In the Footsteps of the Celestial Police (Observing Challenge)
Frances AzarenDuring Global Astronomy Month (GAM), AWB shares a series of observing challenges, developed by John Goss and The Astronomical League for astronomy novices to seasoned pro's. Some of these challenges can be completed in a night while others encourage participation for the full month.
Sidewalk astronomers and astronomy club members are invited to create events and engage the public using any of the observing challenges. Please register your event here.
Share your photos from this challenge with us and the world on Facebook, or Tweet using #GAM2019 hashtag and follow (@awb_org).
A Binocular Activity
Eighteenth century astronomers felt there was something wrong with our solar system. They suspected that an unknown planet existed, moving between the orbits of Mars and Jupiter at 2.8 Astronomical Units from the sun. A curious mathematical relationship, eventually called the Bode–Titus Law (BT), had been formulated which seemed to satisfactorily describe the relative spacing of the planetary orbits. A planet was predicted orbiting 2.8 AU from the sun, but nothing was seen.
Planetary Spacing Table
| Planet | B–T Actual value (AU) |
Actual value (AU) |
| Mercury | 0.40 | 0.39 |
| Venus | 0.70 | 0.72 |
| Earth | 1.00 | 1.00 |
| Mars | 1.60 | 1.52 |
| ? | 2.80 | ---- |
| Jupiter | 5.20 | 5.20 |
| Saturn | 10.0 | 9.54 |
| Uranus | 19.60 | 19.19 |
Neptune was not known at the time
European astronomers felt strongly enough about the reality of this unknown planet that they formed a team, nicknamed the “Celestial Police,” to search for it. However, a new body was spotted shortly before they could begin their organized search. On the night of January 1, 1801, team member Guiseppe Piazzi spied a starlike object that had moved slightly in the heavens between the Hyades and Pleiades star clusters. It was soon realized that it was a small body located near the same distance from the sun as was the “missing” planet predicted by the Bode-Titus law. It was eventually called Ceres.
Three other small bodies were discovered over the next few years, all lying about the same distance from the sun as Ceres. They were soon named Pallas, Juno, and Vesta. Over the years, many thousands of these small planetoids were found. They became known as asteroids.
Within the past twenty years, Ceres has been reclassified as a “dwarf planet.” The rest, including Pallas, Juno, and Vesta, are still referred to as asteroids.
Binocular Program: Tracking the asteroid 2 Pallas in its orbital path
How to find Pallas (2 Pallas will appear starlike, even through a telescope. It will not be bright, but binoculars should reveal it.)
