Alpha Centauri, the closest star system to Earth, is home to
three stars, one of which is so tantalizingly similar to our
sun that many experts speculate that its solar system might
contain habitable planets. But Alpha Centauri is about 4.3
light-years, or 25 trillion miles, from Earth. It would take a
spacecraft over 25,000 years—more than 300 lifetimes of
an astronomer—to reach it. When astronomers want to
investigate Alpha Centauri, other nearby star systems, or even
more remote objects like galaxies, they cannot rely on space
missions. Instead, they resort to the primary scientific
method of their discipline, a light analysis technique called
spectroscopy. In this interactive, learn the basics of
spectroscopy and use the technique to reveal the composition
of four different cosmic objects. To launch the
interactive, click on
the image at left.—Lexi Krock
