they study the stars, watch them for long periods to discover if they wobble. if they do then they have a gravitational pull on a planet
Perhaps orbiting around other stars, but we have yet to find them.
No. Kepler is a telescope created to find planets orbiting other stars. Planets found using it are given designations beginning with Kepler, such as Kepler 440b.
In a solar system you find a few planets orbiting a star. In a galaxy you find billions of stars orbiting a galactic nucleus (probably a super massive black hole).
You can find the names of some 260 different stars with planets circling them here: http://exoplanet.eu/
Its most likely that they do. Any planet with an axial tilt will have seasons throughout its orbit. Eclipses of orbiting moons are also likely to occur on these exoplanets, though it would be rare to find an orbiting moon that is almost the same apparent size as the star - as with Earth.
The scientist used an astrolabe to find the altitude of the sun and stars.
ya,ofcourse from my view
There is absolutely no way to know how many natural satellites are in space. We are still finding some in our own solar system. Currently we can find some planets orbiting nearby stars but most that we can find are Jupiter like planets. The technology isn't accurate enough for detecting moons.
Planets are not active emitters of energy, that would be Stars. Planets only reflect the energy (light) from nearby stars that they orbit. That is what makes it so difficult to find planets outside of our Solar System.
In our solar system? No. There are only the eight planets. But beyond our solar system, orbiting other stars, we have found several thousand worlds. Most of the exoplanets (planets orbiting other stars) are large gas giants orbiting close, because those are what is easiest to find. But the Kepler Mission has discovered nearly half the new known worlds in just the past year and a half, and is closing in on earth sized planets orbiting in the habitable zone. There ARE new "dwarf" planets recently discovered in our solar system. The asteroid Ceres has been known for more than a century, but Pluto coorbits the sun with another dwarf, Charon. Beyond Pluto there is Eris, which is even bigger than Pluto, and a few other bodies large enough gravity has pulled them into a spherical shape.
Because stars not like planets revolve and stars last at the night sky for many many years even at your lifetime.
Planets orbit stars, stars orbit a galaxy. Planets are not "on" anything. A lot of stars out there have planets - we are just finding out how many now that we have better techniques to find them. So probably all galaxies have at least some stars with planets.