The Weirdest, And Naughtiest, Star in The Galaxy

It was an interesting ringtone — aggressive but feminine, with a hint of desperation.  And it was a ringtone I hadn’t programmed into my phone.  The number was intriguing, too — 710-555-1701.  It didn’t add up, so I answered the ring. “Moire here.”

“Hello, Mr Moire, this is Victoria Baird.”

It’s been a long time, Ms Baird.  What can I do for you?”  Her voice and the memory of her pointed ears sent chills down my spine.

“This time it’s what I can do for you, Mr Moire.  Here’s a tip — Tabby’s star.”  I could hear the italics.  I wanted to ask questions but the line went dead.

Considering the context, I called my Astronomy Department source.  “Morning, Cathleen.  It’s break time, can I buy you some of Al’s coffee and a scone?”

“You’re going to ask me questions, aren’t you?  What am I going to have to bone up on?  I know, it’s Tabby’s Star, right?”

“Got it in one, Cathleen.  Meet you at Al’s?”

“Yeah, give me 15 minutes.”Tabbystar 400

A quarter-hour later we had a table, two mugs of coffee and a plate of scones in front of us.  “So how’d you know I’d be asking about Tabby’s star?  And what is it?  And who is Tabby?”

“Tabby is Tabetha (she spells it with an ‘e’) Boyajian, PhD.  She teaches Astronomy at Louisiana State, does research specializing in high-precision star measurement.  In her spare time she manages a citizen-scientist project called Planet Hunters.  The Hunters get their kicks combing through databases from the Kepler satellite telescope.  They get all excited if the records indicate that a star’s been transited.”

“Oh, like that star-dimming that found the TRAPPIST-1 planets?”

“Exactly.  I think they’ve got over a hundred candidate planetary systems and a couple-dozen confirmed ones to their credit by now.  Anyhow, 2012 was a banner year for them, ’cause they raised an alert on what’s now being called the weirdest star in the galaxy.”

“Which would be Tabby’s Star.  Got it.  But what’s weird about it?”

“Poets like to write about ‘the constant stars.’  This star is world-champion not-constant.  You know how stars seem to flicker when you look at them?”

“Yeah, that’s how I tell them apart from planets.”

“Then you know that the flickering comes from starlight getting messed up going through our turbulent atmosphere.  Astronauts don’t see the flickering.  Neither does Kepler up there, so it can reliably detect miniscule variations in a star’s output.  Virtually all of the 150,000 stars it tracked for four years had rock-steady production.  A few of them occasionally dimmed or flared by maybe a percent, but Tabby’s Star (formally known as KIC 8462852) got the Hunters’ attention when it dimmed by 16%.”

“Twenty times a normal dimming!  Did it stay that way or did the light come back up again?”

“Oh, it came back all right, but the curve on the way up didn’t match the curve on the way down.  That was even weirder.  So the team scoured through the star’s 4-year record and found a dozen events on the 0.05-2% scale, plus one at 8% and another at 21%.”

“21%?  That’s a big shadow.”

“Ya think?  Especially since the between-event timing was seriously irregular and some of those events were complex with three or more separate components.  But that’s not all the weirdness. Those dips lasted for hours or even days, longer than most planetary transits.  After Boyajian and her 48 collaborators published their initial report, which has to have one of the naughtiest titles in the astronomical literature, some other —”

“Wait, a naughty title?  C’mon, don’t tease.”

“OK <sigh>.  The technical term for a star’s light output is flux.  That paper was half about the observations and half about what might be causing the variation.  Assuming the star’s real output is constant, the question becomes, ‘What happened to that missing light?‘  Or as the authors put it, ‘Where’s The Flux?‘  Since then both the paper and the star have been informally referred to as WTF.  OK?”

“OK <sigh>.  So you were saying there’s something else.”

“Yeah.  Some other astronomers went digging in the archives.  WTF has been dimming gradually for at least the past 100 years.  Weird, eh?”

“Yeah.  So what’s causing it?”

“We don’t even have good guesses.”

~~ Rich Olcott

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