The oldest and most distant planet yet discovered has been found 5 600 light years from Earth. It is 800 times bigger than our own planet.
The Jupiter-like gas giant is believed to have been formed 13-billion years ago, more than eight billion years before any other planet identified so far and a mere one billion years after the Big Bang.
The discovery, announced two weeks ago, could force astronomers to rethink theories of how planets are made. The early universe had little of the relatively heavy elements such as carbon, silicon and oxygen, which experts think are needed to kick-start planet creation.
”This offers tantalising evidence that planet formation processes are quite robust and efficient at making use of a small amount of heavier elements,” said Steinn Sigurdsson, the professor at Pennsylvania State University who led the research. ”This implies that planet formation happened very early in the universe.”
His team found the planet by using images taken by the Hubble space telescope of a crowded star system called globular cluster M4 in the constellation Scorpius.
At the heart of the cluster is a bizarre celestial ménage àtrois: a pulsar — a star that emits pulses of radio waves — locked into orbit with a white dwarf — a dying star — and one other previously unidentified object.
It is this mysterious heavenly body that the scientists now say is a planet and probably a gas giant similar to Jupiter. They announced their findings last Friday in the journal Science.
Such globular clusters were thought unable to spawn planets because they lack the necessary heavy ”building blocks”. These heavy elements are churned out of the nuclear furnaces at the cores of stars and are, therefore, only abundant in much younger parts of the universe. The ancient M4 cluster that Sigurdsson’s team studied contains about a 30th of the heavy elements found in our own solar system.
The fact that planets can form in such an unlikely place means there could be a lot more of them than astronomers previously thought.
”It is tremendously encouraging that planets are probably abundant in globular star clusters,” said Harvey Richer, a professor at the University of British Columbia, Canada.
More planets means a greater chance of life; and the chance of forms of life that arose and died out billions of years before the Earth was even formed.
Hugh Jones, a planet hunter at Liverpool John Moores University, England, said the new finding was exciting, but cautioned against reading too much into it.
”This planet was found in rather a special environment,” he said.
The supernova explosion that created the pulsar would have thrown all sorts of material into space, something that could have disrupted the way the planet formed.
”What makes a planet is quite complicated and the processes are not well understood,” Jones said.
Scientists have found more than 100 planets outside our own solar system over the past decade. Two weeks ago Jones announced that he and his colleagues had found one very similar to Jupiter about 90 light years from Earth. — Â