A nearby planet that could potentially support life may be more Earth-like than scientists first believed.
New observations suggest the planet, called GJ 3378b, is smaller and rockier than earlier estimates, making it an even more exciting target in the search for life beyond our solar system.
GJ 3378b is about 25 light-years away from Earth in the direction of the constellation Camelopardalis.
While that is an enormous distance by human standards, it is considered relatively close in astronomy. The planet orbits a small, cool red dwarf star.
One reason GJ 3378b has attracted so much attention is that it lies in the star’s “habitable zone.” This is the region around a star where temperatures may allow liquid water to exist on a planet’s surface.
Since all known life on Earth depends on water, scientists often begin their search for life by looking for planets in these zones.
“Our mantra is ‘follow the water,'” said lead researcher Paul Robertson from the University of California, Irvine. If liquid water can exist, there is a better chance that the planet could support life.
Red dwarf stars are much smaller, cooler, and dimmer than our Sun. They are also the most common type of star in the Milky Way, making up about 70% of all stars. Because they are so common, astronomers believe they are important places to search for planets that might be habitable.
Finding small planets around these faint stars is not easy. The research team used the Habitable-zone Planet Finder, an advanced instrument attached to the Hobby-Eberly Telescope at McDonald Observatory in Texas. The instrument is specially designed to detect infrared light, which is the type of light red dwarf stars give off most strongly.
Instead of looking directly at the planet, the scientists watched the tiny wobble of the star caused by the planet’s gravity. By measuring this movement very precisely, they were able to calculate the planet’s size and orbit more accurately.
The new study shows that GJ 3378b is about 2.3 times the mass of Earth instead of five times as previously thought. This is important because smaller “Super Earths” are more likely to be rocky planets rather than worlds covered by thick, crushing atmospheres that would make life much less likely.
The researchers also discovered that the planet completes one orbit around its star every 21 days instead of 25 days. Even though this orbit is much closer than Earth’s, the star is much cooler, allowing the planet to remain within the habitable zone.
However, scientists are also cautious. Because the planet is so close to its star, it may receive strong radiation that could slowly strip away its atmosphere. Without an atmosphere, life as we know it would be difficult to survive. More observations will be needed to determine whether GJ 3378b has managed to keep an atmosphere.
Future giant telescopes, including the Giant Magellan Telescope and the Extremely Large Telescope, will be able to study nearby planets like GJ 3378b in much greater detail. Scientists hope these powerful observatories will one day detect biosignatures—chemical signs that could reveal the presence of life.
For now, GJ 3378b has become one of the most promising nearby worlds in humanity’s ongoing search to answer one of science’s biggest questions: Are we alone in the universe?
