From our tiny blue dot, the universe appears inconceivably vast. In the grand cosmic scheme of things, all the light in the observable universe provides about as much illumination as a 60-watt bulb seen from 2.5 miles away, says Marco Ajello, an astrophysicist at Clemson University, who led a team in 2018 that has measured all of the starlight ever produced throughout the history of the observable universe.
In 2018, a long-hidden and especially tumultuous chapter in the Milky Way’s history was revealed: a smash-up between the young Galaxy and a colossal companion that once orbited the Milky Way like a planet around a star. “The two collided, massively altering the Galactic disk and scattering stars far and wide,” reported Nature about data captured by the Gaia Spacecraft that radically transformed how we see the evolution of our Galaxy. “It is the last-known major crash the Galaxy experienced before it assumed the familiar spiral shape seen today.”
“The interesting thing is: we have no idea!” says Pieter van Dokkum, Sol Goldman Professor of Astronomy at Yale University, who wrote in an email to The Daily Galaxy about why ultra-diffuse galaxy DF2 contains no dark matter. “The existence of this galaxy shows that there is another pathway to creating galaxies than our standard picture, but what that might be is anyone’s guess.”
“Not only are the galaxies spinning, but also the stars within the galaxies, and the Earth is spinning, and the Earth around the sun and the moon around the Earth. Pretty much the whole universe is spinning,” says Noam Libeskind at the Leibniz Institute for Astrophysics. “We don’t really know why, and one way to try to answer that is to figure out where the spinning stops.”
“It was shocking to realize that the Milky Way had a large sibling, and we never knew about it,” said Eric Bell, University of Michigan professor of astronomy in 2018 about his discovery that the Andromeda galaxy (also named M31), our closest large galactic neighbor, shredded and cannibalized a massive galaxy two billion years ago.
An unknown phenomenon has been discovered in the Universe: three dozen dwarf galaxies far from each other had a simultaneous birth of new stars, an unexpected discovery that challenges current theories on how galaxies grow and may enhance our understanding of the universe.