I am interested in several topics related to extrasolar planets (exoplanets), their atmospheres, and stars similar to the Sun (solar twins).

Atmospheric escape and outflows

Most of the exoplanets discovered to date are hot. Very hot. They receive tens to thousands of times more irradiation than the Earth receives from the Sun. And many of them have thick atmospheres mostly made of light elements, such as hydrogen and helium. In these conditions, hot and thick atmospheres literally boil off to space, and can dramatically alter the appearance and composition of the planet. But even temperature planets like the Earth lose part of their atmospheres to space as well, although less intensively.

One of my research branches consists on observing this phenomenon, which is also known as atmospheric escape. Among my discoveries, I found that the temperate mini-Neptune K2-18 b displays a signature of a large hydrogen exosphere around it, possibly fed by atmospheric escape.

Evolution of exoplanets

The most common types of planets we have found so far are what we call super-Earths and sub-Neptunes. As their names imply, these are worlds whose sizes vary between that of Neptune and the Earth. Since we do not have any examples of this type of planet in the Solar System, the nature of these worlds is a mystery.

We believe these planets are prone to losing a significant part of their atmospheres, causing them to “evaporate” and shrink as they age. This evolution is one of the most exciting areas of research in exoplanetary science. I am interested in observing and modeling the process of evaporation. Among my publications, I have shown that the warm Neptune-sized planet HAT-P-11 b is stable against photoevaporation.

Spectroscopy techniques

I have been doing astronomical spectroscopy since 2013, it is my bread and butter. I am particularly interested in spectral time series, spectral extraction, and transmission spectroscopy of exoplanetary atmospheres. Nowadays, I mostly use the Hubble and James Webb Space Telescopes in my research, but I have also experience with ground-based, high-resolution spectrographs, such as ESO/HARPS and Keck/NIRSPEC. In the future, I am looking forward to exploring atmospheres of other worlds using the ELT-class telescopes and the Habitable Worlds Observatory.

Solar twins

I studied the Sun and solar twins mostly during my Master’s. My project focused on their rotational evolution, and how that ties into other planetary systems similar to the Solar System. I am still involved with research projects on this subject, particularly on high-precision spectroscopy using ground-based spectrographs.

Team

At STScI, I lead the Terra Research Group, which seeks to understand the evolution of exoplanet atmospheres through photoevaporation and interactions with their host stars.

Lead

  • Dr. Leonardo Dos Santos

Current members

  • Lakeisha M. Ramos Rosado (since 2022): Johns Hopkins University graduate student (co-supervised with Prof. David Sing).
  • Aislyn Bell (since 2025): Johns Hopkins University graduate student (co-supervised with Prof. Meredith MacGregor).
  • Sierra Gomez (since 2025): STScI staff member.

Previous members

  • Paul Huwe (2025): STScI staff member.
  • William Grant (Summer Internship 2025): Amherst College undergraduate student.
  • Patrick McCreery (2022 - 2024): Johns Hopkins University graduate student (co-supervised with Dr. Néstor Espinoza).
  • Tatiana Ushakova (2023 - 2024): Johns Hopkins University graduate student (co-supervised with Prof. Meredith MacGregor).
  • Sean McCloat (2023 - 2024): University of North Dakota graduate student. Now an engineer in the military industry.
  • Daniel Ramos (National Astronomy Consortium Internship 2022): University of Texas at El Paso undergraduate student.

Members of the Terra team are also part of the broader Transiting Exoplanet Research Group at STScI, a large collaboration focused on understanding the atmospheres of exoplanets through transmission spectroscopy techniques.