A new method could accelerate the discovery of exoplanets and allow to find worlds that until now could not be detected by orbiting too far from its star. It has been developed by an international investigation led by the University of Geneva (Switzerland), which has discovered the exoplanet with the largest orbit to date: it takes ten Earth years to complete a turn around its star. The results have been published this month in the journal Astronomy & Astrophysics .

One of the most efficient methods to find new planets outside the solar system is to observe other stars and record the amount of light that comes from them. If at any moment a planet passes between a star and us, it produces a small eclipse that astronomers call transit. By measuring how the star’s light changes over time, scientists can tell if there is a planet, or several, its size and how long it takes to complete an orbit.

Traditionally, for astronomers to be sure that they have found a new exoplanet, they have to wait for three transits, that is, the planet to complete three orbits around its star. The new method only requires a transit

Traditionally, for astronomers to be sure that they have found a new exoplanet, they have to wait for three transits, that is, the planet to complete three orbits around its star. That is why this method works very well to detect worlds that are very close to their stars and have orbits of a few days or months. On the contrary, more distant planets would require observation times that are not viable today. For example, to discover Jupiter, which takes 11 years to orbit the sun, hypothetical alien astronomers should observe our star for 33 years.

Researchers led by the University of Geneva have used a new method to analyze data from the NASA Kepler Space Telescope, gathered between June and August 2017. From a single transit, they have detected the presence of an exoplanet with an orbit of ten years around the star called EPIC248847494, 1,500 light years from our system. Since it has only happened once between its star and the Earth, astronomers have had to analyze the data with exhaustive rigor to verify that it was not an error and have applied multiple computer models to infer its characteristics.

The discovered exoplanet takes ten years to complete an orbit around its star

The planet orbits its star – which is similar in size to the Sun, according to the Gaia mission of the European Space Agency (ESA) – four times the distance between our planet and the Sun. After observing EPIC248847494 with the Euler telescope , from the La Silla Observatory (Chile), the astronomers concluded that the exoplanet would be a gas giant with a size similar to that of Jupiter.

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Since it would resemble the gaseous giants of our system, it is very likely that it has several satellites. “It is an excellent candidate to try to detect exolunas that could be habitable,” the authors write in Astronomy & Astrophysics , and propose that they be observed by telescopes such as the European Cheops or Plato, which ESA plans to launch in 2019 and 2026, respectively.

This technique could be used to hunt habitable planets like Earth around stars like the Sun. “

In addition, “this technique could be used to hunt habitable planets like Earth around stars like the Sun,” says Helen Giles , lead author of the research, in a statement released by the University of Geneva . Because of the limitation of the transit method, most exoplanets discovered so far orbit red dwarfs, a type of star that can emit radiation that could interfere with the development of life, Giles stresses.