will be the scientists, not astronauts, who serve to inspire and motivate the next generation of space dreamers.

Good Space Books

Look to the Stars (Putnam, 2009) by Buzz Aldrin; illus. by Wendell Minor

Floating in Space [Let’s-Read-and-Find-Out Science] (HarperCollins, 1998) by Franklyn M. Branley; illus. by True Kelley

The International Space Station [Let’s-Read-and-Find-Out Science] (HarperCollins, 2000) by Franklyn M. Branley; illus. by True Kelley

The Moon Seems to Change [Let’s-Read-and-Find-Out Science] (Crowell, 1960) by Franklyn M. Branley; illus. by Helen Borten (reissued by HarperCollins in 1987 with illus. by Barbara and Ed Emberley)

What Makes Day and Night? [Let’s-Read-and-Find-Out Science] (Crowell, 1961) by Franklyn M. Branley; illus. by Helen Borten (reissued by HarperCollins in 1986 with illus. by Arthur Dorros)

Mission Control, This Is Apollo: The Story of the First Voyages to the Moon (Viking, 2009) by Andrew Chaikin; illus. by Alan Bean

Moonshot: The Flight of Apollo 11 (Jackson/Atheneum, 2009) by Brian Floca

Looking for Life in the Universe: The Search for Extraterrestrial Intelligence [Scientists in the Field] (Houghton, 2002) by Ellen Jackson; photos by Nic Bishop

Boy, Were We Wrong about the Solar System! (Dutton, 2008) by Kathleen V. Kudlinski; illus. by John Rocco

If You Decide to Go to the Moon (Scholastic, 2005) by Faith McNulty; illus. by Steven Kellogg

Find the Constellations (Houghton, 1954) by H. A. Rey

The Stars (Houghton, 1952) by H. A. Rey

Exploring our Solar System (Crown, 2003) by Sally Ride and Tam O’Shaughnessy

Mystery of Mars (Crown, 1999) by Sally Ride and Tam O’Shaughnessy

Voyager: An Adventure to the Edge of the Solar System [Face to Face with Science] (Crown, 1992) by Sally Ride and Tam O’Shaughnessy

Space, Stars, and the Beginning of Time: What the Hubble Telescope Saw (Clarion, 2011) by Elaine Scott

Comets, Meteors, and Asteroids (Morrow, 1994) by Seymour Simon

Destination: Space (HarperCollins, 2002) by Seymour Simon

Our Solar System (Morrow, 1992) by Seymour Simon (revised edition from HarperCollins, 2007)

Venus (Morrow, 1992) by Seymour Simon

Starry Messenger: A Book Depicting the Life of a Famous Scientist, Mathematician, Astronomer, Philosopher, Physicist, Galileo Galilei (Foster/Farrar, 1996) by Peter Sís

Cars on Mars: Roving the Red Planet (Charlesbridge, 2009) by Alexandra Siy

Almost Astronauts: 13 Women Who Dared to Dream (Candlewick, 2009) by Tanya Lee Stone

Planet Hunter: Geoff Marcy and the Search for Other Earths (Boyds Mills, 2010) by Vicki Oransky Wittenstein

From the November/December 2011 issue of The Horn Book Magazine.