Detecting Radio Pulses Every 8 Minutes
Astronomers traced a repeating radio signal back to a binary system approximately 5,000 light-years away, housing a dead star flashing every eight minutes.
Designated as GPM J071507−114153, the system features a compact white dwarf spinning and sending out short radio bursts like clockwork, Space reported.
The discovery identifies a rare class of celestial objects known as long-period transients. These sources emit bright radio waves that switch on and off over intervals ranging from minutes to hours, leaving researchers with few confirmed examples since initial discoveries began.
Several previously detected long-period transient systems contain a white dwarf paired with a companion star. However, identifying which specific star generated the radio pulses remained unclear until now, according to Sci.News.
Researchers published their findings on November 12 in the journal Nature Astronomy. The work demonstrates that the pulsing originates from the white dwarf as it orbits its larger companion.
Surprising Discovery of a Sun-Like Partner
Scientists initially utilized the Murchison Widefield Array radio telescope in Western Australia to spot the short flashes arriving every 7.9 minutes. After weeks of silence, the pulses revealed a 32-hour binary orbit visible only during specific alignment windows.
The team used the MeerKAT telescope in South Africa to pinpoint the source to a tiny patch of sky containing a single faint star. Subsequent observations with the Keck telescope in Hawaii recorded the star’s light spectrum.
The result surprised the research team. Instead of a dim red dwarf, the companion turned out to be a G-type star almost matching the mass and temperature of our own sun.
“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,” said Sam McSweeney, an astronomer at the International Centre for Radio Astronomy Research (ICRAR) and a commissioning scientist with the Square Kilometre Array Observatory, as reported by Sci.News: Breaking Science News.
Timing Analysis Rules Out Neutron Stars
Researchers ruled out slow-spinning neutron stars by analyzing the exact timing of the radio pulses. As the pulsing object swings around its orbit, the signals arrive up to four seconds early or late due to varying distances.
The spectrum of the sunlike star shows it barely wobbles as the object orbits. This indicates the sunlike star is much heavier than its partner.
Combining the orbit size, orbital period, and spectrum measurements proved the pulsing object is about two-thirds as heavy as the sun. That mass is too light for a neutron star.
The data confirms the object is a white dwarf pulsar orbiting a sunlike star. The team processed more than 100 hours of radio data at the Pawsey Supercomputing Research Centre to verify the orbital motion.
Observing Stellar Storms Across Space
“The pulses emitted by the white dwarf allowed our team to detect stellar flares on the Sun-like star, similar to those that create aurorae here on Earth,” said Dr. Natasha Hurley-Walker, an astronomer at ICRAR. They also observed the white dwarf passing behind a stellar prominence, which is a massive loop of plasma erupting from the companion’s surface.
“As a bonus, we also saw the white dwarf moving behind a region with a strong magnetic field, most likely a ‘stellar prominence,’ which is a large loop of plasma erupting from a star’s surface,” Natasha Hurley-Walker, an astronomer at ICRAR, told Space.
“It’s amazing that by using radio wavelengths we can detect the storms on a star over 5,000 light-years away,” Hurley-Walker added.
Questions About Binary Evolution
Did you know? White dwarfs are the dense, collapsed cores of dead stars like our sun. When a star swells into a giant during its late life cycle, it can engulf a nearby companion before ejecting its outer layers to form a close binary system.
Astronomers believe systems combining a white dwarf and a bright sunlike star are likely common across the universe. However, optical and X-ray telescopes frequently miss them because the intense glare of the bright companion hides the faint white dwarf.
Radio pulses successfully cut through that stellar glare. Future surveys using next-generation instruments like the SKA Observatory could uncover an entire population of hidden white dwarf binaries.
Common Questions About the Pulsing White Dwarf
How far away is the newly discovered system?
The GPM J071507−114153 binary system sits approximately 5,000 light-years away from Earth. Researchers pinpointed its location using the MeerKAT radio telescope in South Africa.
Why was the companion star unexpected?
Earlier discoveries of long-period transients typically paired white dwarfs with smaller, cooler red dwarfs. Astronomers found a G-type star with nearly the same mass and temperature as the sun, a first for this class of objects.
How frequently do the radio pulses arrive?
The white dwarf emits short flashes of radio waves like clockwork every 7.9 minutes. These pulses appear during a window of approximately six hours within a 32-hour binary orbit.
“If we are already making such discoveries with precursor telescopes, just imagine how many more star systems we will be able to find, and what a beautifully detailed view of their signals we will have, once the SKA telescopes are completely built,” McSweeney told Space.
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