In case anyone was wondering, like me, what the MJy unit in the lower diagram is: It's Mega-Jansky. Just funny that it's then being rescaled by 10^-9. Why didn't they use Milli-Jansky in the first place?
replies(1):
> It's Mega-Jansky... Why didn't they use Milli-Jansky
"All prefix names are printed in lowercase letters, except at the beginning of a sentence.
Unit names are normally printed in upright type and they are treated like ordinary nouns. In English, the names of units start with a lower-case letter (even when the symbol for the unit begins with a capital letter), except at the beginning of a sentence or in capitalized material such as a title...
When the name of a unit is combined with the name of a multiple or sub-multiple prefix, no space or hyphen is used between the prefix name and the unit name...
Examples: pm (picometre), mmol (millimole), GΩ (gigaohm), THz (terahertz)"
Source: https://www.bipm.org/en/publications/si-brochure
However yes, you raise a good question. I was surprised to learn that astronomy and astrophysics prefer CGS, so by convention the diameter of the Sun is given in centimeters, and the mass of the Sun in grams! For janskys there's no excuse though.