A colossal frontal collision between Jupiter and a still-forming planet in the early solar system about 4.5 billion years ago could, according to a study published this week in the journal [19459002veröffentlichtwurdeüberraschendeMesswerteausderJuno-SondederNASAerklären] Nature .
Astronomers from Rice University and Sun Yat-sen University in China say that their direct collision scenario may explain Juno's previously puzzling gravitational measurements, indicating that Jupiter's core is less dense and longer than expected.  "That's puzzling," said travel astronomer and study co-author Andrea Isella. "It indicates that something has happened that has upset the core, and this is where the gigantic influence comes into play."
Isella said leading theories of planet formation suggest that Jupiter began as a dense, rocky or icy planet that later accumulated its thick atmosphere. Isella expressed her skepticism when the lead author of the study, Shang-Fei Liu, first came up with the idea imagined that the data could be explained by a huge impact mixing Jupiter's core poet core content with less dense layers above it. Liu, a former postdoctoral fellow in Isella's group, is now a member of Sun Yat-sen's faculty in Zhuhai, China.
"It sounded very unlikely to me," Isella recalled. But Shang-Fei convinced me by shearing that this is not unlikely. "
The research team carried out thousands of computer simulations and found that a fast-growing Jupiter may have disrupted nearby orbits." planetary embryos, "protoplanets that were in the early stages of planet formation.
Liu said the calculations included estimates of collision probability under different scenarios and distribution of impact angles, in all cases Liu and colleagues had a probability of at least 40%. Jupiter also produced a "strong gravitational focus" that made frontal collisions more common than grazing.
Isella said the collision scenario had become even more convincing after Liu 3D Computer models that showed how a collision would affect Jupiter's core.
"Because the impactor is dense and contains a great deal of energy, it resembles a bullet that passes through the atmosphere and hits the nucleus head-on," she said Isella. "Before the impact you have a very dense Ke surrounded by atmosphere. The direct impact spreads and dilutes the core. "
An impact at a grazing angle may cause the impacting planet to become trapped in gravity and gradually sink in. Jupiter's core and Liu said that smaller planetary embryos are thicker in Jupiter's
"The only scenario that led to a profile of nuclear density similar to what Juno measures today is a direct impact on a planetary embryo about 1
Isella said the calculations suggest that even if this impact occurred 4.5 billion years ago, "it could take many, many billions of years for the heavy material to settle "Isella, who also participates in the NASA-funded CLEVER Planets project on Rice, said the study's implications would go further in our solar system.
"There are astronomical observations of stars that could be explained by this type of event," he said. People have been looking for planets near distant stars and sometimes they see infrared emissions disappearing after a few years, "said Isella. "One idea is that if you look at a star as two rocky planets clash and shatter head-on, you could create a cloud of dust that absorbs and releases the starlight, so you see a flash of lightning, now you have that cloud of dust, the light After a while, the dust dissolves and this emission disappears. "
The Juno mission is designed to help scientists better understand Jupiter's origin and evolution. Launched in 2011, the spaceship has instruments for mapping the gravitational and magnetic fields of Jupiter and examining the deep internal structure of the planet.
Other co-authors of the study are Yasunori Hori from the Astrobiology Center of Japan, Simon Müller and Ravit Xiaochen Zheng from the University of Zurich, from Tsinghua University in Beijing, and Doug Lin from the University of California at Santa Cruz and Tsinghua University in Beijing.
The research was supported by NASA (80NSSC18K0828), the National Science Foundation (AST-1715719) and the Swiss National Science Foundation (200021_169054).