Even in countries using SI units there are exceptions in aviation and nautics.

@StevenGubkin They who only know imperial/American units would have to use converters for all the used units.

You can blame both either the metric or the imperial unit's use for that. I'd say they shouldn't have used metric units in America. If there were no metrication efforts, this wouldn't have happened.

You may hate non-metric units but that's no reason not to convert for English-speaking folks (who're probably a multitude on SE).

Can't we somehow determine whether a star is fusing hydrogen or deuterium and/or also lithium?

@MikeG I think it was black-and-white and it's actually upside down. commons.wikimedia.org/wiki/…

@userLTK If it would become stuck inside the Sun it would be a stellar merger that all in all would have more mass, but eventually the entire merger would become a stellar black hole, wouldn't it?

@fasterthanlight Right, this is what I mean by above comment.

@fasterthanlight It doesn't necessarily have to be the center of the Sun, it doesn't have to go through the Sun's core (but it can). I wonder about multiple options, but in the core there's the most mass of course.

Note that the question assumes the black hole goes through the Sun's polar regions so that it doesn't meddle with the planet's orbits.

The Sun appears yellow through the Earth's atmosphere and whiter in outer space. Near the horizon such as during sunset, the Sun looks orange because you see it through lots of atmosphere. That's the reason why the Moon looks yellow near the horizon. A red giant would probably look orange-ish both from the Earth and from space. Betelgeuse (a red supergiant) actually looks orange-ish in the nightsky.