From Melanie Mueller, Acting Director, Niels Bohr Library & Archives:
The following piece was written by science writer and author Jacob Berkowitz, who visited the Niels Bohr Library & Archives to continue research for his book about the 20th century American astronomer Paul W. Merrill. Merrill’s own papers are held in the Huntington Library in California where Jacob was a Dibner History of Science Fellow. As part of his research in Merrill’s papers, Jacob came across significant correspondence with William F. Meggers, whose papers are held here in the Niels Bohr Library & Archives. Jacob came here to see the 40+ letters from Merrill that appear in the papers of William Meggers, in an effort to read both sides of conversations between Merrill and Meggers that took place between 1918 and 1954.
On the Origins of "We Are Stardust"
Jacob Berkowitz, Author
Most of us are familiar with the saying, made popular by astronomer Carl Sagan, folk singer Joni Mitchell, and countless inspirational posters and billboards—We are stardust. Yet, how do we know that we’re stardust? Put another way, what’s the observational evidence that we’re made of elements forged in dying stars? Part of it is here in the Niels Bohr Library & Archives.
I became interested in the stardust origins question while writing my previous book, The Stardust Revolution, which chronicles the history of astrobiology. When it comes to the discovery of the expanding universe, we’re quick to point to astronomer Edwin Hubble’s iconic observations of galaxies having a greater and greater redshift the further away they are.
I think the observational evidence for our stardust origins was discovered by one of Edwin Hubble’s Mount Wilson Observatory colleagues, Paul Willard Merrill. Hubble provided the observational evidence for cosmic expansion, Merrill for cosmic evolution (evolution in the way biologists rather than astrophysicists use the term).
In a nutshell, the observational clincher for our stardust origins was Merrill’s 1951 detection—using a spectrogram, taken by the newly minted Palomar telescope—of the short-lived radioactive element technetium in the atmosphere of a red giant star. With a half-life of only tens of thousands to several millions of years, astrophysicists quickly surmised that the only way technetium, element 43, could be in the star is if that star were making the element, and by extension, most other elements of the Periodic Table.
So how did Merrill know how to spot technetium in a star light years away? Here’s where we come to the Niels Bohr Library & Archives. It was due to research by Merrill’s one-time Bureau of Standards (now NIST) colleague William Meggers, who’d recently published a detailed description of technetium’s spectrum. Technetium was isolated and identified in 1936, the first human-made element, and thus its name, Greek for artificial. Meggers was one of the world’s leading spectroscopists, and in 1948–49 he spent months painstakingly identifying technetium’s spectral lines and atomic energy levels.
Meggers’ massive (more than 100 linear feet) and detailed collection of correspondence—including letters from his childhood and home movies—is in the AIP Niels Bohr Library & Archives. I’d read Merrill’s correspondence with Meggers in the Merrill collection at the Huntington Library in Pasadena, California. Now I wanted Meggers’ perspective. I found gems, one in particular that reaffirms the value of basic physics research.
In a May 25, 1949, letter to Jesuit Father Alois Gatterer, a spectroscopist at the Vatican Observatory, Meggers wrote:
“At present, I am making descriptions of the arc and spark spectra of artificial elements having atomic numbers 43 and 61. We now have several thousand new spectral lines with wave lengths measured to +/-0.01A [Angstroms], but it is doubtful if they ever have any practical value.”
This from the man who gave Merrill the “eyes,” so to speak, to see our stardust origins.