Yes, it is true, We are Star Dust
“We are stardust, we are golden
And we’ve got to get ourselves back to the garden”
Woodstock written and performed by Joni Mitchell in a nod to the 500,000 strong music festival at Woodstock 1969; she was supposed to perform there but her schedule got really messed up. So, she wrote a song. It has been recorded more than 400 times! Ms. Mitchell grew up in western Saskatchewan (Canada).
Her song still resonates with me after so many years have passed, and today more than ever, it has both a metaphysical and scientific significance. Its memory motivated me to share some science with you that has intrigued me more often these last few years. I am not a cosmologist or astrophysicist but we don’t have to be to enjoy the images that are now easily available to all of us, and especially after they are imprinted in our memories.
Lastly, whether or not we grew up with the “Book of Common Prayer”, most are familiar with this phrase: Dust to dust, ashes to ashes. How more descriptive can it be?
The Take Home Message
- Chemical composition of a “typical human” body.
2. After a survey of 150,000 stars, humans and our Milky Way galaxy share ~97% of the same chemicals.
3. Most recent estimates show that our Milky Way galaxy contains between 100 and 400 BILLION stars. That’s a lot of sharing!
4. Further, “…using our galaxy as a model, we can multiply the number of stars in a typical galaxy (100 billion) by the number of galaxies in the universe (2 trillion) The answer is an absolutely astounding number. There are approximately 200 billion trillion stars in the universe. Or, to put it another way, 200 sextillion.” And yes — -we share so much in common with that vastness!
5. Our Milky Way is estimated to be 13.6 Billion years old. The chemical composition has remained relatively constant for billions of years.
6. Modern humans have been on Earth for at least 200,000 years.
7. Oxygen (O2), 21% of our atmosphere and essential to life, was not an early component of Earth’s atmosphere for the approximately first 200 million years. That changed with the Great Oxygenation Event that now is believed to have begun ~300 B years ago when in the oceans O2 was produced in great quantities by cyanobacteria that emitted O2 during photosynthesis. The concentration grew to near today’s levels in only ~10 million years.
8. Water (H2O)…”Water is indeed essential for all life on, in, and above the Earth”. An “average” adult human male is ~60% water, a woman ~55%. Protecting fresh water is a priority of most countries, including my home. Millions of Environmental Refugees, most without adequate water, are globally in very vulnerable circumstances. North America, Europe and other better off counties are needing to adapt in ways not usually status quo.
9. What about organic molecules that are required for assembling proteins and nucleic acids (DNA and RNA)? In 2020 samples from the surface of the asteroid Ryugu were retuned to Earth by the extraordinary mission accomplished by Japan. Hisayoshi Yurimoto, project leader, stated Ryugu was “…was a type of stony carbon-rich asteroid with a chemical composition that is the most similar to that of the sun. These asteroids, rich in water and organic material, are a possible source of the seeds of life delivered to the nascent Earth billions of years ago.”
10. Have a look at these unique images from the Ryugu mission. https://www.hayabusa2.jaxa.jp/en/galleries/ryugu/
Humans have speculated for many years on how the chemical composition of our bodies came to be. We were only limited by the technology to learn the answer. We knew that these are the major elements: carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. Did those somehow simply become incorporated in situ during our organic evolution on Earth? With ever more powerful telescopes, on land and in space, having learned many years ago about the Hubble’s Law (and red shift) and now the Hubble Space Telescope did it become known that in fact we are composed of the same elements that are found in our cosmos. Spectral analyses of our Milky Way galaxy and now a catalog of the visible Universe where each galaxy contains ~100 billion stars, concludes that we humans (our biosphere) share about 97% of the same elements. The similarities increase as we probe closer to the centre of our galaxy: below, see the Sloan Digital Sky Survey (SDSS)
“For decades, science popularizers have said humans are made of stardust, and now, a new survey of 150,000 stars shows just how true the old cliché is: Humans and their galaxy have about 97 percent of the same kind of atoms, and the elements of life appear to be more prevalent toward the galaxy’s center, the research found.”
Sloan Digital Sky Survey (SDSS)
“The new catalog is already helping astronomers gain a new understanding of the history and structure of our Galaxy, but the catalog also demonstrates a clear human connection to the skies. As the famous astronomer Carl Sagan said, “we are made of starstuff.” Many of the atoms which make up your body were created sometime in the distant past inside of stars, and those atoms have made long journeys from those ancient stars to you.”
Slices through the SDSS 3-dimensional map of the distribution of galaxies. Earth is at the center, and each point represents a galaxy, typically containing about 100 billion stars. Galaxies are colored according to the ages of their stars, with the redder, more strongly clustered points showing galaxies that are made of older stars. The outer circle is at a distance of two billion light years. The region between the wedges was not mapped by the SDSS because dust in our own Galaxy obscures the view of the distant universe in these directions. Both slices contain all galaxies within -1.25 and 1.25 degrees declination.
Credit: M. Blanton and the Sloan Digital Sky Survey.
As a mere human I have a very hard time getting my head around the current estimates of the number of stars in our celestial home, the Milky Way, moreover the Universe. Current estimates range between 100 and 400 BILLION stars! It is inconceivable that we humans, just tiny blobs of protoplasm, are sharing the light and heavy metals that we possess from such an enormous mass of real matter as opposed to that elusive dark matter.
Finally, here’s a number for us to mull over and put or Milky Way in perspective — — currents estimates are that our Universe contains at least 200 billion trillion stars. Belief now is that that number will increase as more data is gathered by the James Webb Space Telescope.
Our Earth is a small, but such a very special grain of sand!
Thank you very much for taking your time to read my writing.
You can reach me at zackflorence2016@gmail.com. Here is a link to my profile: https://sites.google.com/view/zackflorencebiosketch/
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I am a “retired” scientist, in name-only. The diversity in my personal and academic lives have given me a richness in life that I might otherwise have missed.
