The European Space Agency’s Khufu satellite had an unexpected encounter: while exploring two exoplanets in a nearby star system, it discovered a third, rare and “with no known equivalent”.
The mission was studying Nu2 Lupi, a sun-like star 50 light-years from Earth in the constellation Lupus. This is one of only three stars visible to the naked eye as many planets are known to orbit.
The discovery was unexpected, says lead author of the discovery, Letitia Delris, of the University of Liège in Belgium.
“We plan to extend previous studies of Nu2 Lupi and observe planets b and c crossing the face of the star with Khufu, but while transiting planet c, we noticed something amazing: an unexpected transit of planet ‘d’, which is the farthest in the system,” he explained.
Studying these transportation systems is essential to understanding how planets form and evolve, Delrez says, since it’s possible to compare multiple planets around the same star in detail.
Scientists note that Planet D is 2.5 times the radius of the Earth, but it is 8.8 times heavier. It takes about 107 days to orbit the star.
“The bright parent star, the long orbital period, and the readiness for further characterizations make Planet D very exciting – it is an extraordinary object, with no known parallel, and certainly a golden target for further study,” he said. David Ehrenreich of the University of Geneva, Switzerland.
According to the European Space Agency (ESA), most exoplanets with long orbital periods have been found around stars that are too faint to allow for detailed observations. But the Nu2 Lupi is bright enough to be picked up by space telescopes and even large ground-based observatories.
“Because of its general characteristics and orbit, Planet D is a uniquely favored target for studying a temperate-atmospheric exoplanet around a Sun-like star,” Delores said.
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