Today is the 25th Anniversary of the nuclear disaster at Chernobyl. On Saturday, April 26, 1986, reactor number four at the Former Soviet Union’s Chernobyl nuclear power station, exploded and burned. The accident, which occurred during unauthorized testing, emitted large quantities of radioactive material. The heat from the fire was so intense that the glowing reactor could be seen even from space, as shown in the satellite photo below.

“In the photo above: This image, taken from the Russian Mir spacecraft, shows Chernobyl and the surrounding countryside. The power plant is situated on the northwest end of a cooling pond on the Pripyat River, which flows into the Dnepr River just 80 miles north of Kiev.

The main features visible in the image are the massive concrete dams and levees that were constructed to contain elements of the power plant and prevent contaminated runoff from entering the local streams.

The cooling water canals leading to the pond, and the levees in the middle of the pond that channeled the water circulation can also be seen. The darker green regions are forests and the light green areas are cleared land used for agriculture.” -NASA

In the video below PBS science correspondent Miles O’Brien travels to the site of the world’s worst nuclear disaster, which is approaching its 25th anniversary.

Watch the full episode. See more PBS NewsHour.