What is the definition of galactic center and galaxy cluster ?

The Galactic Center (or Galactic Centre) is the rotational center of the Milky Way galaxy; it is a supermassive black hole of 4.100 ± 0.034 million solar masses, which powers the compact radio source Sagittarius A*.

the atmospheric gas that forms a mild acid when dissolved in water is called carbon dioxide. the correct answer is a. 2.) chemical weathering would cause an inscription on a marble headstone to become harder and harder to read over time.