Astronomers Discover Youngest White Dwarf Paired with Millisecond Pulsar in NGC 362D
Astronomers using the MeerKAT radio telescope and archival Hubble Space Telescope data have discovered the youngest white dwarf ever seen to be partnered with a millisecond pulsar, designated NGC 362D. This rare stellar pairing offers a unique laboratory for studying the immediate aftermath of pulsar recycling, a process where a neutron star spins up by stripping material from a companion star. The white dwarf in NGC 362D stopped transferring matter roughly 600 million years ago and is currently emitting less ultraviolet radiation than it should because surrounding ejected material blocks the signal.
Stellar Evolution and Pulsar Recycling in NGC 362D
The binary system houses two distinct dead stars with contrasting origins. The millisecond pulsar component began as a massive star between eight and 12 times the mass of the sun before dying in a supernova explosion, leaving behind a dense core measuring roughly 12 miles across. This extreme compaction caused the newborn neutron star to spin at hundreds of times per second.
In systems like NGC 362D, this rotation rate accelerates further through pulsar recycling. The neutron star accretes matter from its companion star, inheriting angular momentum that speeds up its rotation. This theft strips the companion of its outer layers, ultimately transforming it into the young white dwarf observed today.
Material Surrounds White Dwarf After Matter Transfer Ceased
Data collected by the Hubble Space Telescope between 2006 and 2016 allowed researchers to reconstruct the evolutionary history of the system. The team found that the white dwarf emits less ultraviolet radiation than it should. Team leader Greta Ettorre of the University of Bologna stated that the signal attenuation indicates the presence of material still surrounding the white dwarf following the cessation of matter transfer roughly 600 million years ago.
Emanuele Dalessandro, a researcher at the National Institute for Astrophysics (INAF) and member of the research team, explained that this surrounding material could produce radio signatures in addition to optical ones. These signatures resemble those found in systems with non-degenerate companions, which may help scientists correctly interpret the properties of other young binary systems.
Implications for Pulsar Timing Arrays and General Relativity
The findings, published on September 30 in the journal Astronomy & Astrophysics Letters, provide new data for research involving millisecond pulsars. Because these rapidly rotating neutron stars spin with extraordinary regularity, researchers utilize them as natural cosmic clocks. Measuring the arrival times of their pulses with extreme precision allows physicists to study gravity under extreme conditions and conduct precise tests of general relativity. Understanding the surrounding environment and evolutionary history of systems like NGC 362D is essential for utilizing pulsar timing arrays effectively.
Frequently Asked Questions About NGC 362D
What instruments were used to discover the NGC 362D system?
The system was discovered using the MeerKAT radio telescope in South Africa, while the white dwarf companion was identified using archival data collected by the Hubble Space Telescope between 2006 and 2016.
When were the findings about NGC 362D published?
The research findings were published on September 30 in the journal Astronomy & Astrophysics Letters.
How dense is the neutron star component in NGC 362D?
The neutron star is compressed into a width of around 12 miles (20 kilometers), possessing a density where a single teaspoon of its matter would weigh approximately 10 million tons on Earth.