Answer: is constant
Explanation:
In order to analyze the velocity of the stars within a galaxy, the <u>galaxy rotation curves</u> (developed by the American astronomer Vera Rubin) are used. These graphs are elaborated as a scatter diagram in which the orbital velocity of the stars present in a galaxy is represented on the Y axis and the distance of these stars to the center of the galaxy on the X axis.
Thanks to this diagram, it has been possible to observe a characteristic behavior in the rotation speed of the stars (and gas) present in the galaxies, which differs from the rules of the orbital movement of the planetary systems postulated by Newton and Kepler.
This means that in these galaxy rotation curves it has been observed that the rotation speed of stars and gas is "constant", regardless of the distance to the center of the galaxy. This discrepancy and these results were then used to demonstrate the existence of dark matter in the universe.
 
        
             
        
        
        
 
 
 
The pattern distribution of tropical cyclones are:-Equator,Tropic of cancer,Tropic of Capricorn,Atlantic,Indian Ocean,Pacific,Caribbean,Asia,Australia,North America,South America,Hurricane,Cyclone,Typhoon,will willy,east,West,North,south.
 
        
             
        
        
        
B.the centerpoint formed by low pressure
        
                    
             
        
        
        
Acid - an acid is a chemical species that donates protons for hydrogen ions and or excepts electrons. Most as it’s contain hydrogen atom bonded that can release (dissociate) to yield the cation and anion and water. 
        
                    
             
        
        
        
 chemical weathering of rocks on the continents is one source of elements found in sea water.