The vast majority of asteroids move in orbits between Mars and Jupiter, in what is known as the asteroid belt. Since the formation of the solar system, Jupiter's gravity has prevented this swarm of objects from ‘clumping together’ to form a full-fledged planet. The largest example is Ceres, with a diameter of almost 1000 km, but typically they are only a few kilometers in size. Asteroids whose orbits are well known are given an official number. There are now more than 800,000 of them, of which only about 25,000 have been given an official name. The naming of asteroids is reserved for the Working Group on Small Body Nomenclature (WGSBN) of the IAU.

The asteroid named after De Koter, number 12955, has a diameter of 2,347 km and orbits the sun in approximately 4.3 years. Professor Alex De Koter studies extremely massive stars and was chair of the Minnaert Committee for education and outreach at NOVA, the Netherlands Research School for Astronomy, from 2006 to 2021. In 2024, he also received the Kees de Jager Prize for his innovative approach and tireless dedication to astronomy education. Information about ‘his’ asteroid can be found here. “What a wonderful and special honor to have your name associated with an object in our solar system that has existed for billions of years,” says De Koter.

The asteroid named after Wijers, number 12956, orbits the sun in approximately 3.5 years and there is no information about its diameter. Professor Ralph Wijers studies high-energy explosions such as gamma-ray bursts and is editor-in-chief of the preprint server arXiv. He was also director of astronomy at the University of Amsterdam and chair of the advisory board for Dutch astronomy as a whole. Information about ‘his’ asteroid can be found here. “What a wonderful moment when, as a child and amateur, you looked up at the sky and now something with your name on it is flying around up there, while you were able to turn your hobby into your profession,” says Wijers.

Both objects were discovered in 1973 by Leiden astronomers Ingrid van Houten-Groeneveld and Cees van Houten. Between 1950 and 1970, they discovered a total of no fewer than 4,643 asteroids on photographic plates. These images came from the Palomar Observatory in California (United States) and were taken there by Dutch-born astronomer Tom Gehrels.