New data from ESA's Gaia spacecraft reveals that most dwarf galaxies are passing through for the first time.
A dwarf galaxy is thousands orbillions of stars gathered in one place. Previously, scientists believed that the dwarf galaxies surrounding the Milky Way were its satellites and that they had been here for many billions of years. To test this, the authors of the new work calculated how dwarfs move with unprecedented accuracy.
François Hammer, staff member of the Paris ObservatoryThe University of Science and Literature and colleagues used data from the Gaia apparatus to calculate the motion of 40 dwarf galaxies around the Milky Way. The researchers calculated three-dimensional velocities for each galaxy and angular momentum.
They discovered that these galaxies are movingmuch faster than the giant stars and star clusters that orbit the Milky Way. They do this so quickly because they have never been in orbit around the Milky Way before.
If they were in orbitPreviously, interaction with our galaxy and its contents would have drained their orbital energy and angular momentum. The Milky Way has already destroyed several dwarf galaxies in the past. For example, 8-10 billion years ago this happened to Gaia-Enceladus.
The authors of the new work concluded that the galaxies around us appeared in the last few billion years, which means that they are younger than previously thought.
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