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Two Russian cosmonauts took an important trip outside of the International Space Station (ISS) this week.

Oleg Novitsky and Pyotr Dubrov left the ISS to prepare for the undocking and disposal of an old space station module which has been attached to the spacecraft for almost two decades!

The module will be sent back to Earth before the arrival of a brand new new Russian Multi-Purpose Laboratory Module called 'Nauka' which is Russian for the word science.

It's the very first time either of the cosmonauts, who arrived on the ISS in April this year, has gone on a spacewalk and their special mission lasted over seven hours!

The recent space walk got us thinking about an important question. You've probably heard of astronauts and cosmonauts and both are based on the ISS, but have you ever wondered what the difference is? Well we've got you covered! Read on to find out more.

The ISS is a huge spacecraft that sits about 250 miles above Earth. The first piece of the ISS was launched by a Russian rocket in 1998 and more pieces were added to the spacecraft later on.

The very first crew arrived on the ISS in November 2000 and it's been home to both astronauts and cosmonauts ever since - it hasn't been left unoccupied for more than 20 years! More parts have been added to the craft over time and the space station was completed in 2011.

Nasa says the ISS is as big as a house with six bedrooms! It has six areas where people can sleep, two bathrooms, a gym, and a 360-degree view bay window. A total of eight spaceships can be connected to the craft at any given time.

Astronauts and cosmonauts effectively do the same job, but the difference in their job titles is mainly down to who they're trained up by.

Astronauts are people trained and certified by NASA (National Aeronautics and Space Administration), ESA (European Space Agency), CSA (Canadian Space Agency), or JAXA (Japan Aerospace Exploration Agency) to carry out professional work in space.

Cosmonauts on the other hand are people specifically trained by the Russian Space Agency to work in space. There are also taikonauts, which are Chinese astronauts!

The difference between astronauts and cosmonauts is largely down to something known as the space race.

After World War Two, a big conflict called The Cold War took place between Russia and western countries, including Britain and America.

The Russians operated a communist state called the Soviet Union (from 1922 to 1991), while western countries like the US were capitalist nations.

Throughout the Cold War, the communist and capitalist countries tried to out-do each other, competing to develop the best technologies and weapons.

Both sides also saw space exploration as one of the biggest demonstrations of power and they spent a lot of money to try and get there first.

In the end, it was the Russians that managed to make it into space first in 1957 when their un-manned aircraft, Sputnik 1. They then followed that up by sending a dog into space on Sputnik 2 and in April 1961, Russian born Yuri Gagarin became the first person ever in space.

The success of the first Russian missions brought about the creation of the American Space Agency, Nasa, which was founded in America in July 1958.

During the space race, both America and Russia were thinking about what to name their space explorers. The countries wanted an easy way to help people tell the difference between America space explorers and Russian ones. In the end, American space agency Nasa settled on astronauts and the Soviet Union decided on cosmonauts.

The requirements for becoming either an astronaut or cosmonaut are a little bit different as each country has it's own guidelines which they follow. However, the jobs are pretty much the same!