The Sun's nearest neighbor

Let's put some things into stark perspective: Using current chemical rocket technology, a crewed voyage to Alpha Centauri B would take 32,000 years! Such an impossibly long trek would require a multi-generation starship and vast amounts of fuel; in effect, such a starship would be a miniplanet in its own right with vast living areas, hydroponic gardens and livestock to nurture and sustain many generations of people in flight.

In 1987, NASA and the U.S. Naval Academy proposed Project Longshot, an ultra-fast robot probe intended to fly to Alpha Centauri powered by nuclear-pulse propulsion. As proposed, Longshot could reach the Alpha Centauri system within a century. This advanced rocket technology could be scaled up to power an ultra-fast manned mission-but then who would finance such a bold voyage?

Because Alpha Centauri A is a member of a triple star system, it appears as a single point of light from Earth. Both Alpha Centauri A and B are too close together to distinguish them as individual stars. Alpha Centauri C is simply too dim to be seen with the naked eye from Earth.

Alpha Centauri A and B orbit a shared center of gravity once every 80 years. Approximately 3.6 billion kilometers (2.2 billion miles) separate the two stars-about the distance between our Sun and the planet Uranus. Trio member Alpha Centauri C orbits A and B at 1,500 billion kilometers (930 billion miles) taking several million years to circle its distant stellar companions. Because C is so distant from its larger companions, an inhabitant living on a planet orbiting stars A or B, would have no idea that Proxima was even part of their stellar system.

NASA computer models suggest that Earth-like planets could form close to either Alpha Centauri A and B. Thus, the Alpha Centauri system may hold the best chance for finding extraterrestrial life beyond our solar system.

What's in the Sky: On the early morning of Friday, June 5, you can see a "triple play" of planets in the eastern sky-look for Mercury, Venus and Mars hovering just above the horizon (see accompanying sky map). Special thanks for J. Kirk Edwards for creating the Seeing Stars sky map.

Former NASA science writer Lou Varricchio, M.Sc., is a member of the NASA-JPL Solar System Ambassador program in Vermont. He is a second lieutenant in the U.S. Civil Air Patrol's Rutland Composite Squadron.

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