M106

The target

Say hello to M106 (NGC 4258), a big, bright spiral galaxy sprawling across the little constellation Canes Venatici — the Hunting Dogs. It spans roughly 135,000 light-years, a touch wider than our own Milky Way, and it's got a secret: its core is active. A supermassive black hole weighing around 40 million Suns is busy feeding at the center, and the leftovers blast outward as jets. Those jets light up a pair of ghostly "anomalous arms" — extra spiral arms made not of stars but of superheated, glowing gas. Most galaxies show off their starlight; M106 also glows with the exhaust of its own black hole.

Distance and light

M106 sits about away. Here's the fun part: it's one of the most precisely measured galaxies in the entire universe. A ring of water megamasers — naturally occurring cosmic lasers — orbits its central black hole, and tracking their motion lets astronomers measure the distance , no guesswork required. That makes M106 a key rung on the "cosmic distance ladder" we use to size up everything farther out.