A good and bad example of current science

Our astronomer begs to be allowed to explain what’s really interesting about KIC8462852.

Our astronomer writes:

Articles appeared in the general news media this past fall concerning a certain star with the difficult-to-remember name KIC 8462852.  It is a very interesting star; unfortunately, the media picked it up for the wrong reason, and I’d like to explain a bit.

Start with the Kepler telescope.  It’s a satellite in orbit, not designed to see things in exquisite detail, but to measure the brightness of stars very accurately.  That way, it can tell if something small passed in between the star and the satellite, like a planet orbiting the star.  It has found some thousands of planets this way.  It has also found stars changing brightness for other reasons, of course, like pulsating stars or stars with spots like our Sun.

Kepler makes a lot of measurements of lots of stars, so many that the scientists who operated it analyze them with automatic computer algorithms.  They have also made the data available to the public, so anyone can run their own analysis.  One group that does just that is “The Planet Hunters,” who use volunteers to look for unusual things in the light-curves.  The human eye is very good at detecting patterns and anything out of the ordinary, where a computer program only looks for what it’s designed to find.  The Planet Hunters discovered dips in the brightness of KIC8462852 that were not periodic (like those caused by something in orbit) and were of strange and variable shape (so they couldn’t be caused by a spherical planet).

Other observations of the star showed no excessive brightness in the infrared, as would be caused by dust clouds.  In fact it looks exactly like a normal star slightly bigger and brighter than the Sun.  Except for the dips; those look like no other star we’ve ever seen.  They must be extremely rare, because we’ve observed lots of stars over the years.  The Planet Hunters discussed many possible explanations, rejecting almost all, finally settling on a swarm of comets (a particular type of swarm) as the most probable they could think of.  They left the question open, however.

Another group of astronomers has been thinking about whether, and how, we might detect civilizations around other stars.  If these civilizations had (somehow, for some purpose) had built structures the size of planets, they might (under some circumstances) look something like the dips in KIC8462852, so this team suggested it would be a good target for monitoring with radiotelescopes to try to detect their broadcasts.  They didn’t say the alien explanation was more probable than another, just that it made monitoring this star a better bet than monitoring something else.  (Someone did listen, and found nothing, which is not really conclusive one way or another.)  It’s like saying, on a snowy day, that if your Uncle Herman (who lives in Mongolia) had passed by outside we’d see footprints.  Finding footprints does not mean Uncle Herman was here.

Well, the media picked up only this part, and broadcast stories on the theme of “Alien Megastructures Detected.”  Ignoring what’s really of scientific interest, they emphasized a speculation.  This may be understandable, chasing a sensation in hopes of selling newspapers (or the electronic equivalent); it’s still irresponsible.

KIC8462852 is really interesting, but for other reasons:

• It was found by “citizen science”–professional astronomers set up the search, but ordinary people made the discovery!
• More than seven different telescopes, from the submillimeter to ultraviolet, contributed observations to try to work out what’s going on.
• Many different lines of analysis (calculations, computer models, physical theory) came together to rule out many explanations.

And it’s an even greater puzzle than we thought.  A recent search through old sky photographs has shown that the star has been dimming at an average rate of about 16% per century since about 1880.  That’s hard to put into any explanation.  For scientists, this is the fun part–we don’t know what’s happening, so there’s work to do!