A team of astronomers has uncovered an Earth-like planet orbiting a star located 4,000 light years away from the solar system, potentially offering insights into our distant future. The rocky planet, about the same mass as Earth, revolves around a white dwarf in the constellation Sagittarius. As our Sun enters its final stages, this planetary system offers the best hope that humans can avoid being engulfed by its red giant phase.
Researchers from the University of California, Berkeley, and elsewhere announced the discovery of a potential Earth 2.0 in an article published in Nature this week. Using the Transiting Exoplanet Survey Satellite, or TESS, which is currently scanning the sky for promising exoplanets, they spotted a faint signal that shifted slightly with time—the signature of a planet passing in front of its parent star. They then used their telescopes to track the motion of this planet and discovered that it regularly slipped in and out of the habitable zone of its host star.
The TESS data also showed that the planet’s surface temperatures fluctuated significantly—in some places, it gets so hot that it boils water, while in other areas, it is as cold as an icebox. The team theorized that this erratic behavior could result from a thick atmosphere that the star’s intense radiation has stripped away. But, as they looked at these TESS images more, they noticed that the planet often popped back into the habitable zone.
When searching for a possible Earth analog, scientists consider factors such as the planet’s size and temperature, its distance from its star (which determines whether or not it can support life), its geological activity and plate tectonics, and even its chemical composition. But finding a planet that meets all criteria is like finding a needle in a haystack.
Gliese 12 b is the closest Earth-sized and Earth-temperature planet to date. However, it is 15 times closer to its host star than our planet is to the Sun, which means that the planet is blasted by 16 times as much radiation per second. In addition, its orbit is elliptical, making it difficult for telescopes like the James Webb Space Telescope to probe the planet’s atmosphere.
The upcoming Corot mission, however, is expected to launch this year and will specifically look for planets that occult their stars, making them easier for scientists to study in detail. The fact that Gliese 12 b is so close to its star and its companion planets makes it an ideal candidate for Corot’s attention.
With this new find, astronomers at UCL and other universities have boosted their estimates of the number of sun-like stars—which can host habitable planets—in our galaxy. By analyzing data from the TESS and Kepler space telescopes, they now believe that more than 4.1 billion stars like our own could likely support Earth-like planets.
