DOES OUR MILKY WAY HAVE ANOTHER ARM?

Observing the extent of the Milky Way is not the easiest of tasks. The main problem is that Earth is located inside its disc, so perhaps the best way of seeing our galaxy as a whole would involve stepping foot inside a spaceship, flying far away and turning around to see the Milky Way in its entire glory.

That’s not going to happen any time soon, so astronomers have sought other means to determine its three-dimensional structure, size, volume and whatever is contained within. In 1914, for instance, Harlow Shapley observed pulsating low-mass stars called Cepheid variables and worked out the distance between them to get a better idea of our galaxy’s size.

“WHEN WE OBSERVE AN ATOMIC CLOUD, WE CAN GET ITS POSITION IN THE SKY AND THE FREQUENCY OF THE HI EMISSION”
CHONG LI

He also discovered that the Sun was not at the centre of our galaxy as previously thought, but 26,000 light years away from it near the central plane – and yet he still believed that what we know today as the Milky Way was the entire universe.