Planet Hunters TESS II: results from the first two years

We have some very exciting news: our paper summarising the results from the first two years of Planet Hunters TESS has been accepted for publication! Check out the paper here.

Figure 1: Half of the TESS planet candidates presented in the Planet Hunters TESS method paper.

The paper outlines the ins and outs of planet Hunters TESS project and presents 90 new planet candidates from the first two years of the TESS mission (sectors 1 to 26). These planets wouldn’t have been found without the help of all of the citizen scientists taking part in the Planet Hunters TESS project. The paper includes a link to a site that lists all of the citizen scientists who identified each of these 90 planet candidates mentioned in the paper. This page can also be found here.

The majority (81%) of the planet candidates outlined in the paper only exhibit a single transit event in the TESS lightcurve, meaning that they tend to have longer orbital periods (where the orbital period corresponds to the duration of a ‘year’ on this planet) than the average duration of the planets found by the TESS automated algorithms. This is because automated pipelines often require two or more transit events in order to be able to detect the signal. However, with visual vetting, we are equally sensitive to a single transit event as we are to planets that transit multiple times within the duration of one light curve.

You can see that in the figure below, where the orange and pink points show the PHT candidates, and the blue points show the automated pipeline found Tess Objects of Interest (TOIs). The figure highlights that the planets identified with PHT tend to have longer orbital periods than the TOIs, and therefore allowing us to study the characteristics of a different ‘set’ of planets, and maybe even of planets that are more similar to the planets within our own solar system.

Figure 2: Planet radius vs orbital period for the TOIs (blue) and the single (orange circles) and multi (pink squares) transiting PHT candidates. Use the slider in the figure to add/remove the PHT candidates.

Even though the majority of the planet candidates outlined in the paper are not yet confirmed planets, we are following them up using ground-based telescopes which are situated around the world, including in Australia, Chile, USA and the Canary Islands. Hopefully these observations, including both photometric and radial velocity observations, will allow us to confirm the planetary nature of these objects, and even derive masses for some of them which will allow us to infer their densities and therefore bulk compositions. This is ongoing work and we hope to share some of it with you in the near future.

In addition to the 90 new planet candidates, the paper presents some of the most interesting stellar systems that have been discussed on the Planet Hunters TESS Talk discussion forum. An example of a potential multi stellar system is shown below.

Figure 3: An example candidate multi-stellar system.

Multi stellar systems not only provide very interesting and pretty lightcurves, they also allow us to probe stellar evolution theories in more detail, as all the stars in one system must have necessarily formed at the same time and out of the same material. This highlights some of the other exciting science that results from Planet Hunters TESS and from the continued work of so many citizen scientists.  

Since the launch of the Planet Hunters TESS project, almost exactly 2 years ago, we have had over 25.5 million classifications completed by over 25 thousand citizen scientists from around the word. This huge global effort can help us understand what kind of planets exist within our galaxy, how planets form and evolve over time, as well as bring to light some of the other interesting and bizarre astrophysical phenomena that TESS observed over the last two years.

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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