Using the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have spotted signs of a ‘hot spot’ orbiting Sagittarius A*, the black hole at the centre of our galaxy. The finding helps us better understand the enigmatic and dynamic environment of our supermassive black hole. “We think we’re looking at a hot bubble of gas zipping around Sagittarius A* on an orbit ...

A helium atom in which one of the two electrons has been replaced by a negative pion gives out a composite particle made of one quark and one antiquark. Exotic atoms can help physicists to make exquisitely precise measurements of the fundamental constants of nature, such as the size of the proton. Pionic helium is the latest addition to a ...