This chapter reviews our current knowledge of metal-poor ultracool dwarfs with spectral types later than M7. The current census of M, L, and T subdwarfs is explored. The main color trends of subdwarfs from the optical to the mid-infrared are described and their spectral features presented, which led to a preliminary and tentative spectral

The impact of exoplanet science at the beginning of the twenty-first century is studied from two different approaches: the impact in astronomical science both by professionals and citizen scientists and through public outreach. The impact of exoplanetology on the scientific community as well as on the informed public is presented by several

The star 55 Cancri was one of the first known exoplanet hosts and each of the planets in this system is remarkable. Planets b and c are in a near 1:3 resonance. Planet d has a 14.5 year orbit, and is one of the longest known orbital periods for a gas giant planet. Planet e has a mass of 8 M? and transits this bright star, providing a unique case

ESPRESSO (Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations) is a VLT ultra-stable high-resolution spectrograph that will be installed in Paranal Observatory in Chile at the end of 2017 and offered to the community by 2018. The spectrograph will be located at the Combined Coudé Laboratory of the VLT and will be able to

When an exoplanet passes behind its host star, we can measure the time of the occultation, its depth, and its color. In this chapter we describe how these observables can be used to deduce physical characteristics of the planet such as its averaged dayside emission, departures from uniform disk illumination, or a precise measurement of the orbital

Brown dwarfs are substellar objects unable to stably fuse hydrogen in their interior. Since the discovery of the first brown dwarf in an open cluster, namely, Teide 1 (Rebolo et al. Nature 377:129-131, 1995), many searches for substellar objects have been carried out in young stellar clusters and associations, such as Pleiades, Orion, Upper