| MadSci Network: Astronomy |
Hello,
1. A simple definition of a solar system would be "a star and all the stuff that is gravitationally bound to it". The 'stuff' could include planets, asteroids, comets, dust, or even other stars if it's a multiple star system. 'Gravitationally bound' means that the stuff does not have enough energy to leave the solar system, and is bound in orbit around the central star or stars.
Your definition of a constellation is not what astronomers mean when they use the word. See this MadSci answer for more discussion of what a constellation is.
2. The "next larger center" of which Earth is a part is probably the group of stars the Sun belongs to. These nearby stars are all orbiting around the center of the Milky Way in more or less the same way, and they define the "local standard of rest" (the reference point for measuring velocities of objects in our galaxy). Other than that, there's no specific name for this group that I know of.
3. The center of the Milky Way doesn't have a fancy name - it's generally just called 'the Galactic center' (the G is capitalized when talking about our galaxy, to distinguish it from other galaxies). The universe doesn't have a center (see this MadSci answer for more details), and as far as we know, our universe is all there is - there is nothing 'larger than the universe' (see this answer for clarification).
Pauline
Try the links in the MadSci Library for more information on Astronomy.