Far in Space, a Glance at How Earth May End
By Gautam Naik
Astronomers have made the first direct discovery of a planet being ripped apart by the tremendous forces unleashed by a dying star, a possible glimpse into how the Earth will end its days.
The cosmic drama is occurring 570 light-years from Earth in the constellation Virgo. There, a sun-like star is reaching the end of its life and, in the process, annihilating its solar system. Specifically, the researchers discovered a small planet being vaporized by the star’s searing heat and ripped apart by its gravity.
“The planet is in its death throes,” said Andrew Vanderburg, Ph.D student at the Harvard-Smithsonian Center for Astrophysics and lead author of the study. “Every second, it’s losing up to 10 million kilograms,” or 22 million pounds of material.
The discoveries were made using the planet-hunting space telescope Kepler, operated by the National Aeronautics and Space Administration, as well as ground-based telescopes. Details were published Thursday in the journal Nature.
When a sun-like star runs out of the hydrogen that fuels its nuclear fusion reaction, it swells into an object that is 100-200 times its original size. This “red giant” eventually collapses into a much smaller body known as a white dwarf—an object that possesses intense gravity.
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Our sun will go through a similar process about five billion years from now, scientists say. Because of its nearness to the sun, there’s a chance that Earth will be engulfed by the red giant that forms.
Even if Earth survives the sun’s red giant phase, other forces will claim it. The subsequent white dwarf that is created could destabilize the orbits of planets—including Earth’s—and cause many of them to fall toward the white dwarf and disintegrate. That appears to be the scenario unfolding in Virgo.
“It’s a glimpse into the future of Earth,” said Carole Mundell, head of astrophysics at the University of Bath, England, who wasn’t involved in the Nature study. “It reinforces the idea that we are in a much more hostile environment than we sometimes imagine.”
Kepler searches for planets by looking for a telltale dip in brightness that occurs when an orbiting body crosses a star. In the summer of 2014, Kepler took measurements from 20,000 stars. When Mr. Vanderburg and his team studied the data, one signal jumped out at them: the transit of a body across a white dwarf that was dimming the star by 40%.
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Significantly, the planet is surrounded by a vast cloud of dust and debris. This is the material being blasted off its surface by gravity and the heat of the nearby white dwarf. It is evidence that the planet is disintegrating.
Scientists have speculated that when this happens, dust from the crumbling planet will settle on the surface of the host star. Mr. Vanderburg and his colleagues now plan to analyze that dust and from it infer what the dying planet is made of.
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