# Chandra Observatory Identifies Companion Triggering Periodic Outbursts in Massive Star Astronomers discover a hidden companion causing recurring supernova-like eruptions in a distant giant star. - **Source:** [NASA](https://www.nasa.gov) - **Published:** 2026-11-09 - **Topic:** [science](https://brifing.si/c/science) - **Original article:** - **On Brifing:** https://brifing.si/s/e0f856e0-4533-40a9-b6d3-07c0fb6e634b ## Discovery of Periodic Eruptions Astronomers using NASA’s Chandra X-ray Observatory have identified the mechanism behind repeated outbursts from the massive star AT 2016blu. Located 30 million light-years away in the NGC 4559 galaxy, this star has displayed regular brightness spikes for 15 years. Researchers confirmed these events occur approximately every 113 days, mimicking supernova explosions. ## The Supernova Impostor Phenomenon AT 2016blu is classified as a luminous blue variable, a type of hot, massive star prone to brightness fluctuations. Unlike a true supernova, where a star collapses and is destroyed, this object survives its eruptions. Consequently, scientists refer to it as a supernova impostor, as it repeatedly sheds material without self-destructing. ## Role of a Hidden Companion The study reveals that a previously undetected companion object orbits AT 2016blu, triggering the outbursts. This partner is likely a stellar-mass black hole or a dense neutron star. As the two objects move along their oval-shaped orbit, the companion pulls material away from the massive star, which weighs 33 solar masses. ## X-Ray Emission Mechanism During their closest approach, the companion captures material ejected by the star. This matter orbits at near-light speeds, reaching extreme temperatures that generate intense X-ray emissions. These high-energy blasts heat the surrounding dense gas, causing the system to glow brightly in optical wavelengths, which is what astronomers observe from Earth. ## Chandra’s Precision Imaging Capability The research team utilized Chandra because it provides the sharp spatial resolution required to isolate AT 2016blu from nearby bright X-ray sources. By timing observations to coincide with optical outbursts, researchers confirmed the star was 100 times brighter in X-rays in 2026 compared to baseline data collected between 2001 and 2002. ## Evidence of Binary Interaction Between 2012 and 2026, astronomers recorded at least 27 distinct optical light bursts from the system. This regularity confirms the binary nature of the system, where the 113-day orbital period dictates the frequency of the eruptions. This discovery marks the first X-ray detection of this specific class of erupting stars. ## Ultra-Luminous X-Ray Classification Due to its high X-ray luminosity during outbursts, AT 2016blu is now considered a candidate for an ultra-luminous X-ray source. These rare, bright objects remain a subject of active study. Astronomers believe these sources typically contain either a neutron star or a black hole, consistent with the findings for this system. ## Comparison to Known Variables AT 2016blu shares characteristics with Eta Carinae, a well-known luminous blue variable. However, the rapid, 113-day cycle of AT 2016blu distinguishes it from other variables. While Eta Carinae is famous for its massive eruptions, the periodic nature of AT 2016blu’s outbursts provides a unique laboratory for studying binary star interactions and mass transfer. ## Methodological Challenges Resolved For over a decade, the cause of the star's behavior remained elusive because optical data alone could not explain the energy source. By successfully planning simultaneous X-ray and optical observations, the team proved that the optical flashes are secondary effects powered by the underlying high-energy X-ray blasts from the binary interaction. ## Implications for Stellar Evolution This study provides the first evidence of a black hole or neutron star companion in this type of erupting system. Understanding these interactions helps astronomers refine models of stellar evolution and mass loss in massive binary systems. Future observations will continue to clarify the exact nature of the companion object involved. ## Sources covering this story - [NASA — NASA’s Chandra Reveals Companion Triggering Star’s Periodic Outbursts](https://science.nasa.gov/missions/chandra/nasas-chandra-finds-source-of-stars-mysterious-outbursts/) - [NASA – Recently Published — NASA’s Chandra Reveals Companion Triggering Star’s Periodic Outbursts](https://science.nasa.gov/missions/chandra/nasas-chandra-finds-source-of-stars-mysterious-outbursts/) - [Source — Chandra Observatory Identifies Source of Giant Star's Repeated Outbursts](https://phys.org/news/2026-11-supernova-impostor-chandra-source-giant.html) --- _Summary written by Brifing from the original reporting. Copyright in the original article belongs to its publisher; read the full piece at the link above._