#SATURN MOON ATLAS PANCAKE SERIES#

The model reproduces a number of observed features of the moonlets-their apparent compositional similarity to the ring material, their positioning just outside the main rings' edge, and the seeming contradiction between their orbital motion and the position of the rings. But as Janus continues to migrate outward the rings will expand as well, perhaps turning loose more icy material for new satellites. Once the icy ring particles venture beyond about 140,000 kilometers from Saturn's center, they become unstable, clumping into tiny protomoons and then moonlets.ДЄt present, the orbit of Janus, the largest of the inner moonlets at 180 kilometers across, keeps the rings within the gravitational stability limit. 'Disks in astrophysics are like pancakes-they spread,' he says, adding that collisions within the disk or ring drive the spreading detritus outward. The model tests a mechanism that had been proposed before but had been difficult to computationally confirm, Charnoz says-that the moonlets arise from icy debris spreading outward from the rings, past the point of gravitational stability. 'With this process we see that there is still accretion in the solar system.' 'It is a common idea to say that the solar system had finished its formation by 4.4 billion or 4.5 billion years ago,' he adds. 'We explored the idea that accretion is possible and ongoing at the rings' outer edge,' says lead study author SГ©bastien Charnoz, an astrophysicist at the University of Paris Diderot. ( Scientific American is part of Nature Publishing Group.) What is more, the moonlets appear to have coagulated in recent astronomical time, implying that more moonlets may be forthcoming. The study presents the result of a computer simulation of Saturn's dynamic environment, demonstrating how the moonlets, which dwell just beyond the planet's famed main rings, could have formed from material oozing out of the rings and accreting into clumps. Now, research in the June 10 issue of Nature deals with a population of smaller Saturnian satellites-Atlas, Prometheus, Pandora, Janus and Epimetheus-linking the origin of those so-called moonlets to the celebrated rings themselves. The largest, Titan, has helped draw a bit more attention to the Saturnian satellites in recent days, following an announcement that various chemical abundances on Titan were consistent with but not necessarily indicative of the presence of methane-dwelling, hydrogen-breathing life. The facing page of each chart lists the deep-sky objects shown on the map.Saturn is perhaps best known for its intricate ring system, but the giant planet also boasts a collection of moons, numbering in the dozens, that is nothing to sniff at. The colors make this an attractive atlas when used during the day (for planning sessions or to review a previous nightвЂ™s observations), and they donвЂ™t detract from its usefulness at night. The 20 charts that make up The Cambridge Star Atlas 2000.0 show the sky in multiple colors: Stars are black, the Milky Way is blue, star clusters are yellow, nebulae are green, and galaxies are red. Wil Tirion also created the more detailed The Cambridge Star Atlas 2000.0, which adds about 900 deep-sky objects to maps that plot stars to magnitude 6.5.

#SATURN MOON ATLAS PANCAKE SERIES#

A keyed series of six finder charts shows readers how the atlas maps relate to the current night sky. Magnified inset charts show the Pleiades (M45) and the region around OrionвЂ™s Sword. The maps include constellation boundaries but no constellation figures. The Bright Star Atlas divides the sky into four polar and six equatorial zones. It also includes about 600 double stars, variable stars, and deep-sky objects. Aimed at users of the smallest backyard telescopes, the Bright Star Atlas shows stars to magnitude 6.5. Another favorite atlas in the beginner category is the Bright Star Atlas by Wil Tirion.

Saturn moon atlas pancake