Astronomy Picture of the Day

Explanation: What causes this unusual structure near the centre of our Galaxy? The long parallel rays slanting across the top of the above radio image are known collectively as the Galactic Centre Radio Arc and jut straight out from the Galactic plane. The Radio Arc is connected to the Galactic centre by strange curving filaments known as the Arches. The bright radio structure at the bottom right likely surrounds a black hole at the Galactic centre and is known as Sagittarius A*. One origin hypothesis holds that the Radio Arc and the Arches have their geometry because they contain hot plasma flowing along lines of constant magnetic field. Recent images from the Chandra X-ray Observatory appear to show this plasma colliding with a nearby cloud of cold gas.