Potential Giant World Circles a Tiny Star

The object, called WD 1856 b, is about seven times larger than the white dwarf. Based on the object’s size, astronomers think it’s a giant gaseous planet, which future observations and research may confirm. They also estimate it’s no more than 14 times Jupiter’s mass. The potential world circles the white dwarf every 34 hours, over 60 times faster than Mercury orbits our Sun.

The system may have looked very different prior to 6 billion years ago, though. When a Sun-like star runs out of fuel, it swells up to hundreds to thousands of times its original size, forming a cooler red giant star. Eventually it ejects its outer layers of gas, losing up to 80% of its mass. The remaining hot core becomes a white dwarf. Any nearby objects are engulfed and incinerated during this process, which in this system would have included WD 1856 b in its current orbit. Astronomers estimate the possible planet must have originated at least 50 times farther away.

The team suggests several scenarios that could have nudged WD 1856 b onto an elliptical path around the white dwarf. This trajectory would have become more circular over time as the star’s gravity stretched the object, creating enormous tides that dissipated its orbital energy.