Milky Way Still Presents The Effects Of The Ancient Collision With Antlia 2 “Ghost Galaxy”


In 2018, a team of scientists spotted the so-called Antlia 2 galaxy that’s orbiting the Milky Way, but a recent study concluded that the before-mentioned “ghost galaxy” was involved in an ancient collision with our home galaxy. The impact left some signs in the Milky Way as it’s still reeling due to that ancient collision. Another effect of that cosmic event would be the Milky Way’s wobbly galactic disc.

Our vision on the Milky Way galaxy relies on the observations we made on other spiral galaxies in the Universe. Also, astronomers know that Milky Way is mostly like a flat disc with a bulging core and spiral arms made of stars, dust, and gas. Recent observations, though, revealed that our galaxy’s disc is vertically rippled, and that would be the effect of the gravitational aftershocks caused by the ancient collision with Antlia 2 “ghost galaxy.”

Antlia 2 remained “hidden” until 2018 when ESA’s Gaia mission has spotted it. According to the data from the space probe, Antlia 2 is a quite unusual dwarf galaxy orbiting the Milky Way from a distance of 130,000 light years.

Milky Way Still Presents The Effects Of The Ancient Collision With A “Ghost Galaxy”

While Antlia 2 “ghost galaxy” is more massive than other dwarf galaxies, it’s unusually fainter than the others. Thus, it managed to remain unseen until 2018. Besides, Antlia 2’s orbit is hiding behind Milky Way’s bulge of stars from our galactic core. Accordingly, spotting the so-called “ghost galaxy” was challenging.

Thanks to the data gathered by ESA’ Gaia mission, the scientists from Rochester University managed to recreate o simulation of the ancient collision between Antlia 2 and Milky Way. The team of astronomers found out the effects of that past collision and managed to come up with a reliable model of those.

As reported in the Astrophysical Journal Letters, Antlia 2 “ghost galaxy” was the culprit of a “hit-and-run” that caused the wobbly galactic disc that Milky Way presents nowadays. Also, the galactic clash left some marks on Antlia 2, and the researchers hope that upcoming data from ESA’s Gaia satellite would help them better understand the ancient collision between the two galaxies.


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