Hubble's law

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Across
  1. 4. man who created the theory
  2. 5. massive, self-luminous spheres of hot plasma held together by their own gravity
  3. 6. bound system of stars
  4. 7. Hubble constant × distance =?
Down
  1. 1. law law that further a galaxy is the faster its moving away.
  2. 2. man who helped Hubble create the theory
  3. 3. thing that looks at stars from far away