The number of planets in other solar systems has gone up. We don't know how big they are or what they're made of.
The University of Chicago undergraduate was able to tease out some clues from the data.
He spent six months analyzing the data. The data was full of statistical noise, making it hard to differentiate planets from other phenomena, but Siegel and his advisor were able to extract useful information about these planets.
Siegel, who graduated this spring, said that the results kept getting more exciting.
The results of Siegel's undergrad thesis have been published.
Planets have problems.
Siegel and Rogers were looking at the data from the NASA space telescope, which was used for nine years to track the light from distant stars. As a planet passes in front of a star, it can dim its light.
More than 2,600 exoplanets were found by many scientists after analyzing this data. Siegel and Rogers wondered if statistical methods could be used to tease out more insights.
Their approach was based on the fact that many stars have multiple planets around them, just like Earth and its sister planets around the sun. If there was only one planet around a star, the tug of the planets' gravity would affect how they moved. The bigger the planets, the stronger they are.
Siegel and Rogers thought that they could say something about how massive some of the planets could be.
Siegel explained that the planets can't be massive if we know there are multiple planets in a system. They are probably not Jupiter-mass, because they would be pulling on each other.
This logic was applied to a sample of 170 planets. About 50 of the planets had an upper bound on their mass.
The scientists said that this helps because they can start ruling out options for the planet. Siegel said that you could say that the planet is too light to be made of iron. Over twenty planets can be said to be too light to be made of Earth-like material.
Scientists are able to better understand the population of exoplanets. Rogers wants to know how many planets are likely to be rocky or waterworlds.
There are non- linear paths.
The scientists said the biggest challenge was accounting for the noise in the data.
Siegel said that many of the stars are very dim. There is a lot of noise coming from the stars and it can be difficult to disentangle the planet signal. The system may be on an incline. We spent a lot of time thinking about how data could be messy, so we took all these possibilities into account.
Siegel began doing research with faculty scientists during the winter of his first year at the University, but had not yet been in charge of the project.
There's always that desire to find the answer in the back of the book. Siegel said that with this type of research you can't. As it became clear that this group of stars could help inform our understanding of the rest of the population, it just got more and more exciting.
Rogers said it was gratifying to see a student work through the non- linear path to find an interesting problem to work on and make a novel contribution to the characterization of planets.
Siegel is a research fellow at the National Science Foundation and he is studying astronomy.
More information: Jared C. Siegel et al, Mass Upper Bounds for Over 50 Kepler Planets Using Low-S/N Transit Timing Variations, The Astronomical Journal (2022). DOI: 10.3847/1538-3881/ac8985 Journal information: Astronomical Journal
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