Sagittarius dwarf galaxy tagged posts

Data from ESA’s Gaia mission is re-writing the history of our galaxy, the Milky Way. What had traditionally been thought of as satellite galaxies to the Milky Way are now revealed to be mostly newcomers to our galactic environment.

A dwarf galaxy is a collection of between thousand and several billion stars. For decades it has been widely believed that the dwarf galaxies that surround the Milky Way are satellites, meaning that they are caught in orbit around our galaxy, and have been our constant companions for many billions of years. Now the motions of these dwarf galaxies have been computed with unprecedented precision thanks to data from Gaia’s early third data release and the results are surprising.

François Hammer, Observatoire de Paris—Un...

Artist’s impression of a perturbation in the velocities of stars in our Galaxy, the Milky Way, that was revealed by ESA’s star mapping mission, Gaia. Credit: ESA, CC BY-SA 3.0 IGO

ESA’s star mapping mission, Gaia, has shown our Milky Way galaxy is still enduring the effects of a near collision that set millions of stars moving like ripples on a pond. The close encounter likely took place sometime in the past 300-900 million years. It was discovered because of the pattern of movement it has given to stars in the Milky Way disc – one of the major components of our Galaxy.

The pattern was revealed because Gaia not only accurately measures the positions of more than a billion stars but also precisely measures their velocities on the plane of the sky...

This image shows the model of the tidally shredded Sagittarius dwarf galaxy wrapping around a 3-D representation of the Milky Way disk (flattened blue spiral). The yellow dot represents the position of the Sun. Credit: David R. Law/UCLA.

An international team has performed detailed measurements of the chemical composition of 158 red giant stars in the nearby Sagittarius dwarf galaxy. The study is so far the largest and most chemically extensive high-resolution survey of this galaxy. Discovered in 1994, Sagittarius is a nearby, massive, elliptical loop-shaped satellite galaxy of the Milky Way. The dwarf is currently merging with our galaxy, resulting in massive tidal tails that can be found in the Galactic halo...