Life under a blue sun?

There's a beautiful HD 1618033 out this evening...So an article I wrote for Discovery last week revisited the idea of whether life could survive under a red sun, and what challenges it might face. Thing is, while red dwarfs may be exceptionally cantankerous little things, it seems there may be 13.5 billion Earth-sized worlds in orbit around red dwarfs in our galaxy alone. That means that even if the odds of finding a habitable world are about the same as winning the National Lottery, there have to still be quite a few.

So here’s the thing. What about the other end of the scale? Blue stars are hazardous, and not typically considered as being suitable places for planets to form, let alone look for them. Or are they?

The hottest and most massive stars are O-stars. These are also the bluest, and they can be so immensely powerful that some of them could probably fry an egg at a one light year distance.* On the other hand, stars can be visually blue through class B right down to the hottest members of class A. That’s a little closer to home. Literally – Sirius A is an A-star.

A lot of people would argue that the radiation pressure and stellar wind emitted by your average blue star should be powerful enough to blow away any planet forming disks, not only around the star itself but around any other stars which stray too near. This is true. But it doesn’t change what we’ve seen.

In the Large Magellanic Cloud (one of our satellite galaxies), there are two blue hypergiants named R66 and R126. They’re both dramatically more massive than the Sun, and heavy enough to swallow our entire solar system almost whole. Interestingly, both of these gargantuan blue stars seem to have dusty disks around them. Disks with several Jupiter masses worth of material in them. Disks are often associated with planet formation, and due to the short lived nature of hypergiants, these disks would probably still be young enough to form planets.

Of course, there’s nothing to suggest that planets may be forming around these stars, but if the stellar equivalents of the Incredible Hulk can carry a dusty disk, then surely a more modestly sized B-star must be able to.

Perhaps some world somewhere really does have a blue sun. I’d suggest any visitors don’t forget to wear sunscreen. The UV index out there would be rather perilous!

I never fail to be impressed by the sizes some individual stars can reach!

* I haven’t done any calculations to confirm this, but for a blue hypergiant like Eta Carinae, I wouldn’t be too surprised.

Upper – Photomanipulation by yours truly. Original images from Wikimedia Commons: 12345678
Lower – NASA/JPL-Caltech

About Invader Xan

Molecular astrophysicist, usually found writing frenziedly, staring at the sky, or drinking mojitos.
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5 Responses to Life under a blue sun?

  1. Paul says:

    No star can fry an egg at 1 ly. That would require a source billions of times brighter than our sun. A quasar could do it.

    • invaderxan says:

      I’ll admit, that was pure hyperbole for dramatic effect. Even R136a1 in the LMC, probably the most luminous known star, only has a bolometric luminosity a bit under 9 million times that of the Sun. Heh… “only”.

      • Devon Jolly says:

        while this talks about the challenges of forming a planet near a blue star, there’s literally nothing here about how one might support life near a blue star. Proportional distances needed to have similar planetary surface heat, the fact that an active magnetosphere is a LOT more important to atmosphere than distance from the sun (earth vs mars hello) and what the sky or plants might look like assuming earth-like conditions were achieved near one.

        • invaderxan says:

          Frankly, the title was intended purely as a counterpart to the other article. The prospects of actually supporting life around a massive star? Well, that’s a can of worms (and speculations) which one should open with caution.

          Though sadly, the bottom line is that blue stars (O and B type) only live for around 10-100 million years, which is barely a heartbeat in astronomical terms. Life on Earth appears to have evolved 3.5 billion years ago, which was around 500 million years after Earth first formed (give or take a couple of hundred million years). In other words, either life would need to evolve a lot faster than we think it did, or it needs to be transplanted from elsewhere (panspermia). Otherwise, we’re unlikely to find any indigenous life under a blue sun…

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