Saturday SAVY, Day 2 – “Observing the Cosmos” (5th/6th)
Day 2 of Observing the Cosmos focused on scale and distance in the cosmos — how massive celestial objects are and how far apart they lie. We began by reviewing the primary tool for astronomers, which is light. We briefly introduced spectroscopy and how absorption and emission spectra reveal basic properties of stars. We also examined how astronomers measure stellar distances and how apparent groupings form the constellations we use to navigate the night sky.
Because stars lie at different distances and move slowly relative to us, constellations change shape over millennia. Using 3D models of Ursa Major (the Big Dipper) and Orion with stars placed at different X, Y, Z coordinates, students viewed the models from a specific vantage point to see how familiar patterns appear. They then
made Orion take-home models based on real stellar distances to experience firsthand how vantage point and distance affect perceived groupings.
After lunch, we explored the scales within our solar system. We also examined scaled representations of the terrestrial (rocky) planets and the Jovian gas giants relative to the Sun. To get a sense of distance, we completed a planet walk using a 1:18,000,000,000 scale (the Sun modeled as a 3-inch sphere). Students estimated planet distances and observed how the terrestrial planets cluster near the Sun while the gas giants lie much farther out. By Neptune, we reached Edgehill Ave across from the Wyatt Center, where we began.
Back inside, we modeled cosmic expansion and Hubble’s Law with balloons. We discussed Edwin Hubble’s discovery that what were once considered nebulae are actually distant galaxies, and that galaxies recede from us at speeds roughly proportional to their distance — evidence that the universe is expanding. For the demonstration, colored sticky dots on an inflating balloon represented galaxies; as the balloon expanded, the distances between dots and the wavelength of a drawn wave increased, illustrating redshift and recession.
Thought Inspirations and Questions for your Budding Astronomers:
- What fundamental property does an astronomer use to study stars and other celestial objects? (Light)
- How does splitting light (spectroscopy) help us learn what a star is made of? (Absorption/emission lines reveal gases)
- Why will constellations look different thousands of years from now? (Stars are at different distances and move over time.)
- In our planet walk, which planets were clustered near the Sun, and which were much farther away? (Terrestrial vs. Jovian)
- What does Hubble’s Law tell us about the motion of galaxies and the universe? (Galaxies recede with speed roughly proportional to distance; the universe is expanding.)
It was wonderful spending some more time with your children learning more about the cosmos, and we look forward to exploring Hubble’s Law and Photometry next week!
NOTE: Not all students completed the Orion model activity in class, so we provided materials for them to complete it at home if they wish. The stellar distances for placing their stars in shown below. As a reminder, the X/Y grid on the model is 25 ly each way per mark. The X-axis is shorter. The Y-axis is longer, and Z is the space between the top and bottom foam plates. For the paper rulers, each tick mark on the Z scale is x10 ly. For example, a tick mark at 2 indicates a distance of 20 ly (measured from the bottom of the model up).
NAME X Y Z
Rigel 101 329 33
Betelgeuse 30 161 117
Bellatrix 44 69 102
Alnilam 94 606 75
Alnitak 60 364 75
Saiph 44 309 27
Mintaka 82 413 86
