Bellatrix – a blue-ish pixel,
Fairly bright, as bright stars go.
Drifting lonely through Orion –
Closer than her neighbours, though.
That means she must be smaller –
And she’s just too small to go off pop –
Strange that seven solar-masses
Makes her baby of the crop.
Was she born, like many of her cohort,
In Orion’s cloud ?
Maybe not – perhaps adopted,
Hanging with the big boys’ crowd.
But they’ll grow tall and all be gone one day,
While she’s a quieter kind –
She may turn red, but end up white,
Forever left behind.
If we take a look at the vital statistics (according to Wikipedia, and I’ve rounded them off a bit) of the eight brightest stars in Orion, they are (by descending declination):
Meissa – (rhymes with ‘nicer’) – a double star: A is ≈28 solar masses, B is ≈10 solar masses.
Betelgeuse – (‘BEETLE-juice’. Yes, that’s right, that’s precisely how most people say it, because how can we not !) –
≈16-19 solar masses, depending on how far away he is, which is surprisingly hard to determine. (Bizarrely, according to the OED this name has only been in use in English since 1796.)
Bellatrix – (‘BELL-a-tricks’, just as you’d expect) – there seems to be some confusion as apparently Bellatrix is older that a star of her mass should be (7-8 solar masses) without having evolved into a giant, and it has been suggested that she is infact twins – a spectroscopic binary of two smaller, longer-lived stars, which would presumably make her Bellatrices ?
Mintaka – (‘MINN-tacka’) – a multiple-star system, but we’ll only worry about the two most massive: Aa1 is ≈24, while Ab is ≈22.
Alnilam – (‘AL-nillam’) – a whopping 40-44 solar masses.
Alnitak – (‘AL-nittack’) – again a multiple, Aa is ≈33, Ab a mere 14 or so.
Rigel – (either ‘RYE-gull’ or ‘RYE-jull’) – and now we come to the brightest of the lot (from our perspective) and another collective, with the main component being ≈21. (This name was first recorded in English in 1594 – no, I don’t know what the locals called it before then either.)
Saiph – (‘SAFE’) – and finally, a ≈15 tiddler to round us off.
Of these, all bar Betelgeuse are hot blue stars, but anything of a similar mass (so 20-ish or less) will presumably follow suit and swell up in the next few million years before exploding in a blaze of glory and leaving behind a neutron star.
The fate of the heavyweights is less clear – they’ll certainly go super, but may never turn red, and some if not all of these will simply implode into a black hole denying us the spectacular brightening. Anything over ≈8 solar masses is thought to end as a Type II (though future bouts of mass-loss complicate things), with Bellatrix thought to be just too short to ride that particular rollercoaster.
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