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Across 1. The collection of planets and their moons in orbit around a sun, together with smaller bodies such as asteroids, meteoroids, and comets 3. An artificial body placed in orbit around the earth or another planet in order to collect information or for communication 13. A unit of astronomical distance equivalent to the distance that light travels in one year 14. Two single stars orbiting one another 16. An imaginary line about which a body rotates 17. A layer in the earth's stratosphere that absorbs most of the ultraviolet radiation from the sun 19. A cloud of gas and dust in outer space 20. The trapping of the sun's warmth in a planet's lower atmosphere 21. Large eruptions of luminous hydrogen gas that rise thousands of kilometers above the chromosphere 22. Any of the millions of small planets between the orbits of Mars and Jupiter 28. A sudden brightening observed over the Sun surface or the solar limb, which is interpreted as a large energy release 32. The gradual increase in the temperature of the earth's atmosphere, believed to be due to the greenhouse effect 33. Sun-Centered model of the solar system 35. A star that suddenly increases greatly in brightness because of a catastrophic explosion that ejects most of its mass 37. A prominent pattern or group of stars, typically having a popular name but smaller than a constellation 38. A planet whose orbit lies outside the asteroid belt 39. A celestial object consisting of a nucleus of ice and dust 40. Move in a circle around an axis or center

Down 2. The region surrounding the earth or another astronomical body in which its magnetic field is the predominant effective magnetic field 4. A unit of length equal to about 149,597,870.7 kilometers 5. A meteor that survives its passage through the earth's atmosphere such that part of it strikes the ground 6. A massive, gravitationally bound system that consists of stars and stellar remnants 7. The theory that the universe originated sometime between 10 billion and 20 billion years ago from the cataclysmic explosion of a small volume of matter at extremely high density and temperature 8. Shifting Patterns of coloured light that appear in the night sky in northern latitudes 9. A region of space having a gravitational field so intense that no matter or radiation can escape 10. Temporary phenomena on the photosphere of the Sun that appear visibly as dark spots compared to surrounding regions 11. An increase (or decrease) in the frequency of sound, light, or other waves as the source and observer move toward (or away from) each other 12. A group of stars forming a pattern that is traditionally named after its apparent form or identified with a mythological figure 15. The direction opposite to the movement of something else 18. A massive and extremely remote celestial object, emitting exceptionally large amounts of energy, and typically having a starlike image in a telescope 23. A planet whose orbit lies within the asteroid belt 24. Earth-Centered model of the solar system 25. The effect whereby the position or direction of an object appears to differ when viewed from different positions 26. The luminous envelope of a star from which its light and heat radiate 27. The tracing and measurement of a series or network of triangles in order to determine the distances and relative positions of points spread over a territory or region 29. The intrinsic brightness of a celestial object 30. The process or result of joining two or more things together to form a single entity 31. The rarefied gaseous envelope of the sun and other stars 34. Move in a circle on a central axis 36. An angular measurement in a spherical coordinate system