The Milky Way Is Made Out Of Extragalactic Matter

milky way extragalactic matter

The Milky Way and all the stars, planets, and people in it may be made out of extragalactic matter.

In the beginning, the first stars formed from early hydrogen, creating helium. Eventually, as those stars collapsed and burst, they built carbon, oxygen, and, after a few cycles, iron, silver, and gold. The Milky Way is a later generation galaxy, and now scientists at the Northwestern University in Illinois have modeled how much of the matter that makes up our own galaxy originated during the supernovae in others. This means we all may be at least half composed of extragalactic matter.


We Are Aliens in Our Own Galaxy

Part of the theory involves the massive explosion of a supernova casting matter out into the void between galaxies, where then, over eons of time, other galaxies pass through, picking up this stray material. Another part involves “powerful galactic winds” that push the matter toward other galaxies after the explosions.

The Northwestern post-doctoral fellow Daniel Angles-Alcazar who led the study stated that the team ran very “sophisticated simulations”. Ones that were “looking at the formation of galaxies from shortly after the Big Bang and traced their development to today. We found that when we completed these simulations that we could say … that the atoms which formed the solar system and so which form us, may have existed in other galaxies.”

Scientists involved with the study, which was published in the Royal Astronomical Society’s Monthly Notices, found from the simulations that the winds would carry so much matter from galaxy to galaxy that half of the matter of which we are made might have originated in stars up to a million light years away. This extragalactic matter would take billions of years to make the journey. The nearest galaxy to the Milky Way is Andromeda, 2.5 million light years distant.

“Given how much of the matter out of which we formed may have come from other galaxies, we could consider ourselves space travelers or extragalactic immigrants,” Angles-Alcazar added.

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