Well, there are three separate phenomena sort of loosely stapled together in that article.
1. White dwarf nova: "It takes more than 100 thousand years for enough hydrogen to fall onto the white dwarf and accumulate as a thick layer on the surface. When the layer exceeds its critical mass, thermonuclear fusion of hydrogen to helium occurs, creating a cosmic-sized hydrogen bomb blast. The outer layers of the white dwarf are blown away, producing a nova outburst that can be observed for a period of months as the material expands into space."
Reference
2. Interstellar gas clouds, typically hydrogen at densities of 1 to 1000 molecules per cubic centimeter.
See here for info
3. The Mayan calendar.
See here. "The Long Count is really a mixed base-20/base-18 representation of a number, representing the number of days since the start of the Mayan era." Mixed base 20 and base 18 numbers? I did not know that.
Now, the first two things are not really closely related. As far as I know white dwarfs drifting through interstellar gas clouds do not go nova; the only mention of this kind of nova refers to dwarfs that take material from a red-giant companion. And as far as I know main-sequence stars like the Sun are not known to go nova when
they drift through interstellar gas clouds.
So (again, as far as I know) the evidence that this scenario is realistic is zilch. Nada.
If the Mayans had witnessed the Sun go nova, they would not have left a record of it, and we would not be around. So they had no experience of the Sun ever having gone nova. That's impossible.
Therefore Mayans had no way other than Magickal Pooooowers to guess that the Sun would go nova in the year 2012. I, personally, don't believe in Magickal Pooooowers. So I'm inclined to think the whole scenario is silly as flying cows.
Sillier, really, because I have seen video of a flying cow. It was in
Monty Python and the Holy Grail, and was, technically, a ballistic cow. But it was definitely airborne.
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Aw, no worries bmpbmp. The Sun ain't gonna go nova. But thanks for the query, because that bit about Mayan mathematics is interesting and was new to me.
Addendum: But I'll bet HUb' knows that curious fact about the Long Count Mayan calendar!