Astronomers have discovered the oldest and most distant planet known in the universe. The planet is so far away that it takes light 7,200 years to get here from there.

Artist's view of the planet (top) orbiting a pulsar and its white dwarf companion (two brightest dots at lower left) in the globular cluster M4.

NASA and G. Bacon/STScI

The new discovery is full of surprises. For one thing, scientists found it deep inside a dense cluster of stars called M4, which is about 12.5 billion years old. This means the planet itself is about that old, so it formed when the universe was just a baby.

Most planets found so far outside of our solar system orbit much younger stars. Our own sun and Earth are just under 5 billion years old. The new finding suggests that planets may have formed soon after the universe started, much earlier than scientists used to think.

To detect the new planet, Steinn Sigurdsson of Pennsylvania State University and his colleagues used observations from the Hubble Space Telescope and from a telescope on Earth that detects radio waves.

After comparing data from both sources, the researchers concluded that the new planet weighs 2.5 times as much as Jupiter. It orbits two stars at about the distance that Uranus orbits our sun.

Astronomers can now start looking for other planets in distant, old star clusters like M4. Maybe you can teach an old star new tricks!—E. Sohn