While there has been talk of "End Times" in recent years, what happens if we fast forward really far into our future, say around 8 billion years down the road? A distant rocky planet has recently offered scientists clues as to what might be in store for our home world.
The planet, known as KMT-2020-BLG-0414, with a mass about 1.9 times that of Earth, is orbiting a white dwarf about 4,200 light-years away from our solar system according to data from Hawaii-based telescopes. The white dwarf began as a star around 1-2 times the mass of our sun but its current size is a mere shell of that.
The planet originally orbited at about the same distance as Earth is to the sun. Following its star's demise, it is now twice that distance. "It's currently a freezing world because the white dwarf, which is in fact smaller than the planet, is extremely faint compared to when it was a normal star," said University of California, San Diego astronomer Keming Zhang, lead author of the study published in the journal Nature Astronomy.
Our sun, roughly four and a half billion years old, is eventually destined to become a white dwarf, just like KMT's. "At the end of our sun's life, it will puff up to enormous size — astronomers call it a red giant — and gently blow off its outer layers in a wind," UC-Berkeley astronomer and study co-author Jessica Lu said. "As our sun loses mass, the planets' orbits will expand to larger sizes. Eventually, the sun loses all of its outer layers and leaves behind a hot, compact core."
Astronomers have debated whether Earth would be engulfed and destroyed when the sun expands during its red giant phase. "Theoretical models disagree as to whether Earth could survive. Venus will most certainly be engulfed whereas Mars will most certainly survive. Our modeling shows that this planet very likely had a similar orbit to Earth before its host star became a red giant. It implies that Earth's chances for survival may be higher than currently thought," Zhang reported, adding that before our planet becomes a frozen wasteland, we might be able to escape to the icy moons Europa and Enceladus, which will become relatively balmy water worlds in our sun's latter days.