Selections from 2022: New Observations of a Spectacular Active Galactic Nucleus

Editor’s Note: In these last two weeks of 2022, we’ll be looking at a few selections that we haven’t yet discussed on AAS Nova from among the most-downloaded articles published in AAS journals this year. The usual posting schedule will resume in January.

Probing the Innermost Regions of AGN Jets and Their Magnetic Fields with RadioAstron. V. Space and Ground Millimeter-VLBI Imaging of OJ 287

Published January 2022

Main takeaway:

A team led by José Gómez (Institute of Astrophysics of Andalusia – Spanish National Research Council) presented new observations of OJ 287, an active galactic nucleus that hosts one of the most massive supermassive black holes currently known. These new data allowed researchers to study the magnetic fields very close to this superlative active galactic nucleus.

Why it’s interesting:

Radio flare seen from OJ 287

An example of a flare from OJ 287, seen at multiple radio frequencies. Click to enlarge. [Gómez et al. 2022]

OJ 287 is a well-studied target that has shown intriguing behavior in the past. Even among active galactic nuclei, OJ 287 is active, flaring so brightly due to material accreting onto its supermassive black hole that its outbursts were captured on photographic plates in the late 19th century. Notably, its outbursts follow a roughly 12-year pattern, which astronomers believe is due to the presence of a second supermassive black hole in orbit about the first. OJ 287 also emits a jet, the orientation of which is thought to vary considerably every 24–30 years, though the reason for this variation is unclear.

More details on these new observations:

Gómez and collaborators used arrays of radio telescopes (including one telescope in space!) to perform long-baseline interferometry. This technique combines data from multiple telescopes to yield the same resolving power as a single telescope as large as the greatest distance between two telescopes in the array. These data included information about the polarization (i.e., orientation) of the radio waves, which in turn helped the team understand OJ 287’s magnetic field structure. The new observations showed that the jet emitted by OJ 287 is bent — likely due to the accretion disk very close to the central black hole changing over time — and has a helical magnetic field. The observed magnetic field structure aligns with our theories of how active galactic nucleus jets are produced.


José L. Gómez et al 2022 ApJ 924 122. doi:10.3847/1538-4357/ac3bcc