"The Milky Way, our home galaxy, has been discovered to be too big for its surroundings.
Our galaxy is larger than should be expected for galaxies within our "cosmological wall," a local flat cluster of galaxies known as the Local Sheet, as described in a paper published in the journal Monthly Notices of the Royal Astronomical Society: Letters.
Galaxies within a wall tend to be a certain size relative to the overall size of the wall. The Milky Way, however, is much larger than would be expected based on the size of our Local Sheet, despite not being an uncommonly large galaxy on a universal scale. They discovered that a galaxy as large as the Milky Way existing in a cosmological wall of the scale of our Local Sheet was uncommon.
"So the Milky Way is, in a way, special," said Miguel Aragón, lead author and astronomer at Instituto de Astronomía in Mexico.
"The Earth is very obviously special, the only home of life that we know. But it's not the center of the universe, or even the solar system. And the sun is just an ordinary star among billions in the Milky Way. Even our galaxy seemed to be just another spiral galaxy among billions of others in the observable universe."
"You might have to travel half a billion light years from the Milky Way, past many, many galaxies, to find another cosmological wall with a galaxy like ours," Aragón said. He added: "That's a couple of hundred times farther away than the nearest large galaxy around us, Andromeda." But we think this 'too big for its wall' property is physically meaningful and observationally relevant enough to call out as really being special."
They found that to find another galaxy just as outsized in its own wall as the Milky Way is, you'd have to travel 160–200 megaparsecs, or between around 521,600,000 and 652,000,000 light years. In relative terms, the distance between the Earth and the sun is 0.000015565 light years—8 light minutes—and the distance between us and our nearest star system, Alpha Centauri, is around 4 light years.
The researchers note that their study combats our "Copernican bias," which is the assumption that our home galaxy is a completely average and uninteresting place."
Newsweek