As the Earth becomes less able to support our rapidly increasing population, we are inclined to search for exoplanets, planets which are outside of our own Solar System. There are plenty of ongoing exoplanet search projects, several of which are succeeding in their objectives, and a considerable number more which have sadly yet to discover their first one. In any case, the data collected is not always explainable…

How does one go about searching for an exoplanet? Any rocky bodies which are similar in size to our Earth are barely visible from thousands of light years away, even in the light of their host stars.

One technique is by observing transits. As a planet traverses in front of its star, a slight reduction in the brightness of the star is observed.

Image: ragerallyway

The data collected may appear something like this:

Transit Light Curve
Image: Richard L. Bowman and David Koch

A light curve, such as the one above, reveals two important features of an exoplanet. Firstly, the time period between two ‘dips’ gives the time period of the orbit of the planet around the star, as a transit occurs once every complete orbit. If we know the mass of the star, we can use classical mechanics to calculate how far the planet is away from the star. Secondly, the depth of a dip gives information on the size of the planet, as a larger planet will reduce the brightness by a greater proportion. Other pieces of information such as the temperature of the star can help scientists analyse if the planet is suitable for life (a common phrase is the Goldilocks zone).

There is often too much data for a limited number of astronomers to look through, so they programme computers to look for patterns within the data. Nonetheless computers don’t have quite the observational skills of humans when it comes to identifying unusual patterns or anomalous data, so many scientific projects involve citizen science. Citizen science incorporates amateur science enthusiasts to help scientists conduct research, an effective way to help the general public engage in scientific activities and become more scientifically literate.

NASA initiated their own citizen science program, which they named Planet Hunters. Planet Hunters had their participants sift through innumerable pieces of data collected by the space telescope Kepler. NASA launched Kepler in 2009 as part of the Kepler Space Mission in order to search for exoplanets within our Milky Way galaxy.

A very intriguing piece of data emerged from Planet Hunters. This piece of data was the light curve of KIC 8462852, a star located approximately 1,300 light years away. The light curve was found to contain irregular dimmings, something which computers would have missed as it wasn’t something that they were programmed to look for. Not only do the dips occur at irregular intervals, but they also have varying depths.

KIC 8462852 Light Curve.png
Image: T. S. Boyajian et al.

Astronomers have proposed several explanations for these bizarre observations, one of which involves the construction of megastructures by advanced extraterrestrial civilisations. The irregular decreases in the flux (energy) observed has led the star to be named the WTF star after the initial study’s subtitle, ‘Where’s the Flux?’. It has also been named Tabby’s Star and Boyajian’s Star, in honour of the lead author of the study, Tabetha S. Boyajian.

If you have a few moments to spare next fortnight I’ll be here to unearth these equally bizarre explanations.


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