Y: In 1967 a team of astronomers in Great Britain thought they had found extraterrestrial intelligence. They discovered radio sources in deep space that produced pulses of energy at very precise intervals ranging from milliseconds to seconds. At first, the famed astronomer Carl Sagan thought the sources might be navigation beacons that aliens built to guide their starships through the galaxy.
D: Yeah, but it all turned out to be a false alarm. The energy sources are collapsed stars made of neutrons. They emit beams of energy that seem like pulses, because the stars rotate on their axes in less than a second. Astronomers named the stars pulsars.
Y: Still though, the idea that pulsar signals could be used for space navigation is a very good one.
D: But don't scientists track spacecraft through the solar system from stations here on Earth?
Y: Yes, but it's difficult, expensive, and gets less accurate as you go farther from Earth. In 2016 a team of European astronomers proposed using pulsar signals to navigate in deep space, much like we use the global positioning system here on Earth.
D: That sounds like you'd have to carry lots of bulky equipment on the spacecraft, instead of leaving it on Earth.
Y: No, the researchers don't need to put a giant radio telescope dish on the spacecraft. They can detect the pulses as x‑rays, with an x‑ray telescope just a few inches across. You'd also need a high performance atomic clock. The scientists plan to test their idea on a spacecraft that Europe will launch to the planet Mercury in 2018.D: Maybe, someday, we really will use pulsars as navigation beacons to guide our starships through the galaxy.