A large portion of all atoms could descend from distant galaxies

Surprisingly foreign: About half of all atoms in the milky way - and in our bodies - could descend from different galaxies. The "foreign" material was brought to our galaxy by intergalactic winds and made star formation possible, as a simulation suggests. This matter-import could even have been temporarily playing the dominant role for evolution of galaxies in the univers, astronomers assume.

© NASA/JPL-Caltech/ ESO/R. Hurt

Our galaxy is not floating isolated in space: It is surrounded by a manifold of dwarf galaxies and far away from bigger neighbors like the Andromeda-Galaxy. For quite some time, there are indices that there is kind of a matter-exchange between those galaxies: The milky way exhausts streams of gas from its neighbors and even "steals" stars sometimes.

On the scent of galactic winds

Which amazing extent this intergalactic exchange is able to reach, Daniel Anglés-Alcázar from the Northwestern University and his colleague were able to discover. For this study they have used a numeric simulation, the realistic 3D-models of a galaxy and the defining processes generated by intergalactic winds.

"This is the way we retrace the origin of stars and determined if the star emerged from matter of the galaxy or if it was built from gas coming from a different galaxy."

Anglés-Alcázar explains.

50 percent was blown in

The results show: Galaxies like our milky way are surprisingly strongly shaped by such intergalactic winds. They constantly release big amounts of gas and dust, which is transported away by the winds and partly channeled back into the center of the galaxy.

"This wind-recycling dominates the gas reactions during the majority of the galaxy's time of evolution, the astronomers report."

The simulations reveal, that about 30 percent of the material bound by the star has once been recycled by its own galactic wind. But interestingly another 50 percent are of foreign origin: This atoms were exhausted by intergalactic winds from distant galaxies. This gas streams are moving with a few hundred kilometers per second through space and are even able to bypass long distances between galaxies over the time of millions of years.

Galaxy's half is foreign

This means, that our milky way could also consist of foreign material.

"It is very likely, that a majority of the matter in our galaxy has been in other galaxies at some time. It has been ripped out by strong winds and carried along through space, on its way to find a new homeland."

According to this, half of all atoms in our home-galaxy, the solar system and on Earth, could be from galaxies which lie millions of light-years away. Over time this galaxies delivered the building material for new stars and planets in our galaxy.

"Therefor it can be said, that all of us consist in a great part of extragalactic matter."

According to Anglés-Alcázar.

A new view on galaxy growth

"This results transform our understanding of how galaxies emerged after the Big Bang."

Claude-André Faucher-Giguère from the Northwestern University says. Its a long time, that astronomers suppose that matter transfer, i.e. through the collision of galaxies has been a driving power in the genesis of big galaxies.

But now it gets clear, that also the unobtrusive galaxy wind is playing a major role. Especially in the cosmic era this gas streams could be the dominant process, according to the astronomers.

"Our origins are much less local than we have thought before."

Tells us Faucher-Giguère.

"This study gives us an impression of how things around us are even connected to celestial objects that are far away."

Source: The cosmic baryon cycle and galaxy mass assembly in the FIRE simulations