Gart Westerhout died Oct. 14. He was 85. (Family Photo)

Gart Westerhout, a Dutch-born astronomer who gained international renown in the early 1950s when he helped chart the Milky Way galaxy with unprecedented precision, and who later created the astronomy program at the University of Maryland, died Oct. 14 at a senior living community in Catonsville, Md.

He was 85 and had retired in 1993 as scientific director at the U.S. Naval Observatory in Northwest Washington. His death was confirmed by his daughter Magda Westerhout Mobley.

Dr. Westerhout first came to prominence — principally in a field known as radio astronomy — in Holland in the years after World War II. He was among the youngest in a pioneering group of scientists taught and led at the University of Leiden by astronomer Jan Oort, who has been compared to a “modern Copernicus.”

For centuries, astronomers have observed the universe with the human eye, aided by tools such as telescopes. Dr. Westerhout joined the nascent field of radio astronomy and set out to study the heavens using radio waves emitted by stars, galaxies and other celestial bodies.

He conducted his early research on a relic of World War II — a large radar antenna left behind by the German military and later commandeered by the Dutch scientific community. Together with his colleagues, and on increasingly sophisticated equipment, Dr. Westerhout tracked the radio waves emitted by interstellar hydrogen gas to compile the first detailed map of the spiral structure of the Milky Way.

Astronomers describe that achievement as a major advance in the field. Scientists had long suspected that the Milky Way had the spiral structure of other galaxies, said Bill Howard, a radio astronomer who today lives in McLean and first met Dr. Westerhout in Leiden. But before Dr. Westerhout’s findings, he said, they were too “deeply immersed within the dust and gas within in our galaxy” to know for sure.

“For the first time, we could see with some precision that what appears to be a random collection of stars up there is really organized,” said Kurt Riegel, who was Dr. Westerhout’s first PhD student at the University of Maryland and later headed the national astronomy centers at the National Science Foundation. “The radio observations . . . allowed astronomers to get a handle on our own galaxy.”

At the time, Dr. Westerhout had not yet turned 30.

His work attracted the attention of scientist John Toll, a future president of the University of Maryland who at the time was building the school’s physics department. In 1961, Dr. Westerhout received an invitation from Toll — “out of the blue,” he once recalled — to come to Maryland and create an astronomy program.

Dr. Westerhout arrived in 1962 and built a program that later became a full-fledged department with undergraduate and graduate programs. “He basically got the program going,” said Stuart Vogel, the current department chair. “He was the one who hired a lot of our astronomers and made us into what we are.”

“If a person gets a PhD at Maryland,” Howard said, “he is very well educated in the research area to make major contributions to the field.”

In 1977, Dr. Westerhout left the University of Maryland to become scientific director at the U.S. Naval Observatory. Established in 1830, it is one of the oldest scientific institutions in the United States and was once located in the swampy area around Foggy Bottom— until “slowly but surely,” Dr. Westerhout once noted, “the astronomers were dying from malaria.”

Today, the observatory is on Massachusetts Avenue NW, with the vice president’s residence located on its grounds. The institution is most popularly known for its timekeeping mission, as the home of the nation’s master clock. It also is tasked with following the positions of celestial bodies and the motions of the Earth.

Gart Westerhout was born June 15, 1927, in The Hague. His mother wrote romantic novels; his father was an architect.

Dr. Westerhout became interested in astronomy after seeing his father’s design for a sanitarium for tuberculosis patients. The elder Westerhout had drawn up plans for the ceiling of the recreation hall to be painted with the constellations and the signs of the zodiac so that the patients might have something to look at as they lay on their backs.

Dr. Westerhout graduated from high school shortly before World War II ended. He studied mathematics, physics and astronomy at the University of Leiden and received the equivalent of a bachelor’s degree in 1950, the equivalent of a master’s degree in 1954 and a doctorate in 1958.

In the United States, where he became a naturalized citizen, Dr. Westerhout deepened his research through use of the Green Bank Telescope at the National Radio Astronomy Observatory in West Virginia. Besides his work on mapping the Milky Way, he created a catalogue of radio sources in the cosmos, which include supernova remnants, colliding galaxies and what were later identified as quasars.

Dr. Westerhout had lived for three decades in Adelphi before moving to Baltimore and later to Catonsville. Survivors include his wife of 56 years, the former Judith Monaghan, of Catonsville; four children, Magda Westerhout Mobley and Brigit Molony, both of Baltimore, Gart Westerhout of Osugi, Japan, and Julian Westerhout of Bloomington, Ill.; one sister; and six grandchildren.

As a young man, Dr. Westerhout fashioned his first telescope from an eyeglass lens and a magnifying glass. It helped him find a degree of comfort during the deprivations of World War II. With the skies darkened because of blackouts, he wrote in a biographical sketch, he “had a beautiful view of the skies.”