Artist’s illustration of a distant white dwarf with an Earth-like planet orbiting just behind it … (+)
WM Keck Observatory/Adam Makarenko
What happens at the end of our world? Scientists have found an Earth-like planet orbiting a star 4,000 light-years away from the solar system, which could reveal our planet’s ultimate fate.
The rocky planet with a similar mass to Earth orbits a white dwarf star — the dense remains of a star that has exhausted its nuclear fuel and shed its outer layers — in the constellation Sagittarius.
Its existence means Earth can escape the fiery clutches of an expanding sun – and make it possible for humans to flee to the outer solar system, possibly to moons like Europa, Callisto and Ganymede near Jupiter and Enceladus around Saturn .
What is a white dwarf star?
A white dwarf is the inevitable end state of our Sun, but before it reaches that state it will go through a much more violent process. As it begins to run out of fuel, it will become a red giant star, expanding into the solar system before shrinking and becoming a white dwarf.
How far the red giant expands will determine which planets will be engulfed and destroyed – with Mercury and Venus likely to be consumed. What about the Earth?
What happened to the Earth-like planet?
In a paper published in Nature Astronomya team from the University of California, Berkeley, used the Keck Telescope in Hawaii to study a system called KMT-2020-BLG-0414, which found a white dwarf with an Earth-sized planet in orbit which is twice as large as that of Earth. Sun. There is also a brown dwarf – a huge planet about 17 times the mass of Jupiter – orbiting Earth.
This example of a planet – likely an Earth-like planet originally in a similar orbit to Earth – surviving the red giant phase of its host star lends credence to the theory that as the Sun expands and becomes a red giant, the its decreasing mass will force planets to migrate to more distant orbits, saving Earth from destruction.
“Whether life on Earth can survive during that (red giant) period is unknown. But the most important thing is that the Earth is not swallowed by the sun when it becomes a red giant.” said Jessica Lu, associate professor and chair of astronomy at UC Berkeley.
What will happen to Earth when the Sun enters its red giant phase?
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What will happen to the Earth?
Earth can technically survive the sun’s red giant phase, but its future is not bright. Scientists think the sun could bulge in as little as a billion years or even six billion years. In any case, despite doubling the size of Earth’s orbital path, the expansion of the Sun will eventually evaporate Earth’s oceans, leaving it a hot lava planet and completely uninhabitable. By eight billion years, what’s left of Earth could be orbiting a white dwarf.
“We currently have no consensus on whether Earth can avoid being engulfed by the red giant sun within six billion years,” said Keming Zhang, the lead author and former doctoral student at UC Berkeley who is now Eric and Wendy Schmidt. AI in Science Postdoctoral Fellow at UC San Diego. “In any case, Planet Earth will only be habitable for another billion years, after which Earth’s oceans will evaporate due to the runaway greenhouse effect – long before it is at risk of being swallowed by the red giant.”
Could humanity find refuge in the outer solar system? “If the Sun becomes a red giant, the habitable zone will move around the orbit of Jupiter and Saturn, and many of these moons will become ocean planets,” says Zhang. “Humanity could migrate there.”
I wish you clear skies and big eyes.