Ancient Planet

Thirteen billion years ago, a large planet formed in a distant cluster of stars. Remarkably, it's still there.

During the first billion years after the Big Bang, heavy elements like carbon, silicate and iron were rare in the Universe, since they had not yet been cooked up in large batches by the fiery furnaces of the stars. Until recently, most astronomers believed that planets could not have existed during this time, since most known planets are made from heavier elements. However, new data from NASA's Hubble Space Telescope suggests that at least one planet - a gaseous giant about 2.5 times the size of Jupiter - formed some thirteen billion years ago, long before our Sun and Earth ever existed.

The oldest and most distant planet found to date, this record-setter orbits a peculiar pair of burned-out stars in the crowded core of a globular star cluster called M4, which is located about 5,600 light-years away in the Scorpius constellation. Orbital measurements and other Hubble data have allowed astronomers to construct a rough history for this ancient planet, which originally orbited a sunlike star near the outside of the M4 cluster. Over time, the planet and its star were gravitationally captured by a neutron star, the sunlike star burned up its fuel, and the neutron star became a pulsar, sending out radio signals that eventually attracted the attention of astronomers.

The new find implies that planets could be much more abundant than astronomers previously thought, since many other ancient globular clusters could contain the same type of gaseous planets.

In this image, taken by NASA's Hubble Space Telescope, the white arrow points to a burned-out white dwarf star - one of the two stars that the ancient planet orbits. NASA and H. Richer (University of British Columbia)
An artist's rendering of the planet orbiting two stars - a neutron star and a white dwarf - in the globular cluster M4. The skies of the densely-packed cluster are remarkably starry. NASA and G. Bacon