Sciency Words: Light Curve

February 24, 2017

It’s been almost a week since I arrived at KIC 8462852, better known as Tabby’s Star, and discovered that the aliens really are building a megastructure. I still have a lot of questions, but the aliens aren’t giving me a lot of answers, and I think it’s time I moved on.

Which brings me to today’s edition of Sciency Words.

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Each week, we take a closer look at some science or science-related term to help us all expand our scientific vocabularies together. Today’s term is:

LIGHT CURVE

We met astronomer Bradley Schaefer in Wednesday’s post. Writing for Scientific American, he defines a light curve as “a measure of brightness as a function of time.”

So the light curve of a star with a constant brightness would be a straight line. If you found small, symmetrical dips in that line, that might mean there’s a planet in orbit, especially if the dips appear at regular intervals. Here’s an example of what that looks like, courtesy of NASA.

Other patterns of dips or spikes along a light curve could tell you if you’re looking at a binary star, or a flare star, or a variable star… looking at light curves is a great way to study stars.

As for Tabby’s star, its light curve is apparently a straight line most of the time, aside from tiny fluctuations that typically indicate solar flares and/or sunspots. In other words, Tabby’s star looks normal.

And then abruptly, dips appear in the light curve. Asymmetrical dips, as opposed to the symmetrical dips caused by transiting planets. In some cases, the line doesn’t so much dip as plunge downward, and that means… umm… astronomers do not know what that means.

Any serious discussion about Tabby’s Star should really begin with its weird, almost spastic light curve. I’m choosing to end here, however, because the aliens have made it clear that I’m not welcome.

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Now I need to find another megastructure to study, and the best way to do that is to examine the light curves of other stars.


More Megastructure Mystery

February 22, 2017

On Monday, I arrived at KIC 8462852, better known as Tabby’s Star, and discovered that yes, the aliens really are building a megastructure. My next question is: how long has this been going on?

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These aliens are not turning out to be all that friendly. Fortunately, there’s been some investigative work done back on Earth.

Astrophotography has been around for well over a century now. Even though no one paid much attention to Tabby’s Star until recently, that region of the sky has been photographed before. So following the publication of Tabetha Boyajian’s WTF paper, astronomer Bradley Schaefer started checking those old photographic plates.

And according to Schaefer’s findings, Tabby’s Star has been decreasing in brightness since at least 1890. It would seem the megastructure has been growing in size, obscuring more and more of the star, for quite some time now.

But can we trust the accuracy of those old photographic plates? According to astronomer Michael Hippke and colleagues, no. No we can’t. The degree of uncertainty is too high, Hippke claims, to make a conclusive determination about Tabby’s Star’s brightness over time.

There’s been a pretty intense argument between Schaefer and Hippke ever since. If nothing else, it’s an excellent example of how scientists debate each other. Click here to read Schaefer’s side of it, and click here for Hippke’s.

So if Schaefer is right, construction of the megastructure may have been underway circa 614 C.E. (that’s 1890 C.E. minus the 1276 years it takes for light from Tabby’s Star to reach Earth). And if Hippke’s right… well, who knows when the aliens got started? They’re certainly not telling.


Tabby’s Megastructure Mystery

February 20, 2017

So I’ve flown my spaceship all the way out to KIC 8462852, better known as Tabby’s Star, and what do you know? The aliens really are building a megastructure out here.

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This whole situation is pretty weird, I know; but the weirdest thing is that when I check my ship’s sensors, I can’t detect any thermal emissions from the megastructure or any of the spaceships involved in constructing it.

The lack of thermal emissions (or the lack of an “infrared excess,” as the experts call it) is one of the main reasons why Tabetha Boyajian and other legitimate scientists don’t really buy the alien megastructure hypothosis.

Think about it. If Tabby’s Star hosts an active work zone, with spaceships flying around and construction workers welding space girders and stuff, you’d expect all that activity to produce some heat. Even without the construction activity, the megastructure itself should be pretty warm due to the star it encircles.

And all that heat should be detectable in the form of infrared radiation. But whether you observe Tabby’s Star with a telescope back on Earth or the sensor grid of my imaginary spaceship, the total amount of infrared light is exactly what you’d expect from an F-type main-sequence star. No more, no less.

Since I’m here, I decided to ask one of the alien construction workers about this. Here’s what he told me: “Yeah, we been masking our thermal emissions. What of it? We don’ts wants nobody snooping in our business. Now scram, smelly human!”

Not exactly the answer I was expecting, but I guess I’ll take what I can get.

P.S.: If you want to learn more about Tabby’s Star and how citizen science helped uncover its mysterious behavior, I strongly recommend this SciShow interview with Tabetha Boyajian. That’s where I first learned about the “infrared excess” issue that I discussed in today’s post.


Sciency Words: Tabby’s Star

February 17, 2017

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Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:

TABBY’S STAR

Something’s wrong with a star named KIC 8462852. It flickers. It dims by as much as 22% for no apparent reason. This is an F-type main-sequence star, meaning it’s only a little bit larger than our Sun. F-type stars shouldn’t behave like this.

KIC 8462852 is sometimes called the WTF Star, because of the paper that first described its abnormal fluctuations in brightness. That paper was subtitled “Where’s the Flux?”

The star is also known (and perhaps better known) as Tabby’s Star, in honor of Tabetha Boyajian, the lead author on that paper.

There are several possible explanations for what might be happening to Tabby’s Star, but it’s the least likely explanation that’s gotten the most hype. Could it be aliens? SETI decided to check it out. They didn’t find anything. But still… it could be aliens.

Massive alien starships might be transiting the star, blocking some of its light. Or perhaps there are enormous space stations orbiting the star. Or maybe we’ve caught an advanced alien civilization in the act of building some kind of megastructure (like a Dyson sphere) completely encircling their sun.

Most professional astronomers do not think it’s aliens. Tabetha Boyajian herself doesn’t seem to take the idea seriously and often jokes about the crazy emails she gets from people who do. And to be perfectly clear, I do not take this alien megastructure hypothesis seriously either.

But just to be sure, I’ve decided to hop into my imaginary spaceship and fly out to KIC 8462852, just so I can see for myself what’s really going on. Wish me luck! I’ll let you know what I find next week.

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