Oct. 18, 1977: The enigma of Chiron

Today in the history of astronomy, the first Centaur is discovered.
By | Published: October 18, 2025

Gemini Sparkle

Key Takeaways:

  • On October 18, 1977, Charles Kowal utilized the 1.2-meter Schmidt telescope at Palomar Observatory and a blink comparator to discover an 18th-magnitude object moving slowly between Saturn and Uranus.
  • Initially designated asteroid 2060 and subsequently named Chiron, this object presented an anomalous orbit and size for its observed location, posing a scientific puzzle.
  • Chiron was later identified as the inaugural member of an entirely new class of celestial bodies known as Centaurs.
  • Centaurs are defined as objects dislodged from the Kuiper Belt, serving as a transitional link between small planetesimals and mature planets, thus offering valuable insights into planetary formation mechanisms.

On Oct. 18, 1977, Charles Kowal was at the 1.2-meter Schmidt telescope at Palomar Observatory in California – reportedly his favorite equipment at the facility to observe with – when he unwittingly discovered an entirely new class of objects.

Kowal was conducting a survey for slow-moving objects beyond the Main Belt, taking two plates of the same location a few hours apart and searching them for differences using a blink comparator. He spotted one such difference – an 18th-magnitude object moving at a rate of only 3 arcminutes per day between Saturn and Uranus that was initially designated an asteroid, 2060. (Later, Kowal would name it Chiron, after a mythological centaur who was the son of Saturn and grandson of Uranus.) Chiron was a puzzle, with an orbit and size that didn’t fit its location. It would eventually be recognized as the first in a new class of cosmic objects: Centaurs. These travelers dislodged from the Kuiper Belt are the bridge between small planetesimals and full-fledged planets, making them a valuable evolutionary link for understanding planet formation.