The Romans knew our Galaxy as the Via Lactea or âroad of milkâ. From its gauzy white haze in the sky, it does certainly seem like a fresh, bright line of milk spilled across the speckled dark. Greek myths told the story of Hera pushing away an infant Heracles while she was breastfeeding, spilling drops of her milk that became the array of galaxies we see today. This image of our galaxy (indeed even the word âgalaâ in Greek means milk) has persisted since the existence of mankind. Whether it be the luminous stripe across the sky or whether it be the flat spiral we visualize looming in deep space, there is a certain image of our home galaxy that we have known for hundreds of thousands of years. And yet, in the universe, nothing is forever.On moonless nights the Andromeda galaxy is bright enough to see with the naked eye, a sister galaxy to the Milky Way with a familiar spiral structure and over a trillion stars â twice that of our own galaxy. It was thought to be a nebula when it was first spotted. In the 1700âs it was described as an âisland universeâ with a pool of stars separate from our own. We now know itâs actually the largest galaxy of our local group, followed by the Milky Way and the Triangulum Galaxy. It is these three bodies which are set to collide in the next few billion years, forever erasing the image of the Milky Way weâve come to know and creating a truly mesmerizing spectacle for anyone lucky enough to see it.Although Andromeda is 2.5 million light years away, itâs heading towards us at a rate of 250,000 miles (402,000 km) per hour. Itâs the proximity of these two galaxies which caused them to attract while all other galaxies in our local group speed away, receding from view as the universe continues to expand. This phenomenon was first noticed in the 1900âs when a scientist studied light waves from Andromeda arriving here on our planet. When objects move away, their light waves become stretched and red-shifted. But light waves from Andromeda were blue-shifted, meaning that they were compressing as the galaxy came closer....
