A star with planets and other objects in orbit around it

(a)  

1. A large system of dust, gas, stars, and other celestial bodies that has a  

particular shape.

1. The ratio between the measurements on a map or model and the actual  measurements of an object.

1. a unit of linear measurement of magnifying power

1. a calendar year of 366 days, occurs every four years

1. The time it takes a planet to complete one rotation on its axis

1.  the galaxy that includes the Solar System, with the name describing the galaxy's appearance from Earth

1. The curved path of one object, such as a planet or moon, around a central object, such as a star or planet

1. A period of 28 days or four weeks

1. The movement of one object around a central object

1. The movement of one object as it turns or spins around a central point, or axis

1. Seeming real or true

1. referred to how large an object looks

1.  the third planet from the Sun and the only astronomical object known to harbor life

1. A sphere of hot, glowing gases that releases energy in the form of heat and light

1. The star in the center of our solar system around which Earth and seven other planets revolve.

1. A body that orbits a planet; a natural satellite.

1. A natural or artificial object that orbits another object in space.

1. A representation that is used to study objects, ideas, or systems that are too complex, distant, large, or small to study easily firsthand.