Moscow Institute of Physics and Technology | 2019 Apr 24
Until recently, quasars were thought to have essentially fixed positions in the sky. While near-Earth objects move along complex trajectories, quasars are so remote that they were believed to offer stable and reliable reference points for use in navigation and plate tectonics research. Now, an international team of astrophysicists ... has found that quasars are not entirely motionless and explained this behavior. ...
Quasars belong to a broader class of astronomical objects known as active galactic nuclei. Fortunately, none of them are located close to Earth. An AGN is basically a “fire-breathing” black hole incinerating its surroundings with two oppositely directed jets of plasma moving at relativistic speeds. Lurking at the heart of an AGN, the black hole itself is, naturally, invisible. This central object is shrouded with a region penetrable only to the highest-frequency radiation. As a result, an Earth-based observer sees an AGN differently depending on the radiation frequency used. For example, while optical observations reveal the jet and the glow around its source, radio telescopes can only discern the part of the quasar “tail” directed at us.
The most precise currently available technique for radio observation of remote objects is known as very long baseline interferometry. It relies on an emulated giant telescope that draws on many regular instruments scattered across the globe. Such a “virtual” telescope can obtain high-resolution data about a remote radio source. However, data reduction and restoring “a photo” of the target is not a trivial thing, because researchers need to retrieve an image from the bits of information gathered by many instruments.
The team developed an automated procedure for solving that task. They found that the apparent coordinate of the jet apex does not remain static but fluctuates back-and-forth along the axis of the jet. It would appear that the source itself “wiggles.” However, astrophysicists consider these fluctuations to be a sort of an illusion. They explain the phenomenon in terms of the complex nature of radiation. This implies that the quasar nuclei themselves do not actually undergo any motion in space. ...
Significant core shift variability in parsec-scale jets of active galactic nuclei ~ A.V. Plavin et al
- Monthly Notices of the RAS 485(2):1822 (May 2019) DOI: 10.1093/mnras/stz504
arXiv.org > astro-ph > arXiv:1811.02544 > 06 Nov 2018 (v1), 18 Feb 2019 (v2)