The University of New Mexico's Department of Physics and Astronomy received a $750,000 grant from NASA for its research on exoplanets. With NASA's assistance, the Department of Physics and Astronomy is able to utilize the TESS (Transiting Exoplanet Survey Satellite) telescope and analyze data to determine the existence of exoplanets. 

Diana Dragomir, assistant professor, defines exoplanets as, "any planet outside the solar system that orbits another star, other than the sun; that's what we call an exoplanet." Various methods exist for discovering exoplanets. The TESS telescope employs the transit method, which involves observing numerous stars in the hope of finding an exoplanet.

Credit European Space Agency, European Southern Observatory and NASA’s Goddard Space Flight Center/Provided
TESS Telescope

The TESS telescope, described by Dragomir as slightly larger than a fridge, follows an elliptical orbit reaching a distance equivalent to that between the Earth and the Moon. This survey satellite is equipped with four cameras, capturing rectangular images spanning from the celestial equator to the pole. It conducts a 27-day-long sky survey during which it remains oriented on a specific plane.

Dragomir explains, "In cases where that plane aligns with our line of sight and a planet passes between the star and our telescope, we may observe a transit—a temporary dimming of the star's brightness caused by the planet crossing in front of it from our viewpoint." The telescope's primary objective is to identify transiting exoplanets orbiting nearby bright stars, enabling more detailed studies of exoplanets than was previously possible.

The exoplanets’ orbital period – the time it takes to complete one orbit around their star – can be determined from the time elapsed between two consecutive transits. "What happens if the planet has a period longer than 27 days and it transits? Well, we might see just one transit, and we will have to use other methods to determine its orbital period. But these 'longer-period' transiting exoplanets are important to find and study because they may be more similar to the Solar System planets.”

If there is only one observed transit, the period and orbit of the planet are unknown. In such situations, ground-based observations are employed to confirm whether the exoplanet candidate is indeed a planet. "Now that I know there's a potential planet, I plan to explore other observational methods to verify its existence and measure its period," states Dragomir. "It's a rare occurrence to capture a transit that happens only once every ten years. When TESS is observing, it's already considered incredibly fortunate, but the alignment needs to be even more precise for a transit to occur from our vantage point. While we may not find a true Jupiter analogue with this method, we are discovering planets with Jupiter-like sizes and orbits similar to that of Earth," states Dragomir. 

TESS has the capability to observe a wide expanse of the sky simultaneously, enabling the tracking and monitoring of stars over time. Every three minutes, TESS captures a comprehensive image of the sky, which astronomers and researchers can subsequently download. This allows for the tracking of stars every two to three minutes, enabling the detection of any changes in brightness.

NASA/JPL-Caltech/R. Hurt

“Only a small portion of the planet's orbit will be observable during a transit. Out of the over 600 planet candidates we've tested, many are potential planets, but confirming them requires extensive effort," explains Dragomir. So far, a few dozen longer-period TESS planets have been confirmed. Due to the significant resources involved, including telescopes and personnel, confirming each candidate becomes challenging. "It's a substantial undertaking. Identifying these longer-period exoplanets can be rare due to the intricate alignment of various factors.”

The grant will support the ongoing work of confirming and measuring the periods of these cooler, more temperate exoplanets.

“The goal is to find longer period transiting planets, because what a transit does is it tells us the size of the planet and if we have the size of the planet, we can start comparing it with the solar system.”

When the mass of an exoplanet is determined along with the radius (possible only for planets around bright stars, like those found by TESS), the resulting density provides valuable insight into the planet's composition. Although density is just a single value, it plays a crucial role in understanding the characteristics of the planet and helps astronomers understand what the planet might look like.

While previous missions like Kepler have identified some long-period planets, the ones being found by UNM astronomers with TESS offer an opportunity for more comprehensive studies. These studies extend beyond size determination and enable astronomers to gather additional information about the composition and origins of these planets.

“The significance of this finding extends not only to astronomers who study planets but also within a broader context. Questions about our origins and the existence of life elsewhere arise. Where do we come from? Is there life elsewhere? However, reaching a conclusive answer requires numerous steps and extensive investigation. And even thinking beyond the question of life, why is a planetary system the way it is? Astronomers have discovered thousands of exoplanets, so we know they are common, but many exoplanetary systems are already very different from ours. We're starting to see that many are different because they have these inner planets really close in, often orbiting even closer than the distance between Mercury and our own Sun. But it's actually pretty hard to find planets further out from their star.”

NASA's Goddard Space Flight Center/Chris Smith (USRA)

By studying the planets found through this grant both individually and as a population, valuable insights can be gained into the characteristics of temperate, cooler planets present around other stars.

This research endeavor significantly improves understanding of the solar system and the general process of planet formation. The current focus on close-in planets prompts questions about their prevalence compared to longer-period planets, as it remains uncertain whether planet formation follows consistent patterns across all stars or exhibits significant variations.

Dragomir concludes that this research will contribute to a deeper understanding of our solar system and shed light on the question of whether Earth and our solar system are unique. "Through this endeavor, we aim to enhance our understanding of the solar system, including the context in which it exists. Our primary objective is to explore uncharted regions of parameter space, a term commonly used in scientific discourse. While we have discovered numerous exoplanets, it is important to note that they exhibit not only certain properties but also a range of other distinct characteristics."

Part of this grant will be in collaboration with colleague, Dr. Andrew Mann, based at the University of North Carolina. The University of New Mexico Physics and Astronomy Department will also be gaining a new Postdoc, Zahra Essack, from Massachusetts Institute of Technology (MIT) to help further this research.