Is there Extraterrestrial intelligent life in our Milky Way, which is capable of interstellar space travel ?

Aliens able to conduct space traveling ?
At what life should be regarded as intelligent, a very difficult question to which there are many different answers. In the following considerations in intelligent life is a technologically advanced intelligent civilization are understood to be in a position to operate interstellar space travel and interstellar communication. Humanity would therefore most rudimentary meet this definition. Perhaps this definition narrowed the concept of a  highly intelligent life. It should be used here anyway because we intelligent extraterrestrial beings can only notice when they reach the earth, or if we catch their radio signals.

It is difficult to estimate how large the probability is that on a planet where life originated, is also developed intelligent life. On earth there is life since about 3 and a half billion years ago. Homo sapiens has only existed for about 160 thousand years ago, until very recently. Now there are on Earth but also other living beings with a certain intelligence. One can therefore ask whether the earth has in the past may have lived a technologically advanced intelligent species that is extinct for unknown reasons again. It is known that we have innumerable traces of life found its beginnings up to, but we have so far met with no foreign technical works. The equipment and structures created by us but should be no great difficulty also detected in the distant future. So we must assume that we are the first and only technologically advanced intelligent species on earth.

However, should the  requirements for planets that intelligent life may bring, will be substantially higher than the requirements, the planets must, in order for life is possible. Perhaps intelligent life on a moon is always required, which can stabilize the planetary axis, thereby preventing excessive fluctuations in climate. And perhaps the planet should be a great neighbor planet offers some protection against catastrophic meteorite impacts. Another problem is that on the one hand habitable planets can form only from stellar ash that has been thrown by supernova explosions in space. On the other hand, are close to supernova explosions is at least for higher life forms evolved a threat that threatens their existence. Such planets should not be in an area with many supernova explosions. The inner region of our Milky Way would therefore not a suitable place. In the outer regions of our Milky Way could be too little material from supernova explosions to be present to give rise to suitable planets. Finally, the central star radiation over long periods of constant, as it would be necessary for the survival of many simple life forms. It seems therefore not unreasonable to assume that only about 1 per thousand of the living planet, the conditions are so good that there may also arise intelligent life.So that would be at about 400 000 cases of the planet. The intelligent life on this planet, however, would not last 4 billion years ago, but - on average only developed about 3.5 billion after development of the first forms of life - how on Earth. Accordingly, since only about 500 million years ago the first intelligent life forms would have arisen.