A Jupiter-sized planet has been found orbiting a white dwarf star in the Milky Way, providing clues as to what will happen in our solar system when the sun finally dies.
An international team of astronomers has observed the phenomenon that occurs when a star runs out of nuclear fuel to burn and dies.
The distant planet, a gas giant 1.4 times the mass of Jupiter, survived the death of its host star.
The scientists say the discovery is in line with previous calculations that more than half of white dwarf stars may have similar giant planets. Although this phenomenon was predicted, it had never been observed before.
The study’s first author, Joshua Blackman of the University of Tasmania, said: “We estimate that this planet is some distance away. [from the white dwarf] Similar to Jupiter’s, it’s between 2.5 and six times Earth’s distance from the sun.”
Blackman said the discovery sheds light on what happens when the sun runs out of fuel. “We found a system that looks like what we expect to happen to our solar system five or six billion years from now.”
Within five billion years, the sun is expected to expand and transform into what is known as a red giant. “In this process, where the sun becomes a red giant, it will most likely destroy the inner planets… possibly Mercury and Venus will be destroyed,” Blackman said. Earth may survive the event, but it will not be habitable.
When the sun has completely run out of fuel, it will turn into a cold stellar corpse – a white dwarf.
Themiya Nanayakkara, an astronomer at Swinburne University of Technology who was not involved in the research, said the discovery suggests that outer gas giant planets like Jupiter and Saturn could survive the death of the sun.
“It rules out theories in the past that said planets couldn’t exist around white dwarfs,” Nanayakkara said.
A star’s size determines what it will eventually turn into: larger, heavier stars may instead become black holes or neutron stars.
Blackman said that about 95% of all stars in the Milky Way are eventually destined to become white dwarfs. “The universe is not yet old enough for that to happen.”
White dwarfs emit only weak light, making them nearly impossible to observe directly from ground-based telescopes. Instead, the team found the dead star using a technique known as gravitational microlensing, where light from a distant planet — the Jupiter-sized gas giant — is bent by the gravity of a closer star — in this case, a white dwarf.
Blackman said the discovery was “completely accidental.” “We expected to see a normal star like our sun. So we spent a lot of time fiddling with the data to determine if we made a mistake.”
Based on their observations, the team was able to rule out other possibilities for the dead star, such as a black hole or neutron star.
The study was published in the journal Nature.