This would be the Milky Way's most massive star... if not for one tiny detailS

That tiny, insignificant detail? Well, it turns out that the brightest star in the Pismis 24 cluster is actually three stars, possibly more. But don't feel bad for these stars: they're both still 100 times as massive as our Sun.

That's certainly impressive in its own right, but the star Pismis 24-1 was originally thought to weigh in at anywhere from 200 to 300 solar masses. That would make it by far the most massive star in the Milky Way, and indeed there's only one known star — R136a1 in the nearby Large Magellanic Cloud, which is about 265 solar masses — that currently sits in the 200-plus weight class.

This would be the Milky Way's most massive star... if not for one tiny detailS

But, alas, images from the Hubble Telescope confirmed that what appeared to be one utterly gargantuan star was really just a bunch of hugely massive stars, each of which likely weighs in at around 70 solar masses, with 100 solar masses the likely upper limit. This conglomeration of closely packed mega-stars is responsible for that particularly large, bright dot in the image above. You can get a complete view of this section of space, including the gorgeous, vaguely cathedral-shaped nebula NGC 6357, in the full image on the left.

While this might seem like a disappointment to hunters of giant stars, the very fact that so many leviathan stars are in close enough proximity to create an illusion of an even bigger star is remarkable in its own right. For more, let's go to an earlier article from the Hubble Site:

Its mass is around 100 times that of our Sun and brings the total number of heavy stars within this cluster to at least three, which is a very rare occurrence for a cluster this small: In our Milky Way, for every star with 65 solar masses or more that is born, another 18,000 solar-mass stars are produced. Furthermore, since a 65 solar-mass star lives for only 3 million years while a solar mass star can live for more than 3,000 times that long, there are actually millions of solar-mass stars for each very massive star... Although each of the three stars would then only average 70 solar masses, they would still make it to the top twenty-five for "Milky Way heavyweights", but only for a few million years as they would be sure to end their lives as supernovae and then turn into black holes.

Via NASA's Astronomy Picture of the Day.