вторник, 28 августа 2018 г.

The growth crisis of Jupiter explained


Astronomy – Astrophysics logo.


August 27, 2018


For two million years, the largest planet in our system has grown slowly. We know today the cause.



The growth of Jupiter has gone through several distinct phases

Image above: This true color mosaic of Jupiter was constructed from images taken by the narrow angle camera onboard NASA’s Cassini spacecraft on December 29, 2000, during its closest approach to the giant planet at a distance of approximately 10 million kilometers (6.2 million miles). Image Credits: NASA/JPL/Space Science Institute.


Jupiter is the largest planet in our solar system, but for a while it has had growth problems. Swiss researchers have clarified this mystery, announced Monday the University of Bern in a statement.


For two million years, Jupiter grew slowly, according to studies on meteorites. A phenomenon that astronomers from the Universities of Berne and Zurich and ETH Zurich have tried to understand. Using a new model, they traced the origin of the gas giant and solved the mystery.



Animation above: Time-lapse sequence from the approach of Voyager 1, showing the motion of atmospheric bands and circulation of the Great Red Spot. Recorded over 32 days with one photograph taken every 10 hours (once per Jovian day). Animation Credit: NASA.


“We were able to show that Jupiter has grown through different phases,” says Julia Venturini from the University of Zurich, which summarizes the results she and her colleagues have published in the journal Nature Astronomy. During these phases, the mass of Jupiter did not develop uniformly.


Less growth, more energy


In the beginning, the planet embryo collected small pebbles of only a few centimeters and rapidly formed a planetary nucleus during the first million years, explains the University of Bern. In the second phase, during the next two million years, the growth of the planet has progressed more slowly.


Collisions with one-kilometer diameter blocks then only slowly added more mass, but provided a lot of energy, which was even more important.



Animation above: Asteroid Impact on Jupiter on March 17, 2016 by amateur Austrian astronomer. This is not the first time we’ve seen Jupiter get struck by an object. Back in 1994 it was hit by cometary fragments from Shoemaker-Levy 9, and again in 2010 and 2012.


Collisions with these blocks released heat. This heat warmed the gaseous atmosphere of the young planet, preventing rapid cooling, contraction and further enrichment of the gas. This explains the relatively long time that Jupiter spent in the mass phase from 15 to 50 times that of the Earth, as the researchers explain.


It was not until the third phase that the gases finally accumulated and made Jupiter a gaseous giant about 300 times the mass of the earth and about 143’000 kilometers in diameter.


Jupiter as a barrier


The study was inspired by new data on meteorites, says the University of Bern. These showed that the young solar system, while still a disk of dust and gas, was divided into two regions. Jupiter then served as a barrier of separation between the two.



Animation above: How Jupiter protects Earth from asteroids. Animation Credit: Petr Scheirich.


For two million years, when Jupiter went from 20 to 50 times the mass of earth, she apparently disrupted the dust disk and had to create a seal. Materials outside its orbit could not mix with those inside its orbit. This separation lasted until Jupiter reached a mass sufficient to deflect the rock and disperse it into the inner regions of the solar system.


University of Bern: http://www.unibe.ch/index_eng.html


University of Bern release: http://www.unibe.ch/news/media_news/media_relations_e/media_releases/2018/medienmitteilungen_2018/jupiter_had_growth_disorders/index_eng.html


Image (mentioned), Animations (mentioned), Text, Credits: ATS/University of Bern/University of Zurich/ETHZ/Orbiter.ch Aerospace/Roland Berga.


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