# From Centaurs to comets - 40 years

## TL;DR

This paper reviews 40 years of research on Centaurs, a transitional class of minor bodies between TNOs and comets, highlighting discoveries, their diverse properties, and ongoing mysteries about their nature.

## Contribution

It provides a comprehensive overview of the evolution of knowledge about Centaurs over four decades, emphasizing their unique characteristics and the remaining questions.

## Key findings

- Centaurs can exhibit cometary activity and outbursts.
- They have diverse surface colors and spectral properties.
- Their population remains poorly understood despite extensive studies.

## Abstract

In 1977, while Apple II and Atari computers were being sold, a tiny dot was observed in an inconvenient orbit. The minor body 1977 UB, to be named (2060) Chiron, with an orbit between Saturn and Uranus, became the first Centaur, a new class of minor bodies orbiting roughly between Jupiter and Neptune. The observed overabundance of short-period comets lead to the downfall of the Oort Cloud as exclusive source of comets and to the rise of the need for a Trans-Neptunian comet belt. Centaurs were rapidly seen as the transition phase between Kuiper Belt Objects (KBOs), also known as Trans-Neptunian Objects (TNOs) and the Jupiter-Family Comets (JFCs). Since then, a lot more has been discovered about Centaurs: they can have cometary activity and outbursts, satellites, and even rings. Over the past four decades since the discovery of the first Centaur, rotation periods, surface colors, reflectivity spectra and albedos have been measured and analyzed. However, despite such a large number of studies and complementary techniques, the Centaur population remains a mystery as they are in so many ways different from the TNOs and even more so from the JFCs.