Published in 1998, Astronomy and Astrophysics Review, 9, 1-32

Abstract. We review the observed properties of the bright quasar 3C 273 and discuss the implications of these observations for the emission processes and in view of gaining a more global understanding of the object.

Continuum and line emission are discussed. The emission from the radio domain to gamma rays are reviewed. Emphasis is given to variability studies across the spectrum as a means to gain some understanding on the relationships between the emission components.

3C 273 has a small scale jet and a large scale jet. The properties of these jets are described. It is also attempted to relate the activity in the small scale jet to that observed in the radio and infrared continuum.

Table of Contents

• INTRODUCTION
• DISCOVERY AND EARLY WORK
• CONTINUUM EMISSION
• Radio Emission
• Millimetre and infrared emission
• Variability of the millimetre-IR emission
• The blue bump
• The variability of the blue bump
• X and gamma-ray emission
• The soft excess
• The medium energy component
• The Fe line
• The high energy component
• X-ray variability
• The Overall continuum spectral energy distribution
• THE MULTI-WAVELENGTH APPROACH TO THE CONTINUUM EMISSION
• LINE EMISSION
• Line variability
• THE JET
• The radio-optical jet
• The VLBI Jet
• THE HOST GALAXY
• UNDERSTANDING IT
• REFERENCES