Planet Hunters TESS Mobile: swipe right for planets

It has been an extremely exciting year for Planter Hunters TESS and we have identified multiple potential new planetary systems. Due to the success of the project, we have decided to expand by bringing PHT to your mobile device!

PHTmobile_logo

To date, all of the data that we have looked at have been from the targeted bright, nearby stars that TESS observes every 2-minutes. However, in addition to these targeted stars TESS monitors the brightness of millions of other stars, both bright and faint, recording their brightness every 30-minutes. These stars are found in what are known as TESS’s Full Frame Images (or FFIs), and the time has come for us to start looking for planets there.

PHT_FFI

Example TESS Full Frame Images. Photo credit NASA/MIT

Due to the huge number of stars contained within these Full Frame Images, we decided to first analyse the data using a computer algorithm. This code, which was developed by Chelsea Huang at MIT pre-selects the best lightcurves for us to look at in more detail.

The automated search has two parts. First, it runs searched for periodic signals using an algorithm called Box Least Squares (BLS). This algorithm ‘folds’ the lightcurve at various trial orbital periods. If a trial period corresponds to the orbital period of an existing planet in the system the dips cause by a transiting object will overlap, suggesting the existence of a possible planet. The second part of the search uses machine learning, to look at the lightcurves that pass the BLS search, in order to assess whether the periodic signal could be the result of a transiting planet.

For many lightcurves the code is extremely good at identifying the good planet candidates without any human vetting. However, there are also a huge number of marginal cases where the machines are unsure as to whether there is a planetary signal present or not, and it is these cases that we need your help on.

good_example2

Examples of GOOD planet candidate as seen in on the app

The images that we show on the site have been folded at the orbital periods determined by the BLS search so that multiple dips should overlap with one another. We are showing the odd and the even (alternating) dips in red and white. This is because any difference in odd and even transit depth and shape is a tell-tale sign of the dips being the result of two stars of different sizes orbiting around one another in an eclipsing binary. Please discard these lightcurves on the app by swiping left or pressing the ‘discard’ button on your screen.

In this project we are also want to pay close attention to the shape of the dips. Transits due to eclipsing binaries tend to be very V-shaped, whereas transits due to planets are more U-shaped or have a flat bottom so look out for these!

bad_examples_app2

Examples of BAD candidates. Many of these are Eclipsing Binaries or dips caused by systematics

See what you can find by downloading the Zooniverse app onto your mobile and looking for the Planet Hunters TESS project.

We hope you enjoy this new version of Planet Hunters TESS and can’t wait to see what kind of systems we can find!

About Nora Eisner

Project leader of the Zooniverse citizen science project Planet Hunters TESS and PhD Student at the University of Oxford.

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