STOCKHOLM, Sweden (AP) _ Americans John C. Mather and George F. Smoot won the 2006 Nobel Prize in physics on Tuesday for work that helped cement the big-bang theory of the universe and deepen understanding of the origin of galaxies and stars.
Mather, 60, works at the NASA Goddard Space Flight Center in Greenbelt, Md., and Smoot, 61, works at the Lawrence Berkeley National Laboratory in Berkeley, Calif.
Their work was based on measurements done with the help of NASA's COBE satellite launched in 1989. They were able to observe the universe in its early stages about 380,000 years after it was born. Ripples in the light they detected also helped demonstrate how galaxies came together over time.
``The COBE results provided increased support for the big-bang scenario for the origin of the Universe, as this is the only scenario that predicts the kind of cosmic microwave background radiation measured by COBE,'' the academy said in its citation.
The big-bang theory states that the universe was born billions of years ago from a rapidly expanding dense and incredibly hot state.
Mather, reached at his home in Maryland, said he was ``thrilled and amazed.''
``We did not know how important this was at the time when it happened. We only knew it was important,'' he said.
With their findings, the scientists transformed the study of the early universe from a largely theoretical pursuit into a new era of direct observation and measurement.
``The very detailed observations that the laureates have carried out from the COBE satellite have played a major role in the development of modern cosmology into a precise science,'' the academy said.
Last year, Americans John L. Hall and Roy J. Glauber and German Theodor W. Haensch won the prize for work that could improve long-distance communication and navigation.
This year's award announcements began Monday with the Nobel Prize in medicine going to Americans Andrew Z. Fire and Craig C. Mello for discovering a powerful way to turn off the effect of specific genes. RNA interference opens a potential new avenue for fighting diseases as diverse as cancer and AIDS.
The winner of the Nobel Prize in chemistry will be named Wednesday. The Bank of Sweden Prize in Economic Sciences in Memory of Alfred Nobel will be announced Oct. 9.
The winner of the peace prize _ the only one not awarded in Sweden _ will be announced Oct. 13 in Oslo, Norway.
A date for the literature prize has not yet been set.
The prizes, which include a $1.4 million check, a gold medal and a diploma, are presented on Dec. 10, the anniversary of Nobel's death in 1896.