The International System of Units (SI)
Bureau International des Poids et Mesures
Multiples and Submultiples from International System of Unit

Submultiples Symbol Value Multiples Symbol Value
deci d 10e-1 deca da 10e1
centi c 10e-2 hecto h 10e2
mili m 10e-3 kilo k 10e3
micro u 10e-6 mega M 10e6
nano n 10e-9 giga G 10e9
pico p 10e-12 tera T 10e12
femto f 10e-15 peta P 10e15
atto a 10e-18 exa E 10e18
zepto z 10e-21 zetta Z 10e21
yocto y 10e-25 yotta Y 10e25

Fundamental measurement unit: metre kilogram second amper kelvin candela
Complementary measurement unit: radian steradian
Aditional measurement unit: bit, byte

Related the distances measured in year light, at intergalactic dimesions, year-light become a too litle measurement unit. For example the visible universe ray is 15 000 000 000 light-year (a too unhandy number). If it used as example the petametre (Pm) or exametre (Em) It plied with digits much more just subunitary . If we using zettametre or yottametre (Zm, Ym) then the year light is a very little unit.
For example in a astronomic year is 365 days 5h 48min 46s. Results that a year=31 556 926 seconds.
At light speed in vacuum of (299.79245620.0000011)e+03 m/s accepting 299 792.458 km/s results a un year light = 9 460 528 412 464.108 km what means 9.46 Pm or 0.009 Em or 0.000 009 Zm or ... 0.000 000 009 Ym !! It can see what little is 1 year light besides 1 Ym !!! Then at distance of order of millions of year light can using zettametre and yottametre.

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