In the Footsteps of Celestial Police

In the footsteps of the Celestial Police
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 value                     Actual value     
Mercury 0.40 AU 0.39 AU
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 19.6 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 near 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 Vesta in its orbital path

How to find Vesta (It will appear starlike, even through a telescope. Vesta will not be bright, but binoculars should reveal it.)
1. Gaze high in the west-northwest 90 minutes after sunset. See Map A.
2. Look for Orion and its bright stars Rigel and Betelgeuse.
3. Draw a line from Rigel to Betelgeuse and extend it for the same length. It ends at the 3rd magnitude Epsilon Geminorum (also known as Mebsuta).
4. Place Mebsuta on the northeastern side of the binocular field. On the southwestern 
edge is the 2.8 magnitude Mu Geminorum. 
5. Directly to its west is 3.3 magnitude Eta Geminorum. Place Eta in the field’s center.
6. See Map B
7. To the northwest of Eta lies the magnificent open cluster M35. Place it in the field’s 
8. Use Map C to identify Vesta.
9. On April 7, 8, and 9, Vesta passes immediately north of M35. 

Track its changing position from April 6 to April 11. You will quickly discover that it moves!

Bright moonlight will significantly hamper observations after April 11.

 Click on the image to print/view PDF

Map A - Vesta 2024

Map B - Vesta 2024

Map C - Vesta 2024