In the vast expanse of space, a peculiar phenomenon known as “spider pulsars” is captivating astronomers’ attention. These dead stars, aptly named for their predatory behavior, are wreaking havoc on their companion stars within the Omega Centauri globular cluster. NASA’s Chandra X-ray Observatory is at the forefront of unraveling the mysteries surrounding these cosmic predators, shedding light on their impact on nearby stellar companions.
Pulsars, remnants of massive stars that have undergone gravitational collapse, are dense cores that remain after this cataclysmic event. Rapidly rotating neutron stars generate beams of radiation, akin to a lighthouse’s revolving beam. These pulsating sources, or pulsars, include a special class known as millisecond pulsars, with some spinning hundreds of times per second.
The intriguing subset, dubbed “spider pulsars,” earns its moniker from the deleterious effect they inflict on smaller companion stars orbiting in proximity. Energetic particle winds emanating from these pulsars systematically strip away the outer layers of their stellar companions, unveiling a cosmic dance of destruction.
Recent discoveries of 18 millisecond pulsars within the Omega Centauri globular cluster, located approximately 17,700 light-years from Earth, were made possible by the Parkes and MeerKAT radio telescopes. To probe further into the nature of these pulsars, a pair of astronomers from the University of Alberta examined Chandra data of Omega Centauri, specifically focusing on X-ray emissions from the millisecond pulsars.
The analysis revealed that 11 of the millisecond pulsars emitted X-rays, with five falling into the category of spider pulsars concentrated near the cluster’s center. This led researchers to broaden their investigation by combining the data from Omega Centauri with Chandra observations of 26 spider pulsars in 12 other globular clusters.
Spider pulsars are categorized into two types based on the mass of the companion star they are dismantling. “Redback” spider pulsars target companion stars weighing between a tenth and half the mass of the Sun, while “black widow” spider pulsars prey on companions with less than 5 percent of the Sun’s mass.
An interesting revelation from the study is the distinction between these two classes of spider pulsars. Redbacks were found to be brighter in X-rays compared to black widows, corroborating prior research. Importantly, this study is the first to establish a general correlation between X-ray brightness and companion mass for spider pulsars, indicating that the mass of the companion influences the X-ray dosage the star receives.
Chandra’s detection of X-rays is attributed to the collision of particle winds from the pulsars with the matter streaming away from the companion stars, producing shock waves similar to those generated by supersonic aircraft. The proximity of spider pulsars to their companions, usually one to 14 times the distance between the Earth and Moon, intensifies the damage caused by the energetic particles.
The study aligns with existing theoretical models, suggesting that more massive companion stars produce denser particle winds, resulting in more substantial shock waves and consequently brighter X-rays when colliding with the pulsar’s particle stream. This proximity amplifies the destructive potential of the X-rays on the companion stars, accentuating the intricate interplay within these cosmic relationships.
Chandra’s role in this research is pivotal, thanks to its sharp X-ray vision, crucial for studying millisecond pulsars in globular clusters. The challenging task involves differentiating between numerous X-ray sources in a confined area of the sky. Several millisecond pulsars in Omega Centauri exhibited unrelated X-ray sources a few arc seconds away, emphasizing the need for Chandra’s precision.
The forthcoming publication of these findings in the December issue of the Monthly Notices of the Royal Astronomical Society will provide a comprehensive overview. Authored by Jiaqi (Jake) Zhao and Craig Heinke from the University of Alberta in Canada, this research showcases the invaluable contribution of NASA’s Chandra X-ray Observatory to the understanding of our high-energy universe.
Since its launch on July 23, 1999, Chandra has been NASA’s flagship mission for X-ray astronomy. Orbiting above Earth’s atmosphere at an altitude of 139,000 km (86,500 mi), Chandra specializes in detecting X-ray emissions from extremely hot regions of the Universe, such as exploded stars, galaxy clusters, and matter around black holes.
The Chandra X-ray Center, operated by the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, manages science operations and processes data for analysis by scientists globally. Chandra’s legacy includes groundbreaking discoveries, from exploring the remnants of exploded stars to observing supermassive black holes across the cosmos. As Chandra continues its mission, the telescope remains at the forefront of unraveling the profound mysteries of our high-energy universe.