Produced by: Mohsin Shaikh
Credit: NASA
NASA’s Swift Observatory detected AT 2021hdr, a unique repeating signal from two black holes a billion light-years away, revealing secrets of cosmic interaction.
The black holes orbit each other, disturbing a gas cloud in the galaxy 2MASX J21240027+3409114, creating periodic light waves across ultraviolet and X-ray wavelengths.
Lorena Hernández-García, leading the study published in Astronomy and Astrophysics, described AT 2021hdr as “a very weird event” due to its consistent light oscillations.
The two black holes, located 16 billion miles apart in Cygnus, possess 40 million times the Sun's mass, completing one orbit every 130 days with intense gravitational force.
Representative pic
AT 2021hdr was initially flagged by ALeRCE’s AI tools at Caltech’s Zwicky Transient Facility, with co-author Alejandra Muñoz-Arancibia noting how 2022 outbursts deepened understanding.
The black holes' orbit disrupts and heats a surrounding gas cloud, ejecting parts of it each cycle. Swift and ZTF telescopes capture the fluctuating light pattern from these ejections.
Representative pic
Scientists ruled out other events like galactic activity and star disruptions, concluding that the black holes are tidally disturbing a vast gas cloud, generating unique oscillations.
Representative pic
The host galaxy is merging with another, adding complexity to the study. Hernández-García’s team aims to observe further to refine models and unlock more cosmic secrets.
As Swift approaches its 20th anniversary, Principal Investigator S. Bradley Cenko celebrates its contributions to cosmic discovery, revealing new mysteries in our evolving universe.