Discovery of 21 "Dark" Neutron Stars Orbiting Sun-like Stars

A recent analysis of data from the European Space Agency's Gaia mission has unveiled a fascinating discovery: 21 Sun-like stars in mutual orbit with "dark" neutron stars, Sky and Telescope reports. While most massive stars ultimately destroy their stellar siblings, these rare systems have managed to survive unscathed. By charting the precise positions of over a billion Milky Way stars, Gaia was able to detect the wobbles in the home stars caused by the presence of these dark neutron star companions.

Traditionally, neutron stars are identified through their radio emissions, but these 21 newfound neutron stars were discovered through the gravitational influence they exerted on their companion stars. In the extensive Gaia catalog, which includes data on 170,000 binary systems, researchers discovered 177 binaries with a luminous star orbiting a dark companion, potentially a white dwarf, neutron star, or black hole. Of those binaries, the team focused on 50 suspected to host a neutron star and obtained spectra from several ground-based telescopes to determine the exact mass of the dark companions.

Out of the 50 systems observed, 21 showed evidence of a luminous Sun-like star in mutual orbit with a dark neutron star-mass object. This finding challenges existing models of how these binaries are formed. Typically, a supernova explosion imparts a kick to the compacted core of a massive star, causing the resulting neutron star to escape the system. The surviving binaries defy expectations, as their progenitor stars should have undergone significant interactions with their companion stars during their late-stage evolution. It is believed that the majority of similar binaries are destroyed, making the detection of these survivors significant.

The identification of these 21 dark neutron star systems is a remarkable achievement, as they are extremely uncommon. Binaries with a neutron star are typically hard to find, as the neutron star's accretion of material from its companion causes it to emit bright X-rays. These dark, neutron star–luminous star binaries, with their slightly more common occurrence of about one in a million, provide valuable insights into the formation and evolution of binary systems.

Nonetheless, there remains some uncertainty about whether the companions in these systems are truly neutron stars or perhaps unusually massive white dwarfs, or even a closely paired duo of less massive white dwarfs. Further observations and data analysis will be necessary to confirm the nature of these dark stellar cores and reassess their rarity.

The groundbreaking research by Kareem El-Badry of Caltech and his team not only sheds light on an intriguing aspect of astrophysics but also raises new questions for astronomers to explore. It showcases the power of missions like Gaia in uncovering hidden cosmic phenomena and opens exciting possibilities for future studies to unravel the mysteries of binary system evolution.

Earlier, SSP told about the new findings that shed light on the earliest European hominids.