Dead star spinning every 8 minutes found orbiting a Sun-like star

Astronomers have traced mysterious radio pulses to an unusual pair of stars more than 5,000 light-years from Earth, in which a dead star that rotates every eight minutes orbits a companion much like our Sun. The finding, reported by researchers at the Curtin University branch of the International Centre for Radio Astronomy Research, marks the first time such signals have been identified in a system where a white dwarf circles a Sun-like star.

A rare stellar pairing

According to ScienceDaily, the system, designated GPM J071507-114153, contains a white dwarf, the extremely dense remnant left when a star exhausts its nuclear fuel and sheds its outer layers, and a G-type star that belongs to the same general category as the Sun.

The pair belongs to an emerging class of objects called long-period transients (LPTs), which emit radio waves that appear and disappear over periods lasting from several minutes to hours. Their origins remain poorly understood. The same ICRAR team discovered the first known example in 2021, and only about a dozen have been identified since.

Until now, similar radio pulses had been detected in systems pairing white dwarfs with smaller, cooler red dwarfs. This is the first such signal found alongside a Sun-like star, the researchers said.

Pinpointing the source

For the first time, the observations were detailed enough to follow the white dwarf as it travelled around its companion, allowing the team to locate the likely origin of the pulses far more precisely.

"This is the first time the pulses are clear enough to see the white dwarf moving in its orbit around its companion, so we know that the pulsations are coming from a region close to the white dwarf, or possibly even from the white dwarf itself," lead author Dr. Sam McSweeney said.

McSweeney, now a commissioning scientist with the Square Kilometre Array Observatory, made the discovery while working at Curtin University's ICRAR branch. The researchers analyzed more than 100 hours of radio observations using computing resources at the Pawsey Supercomputing Research Centre. The signals also revealed massive magnetic storms on the companion star.

The study, "A long-period transient with a Sun-like companion," was published in Nature Astronomy, which said the system raises questions about the role of binary interactions and magnetic activity in these puzzling signals.