Footsteps of 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 4 Vesta in its orbital path

How to find Vesta (4 Vesta will appear starlike, even through a telescope. It will not be bright, but binoculars should reveal it.)
1. Gaze towards the east-southeast 75 minutes before sunrise toward brilliant Venus, and Saturn and Mars. See Map A.
2. Look immediately west of those three planets for the “chevron” shaped constellation Capricornus. It lies east of the more familiar “Teapot” of Sagittarius. See Maps A & B.
3. Vesta lies near the center of the chevron at the beginning of April. Identify Theta and 19 Capricorni. See Map C.
4. Triangulate along the line of these stars during the month: 19, Theta, Iota, Gamma, Delta, all easily seen in binoculars.
5. Mars and Saturn are in eastern Capricornus below brilliant Venus, far from Vesta’s position. Red Mars quickly moves eastward, passing the bright Saturn by April 5.
6. Vesta will be closest to Theta on April 10 and 11, and Iota on April 20, passing to their north. By the end of April, it will have moved north of Gamma.

 Click on the image to print/view PDF

Map A - Vesta 2022

Map B - Vesta 2022

Map C - Vesta 2022


  •  4 Vesta is 325 miles (525 km) in diameter (15% that of our moon).
  • At the beginning of April, it lies 230 million miles (371 million km) from Earth, and at the end of the month, it moves farther away to 202 million miles (326 million km).