(ORDO NEWS) — Over the past decades, the number of known exoplanets has increased dramatically. But we still know very little about some of their characteristics, such as composition or massiveness.
Jared Siegel, a student at the University of Chicago, was able to extract some clues from NASA data that scientists had overlooked. He analyzed data obtained by NASA’s Kepler spacecraft.
Some of this data was full of statistical noise, but Siegel and his mentor, astrophysicist Leslie Rogers, were able to extract useful information about exoplanets by setting an upper bound on how massive they could be.
The research results for Siegel’s master’s thesis were published in The Astronomical Journal.
Siegel and Rogers studied data from the Kepler space telescope, which tracked bursts of light from distant stars for nine years. These flashes can occur when a planet passes in front of a star, temporarily dimming its light.
Many scientists have already analyzed this data, finding evidence of more than 2,600 exoplanets. But Siegel and Rogers wondered if there was a way to use statistical methods to get even more information.
Their approach was based on the fact that the Kepler telescope had found many stars that appeared to be orbiting several planets.
The mutual attraction of these planets should slightly change their orbits compared to how they could move if only one planet orbited the star. The more massive the planets, the stronger these perturbations.
“If we know that there are several planets in the system, but do not see large perturbations in transit time, then we can say that these planets are not particularly massive,” Siegel explained.
“For example, we could say that they most likely do not have the mass of Jupiter, because then they will noticeably attract each other.”
They applied this logic to a sample of 170 planets in 80 different star systems. For about 50 of these planets, they were able to establish an upper mass limit.
Scientists explained that this is important information because they can start to rule out options for what the planet is made of.
“For example, you might say, ‘Well, this planet is too light to be made of pure iron,'” Siegel said. “For more than twenty planets, we can say, ‘This planet is too light to be like Earth.'”
This information also helps scientists better understand the population of exoplanets. “We want to know how many planets in a given mass range could be rocky, water or gas planets,” Rogers said.
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