NASA’s Kepler mission ended in 2018 after more than nine years of fruitful planetary exploration. The space telescope has discovered thousands of planets, many of which bear his name. But it also created vast amounts of data that exoplanet researchers are still analyzing. Now a research team has shed new light on the seven-planet system in Kepler’s ocean of data.

The star is called Kepler 385 and is located approximately 4,670 light-years away. Some of its planets were confirmed as early as 2014, while others remain candidates. But in the newly updated catalogue, scientists confirmed the rest of the planets and revealed new details of this rare system.

The article announcing the new catalog is titled “Updated Kepler Planet Candidate Catalog: Focus on Accuracy and Orbital Periods.” The lead author is Jack Lissauer, a research scientist at NASA’s Ames Research Center. The article will be published on: Journal of Planetary Science and placed on the preprint server arXiv.

“We have compiled the most accurate list to date of Kepler candidate planets and their properties,” Lissauer said. “NASA’s Kepler mission has discovered many of the known exoplanets, and this new catalog will allow astronomers to learn more about the properties of these planets.”

Scientists have known about the Kepler 385 planetary system for many years. Some of its planets were confirmed as early as 2014, while others remained candidates. But updated methods and improved data have led to new insights and discoveries.

The research team that created the catalog says it only lists all known Kepler candidate planets orbiting and passing by a star. One of the most intriguing systems is Kepler 385, which has seven planets very close to their star and bathed in their star’s warmth. All seven are larger than Earth but smaller than Neptune.

Kepler 385 is similar to the Sun but slightly larger and hotter. It is 10% larger and about 5% hotter. It is one of the very few stars with more than six planets or candidate planets orbiting it.

Both inner planets are slightly larger than Earth. According to the new catalogue, both are probably intact. They may even have an atmosphere, but if it does it is very thin. The remaining five planets have radii about twice that of Earth and likely have thick atmospheres.

“Our revision of the Kepler exoplanet catalog provides the first true unified analysis of exoplanet properties,” said co-author Jason Rowe, Canadian Chair in Exoplanet Astrophysics and Professor at Bishop University in Quebec, Canada. “The refinement of all planetary and star properties allowed us to conduct an in-depth study of the fundamental properties of exoplanet systems to better understand exoplanets and directly compare these distant worlds with our own Solar System, as well as to focus on the details of individual systems such as Kepler-385.”

But the new catalog contains much more than this rare and interesting system. Kepler 385 is just one of the most important of the nearly 4,400 planet candidates and 700 multi-planet systems it is studying.

Thanks to improved measurements of the stars hosting all these planets, particularly from ESA’s Gaia stargazing spacecraft, researchers were able to better analyze the distribution of transit times. Transit time is an important tool for studying the distribution of exoplanets. This is true for orbital eccentricities ranging from circular orbits with zero eccentricity to extremely elongated orbits.

There is not enough data to measure the eccentricity of most exoplanets individually. However, researchers have developed methods that can characterize the eccentricity distribution of the transiting exoplanet population. This is a key component of Kepler’s new catalog and has led researchers to some new conclusions.

The most important of these concerns the nature of the orbits of planets in multi-planet systems.

“While previous studies concluded that minor planets and systems with more transiting planets have lower orbital eccentricities, these results were based on complex models,” said co-author Eric Ford of the Department of Astronomy and Astrophysics at Penn State University. “Our new result provides more direct, model-independent evidence that systems with more transiting planets have more circular orbits.”

In terms of potential habitability, the Kepler 385 system is very simple.

All seven planets are well inside the habitable zone and covered in intense radiation. In fact, all seven receive more heat from their stars per area than any other planet in our solar system. But this new study isn’t about feasibility.

This is the new Kepler catalogue, which is more detailed and accurate than its predecessors.

“More than a decade has passed since Kepler stopped collecting data from its primary field of view,” the authors write. “Nevertheless, the Kepler planet candidate list remains the largest and most homogeneous collection of exoplanets known.”