New mass estimate reveals rocky composition
A team led by UC Irvine astronomer Paul Robertson has refined the mass of exoplanet GJ 3378b from 5.3 Earth masses down to just 2.3 Earth masses, using the Habitable-zone Planet Finder instrument on the Hobby-Eberly Telescope at McDonald Observatory. The lower mass means the planet is almost certainly rocky rather than gaseous, making it a much better candidate for hosting life. The findings were published in The Astrophysical Journal.
Planet receives Earth-like starlight amounts
GJ 3378b orbits a red dwarf star called GJ 3378 in the constellation Camelopardalis, just 25 light-years from Earth. The planet receives almost the same amount of starlight as Earth does from the Sun, placing it securely within the habitable zone — the region where temperatures could allow liquid water to exist on the surface. "Our mantra is 'follow the water,'" said Robertson, explaining why this planet is a priority target for further study.
Next step: searching for biosignatures
UC Irvine student Gogod James, who worked to characterize the planet's size, said the team is eager to search for atmospheric biosignatures. "If a planet in the habitable zone has a proper atmosphere, we can justify further research looking for biosignatures, liquid water or other signs of life," he said. At only 25 light-years away, GJ 3378b is close enough for next-generation telescopes to analyze its atmosphere for potential markers of biological activity.