Our Milky Way is Apparently a Cannibal

Did you know that galaxies - like our own Milky Way - orbit each other like planets orbit stars? 

We’ve already discovered more than 50 galaxies that, like satellites, orbit our galaxy. The largest of these is called the Large Magellanic Cloud or LMC. It is a dwarf galaxy that looks like a faint cloud in the night sky. 

Milky Way tearing apart LMC:

Research highlights that many of the small 'dwarf' galaxies orbiting the Milky Way galaxy are actually stolen from the neighbouring Large Magellanic Cloud, or LMC. It includes several ultra faint dwarfs and bright well known satellite galaxies such as Carina and Fornax.

How was this discovered?

The discovery was made by observing the motion of nearby galaxies using the Gaia space telescope and then feeding the information to hydrodynamical simulations. Scientists used the positions in the sky and predicted the velocities of materials such as dark matter near the LMC. These observations show that at least four ultra faint dwarfs and two classical dwarfs, Carina and Fornax, used to be satellites of the LMC. 

The reports suggest that the Milky Way galaxy used its gravitational field to tear apart the LMC and steal these satellites.

Laura Sales, the lead of the research team says “These results are an important confirmation of our cosmological models, which predict that small dwarf galaxies in the universe should also be surrounded by a population of smaller fainter galaxy companions.” 

She added, “This is the first time that we are able to map the hierarchy of structure formation to such faint and ultra faint dwarfs.”

What does this indicate and how is it important?

These findings play an important role in knowing about the formation of the Milky Way galaxy and also about the total mass of the LMC.

“If so many dwarfs came along with the LMC only recently, that means the properties of the Milky Way satellite population just 1 billion years ago were radically different, impacting our understanding of how the faintest galaxies form and evolve,” Sales said. 

What’s next?

The next objective of the team is to study how stars are formed in the satellites of LMC sized galaxies, and how this relates to dark matter mass present in these galaxies. 

“It will be interesting to see if they form differently than satellites of Milky Way-like galaxies,” Sales said. 

More about LMC: 

LMC and galaxies similar to it host numerous tiny dwarf galaxies, many of which contain no stars at all — only dark matter. 

The LMC used to be isolated but it became a satellite of the Milky Way galaxy after it was pulled by its gravitational forces. 

“The LMC hosted at least seven satellite galaxies of its own, including the Small Magellanic Cloud in the Southern Sky, prior to them being captured by the Milky Way,” says one of the scientists. 

Scientists expect that the number of tiny dwarf galaxies hosted by LMC might be higher than estimated. Many of these galaxies inside LMC might not contain any star too.