Sisters of the Sun
Study Guide for Episode 8
Episode 8: Sisters of the Sun
People
• Edward Charles Pickering, Harvard astronomer who employed a team of women [his “computers”] to analyze star spectra. By the way, he did not originate the term computer as a job title for one who computes.
• Annie Jump Cannon, "computer" team leader, who devised the classification of star types that astronomers still use today.
• Henrietta Swan Leavitt, a leading team member, who found a way to measure distances to certain types of stars, also still widely used——Edwin Hubble suggested that she should have received the Nobel Prize for this discovery, but she died before he received his prize, which recognized work in which he used her Leavitt's tools to discover that the universe is expanding.
• Cecilia Payne-Gaposchkin, who first determined the elemental composition of stars, and was the first to surmise correctly that young stars are composed almost completely of hydrogen. She also pioneered the movement of women into main-stream astronomy when she earned a PhD at Harvard.
Ideas
• Stellar spectroscopy, composition of stars (that is, the elements they contain), star classification.
• Star spectra are revealed by allowing starlight to pass through a prism, which sends the different wavelengths of white light in slightly different directions, dispersing it into its component colors. See an animation of this process in the Wikipedia article on prisms, HERE.
• The light from stars is one form of electromagnetic radiation (EM). Learn more about EM HERE.
• How far away is that star? Different methods of measurement are used for stars that are near (closer than 500 light years), at intermediate distance (out to tens of millions of light years), or very far away (in other galaxies). The methods rely upon, respectively, on parallax, Cepheid variable stars, or Type-Ia supernovae (an example shown during this episode). Click HERE to learn more. To learn even more, look up each method in Wikipedia: parallax ---- Cepheid variable stars ---- type Ia supernovae. Look HERE for a pretty clear description of the current limitations of determining distances by the parallax method.
• Standard candles: Cepheid variables and Type Ia supernovae are called standard candles. Their inherent brightness is known (because of the physics that produces their light), and so their apparent brightness can tell us their distance (their light dims with the square of their distance). They help scientists measure absolute distances to stars and galaxies.
Updates
• Regarding myths about the Pleiades. The evolution of myths can be studied by the same methods used to make evolutionary trees from genetic information. Scientific American, December 2016. (Please let me know if you are told that you need a subscription to to see this article.)
• Seeing invisible stars. Detection of gravity waves gives the first direct evidence of black holes. Read more HERE.
• REALLY seeing invisible stars. A earth-sized telescope aims to image the silhouette of the event horizon of our galaxy's supermassive black hole. Read more HERE about the Event Horizon Telescope.
• The idea of early inflation of the universe is somewhat under siege (see second item under Updates for Episode 5). In addition, both dark matter and dark energy are being intensively questioned, because some of their predicted effects have so far eluded detection.
• The last figure in the Wikipedia entry on EM shows the affect of our atmosphere on incoming and outgoing EM. Note that our atmosphere is very transparent to radio waves, visible light, and some wavelengths of IR. New plastics show promise for using the largest IR window (at 10 um) for cooling by sending heat directly to outer space via that window. New plastics would absorb heat over the full IR range, but retransmit it at 10 um, meaning that it will go directly to outer space at the speed of light. Sounds like science fiction? More HERE.
Readings
• Have you seen the recent movie, "Hidden Figures"? It depicts another group of unsung scientific heroes who held jobs with the title "computer".
• Poem: "Telescope," by Louise Glück. Read it HERE.
• Edward Charles Pickering, Harvard astronomer who employed a team of women [his “computers”] to analyze star spectra. By the way, he did not originate the term computer as a job title for one who computes.
• Annie Jump Cannon, "computer" team leader, who devised the classification of star types that astronomers still use today.
• Henrietta Swan Leavitt, a leading team member, who found a way to measure distances to certain types of stars, also still widely used——Edwin Hubble suggested that she should have received the Nobel Prize for this discovery, but she died before he received his prize, which recognized work in which he used her Leavitt's tools to discover that the universe is expanding.
• Cecilia Payne-Gaposchkin, who first determined the elemental composition of stars, and was the first to surmise correctly that young stars are composed almost completely of hydrogen. She also pioneered the movement of women into main-stream astronomy when she earned a PhD at Harvard.
• Stellar spectroscopy, composition of stars (that is, the elements they contain), star classification.
• Star spectra are revealed by allowing starlight to pass through a prism, which sends the different wavelengths of white light in slightly different directions, dispersing it into its component colors. See an animation of this process in the Wikipedia article on prisms, HERE.
• The light from stars is one form of electromagnetic radiation (EM). Learn more about EM HERE.
• How far away is that star? Different methods of measurement are used for stars that are near (closer than 500 light years), at intermediate distance (out to tens of millions of light years), or very far away (in other galaxies). The methods rely upon, respectively, on parallax, Cepheid variable stars, or Type-Ia supernovae (an example shown during this episode). Click HERE to learn more. To learn even more, look up each method in Wikipedia: parallax ---- Cepheid variable stars ---- type Ia supernovae. Look HERE for a pretty clear description of the current limitations of determining distances by the parallax method.
• Standard candles: Cepheid variables and Type Ia supernovae are called standard candles. Their inherent brightness is known (because of the physics that produces their light), and so their apparent brightness can tell us their distance (their light dims with the square of their distance). They help scientists measure absolute distances to stars and galaxies.
Updates
• Regarding myths about the Pleiades. The evolution of myths can be studied by the same methods used to make evolutionary trees from genetic information. Scientific American, December 2016. (Please let me know if you are told that you need a subscription to to see this article.)
• Seeing invisible stars. Detection of gravity waves gives the first direct evidence of black holes. Read more HERE.
• REALLY seeing invisible stars. A earth-sized telescope aims to image the silhouette of the event horizon of our galaxy's supermassive black hole. Read more HERE about the Event Horizon Telescope.
• The idea of early inflation of the universe is somewhat under siege (see second item under Updates for Episode 5). In addition, both dark matter and dark energy are being intensively questioned, because some of their predicted effects have so far eluded detection.
• The last figure in the Wikipedia entry on EM shows the affect of our atmosphere on incoming and outgoing EM. Note that our atmosphere is very transparent to radio waves, visible light, and some wavelengths of IR. New plastics show promise for using the largest IR window (at 10 um) for cooling by sending heat directly to outer space via that window. New plastics would absorb heat over the full IR range, but retransmit it at 10 um, meaning that it will go directly to outer space at the speed of light. Sounds like science fiction? More HERE.
Readings
• Have you seen the recent movie, "Hidden Figures"? It depicts another group of unsung scientific heroes who held jobs with the title "computer".
• Poem: "Telescope," by Louise Glück. Read it HERE.
