Controversy and questions persist around 'alien megastructure' star

The mystery of “Tabby’s Star,” aka KIC 8462852, made headlines around the globe after some astronomers posited it could be dimming due to the construction of an alien megastructure. For a hot second it seemed to be explained away by a ring of giant comets — but now it seems the alien megastructure option is back on the table.

Astronomer Bradley Schaefer, who is working with a crowdfunding push to have the star monitored by the Las Cumbres Observatory Global Telescope Network, has written a scathing blog post aimed at a recent report looking to debunk his own findings. Put simply: Schaefer studied telescope data from the Harvard plates going back 100 years and seemed to find evidence the star had been dimming for quite some time.

But grad student Michael Lund and data analyst Michael Hippke put together a separate report and came to the conclusion that the “dimming” was actually just an anomaly created by the different telescopes used over the century. This was somewhat misreported to indicate it had proven the asteroid theory as mostly conclusive, but instead it just cast doubt on the long-term dimming theory. 

Which brings us to now: Schaefer has put out a statement throwing shade at Lund and Hippke’s findings, saying their report is “definitely wrong.” Schaefer says their data looked at stars too close together, which would cause the data to be unreliable. He also claims their report used the wrong calibration technique.

Here’s an excerpt from Schaefer’s post:

“Mistake #1 is that they selected many check stars that have some random nearby star at just the right distance so as to produce overlapping star images on the Harvard plates with large plate scales. The DASCH photometry uses SExtractor, and the algorithm returns something like the combined magnitude when the two star images overlap. This overlap produces an erroneously-bright magnitude for some plates. This occurs for most of the plates after the 1953-1969 Menzel gap (the Damon plates), resulting in an apparent jump across the Menzel gap. When the whole light curve is fit to a straight line, it will also result in an apparently brightening light curve…

Mistake #2 is that they have used the KIC magnitudes for calibration, rather than the APASS magnitudes as strongly recommended by DASCH in many places. The KIC calibration is based on the ‘g’ magnitudes as used by the Kepler satellite, whereas the APASS magnitudes directly give ‘B’ magnitudes. The native system of the Harvard plates is ‘B’. So the use of the KIC-calibration will always be problematic for some purposes because there must always be color terms needing correction. It is only a historical relic that the DASCH database allows the use of the KIC calibration. Yet most of Hippke’s and Lund’s results were made with the KIC calibration.”

If you’re a space or science geek, his lengthy post is well worth a read. So, what does this all boil down to? We’re still high on theories and short on answers. Scientists still don’t know what is causing the star to dim, but man, how cool would it be if there really are aliens out there using a Dyson sphere to siphon off the energy from this star?

(Via Popular Science, Centauri Dreams)

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