Research

This is currently my main line of research. We know that in the frame of a two-body system (e.g., a star and a planet), there are five equilibrium points (called Lagrangian points) among which two (L4 and L5) are stable to small perturbations (i.e., they are gravitational wells or valleys) as opposed to the other three (L1, L2, and L3)that are unstable (i.e., they are gravitational hills). These L4/L5 points are located in the same orbit as the planet but 60 degrees ahead or before the planet. Bodies (even as large as planet-size) sitting in these points can remain stable and co-orbit with the planet under many different configurations.

Jupiter trojans. Credit: Nick Anthony Fiorenza

The high-precision instrumentation coupled with the long theoretical basis of co-orbital bodies (driven by the goals of explaining the trojan rocks at the Lagrangian points of Solar System planets) encourages the search of these co-orbital bodies to extrasolar planets. On top of this, we are aware of many of the Solar System components in extrasolar systems. However, the detection of exomoons and exotrojans is still a scientific and/or technological challenge. We know these bodies exist in nature and so detecting them is a matter of putting the effort on developing techniques and performing dedicated observations to that end. The TROY project is the first multi-technique, large effort to detect these bodies. And although other colleagues have tried to look for these co-orbital planets, unfortunately none has been discovered yet. TROY is leading this effort and the first results in our exploratory works are revealing interesting conclusions (see, e.g., Lillo-Box et al., 2018a; Lillo-Box et al., 2018b ).

Possible co-orbital configurations of a third body trapped in the two-body gravitational field of a star and a planet. Credit: Helena Morais & Fathi Namouni

My main activity as a professional astronomer has been devoted to the detection and characterization of extrasolar planetary systems through different techniques. I have been involved and focused in the follow-up of the planet candidates form the Kepler mission between 2011-2016 as part of the Kepler Extended Team by contributing with high-spatial resolution images using the AstraLux instrument at Calar Alto Observatory (see Lillo-Box et al. 2012, Lillo-Box et al., 2014b) and through the radial velocity monitoring of the candidates to confirm their planetary nature, mainly with the CAFE instrument at the same observatory (e.g., Lillo-Box et al. 2014c, Lillo-Box et al. 2015). The main focus of this follow-up was put on the confirmation of planets around giant star. Indeed, I could confirm Kepler-91b being the closest planet to a red giant star and the first confirmed planet to transit a giant star (Lillo-Box et al., 2014a). Other discoveries I have lead or participated in related to this parameter space are Kepler-447b (Lillo-Box et al., 2015), Kepler-432b (Ciceri et al., 2015), and Kepler-539 (Mancini et al., 2016).

After the Kepler prime mission, I have been involved in a European consortium lead by Dr. Alexsandre Santerne and devoted to the detection and confirmation of planet candidates from the second part of the Kepler mission (K2) and focused on the determination of precise parameters for rocky- to Neptune-like planets. This successful effort has led to relevant discoveries such as the Earth-like planet with a composition similar to Mercury (K2-229b, Santerne et al., 2018) or the planetary system around K2-19 (Armstrong et al. 2015, Barros et al. 2015).

I am particularly interested in the architecture and composition of planetary systems and the dynamical influence that other planets have on their neighbors. For instance, on the influence that external planets can have in preventing the planet engulfment of hot-Jupiters once the star leaves the main-sequence on its way to the red giant branch (see Lillo-Box et al., 2015). 

I also participate in papers related to the early stages of planet formation. In particular, related to the investigation of the composition of protoplanetary disks (e.g., Riviere-Marichalar et al., 2014) and the search for proto-planets (e.g., Huélamo et al., 2018).

I am also very interested in the different components of the Solar System as a laboratory to understand extrasolar system effects. In this regard, I have participated in some works related to the study of the atmosphere of Saturn: a follow-up of the Great White Storm of the planet during 2011 (Sánchez-Lavega et al., 2012) and a characterisation of the hexagonal storm in the North pole of Saturn (Sánchez-Lavega et al., 2014). 

I have also participated (and lead) works about different aspects of the stellar physics field. In particular, related to the detection of low-mass binaries (Lillo-Box et al. 2015; Lillo-Box et al. 2016), the study of  young stellar associations (e.g., Cody et al. 2014, Bouvier et al. 2018, Barrado et al. 2016), or the search for binaries as central stars of planetary nebula (Aller et al., 2018).