a project to monitor the ephemerides of transiting exoplanets

by the ARIEL Ephemerides Working Group

The ARIEL Space mission

ARIEL, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey, was selected as the fourth medium-class mission in ESA’s Cosmic Vision programme. During its 4-year mission, ARIEL will study what exoplanets are made of, how they formed and how they evolved, by surveying a diverse sample of about 1000 extrasolar planets, simultaneously in visible and infrared wavelengths. It is the first mission dedicated to measuring the chemical composition and thermal structures of hundreds of transiting exoplanets, enabling planetary science far beyond the boundaries of the Solar System.

More details on how ARIEL will expand our knowledge on exoplanets:

For more information, visit the mission's official website:

How can ground based observations contribute to the mission?

ARIEL will observe known exoplanets to obtain their spectra and characterise their chemical consistency. For this technique to be as efficient as possible and to organise large-scale surveys we need to have a good knowledge of each exoplanet's expected transit time and also monitor the stellar variability of the host stars. The ARIEL Ephemerides Working Group is responsible for keeping this information up-to-date and this is where small and medium-scale telescopes can contribute significantly and make a difference, through the ExoClock project.

Be part of the mission!

We strongly believe that everyone can contribute to real research and become part of a bigger project, such as a space mission. In the ExoClock project we have created special tools and educational guides for any observatory that would like to support the future of exoplanets. We can all collaborate towards answering the most intriguing questions of science and society: How do planets form? Are there other planets like the Earth? Could they host life? Is there any other type of life?

Who can become part of the mission?
Everyone that has some basic equipment including a telescope and a CCD camera can participate in the effort of monitoring the planets' host stars. You will be asked to create a free ExoClock account, where you will be able to set up an observatory profile (or more than one!), with your equipment and geographical coordinates. In this way, you will get personalised information on the transits that fit best to your equipment and your location. You will be receiving also relevant updates, and notifications for special observations. Finally, you will have the chance to interact with our team for any questions you might have and get feedback on your observations.

Start observing
If you don't have any experience with transiting exoplanets, all the guidelines on how to record an exoplanet transit are outlined here:

Following the observation, you can carry out the data analysis by using the software HOPS that our team has especially designed for transiting exoplanets. You can find all the guidelines for the software installation and use here:

You are more than welcome to use any other photometric software, however we recommend HOPS to maintain homogeneity in the results. In addition HOPS is very easy to use, fast and compatible with all operating systems.

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