The work revealed seven previously unknown colonies and analysed 44 colonies in total.  The study, conducted by scientists at the British Antarctic Survey and international colleagues, is published in the journal PloS ONE

Being able to assess the total number of birds from space is valuable because the penguins breed in remote and often inaccessible areas, with temperatures as low as -50°C, and so are very hard to study on the ground

"The method we used is an enormous step forward in Antarctic ecology because we can conduct research safely and with little environmental impact, and determine estimates of an entire penguin population,” said Michelle LaRue from the University of Minnesota

British Antarctic Survey biologist Phil Trathan said: “Current research suggests that emperor penguin colonies will be seriously affected by climate change.  An accurate continent-wide census that can be easily repeated on a regular basis will help us monitor more accurately the impacts on this iconic species”

Emperors are the only penguin species to breed through the Antarctic winter.  They form large colonies on the sea-ice, with the female laying a single egg and passing it to the male for incubation.  The females then go to the sea to feed, and return around the time when the chicks are due to hatch, nine weeks later