One.
One
There are two objects in the solar system which currently support life, those being the planet Earth and the international space station.
Kuiper Belt objects
No, our Solar System is not the galaxy. Our Solar System is the Sun, and the planets around it (plus a few other objects, such as asteroids and comets). Our Sun (the center of our Solar System) is a star; in the galaxy there are several hundred billion stars, each of which might be called a solar system. At least if it is confirmed that it has planets - but it has already been confirmed that many stars in our neighborhood have planets.
meteorites
The most distant objects in the Solar System are probably comets. However, as that region of space has not been explored, there could be anything out there, even another planet.
the radio telescope
the radio telescope
So far, life has been confirmed ONLY on the 3rd planet- place called Earth.
Within the solar system the most common method of observing objects that are at a great distant from the Earth is through the use of conventional Optical Telescopes. The Kuiper Belt, the farthest observed edge of the Solar System (although not the limit of), has been viewed using the Hubble Space Telescope (HST), of Newtonian Design. The objects in this belt have both been viewed in optical wavelengths and infrared using the HST.
The existence of the so-called UFOs has not been conclusively confirmed. Therefore, we may be receiving visitors from other planets or moons of our own solar system, from other stars, or we may be receiving no visitors at all.
Planets found outside our own solar system are called exo-solar planets or exoplanets. These are in orbit around other stars. It's ver difficult to detect them due to the distances involved, but with modern techniques, over 500 have been confirmed.