The Milky Way Gets a New Origin Story

The bundles of wires, known as spherical bunches, have indicated additional mergers. Diederich Krijjsen, an astronomer at the University of Heidelberg, Germany, used galaxy simulations to train a neural network to investigate spherical clusters. He had studied his age, makeup and classes. From that data, the neural network can reconstruct collisions that gather galaxies. Then he let it loose on data from the actual Milky Way. The program reconstituted events known as Gaia-Enceladus, as well as an older, more significant merger that the group termed the Kraken.

In August, Kruijssen’s group published Milky Way merger dynasty And dwarf galaxies formed it. They also predicted the existence of 10 additional previous collisions, which they are hoping will be confirmed with independent observations. “We haven’t got the other 10 yet,” Kruijssen said, “but we will.”

All these mergers have led some astronomers suggest That the halo may be composed almost exclusively of immigrant stars. Models from the 1960s and 70s predicted that most Milky Way halo stars should have been formed. But as more and more stars have been identified as galactic interlopers, astronomers may not need to assume that many, if any, stars are natives, Di Mateo said.

A still-growing galaxy

The Milky Way has enjoyed a relatively quiet history in recent eras, but an influx of new people continues. Stargazers in the Southern Hemisphere can spot with the naked eye a pair of dwarf galaxies, called magnanospheric clouds, large and small. Astronomers believed that the pair, like the moons of the Milky Way, are our stable orbiting companions.

A series of again Hubble Space Telescope Overview Between 2006 and 2013 it was found that they were like meteorites to come. Niti Kallivayalil, an astronomer at the University of Virginia, predicted the clouds to warm at a speed of about 330 kilometers per second — which was predicted.

Magellanic clouds, large and small, rise on the active volcano Mount Bromo in Bromo Semru Tanger National Park in Java, Indonesia.Photo: Gilbert Wankel

When a team led by an astronomer Jorge Penaurubia of the Royal Observatory of Edinburgh reduced the number a few years later, he concluded that early clouds should be extremely heavy – perhaps 10 times more powerful than previously thought.

“It’s been surprise after surprise,” Peñarrubia said.

Various groups have predicted that unexpectedly fleshy dwarfs might drag parts of the Milky Way, and this year Peñarrubia teamed up with Peterson to find evidence.

The problem with looking for galaxy-wide motion is that there is a severe outbreak of Milky Way stars, in which astronomers look out over one of the ice pieces. So Peñarrubia and Petersen spent most of the lockdown figuring out how to neutralize the motion of Earth and the Sun, and how to average the motion of the halo stars so that the outer fringe of the halo would serve as a static background. can do.

When they calibrated the data in this way, they found that the Earth, the sun, and the rest of the disk in which they sit are lurking in one direction – not toward the current state of the large Magellanic cloud, but around a billion. Years ago (the Milky Way is a lumbering animal with slow reflexes, Peterson explained). They recently Elaborated their findings In Nature astronomy.

The sliding of the disc against the halo undermines a fundamental assumption: that the Milky Way is an object in equilibrium. It could spin and slip through space, but most astronomers assumed that after billions of years, mature discs and haloes had settled into a stable configuration.

Peñarrubia and Petersen’s analysis disproves that notion. Even after 14 billion years, the merger continues to excavate the overall shape of the galaxy. This realization is just the latest change in how we perceive the great stream of milk in the sky.

“We have a new need to describe what we thought we knew about the future and the history of the Milky Way,” Peterson said. “

Original story Reprinted with permission from Quanta magazine, Editorial independent publication of Simons Foundation Whose mission is to increase public understanding of science by covering the development and trends of research in mathematics and the physical and life sciences.

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