Is this a quasar?

https://www.legacysurvey.org//viewer/?ra=343.5183&dec=0.9058&layer=hsc-dr2&zoom=16

…or is it just a star sitting right on top of an immensely powerful background radio source?

There’s an SDSS spectrum for it (“Galaxy, but with zwarn=4 = uncertain”). Strangely, in the Legacy Surveys imaging it doesn’t look nearly so strangely colored!

This is whats known as a BL Lacertae object

Well that clears everything up, thanks.

BL Lac objects are effectively what happens when a radio galaxy acts as a blazar.

Any idea why it is being tracked by GAIA then? I thought that was tracking stars in the Milky Way?

GAIA’s mission involves detection of objects brighter than 20th mag. Therefore a lot of bright AGN are detected. You can see that it has a parallax of effectively zero, which is a good sign that its extragalactic.

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