Chinese astronomers find real three-star system unlike fiction
Astronomers identified a rare system containing a pulsar, a white dwarf and a sun-like star. The third star’s gravity explains why the pulsar appeared to slow…
Chinese astronomers find real three-star system in which a hidden sun-like star explains why a pulsar appeared to slow unusually fast. Located about 7,000 light years from Earth, the trio includes two dead stars and one still shining.
The discovery differs from the chaotic fictional system in Liu Cixin’s science-fiction hit The Three-Body Problem. Researchers say the stars follow a stable arrangement, and that the system could help test a key idea in Einstein’s theory of gravity.
A rare trio with a puzzling pulsar
The team, led by Han Jinlin of the National Astronomical Observatories in Beijing, identified the system using data from FAST, the world’s biggest single-dish radio telescope, in southwestern China. The finding was reported in The Astrophysical Journal Letters earlier this month.
One member is a pulsar that spins more than 300 times a second. It circles a white dwarf, the dim core left by a smaller star, every eight days. Farther out, a sun-like star takes 73½ years to complete an orbit around the pair.
That distant star helped solve a mystery. Pulsars send radio pulses across space with striking regularity, making them useful as cosmic clocks. This one, first spotted by FAST in 2020, appeared to lose speed about 100 times faster than other pulsars of its kind.
Five years of monitoring by researchers at the Xinjiang Astronomical Observatory established the unusual slowdown. In a paper published in Nature Astronomy in April, the Xinjiang team said the result challenged a standard theory of how such pulsars form and pointed to the possibility of another object in the system.
The researchers behind the new study combined FAST data with observations from other telescopes, including 18 years of gamma-ray data from Nasa’s Fermi space telescope. They concluded that the sun-like star’s gravity tugs the pulsar back and forth, making its spin appear to slow.
Why astronomers are watching
Triple-star systems are fairly common, but systems containing a millisecond pulsar are “extremely rare”, according to the team. The explosion that creates a pulsar can tear a star system apart, making an intact trio of this kind unusual.
That rarity gives researchers a chance to examine how gravity behaves across objects with very different properties. The system could help test the strong equivalence principle, an idea in Einstein’s theory of gravity that says everything falls in the same way, from a feather to a city-sized dead star heavier than the sun.
“The detailed evolution of triple-star systems is complicated and poorly known,” the researchers wrote. They described the newly identified system as “unique” for studying how such stellar families change over time.
The team said the three stars likely formed together from the same cloud of gas, despite having very different masses. The largest, about 20 times the mass of the sun, burned out first and exploded, leaving the pulsar. Another became the white dwarf, while the smallest, about the mass of the sun, survived at a greater distance and continues to shine.
Researchers expect the sun-like star to swing closest to the pair in 2036. Eventually, the team says, it too will burn out, leaving a pulsar and two white dwarfs.
The system is only the second of its kind known. The first was found by a US-led team in 2014, and all three stars in that system were already dead.
Source: thestar.com.my