Most of the atoms in your body likely spent millions of years circling the Milky Way on a cosmic “conveyor belt” before returning to our galaxy prior to the solar system‘s creation, a new study suggests.
Most elements in the universe, except for hydrogen and helium (and a few other weird exceptions), were forged by stars, either through nuclear fusion deep within their cores or during gigantic stellar explosions, known as supernovas. These explosions also disperse the newly forged materials into interstellar space. The matter then forms giant clouds that eventually condense into new stars surrounded by other objects, such as planets, moons, asteroids, comets — and in Earth’s case, people.
For decades, scientists assumed that matter expelled by exploding stars slowly drifted through interstellar space before reforming into new star systems. However, in 2011, scientists discovered that some atoms, including oxygen, iron and other heavier elements, can be expelled from their host galaxy by supernovae and get caught up in giant cosmic currents, known as the circumgalactic medium. These atoms eventually fall back into their original galaxy, including the Milky Way, and get turned into new stuff.
In a new study, published Dec. 27, 2024 in the journal The Astrophysical Journal Letters, researchers studying the circumstellar medium around distant galaxies have shown for the first time that carbon atoms can also be recycled via these cosmic currents. Scientists previously assumed this was unlikely, believing that carbon atoms are too light to be expelled from the galaxy. The team also showed that carbon is one of the most abundant elements within these extragalactic structures.
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This means that “the same carbon in our bodies most likely spent a significant amount of time outside of the galaxy,” study co-author Jessica Werk, an astrophysicist at the University of Washington, said in a statement. Given that other abundant atoms within human bodies, such as oxygen and iron, are also known to travel in the circumstellar medium, it is likely that a majority of the atoms in most people’s bodies have spent time outside the Milky Way.
The researchers made the discovery using data from the Hubble telescope’s Cosmic Origins Spectrograph, which measures how light from distant quasars (brightly glowing objects powered by active black holes) is affected as it passes through the circumstellar mediums of different…
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