![]() That paper called the SDG the “main dynamical architect of the Milky Way disk.” Each time the SDG passed through the Milky Way, it created ripples and compressions in the gas, which lead to accelerated star formation. Image Credit: ESAĪ paper published in 2020, and based on Gaia data, showed that these encounters led to episodes of increased star formation in the Milky Way. One of those encounters may have led to the birth of the Sun. The SGD has collides with the Milky Way at least three times, triggering accelerated star formation. But the encounter also triggers star formation in the Milky Way. Each time it does so, the Milky Way steals some of its stars, and the SDG becomes less massive after each encounter. The slam is more of a gravitational slam an interaction.Īstronomers think that the SGD has struck the Milky Way at least three times already: five or six billion years ago, two billion years ago, and one billion years ago. There’s too much space between all the stars for any to actual physical encounters. Suddenly, Sagittarius fell in and disrupted the equilibrium…” Tomás Ruiz-Lara, Instituto de Astrofísica de Canarias | IACĮach time the SGD orbits the Milky Way, it slams into it. So the Milky Way is something like 10,000 times more massive.īut even though the SGD is tiny compared to the Milky Way, it’s had a huge effect on it, especially on our little corner. While the Milky Way has a few hundred billion stars, its little neighbour has only a few tens of millions of them. It’s been orbiting the much more massive Milky Way for billions of years. One of the Milky Way’s neighbours is the Sagittarius Dwarf Galaxy (SDG). ![]() A Galactic Collision Formed the Sun?Ĭollisions and mergers play a huge role in the Milky Way, and possibly in our very existence. We now know that there’ve been other collisions, and we also know that the Milky Way is in the process of consuming the Magellanic Clouds, starting with their halo of gas. The Milky Way was much smaller then, only about four times larger than Gaia-Enceladus, so the collision must have created enormous upheaval. The lost galaxy, called Gaia-Enceladus, was consumed by the Milky Way. About 10 billion years ago, the Milky Way collided with a galaxy about the size of one of the Magellanic Clouds. Gaia data not only allowed researchers to find this merger remnant, it allowed them to piece together what happened. White circles indicate globular clusters that were observed to follow similar trajectories as the stars from Gaia-Enceladus, indicating that they were originally part of that system cyan star symbols indicate variable stars that are also associated as Gaia-Enceladus debris. The stars of Gaia-Enceladus are represented with different colours depending on their parallax – a measure of their distance – with purple hues indicating the most nearby stars and yellow hues the most distant ones. This graphic shows the distribution of the Gaia-Enceladus stars across the Milky Way. “The collection of stars we found with Gaia has all the properties of what you would expect from the debris of a galactic merger,” said Amina Helmi, lead author of the paper published in Nature. ![]() This group was the result of a galactic merger some time in the past. The team behind that research concluded that this was a separate population of stars. They also stood out from other stars on the Hertzsprung-Russell Diagram. They’re moving in “elongated trajectories in the opposite direction to the majority of the Galaxy’s other hundred billion stars, including the Sun,” according to a press release. But their motion is separate from the rest of the Milky Way. These stars are all around us, interspersed with other stars, and they’re all moving the same speed and direction. ![]() A team of researchers working with Gaia data found a family of 30,000 stars moving through the Milky Way.
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