Sunspots and Star Stuff: The Story of Payne

 

Sunspots, 12 of them to be precise, appear clustered in two active regions (AR2835 and 2836) in this image captured on a Sunday afternoon from my backyard (June 27, 2021). The larger spots show clear definition of umbra and penumbra after image processing. The capture process started with a video clip shot with an SLR attached to a scope, which is then used as a source of numerous stills which are "stacked" by software to produce a single sharp image - an approach I have described on prior posts. 

The "little" spots on the face of the sun are not so little in some ways. The larger ones in the active region AR2835 here, are actually larger in size than the earth.

Sunspot region 11944 at a size of 1480MH as seen by the Solar Dynamics Observatory.
The Earth (about 170MH) has been added for scale. Source: Spaceweatherlive.com

Sunspot sizes are measured in millionths of solar hemisphere (MH). For comparison, the earth is only about 170 MH. The largest sunspots in the above image are around 230 MH and therefore much larger than the earth. Not surprising since the diameter of the earth, is only about 1 % of the sun’s disc.

Sunspots are transient but some last for days. Sometimes long enough to come around a full circle as the sun spins in about 27 (earth) days on average.

What stars are made of:

So sunspots are planet-sized blisters on a gigantic ball of light. But until 1926 we did not know what that ball of light was actually made of. It is common knowledge today that the sun at its core is a nuclear fusion reactor mostly made up of Hydrogen (70% by mass) followed by Helium (27%). However even as late as 1925, scientists, based on spectroscopic comparisons made on earth, believed that the sun is of similar composition as the earth's crust.

In hindsight this seems like a ridiculous proposition. However it took nothing short of a pioneering astrophysicist, Cecilia Payne, and a gritty battle against the status quo, to establish what the Sun, and for that matter most stars, are made of. She correctly concluded, that the sun was mostly made of hydrogen. This was informed by an ionization theory named after the Indian scientist Meghnad Saha, whom she met at Harvard. Payne's PhD thesis finding, was that the variance in solar spectra was a function of levels of ionization at different temperatures, not the relative abundance of elements in the sun and it refuted prevalent wisdom.

Stardom of a different kind:

Cecilia Payne at her desk at the Harvard College Observatory
Smithsonian Institution Archives/ Wikimedia Commons

Cecilia Payne's life can be a case study in overcoming rules stacked against women in a male dominated field. At a time when society did not know what to make of a woman of ambition, that too of a scientific kind, she became a role model for women aspiring to be career scientists. Her journey started in the twentieth century U.K. where she overcame many hurdles to study math and science as a determined school girl. She eventually clinched an all expenses paid scholarship at Cambridge to study the sciences only to be denied a degree since Cambridge didn't award degrees to women at the time. Determined to fulfill her ambitions, she migrated to the U.S. utilizing a fellowship for women at the Harvard College Observatory.

At Harvard, as a lone 24 year old female PhD aspirant in astronomy, she was persuaded to omit the contrarian finding about the sun's composition. This she did, describing her own result as “spurious”. Later a male colleague would reach the same conclusion using different means, and despite acknowledging her prior work, would be often erroneously credited for it.

Unlike many talented women who have languished in obscurity, Payne's career ends on a triumphant note. Scientific achievements aside, she also scored several professional firsts: starting off as the first woman to receive a PhD in astronomy at Harvard, she eventually became the first female professor, and the first woman to become department chair there as well. In a trail blazing career marked by a quiet persistence she had shown the world what stars are truly made of.

-------------------------- References:

January 1, 1925: Cecilia Payne-Gaposchkin and the Day the Universe Changed by Richard Williams