Space crossword

2. the angle between the Earth at one time of year, and the Earth six months later, as measured from a nearby star.
4. graph in which the absolute magnitudes (intrinsic brightness) of stars are plotted against their spectral types (temperatures).
5. an invisible force that pulls objects toward each other.
6. any of certain groupings of stars that were imagined—at least by those who named them—to form conspicuous configurations of objects or creatures in the sky.
7. very bright, distant and active supermassive black hole that is millions to billions of times the mass of the Sun.
8. a dimensionless quantity representing the amount of matter in a particle or object.
12. two light nuclei merge to form a single heavier nucleus.
15. rocky, airless remnants left over from the early formation of our solar system about 4.6 billion years ago.
16. objects in space that range in size from dust grains to small asteroids.
17. the colossal explosion of a star.
19. formed when a massive star runs out of fuel and collapses.
21. a cloud of gas and dust in space believed to develop into a star.
23. typically has a rotating disc with spiral 'arms' that curve out from a dense central region.
24. they travel in a straight line unless there is a force that makes them stop or change.
25. the apparent magnitude an object would have if it were located at a distance of 10 parsecs.

1. electromagnetic radiation that propagates energy and travels through space in the form of waves.
3. one in which two stars orbit around a common center of mass, that is they are gravitationally bound to each other.
9. brightest star in the night sky.
10. a dying star in the final stages of stellar evolution.
11. how bright an object appears in the sky from Earth.
13. gaseous cloud from which, in the so-called nebular hypothesis of the origin of the solar system, the Sun and planets formed by condensation.
14. cosmic snowballs of frozen gasses, rock, and dust that orbit the Sun.
18. rotating neutron stars are observed to have pulses of radiation at very regular intervals that typically range from milliseconds to seconds.
20. the stellar core left behind after a dying star has exhausted its nuclear fuel and expelled its outer layers to form a planetary nebula.
22. a place in space where gravity pulls so much that even light can not get out.