In his timeless statement, Carl Sagan declared, "The cosmos is within us. We are made of star stuff. We are a way for the universe to know itself."
This profound idea, discussed by Sagan before his passing in 1996, is revisited in a recent Chasing Starlight video by the European Southern Observatory (ESO), where astrophysicist Suzanna Randall sheds light on its connection to the elemental composition of our bodies.
Are We Made of Stardust? Revisiting Carl Sagan's Insight on the Cosmic Seeds of Life
From Stardust to Humans: Tracing the Cosmic Cycle of Elements and Life's Origins
Randall explained that after the Big Bang, the universe primarily consisted of hydrogen and helium, along with a trace of heavier elements. However, these elements alone couldn't create complex structures like the human body.
About 100 million years post-Big Bang, nebulas formed from vast clouds of hydrogen and helium, eventually collapsing under gravity to birth the first generation of stars, composed mainly of hydrogen and helium.
The first stars lacked essential heavy elements for body formation. Aging into red giants, they fused helium into crucial components like carbon and oxygen within their cores. While the universe gained life-necessary elements, they were confined to red giants.
Stars with more than eight solar masses continued fusing elements, ultimately exploding as supernovae, scattering forged elements into the cosmos. These elements integrated into nebulas, contributing to the next generation of stars, which were more "metal-rich."
This cosmic cycle, culminating in our sun's creation, formed planets, including Earth, where our bodies' elements originated. In essence, Sagan's statement aligns human existence with stellar life cycles, a realization that humorously noted by Randall, shouldn't evoke excessive pride, as even cockroaches share this cosmic origin.
Panspermia: Exploring Life's Cosmic Seeds
Venturing into the theoretical realm, astrophysicist Z.N. Osmanov, from the Georgian Free University of Tbilisi, explores the concept of panspermia in an academic paper, titled "The possibility of panspermia in the deep cosmos by means of the planetary dust grains" available in the preprint server arXiv. revisits the theory that life on Earth and potentially across the cosmos originates from the same microscopic particles forming stars and planets.
Osmanov proposes that microscopic particles forming stars and planets might be the cosmic seeds of life, with potential hosts numbering around 3×10^7 planets. He envisions the Milky Way as potentially filled with complex molecules if dust particles can traverse significant distances, offering a perspective that challenges current understanding.
The astrophysicist suggests that dust containing life could travel via solar radiation pressure, reaching nearby solar systems within thousands of years. However, Osmanov clarifies that his argument doesn't assert an infinite number of planets with actual life but rather a multitude potentially supporting primitive life forms.
Despite the intriguing concept, critics point out a significant unresolved issue: the origin of the dust and its role in sparking life. This challenge remains a substantial hurdle, keeping this fascinating theory within the realm of the theoretical.
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