#kic 8462

[lhs3020b]

the-demon-colonel said: You seem a good person to ask, so I suppose I will: how far away is this star, again? I can’t recall, even though I’m sure I read it somewhere 

Apparently, it’s 454 parsecs, or 1,480 light years in old money.

[lhs3020b]

Still weird after all these years

(Plot source: Shaefer 2016.)

We’ve talked about KIC 8462852, the supposed ‘Dyson sphere’ star, before. (It’s also known as Tabby’s Star, after Dr. Tabetha Boyajian, the astronomer who first called our attention to its weird behaviour.) Now, as I think I’ve said, I don’t buy the Dyson Sphere hypothesis, but it’s pretty clear that *something* weird is going on here.

And the situation’s just got even stranger. Dr. Bradely Shaefer recently had the incredibly-obvious -in-hindsight idea of looking at the archival data for this object. (This was one of those blindingly obvious ideas that no-one, myself included, thought of. Hidden in plain sight, and all that.)

Anyway, the archives have turned up something even more bizarre.

KIC 8462852 is an F-type Main Sequence star; the whole point of the Main Sequence is that the objects on it are stable and well-behaved. While they do brighten gradually as they age, the luminosity evolution takes millions of years. In five billion years’ time, when the Sun is ready to leave the Main Sequence and expand into a red giant, it will still only be twice as bright as it is today.

The luminosity evolution is slow, and the direction of travel is toward increasing brightness ... except, apparently, for KIC 8462.

Somehow, Tabby’s Star is actually getting fainter. And to top it all off, it’s doing it fast. Shaefer’s work shows that it’s lost 20% of its luminosity since 1890. If that happened to the Sun, well, we’d be in an Ice Age by now. (My back-of the-envelope calculation suggests that’s equivalent to a ~50 °C drop in average temperature for the Earth as a whole, or a planetary average of -36°C. And yes, that’s allowing for +34 degrees of greenhouse warming.)

Tabby’s Star presents as a normal-looking F-type, as I mentioned. As far as I know, there is not physical mechanism within a star that could account for this behaviour. If the rate of fusion at the core declines, the core cools and shrinks, thus raising the pressure and driving the fusion rate back up again. That’s just basic hydrostatic equilbrium, and that principle is why we can have stars in the first place. (The converse applies as well; if the fusion rate rises too high, the core expands, reducing the pressure and slowing the burning. Stars are doubly-stable against expansion and contraction.)

I have absolutely no idea what is going on here, except that it’s fucked up.

Also, you know what else is creepy? Remember Dholen in Mass Effect 2? I’m reminded of that, except inverted.

[universetoday]

Weekly Space Hangout – Jan. 8, 2016: Dr. Steve B. Howell from Kepler

Weekly Space Hangout – Jan. 8, 2016: Dr. Steve B. Howell from Kepler

Host: Fraser Cain (@fcain)

Special Guest: Dr. Steve B. Howell, Project Scientist on Kepler to discuss the great new results coming form the K2 mission – the repurposed Kepler mission.

Guests: Morgan Rehnberg (cosmicchatter.org / @MorganRehnberg ) Alessondra Springmann (@sondy) Paul Sutter (pmsutter.com / @PaulMattSutter) Kimberly Cartier (@AstroKimCartier ) Dave Dickinson (@astroguyz / www.astrog…

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