Riess, a 41-year-old astronomy professor at the university in Baltimore and scientist at the Space Telescope Science Institute, shares the $1.49 million prize with fellow American Saul Perlmutter and U.S.-Australian citizen Brian Schmidt. The Royal Swedish Academy of Sciences selected the three scientists "for the discovery of the accelerating expansion of the universe through observations of distant supernovae," according to the announcement.
Riess said, in the Hopkins release, that the work has been "an incredibly exciting adventure" and called the announcement unexpected and jaw-dropping.
Hopkins President Ronald J. Daniels commended Riess, the 35th Nobel laureate associated with the university and the fourth currently on the faculty, for "his passion to know more and the energy with which he pursues that passion."
At the Space Telescope Science Institute, the mood Tuesday morning was celebratory.
Mario Livio, an astrophysicist who has coauthored papers with Riess, said the award underscores the importance of having access to powerful telescopes such as the Hubble.
"I was essentially certain he would receive the Noble prize someday," Livio said. "The question was, when will they decide to actually give it to him?"
He described Riess' discovery as one of "great significance and magnitude."
Marc Postman, an astronomer at Space Telescope Science Institute, collaborates with Riess on projects.
"Sometimes you meet people and you get a sense they're an extra special talent," he said. "Adam is one of those people."
In 2008, Reiss was the recipient of a grant from the John D. and Catherine T. MacArthur Foundation. He was honored for his work "designing experiments and devices to advance our understanding of the geometry of the universe and to trace the story of both its beginning and its end."
In 1998, Riess was the lead author on the first paper to describe the astonishing discovery — through his study of a type of exploding star called a Type Ia supernova — that the expansion of the universe is accelerating, driven by a still-unexplained force dubbed "dark energy."
Staff writer Luke Broadwater and The Associated Press contributed to this article.