STOCKHOLM, Oct. 3 (Xinhua) -- Two Americans, John C. Mather and George F. Smoot, won the 2006 Nobel Prize in physics on Tuesday.

The scientists were awarded the prize "for their discovery of the black body form and anisotropy of the cosmic microwave background radiation," the Royal Swedish Academy of Sciences in Stockholm said.

Mather, 60, works at the NASA Goddard Space Flight Center in Greenbelt, Maryland, and Smoot, 61, works at the Lawrence Berkeley National Laboratory in Berkeley, California.

"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 in its citation.

Last year, Americans John L. Hall and Roy J. Glauber, and German Theodor W. Haensch won the Nobel Physics Prize for their work in applying modern quantum physics to the study of optics.

The 2006 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, opening a potential new avenue for fighting diseases as diverse as cancer and AIDS.

The Nobel prizes, founded by Swedish industrialist Alfred Nobel, the inventor of dynamite, were first awarded in 1901. The Nobel prizes include such categories as literature, peace, medicine, physics and chemistry.

The Nobel Prize in chemistry will be announced on Wednesday. The Economics prize, awarded by Sweden's central bank, the Riksbank, is scheduled for Oct. 9.

This year's winner of the Nobel Prize in literature will not be announced until Oct. 12 at the earliest.

The winner of the peace prize, the only one not awarded in Sweden, will be announced on Oct. 13 in Oslo, Norway.

Laureates this year will receive a gold medal and share 10 million Swedish kronor (1.37 million U.S. dollars). Enditem