the project aims to find
most optimal telluric planets
whose atmospheres can be analysed

Ultra-cool Stars?

They have masses lower than 15% of the Sun's. They are the smallest and coldest stars that exist. Their properties make them optimal target to discover planets the size of the Earth, having temperatures similar to the Earth's. The most massive star targeted by SPECULOOS has 12% of the Sun's mass.


SPECULOOS consists of four robotic telescopes under construction at ESO's Paranal Observatory, Chile. Their one metre diameter mirrors collect photons onto state-of-the-art deep-depleted CCDs from E2V/Andor. SPECULOOS's design and photometric precision were prototyped on TRAPPIST, a smaller, 60cm robotic telescope.


The project is led by Michaël Gillon.
Funding came from the European Research Council, the Simons, the Saudi Binladin Group and MERAC foundations in addition to the Universities of Liège, Cambridge and King Abdul Aziz. Astelco Systems has been contracted for the construction

SPECULOOS compared to other surveys

The green region shows the type of stars around which the James Webb Space telescope will have the capacity to detect the atmospheric composition of a exoplanet with the size and temperature of the Earth. SPECULOOS is the only photometric survey designed to explore that region. It will provide the best targets for the James Webb. The graph further shows the interest of targeting ultra-cool stars. The vertical axis was calculated for an Earth-size, Earth-temperature planet. The main advantage is the short duration of habitable orbit. For an Earth-analog orbiting a Sun-like star, only one transit happens every year, only during which its atmosphere can be studied. We need to co-add 15 such transit to reach a formal detection of its composition, meaning 15 years of work.
An Earth-analog orbiting a star 10% of the Sun's mass has one transit per week!

The survey has already started
using the TRAPPIST telescope

Luhman 16 A&B

In February 2013, Kevin Luhman announced the presence of a binary brown dwarf only two parsecs from the Solar system. This made it the third closes system to Earth (it is Alpha Centauri's closest neighbour). A nigh later we started monitoring the brightness of this system. The system was observed for nearly a fortnight.

weather elsewhere

Our observations revealed that one of the two brown dwarfs (B) has a variable luminosity which revealed its 4.9 hour rotation period, but also provided the first concrete proof of weather outside of our solar system. Clouds -since confirmed- are forming and disbanding in this exotic atmosphere on timescales of half a day.

non-detection of an Earth-sized planet

After correcting for the variability we could have detected the transit of a two Earth-radius planet over the duration of the observations (top), and of an Earth-sized planet on orbits shorter than 10h (bottom), a first from the ground. This served as a prototype for SPECULOOS.