A US B-29 bomber known as Enola Gay dropped the bomb at 8.15 local time on 6th August 1945, exploding some 600 meters above the city.
The Enola Gay made history as the aircraft that dropped the first atomic bomb on Hiroshima during the Second World War.
The aircraft was flown by Colonel Paul Tibbets, who named the plane in honor of his mother.
Colonel Tibbets in an interview with Guardian in 2002 described seeing the cloud rising up from the city after the bomb was dropped.
“It was black as hell and it had light and colours and white in it and grey colour in it and the top was like a folded-up Christmas tree.” He said.
The uranium bomb dubbed “Little boy” claimed 70,000 people claimed to have been killed in the Japan’s city with many more dying later of horrific injuries due to radiations poisoning.
”Little boy’s Journey to Hiroshima.
The “Little boy” was designed by US Scientists under the Manhattan Project, the name given to the United States efforts to build nuclear weapons during world war two.
To meet the project’s needs, enriched uranium production began at a new facility in Oak Ridge, TN in early 1943, according to www.military magazine.about.com
A gun-type nuclear weapon, Little Boy relied on one mass of uranium-235 hitting another to create a nuclear reaction.
When detonated, the projectile would be propelled down the barrel by a tungsten carbide and steel plug and would create a super-critical mass of uranium at impact.
With United States decision to use the weapon against the Japanese, Hiroshima was selected as the target and Little Boy was loaded aboard the B-29 Superfortress Enola Gay. Commanded by Colonel Tibbets.
Proceeding to Hiroshima on 8th August 1945 in a mission was kept top secret , Enola Gay released Little Boy over the city at 8:15 AM.
Falling for fifty-seven seconds, according to the military history the bomb detonated at the predetermined height of 1,900 feet with a blast equivalent to about 13-15 kilotons of TNT.
Creating an area of complete devastation approximately two miles in diameter, the bomb, with its resulting shock wave and fire storm, effectively destroyed around 4.7 square miles of the city.
The first nuclear weapon used in wartime, it was quickly followed three days later by the use of “Fat Man,” a plutonium bomb, on Nagasaki.
The bombing of Hiroshima and Nagasaki three days later is credited to have brought to an end the World War II.
Hiroshima residents on Thursday gathered to mark 70 years since atomic bomb was dropped by US. Aircraft in the Japanese city.