Andromeda is the closest galaxy to the Milky Way, sitting approximately 2.5 million light-years away. As the universe expands, the majority of galaxies are moving away from ours. However, the gravitational force between the Milky Way and Andromeda is exceptionally strong because the two are so close together.
Ms Thaller, an astronomer who studies binary stars and their life cycles has revealed how the Big Bang is to blame.
She told BigThink on Wednesday: “Space is expanding because of the Big Bang, all of it is expanding in every direction at once.
“That means that it looks like all of the other galaxies are moving away from us.
“But not all the universe appears to be expanding.
“For example, the Earth doesn’t appear to be getting any further away from the sun and the sun isn’t getting any further away from our galaxy.”
However, Ms Thaller, who studied at Harvard University, revealed how gravity will play a massive part in the universe’s future.
She added: “There are things that are stronger than the expansion, though.
“The gravity between the sun and the Earth is stronger than expansion – as is the galaxy.
“Andromeda is different, as it is close enough to the Milky Wayfor the gravity between the two to pull them together.
“Yes space is expanding, but gravity is pulling us towards Andromeda."
The 49-year-old went on to predict when this event would take place.
She continued: “Andromeda will collide with the Milky Way in around 4.5 billion years.
“We see this all over the universe – there are clusters where the galaxies are close enough together that they merge and collide.
“When galaxies are far enough away from each other that the gravitational force is weaker than the outwards expansion, they move apart."