Chad Trujillo

Chadwick A. Trujillo, born on November 22, 1973, is an American astronomer known for discovering many small planets and for co-discovering Eris. Eris is the most massive dwarf planet known in our Solar System.

Trujillo uses computer software to study the paths of objects far beyond the planet Neptune, called trans-Neptunian objects. In 2003, he worked with Michael Brown and David Rabinowitz to discover Eris. This discovery was important because Eris, with its moon Dysnomia, was found to be more massive than Pluto, changing how we understand objects in the outer Solar System.

Career

Chad Trujillo went to school in Oak Park, Illinois and later studied physics at the Massachusetts Institute of Technology. He finished his studies in astronomy at the University of Hawaiʻi.

After finishing his studies, Trujillo worked at Caltech and then became an astronomer at the Gemini Observatory in Hawaii. Later, he led a department at the Gemini Observatory before becoming a teacher at Northern Arizona University.

Trujillo enjoys studying the Kuiper belt and the outer parts of our Solar System.

Discoveries

As of February 2026^[update], Trujillo is credited by the Minor Planet Center with finding and sharing the discovery of 88 numbered minor planets between 1996 and 2017. Many of these are special objects called trans-Neptunian objects from the Kuiper belt (see table). The last big object he helped find, named Eris, was once thought to be the tenth planet. But experts decided it belongs to a group called dwarf planets.

The possible dwarf planets Trujillo helped discover include:

• Quaoar, found with Brown
• Sedna, found with Brown and Rabinowitz, possibly the first known object from the far-out Oort cloud
• Orcus, found with Brown and Rabinowitz
• Eris, found with Brown and Rabinowitz – the biggest known trans-Neptunian object heavier than Pluto
• Haumea, also claimed by the Sierra Nevada Observatory, Spain (also see José Luis Ortiz Moreno).
• Makemake, found with Brown and Rabinowitz in 2005, one of the first five official dwarf planets.

List of discovered minor planets

See also: Category:Discoveries by Chad Trujillo

As of February 2026^[update] Minor Planet Center credits Chad Trujillo with the discovery and co-discovery of 88 minor planets during 1996–2017.

Satellites and uncredited discoveries

Honors and awards

The main-belt asteroid 12101 Trujillo is named for him.

In 2006 he was named one of the Science Spectrum Magazine Trailblazer, a top minority in science.