Spherical Asteroid Might Be Our Solar System's Tiniest Dwarf Planet

Two billion years ago, someplace out past Mars, a tiny world ended. Then, after picking up its pieces, a new world was born. Astronomers call that new world Hygiea, and they just caught their first direct glimpse of it and its catastrophic history. Until now, Hygiea (named after the Greek god of health and hygiene) was just one of millions of asteroids in the asteroid belt, the pre-planetary wreckage that fills the solar system between Mars and Jupiter. But advances in astronomy have brought the body into focus for the first time, revealing a smooth, round form at odds with its cratered, misshapen companions. The new observation, published Monday in Nature Astronomy, suggests that Hygiea hides a cataclysmic past, one that could gain it admission into the exclusive but poorly understood club of dwarf planets—potentially re-shaping the club itself in the process. Asteroids have historically been too small to see clearly from Earth, but with the introduction of adaptive optics—a technology that cancels the atmosphere's blurring effect for crisp Hubble-like photos—astronomers have spent years using the Very Large Telescope in Chile to work their way through the largest, brightest asteroids. At about 270 miles wide, Hygiea ranks fourth largest in the belt, after Ceres, Vesta, and Pallas. While Ceres is big enough for gravity to draw it into a sphere during construction (classifying it as a dwarf planet), Vesta and Pallas aren't, so the punier Hygiea's rotundness puzzled researchers. Franck Marchis says "When we started interpreting the data, we were kind of surprised to see how spherical this asteroid is,” a coauthor and planetary astronomer at the SETI Institute. Instead, the researchers hypothesize that the shape represents a scar from a past trauma. According to their imitation, another asteroid about 50 miles across could have cracked through the originally lumpy pre-Hygiea, basically liquefying it. Some fragment extends in identical orbits today, but gravity collected most of the remains and sculpted them into the smooth world astronomers are now seeing. The study emphasizes that objects in the asteroid belt are more than inert leftovers, that they, like planets, have their own unique stories. “Some have moons, some have been destroyed,” Marchis says. “These boditruly geological worlds.”

By – Abhishek Singh
Content - https://www.popsci.com/spherical-asteroid-smallest-dwarf-planet/