The innards of planets are diverse and mysterious — Earth is rocky, Mercury is iron-rich and Neptune is an ice giant. Astrophysicist Diana Valencia seeks to answer a question she calls simple but elusive: What determines what planets are made of?
The most common celestial objects throughout the galaxy are exoplanets — planets beyond our solar system — that have one to ten times the mass of Earth and one to two times Earth’s radius. Understanding the composition of these planets would not only shed light on how our own solar system formed, but could be critical for finding another habitable world.
“By using many other planets and seeing the variety, then we can understand if our solar system is very unique or if it’s following a normal pathway of planet formation,” says Valencia, associate professor in the department of physical and environmental sciences at U of T Scarborough.
When it comes to exoplanets’ composition, astrophysicists usually have only mass, radius and temperature to work with. Because different measuring instruments are often used, results can’t be reliably compared. Many have suggested that planets’ compositions can be inferred by looking at the stars they orbit, and Valencia’s latest project is putting that theory to the test. She’s working with multiple teams and will lead the analysis of first-of-its-kind data: measurements of low-mass exoplanets and stars that are precise and consistent enough to explore the connection between the composition of stars and planets.
Valencia’s project recently won funding from the 2023 Guggenheim Fellowship, a prestigious award that about 3,000 researchers, scholars and artists apply to each year, and only about 175 win. The fellowship financially supports projects in any field so long as they aim to create knowledge and/or art. Valencia was one of only two Canadians to win, and the only winner in the category Astronomy – Astrophysics.
“I am a woman of colour and the U of T Scarborough campus is so diverse that I want to showcase that. I want to show this is something that people from all walks of careers and life can achieve,” Valencia says.
The study has her drawing on part of what made her a groundbreaker in her field — she was the first to study exoplanets by combining geophysics, the study of Earth’s physical properties and environments, with astrophysics. Valencia is looking at super-Earths, planets with a mass greater than Earth but less than Neptune, that have rocky compositions similar to Earth. Some of the data she’s receiving is on multi-planet systems, letting her compare different rocky planets orbiting the same star to find potential deviations in their composition.
Another key element of the project is determining the role of collisions in planet formation. Much of Valencia’s recent work has been on determining whether exoplanets are more like larger versions of Earth or smaller versions of Neptune — super-Earths and mini-Neptunes respectively.
“It could be that when planets collide, some atmospheres were lost while some others were retained, maybe that can explain that dichotomy,” Valencia says. “This all feeds into our understanding of our own solar system.”