Using an Array in a While Loop

[buran]

Very interesting indeed.
I changed your script a bit to make it more easy to understand and follow

from visual import * # I HATE this
 
myuniv = display(range=vector(7*10**12,7*10**12,7*10**12))
 
G = 6.674*10**-11  #Gravitational constant

# define objects
sun = {'r':9.9*10**10, 'mass':1.989*10**30, 'pos':vector(0,0,0), 'vel':vector(0,0,0), 'acc':vector(0,0,0), 'color':color.yellow}
planets = (('mercury', {'r':2.44*10**6, 'mass':3.285*10**23,'pos':vector(5.791*10**10,0,0), 'vel': vector(0,4.87*10**4,0), 'acc':vector(0,0,0), 'color':color.red}),
           ('venus', {'r':6.052*10**6, 'mass':4.867*10**24, 'pos':vector(1.082*10**11,0,0), 'vel':vector(0,3.502*10**4,0), 'acc':vector(0,0,0), 'color':color.yellow}), # I added color here
           ('earth', {'r':6.371*10**6, 'mass':5.972*10**24, 'pos':vector(1.496*10**11,0,0), 'vel':vector(0,2.98*10**4,0), 'acc':vector(0,0,0), 'color':color.green}),
           ('mars', {'r':3.39*10**6, 'mass':6.39*10**23, 'pos':vector(2.279*10**11,0,0), 'vel':vector(0,2.401*10**4,0), 'acc':vector(0,0,0), 'color':color.red}),
           ('jupiter', {'r':6.99*10**7, 'mass':1.898*10**27, 'pos':vector(7.785*10**11,0,0), 'vel':vector(0,1.307*10**4,0), 'acc':vector(0,0,0), 'color':color.blue}),
           ('saturn', {'r':5.823*10**7, 'mass':5.68*10**26, 'pos':vector(1.429*10**12,0,0), 'vel':vector(0,9.69*10**3,0), 'acc':vector(0,0,0), 'color':color.yellow}),
           ('uranus', {'r':2.536*10**7, 'mass':8.68*10**25, 'pos':vector(2.871*10**12,0,0), 'vel':vector(0,6.81*10**3,0), 'acc':vector(0,0,0), 'color':color.cyan}),
           ('neptune', {'r':2.462*10**7, 'mass':1.024*10**26, 'pos':vector(4.498*10**12,0,00), 'vel':vector(0,5.43*10**3,0), 'acc':vector(0,0,0), 'color':color.blue})) # I added color here

#visualize objects
solar_system = {'sun': sphere(pos=sun['pos'], radius=sun['r'], color=sun['color'], make_trail=True)}
for name, planet in planets:
    solar_system[name] = sphere(pos=planet['pos'], radius=planet['r'], color=planet['color'], make_trail=True)

t = 0.0
dt = 150000

while True:
    for name, planet in planets:
        rate(1000000)
        t=t+dt
        r =  sun['pos'] - planet['pos'] # also possible  r = solar_system['sun'].pos - solar_system[name].pos
        Fnet= ((G*sun['mass']*planet['mass'])/(mag(r)**2))* norm(r) #Calculating the force of gravity from the sun
        planet['acc'] = Fnet/planet['mass']
        planet['vel'] += planet['acc']*dt
        planet['pos'] += planet['vel']*dt
        solar_system[name].pos = planet['pos']

In order to preserve the order of the planets, I used tuple of tuples to define the planets, but you can also use OrderedDict from collections.