The four-year PhD program consists mostly of research under the supervision of the advisor(s). The course work consists of the yearly NOVA fall school (1 week), and attendence of summer/winter schools. Students are expected to participate actively in scientific meetings.
During their thesis, Leiden PhD students are paid as civil servants, which means that they earn competitive salaries (the current gross salary, including allowances, increases from EUR 33.240 (currently about 35.5k USD) in year 1 to EUR 42.468 (currently about 45.4k USD) in year 4) and are eligible for both social security and retirement benefits. PhD positions are funded for four years. At the end of the four-year period, the student submits a PhD thesis, which is ceremoniously defended in the historical Academy building.
PhD students from Leiden succeed exceptionally well on the international job market. One of the most prestigious fellowships in world astronomy is NASA's Hubble fellowship. More astronomers with a doctoral degree from Leiden have won Hubble fellowships than from any other university outside the USA. Many of the faculty members, PhD students, and undergraduates have an international background. English is the common language.