TOPIC 00
Introduction
In January 1999, the Subaru Telescope achieved first light. Then, after nearly a year of testing and adjustments, open use of the telescope started in December 2000. Although there is not an agreed-upon starting point, I would like to define 2019 as the 20th anniversary of the Subaru Telescope. In this article, I will review the achievements made by the Subaru Telescope over the last 20 years.

Two decades, the time it takes for infants to grow to adulthood, seems both long and short. If a telescope’s lifetime is limited, how long would 20 years be? Looking around the world, you will find there are many telescopes that have been operational for more than 50 years. For example, the 188-cm reflector telescope at Okayama Astrophysical Observatory has been operational for 58 years since its construction. Likewise, the Hale telescope at Palomar Observatory is now 70 years old. Compared with these telescopes, the Subaru Telescope is much younger. It seems that, much like humans, the Subaru Telescope has just matured at the age of 20.
However, the Subaru Telescope has demonstrated its incredible ability and produced various scientific achievements since its infancy. The Subaru Telescope has achieved significant results in all the fields of astronomy accessible by optical-infrared observations. Space does not permit listing all of these achievements here, so I will introduce a selection of research topics based on press-releases.