When the astronauts go up in the space, they wear specialized spacesuits to make sure the environment of outer space does no damage to their bodies. It could either be freezing temperature when they are on the side opposite to the sun, but when in direct exposure to the sun on the day side of the earth, you might be having your own roast arm for lunch.
Some astronauts have mentioned that their gloves sometimes get extremely hot when they are out on an extravehicular activity, as the satellite orbits the Earth many times, going from the night side to the day side in just hours. Whichever way it is, if your arm is out naked in the space, one thing is sure to happen. Your arm will swell up, bringing your blood vessels even closer to the surface and there is actually a good chance of some of them bursting open.
The low pressure of the space will make the moisture on your skin evaporate in a matter of seconds. Water vapor pockets will build up in your blood vessels, blocking the circulation to the entire arm. If the exposure lasts for minutes, the tissues of your arm are sure to begin dying. Even if you retract your arm into the pressurized vessel in time, there is a high chance you will be left with gangrene.
It is, however, good news if this happens when you are on the night side of the planet because the heat radiation will be slow and the freezing process will take much longer. But if you are on the day side, you will have a severe case of sunburn, immediately.
A skydiver Joseph Kittinger went up to an altitude of 31 kilometers (101,800 feet) in a hot air balloon to break an altitude jumping record. Pressurization failure in one glove of his suit resulted in a swelling in his arm. Kittinger’s arm swelled to twice its original volume with terrible pain. When he reached back to the ground level, it took some two hours for the swelling to reduce and the arm to return to its operational state.
For Joseph Kittinger, the altitude was not nearly as high as that of the low earth orbit, so he was saved without any severe injury. If the same were to happen to as astronaut in space, there is nearly 100 percent chance that they would require an amputation.