The RadioAstron mission is observing hundreds of radio-loud Active Galactic Nuclei (AGN) at the highest angular resolutions ever achieved, with the use of VLBI between a 10-m diameter space radio telescope (SRT), and larger radio telescopes on the ground. The SRT travels on a 9-day elliptical orbit around the Earth, reaching distances of up to 360,000 km — almost the distance to the moon! Using this technique, we can study the central emission regions of AGN, close to the supermassive black hole central engines, and determine just how hot these ultra-compact jets can be and what physics enables them to emit such large amounts of radiation from such small regions.
We are using the Australia Telescope Compact Array to measure intra-day and longer term variations of AGN being observed with RadioAstron, under ATCA project code C2898. The variability provides information complementary to the RadioAstron VLBI measurements, and it is important to determine the effect of interstellar scattering on the Space VLBI observations. Interstellar scattering, which occurs as the radio emission passes through the turbulent, ionised interstellar medium of our Galaxy, causes radio sources to “twinkle” — their apparent brightness varies with time, sometimes on timescales as short as minutes to hours — and they can appear “smeared out” when observed with very high angular resolution.
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