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23 ASTRO PUBLISHING JULY-AUGUST 2022 A rtist’s impression of a giant galaxy with a high-energy jet. [ALMA (ESO/NAOJ/NRAO)] When you see a car’s headlight, the dazzling brightness makes it chal- lenging to see the darker surround- ings. The same thing happens to telescopes when you observe bright objects. Dynamic range is the con- trast between the most brilliant and darkest tones in an image. You need a high dynamic range to reveal both the bright and dark parts in a tele- scope’s single shot. ALMA can regu- larly attain imaging dynamic ranges up to around 100, but commercially available digital cameras would typ- ically have a dynamic range of sev- eral thousands. Radio telescopes aren’t very good at seeing objects with significant contrast. 3C273 has been known for decades as the most famous quasar, but knowledge has been concentrated on its bright central nuclei, where most radio waves come from. How- ever, much less has been known about its host galaxy itself because the combination of the faint and dif- fuse galaxy with the 3C273 nucleus required such high dynamic ranges to detect. The research team used a technique called self-calibration to reduce the leakage of radio waves from 3C273 to the galaxy, which used 3C273 itself to correct for the effects of Earth’s atmospheric fluctu- ations on the telescope system. They reached an imaging dynamic range of 85000, an ALMA record for extra- galactic objects. As a result of achiev- ing high imaging dynamic range, the team discovered the faint radio emission extending for tens of thou- sands of light-years over the host galaxy of 3C273. Radio emission around quasars typically suggests synchrotron emission, which comes from highly energetic events like bursts of star formation or ultra-fast