Radio Pulses Every Eight Minutes Traced to a Dead Star Orbiting a Sun-Like One
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Astronomers have tracked a mysterious repeating radio signal to a pairing of a white dwarf, the remnant of a dead star, and a living star much like the sun, Space.com reported. The system, called GPM J071507−114153, sits about 5,000 light-years away, and its white dwarf spins once every eight minutes while sending out radio pulses.
The pulses were clear enough for the team to see the white dwarf moving in its orbit, which points to the signal's source being close to the white dwarf or possibly the white dwarf itself. The work was published Thursday (Nov. 12) in the journal Nature Astronomy.
The key numbers behind the discovery
- About 5,000 light-years: the distance to the system, according to Space.com.
- Eight minutes: how long the white dwarf takes to spin once, producing one cycle of radio pulses.
- Around a dozen: the number of long-period transients detected so far, according to Space.com.
- 2021: the year the same research team found the first object of this kind.
What long-period transients are
The system belongs to a class of objects called long-period transients, whose radio signals switch on and off over minutes or hours. Several earlier examples also contain a white dwarf and a companion star, but it was unclear which of the two produced the pulses. Radio pulses of this kind have been seen before from pairs that include smaller, cooler red dwarf stars, but rarely from a system like this one.
Team leader Sam McSweeney, a commissioning scientist with the Square Kilometre Array Observatory, said this was the first time the pulses were clear enough to watch the white dwarf's orbit around its companion.
How the system was found and confirmed
Natasha Hurley-Walker of the International Centre for Radio Astronomy Research at Curtin University in Australia said the team spotted the system in a large survey with the Murchison Widefield Array, which scanned the whole Milky Way visible from Australia. The MeerKAT radio telescope in South Africa then pinned down its precise position.
The W.M. Keck Observatory on Maunakea in Hawaii confirmed the detection. Its visible-light follow-up showed that the companion is a G-type star, the same class as the sun.
A bonus: storms on a distant star
The pulses also let the researchers detect flares erupting on the sun-like star. In addition, they saw the white dwarf pass behind a region with a strong magnetic field, most likely a stellar prominence, which is a large loop of plasma rising from a star's surface. Hurley-Walker said it was remarkable that radio waves can reveal storms on a star so far away.
Why it matters
Nobody has yet settled what powers these odd signals. Pinning the pulses to the area around the white dwarf narrows the question that has hung over several of these systems, though the study does not say the white dwarf itself is definitely the emitter.
The finding also hints at what bigger instruments may deliver. MeerKAT and the Murchison Widefield Array are precursors to the Square Kilometre Array, described as the world's largest and most sensitive radio telescope project. McSweeney said that if precursor telescopes already make such discoveries, many more star systems, seen in far greater detail, should turn up once the full array is built.
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Around Prague, based on reporting by Space.com
Cover photo: ESO / Wikimedia Commons, CC BY 4.0, cropped
