One of the most amazing achievements in astronomy in recent decades is the discovery of planets in other star systems — 5,000 of them and counting. And many of those systems are a long way off — hundreds of light-years.

Consider a binary system in Lynx. The faint constellation is in the northeast at nightfall, to the upper right of the Big Dipper. The system has the science fiction-sounding name XO-2. It’s named for the project that discovered the planets. The system is almost 500 light-years away.

Both stars — XO-2N and XO-2S, for north and south — are about the same size and mass as the Sun. The stars are hundreds of billions of miles apart — almost five thousand times the distance from Earth to the Sun.

Each star has two known or suspected planets. The planets of the south star are pretty close in, so they orbit the star in a few weeks or months. One of them is about a third the mass of Jupiter, the giant of our own solar system. The other is a little more massive than Jupiter.

XO-2 North has one confirmed planet and another possible one. The confirmed planet, which is about two-thirds the mass of Jupiter, takes less than three days to orbit the star. The possible world is almost twice Jupiter’s mass, and it takes at least 17 years to circle the star.

Astronomers continue to look for more planets around these distant stars.

Script by Damond Benningfield