[Florin_Andrei]

It must be TNT equivalent. One solar mass is 1.99 × 10^30 kilograms, and we know that 2 solar masses were converted in total, so 4 x 10^30 kilograms, which is far less than the "megatons" mentioned, in terms of pure mass.

I wish folks would avoid mixing military units and general relativity units like this, it's confusing.

[nategri]

I don't think it's that ambiguous.

"Megaton" isn't really used anywhere except for explosive yields, where it always means TNT. As far as the 'native unit' astrophysicists will tend to use ergs for events like supernovae.

https://en.wikipedia.org/wiki/Erg

[kstrauser]

I thought it was ambiguous in the context of an article talking about converting mass to energy. Without running the numbers, I couldn't tell if that was a unit of the input mass or the output energy.

[vog]

Or, at least give the SI unit first, then a day-to-day formulation in parentheses.

The SI units are not just more useful for scientific minded readers, but also for international readers in general, who don't share the same cultural background and hence have no feeling for these "day-to-day formulations" anyway, because it isn't their day-to-day. For example, a German author might write:

| The area is as large as 7.2 km², which are 1000 football fields.

Without the SI unit (7.2 km²), this would be very confusing. Of course, the author meant association football (soccer) fields, not American football fields. But who in the international audience would have caught that, especially if I didn't state author's national background upfront? Even more importantly, which percentage of the international readership has developed a intuition about the size of a football field?

[billforsternz]

A football field is pretty univerally understandable, it doesn't really matter what kind of football it is.