employer pieter johannes van rhijn
Pieter Johannes van Rhijn ( March 24 , 1886 -- May 9 , 1960 ) was a Dutch astronomer . Born in Gouda , he studied at Groningen . He served as director at the Sterrenkundig Laboratorium ( Kapteyn Astronomical Institute ) in Groningen and later served for many years as president of the International Astronomical Union ( 1932 - 1958 ) . He died in Groningen . The crater van Rhijn on the Moon is named after him , as is asteroid 2203 van Rhijn . The Kapteyn Astronomical Institute is the department of astronomy of the ___MASK100___ in the Netherlands . A star is a luminous sphere of plasma held together by its own gravity . The nearest star to Earth is ___MASK20___ . Many other stars are visible to the naked eye from Earth during the night , appearing as a multitude of fixed luminous points in the sky due to their immense distance from Earth . Historically , the most prominent stars were grouped into constellations and asterisms , the brightest of which gained proper names . Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations . However , most of the stars in the Universe , including all stars outside our galaxy , the Milky Way , are invisible to the naked eye from Earth . Indeed , most are invisible from Earth even through the most powerful telescopes . Asteroids are minor planets , especially those of the inner Solar System . The larger ones have also been called planetoids . These terms have historically been applied to any astronomical object orbiting ___MASK20___ that did not show the disc of a planet and was not observed to have the characteristics of an active comet . As minor planets in the outer Solar System were discovered and found to have volatile - based surfaces that resemble those of comets , they were often distinguished from asteroids of the asteroid belt . In this article , the term " asteroid " refers to the minor planets of the inner Solar System including those co - orbital with Jupiter . The Netherlands is the main constituent country of the Kingdom of the Netherlands . It is a densely populated country located in Western Europe with three island territories in the Caribbean . The European part of the Netherlands borders Germany to the east , Belgium to the south , and the North Sea to the northwest , sharing maritime borders with Belgium , the United Kingdom , and Germany . The largest cities in the Netherlands are ___MASK21___ , Rotterdam , The Hague and Utrecht . ___MASK21___ is the country ' s capital , while The Hague holds the Dutch seat of government and parliament . The name " Holland " is used to refer informally to the whole of the country of the Netherlands . The International Astronomical Union ( IAU UAI ) is an international association of professional astronomers , at the PhD level and beyond , active in professional research and education in astronomy . Among other activities , it acts as the internationally recognized authority for assigning designations to celestial bodies ( stars , planets , asteroids , etc .) and any surface features on them . Groningen ( Gronings : " Grunnen ") is the main municipality as well as the ___MASK6___ city of the eponymous province in the Netherlands . With a population of 201 , 865 , it is the largest city in the north of the Netherlands . An old city , Groningen was the regional power of the northern Netherlands , a semi - independent city - state and member of the German Hanseatic League . Groningen is a university city : it houses the ___MASK100___ ( about 30 , 000 students ) and the Hanze University of Applied Sciences ( about 25 , 000 students ). The ___MASK100___ ( abbreviated as UG abbreviated as " RUG ") is a public research university in the city of Groningen in the Netherlands . The university was founded in 1614 and is one of the oldest universities in the Netherlands as well as one of its largest . Since its inception more than 200 , 000 students have graduated . It is a member of the distinguished international Coimbra Group of European universities .