28 July 2011


The moon is not Earth's only orbital traveling companion. According to a PBS Newshour report, a team of Canadian astronomers has found "an asteroid caught in a synchronized orbit with the Earth (see image above), dancing back and forth relative to our planet as both orbit the sun. The object is a Trojan asteroid, meaning that it is held in a delicate balance between a gravitational tug from the sun and an equal gravitational tug from the Earth. [The discovery has been designated 2010 TK7.]

"It's long been known that Jupiter, Neptune and Mars have Trojans orbiting alongside them, but this is the first time one has been found alongside our planet .... Trojans are found in areas called Lagrange triangular points (see illustration below, click to enlarge), where the gravitational pull between the host planet and star ~ in this case Earth and the sun ~ balance out. This Trojan is found at L4, which is 60 degrees ahead of the Earth .... its distance from the Earth ranges from 49.7 million miles to 12.4 million miles."

When you click on the link, be sure to scroll down to the GIF (animated) display of the orbits of the Earth and our Trojan companion as they circle the sun. The more we learn about the solar system (and the cosmos in general), the clearer it becomes that we have so much more yet to learn.

Case in point ~ Science Daily reports that the European Space Agency's Herschel space observatory "has shown that water expelled from the moon Enceladus forms a giant torus of water vapour around Saturn. the discovery solves a 14-year mystery by identifying the source of water in Saturn's upper atmosphere .... Enceladus expels about 250 kg of water vapour every second, through a collection of jets from the southern polar region .... Although most of the water from Enceladus is lost into space, freezes on the rings or perhaps falls onto Saturn's other moons, the small fraction that does fall into the planet is sufficient to explain the water observed in its upper atmosphere."

Enceladus is the only moon in the Solar System known to influence the chemical composition of its parent planet. So far.

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