For more than 40 years, astronomers have been puzzled by strange X-ray signals coming from the Helix Nebula, a cloud of gas left behind by a dying star.
Now, thanks to powerful space telescopes, scientists believe they have found the answer: a nearby planet was torn apart by the white dwarf at the center of the nebula.
The Helix Nebula is about 650 light-years from Earth. At its heart is a white dwarf called WD 2226-210, the leftover core of a star that shed its outer layers long ago.
Normally, white dwarfs don’t give off strong X-rays, but this one has been shining mysteriously for decades.
Scientists first detected these X-rays in 1980 with older telescopes. New data from NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton has helped solve the mystery.
According to the latest study, the X-rays likely come from the remains of a planet that got too close and was destroyed by the white dwarf’s powerful gravity.
“We think this X-ray signal is the death cry of a planet that was ripped apart,” said lead author Sandino Estrada-Dorado from the National Autonomous University of Mexico. “This could finally explain a mystery that has lasted more than 40 years.”
Earlier research suggested that a Neptune-sized planet is orbiting the white dwarf very closely, completing a full orbit in less than three days.
The new study proposes that an even larger planet, possibly the size of Jupiter, once existed even closer to the star. Over time, it may have moved inward due to gravitational interactions with other planets in the system. Eventually, the white dwarf’s intense pull shredded the planet, and its debris is now falling onto the star, heating up and glowing in X-rays.
Co-author Martin Guerrero from the Institute of Astrophysics of Andalusia in Spain explained, “The signal we’ve been seeing might be from the shattered planet’s debris falling onto the white dwarf and heating up. If confirmed, this would be the first time we’ve seen a planet being destroyed inside a planetary nebula.”
Observations from the 1990s and 2000s show that the X-ray brightness has stayed mostly the same, but there may be a subtle change every 2.9 hours. This suggests that leftover debris from the destroyed planet is still orbiting the white dwarf.
The team also considered whether the white dwarf might have destroyed a small star instead of a planet. However, a star would be much more massive and harder to tear apart, making a planet the more likely victim.
Interestingly, WD 2226-210 shares some similarities with two other white dwarfs that are also interacting with nearby planetary material. These discoveries could help scientists understand what happens to planets when their stars grow old and die.
“It’s important to find more systems like this,” said co-author Jesús Toala. “They help us learn about how planets survive—or don’t—when stars like our sun reach the end of their lives.”
This discovery offers a fascinating glimpse into the violent fate that some planets may face when their stars transform into white dwarfs.
Source: KSR.
