Huge “hidden” Saturn ring found

Oct. 7, 2009
Courtesy Nature
and World Science staff

Ob­serva­t­ions from a space tel­e­scope have re­vealed the largest-known plan­e­tary ring in the So­lar Sys­tem, as­tro­no­mers re­port.

The subtle, new­found ring sur­rounds the ga­seous plan­et, but much fur­ther out than its fa­mil­iar, more vis­i­ble rings, scientists said; if it were were vis­i­ble from Earth, the ring’s full cir­cle would ap­pear to be twice the size of the our Moon.

Sat­urn's moon Iap­e­tus. As­tro­no­mers pro­pose is dark­ly col­ored on  one side be­cause of
dust from a new­ly dis­cov­ered ring of Sat­urn. (Im­agecour­te­sy Cas­si­ni Im­ag­ing Team, SSI, JPL, ESA, NA­SA )
 

Ob­serva­t­ions from a space tel­e­scope have re­vealed the largest-known plan­e­tary ring in the So­lar Sys­tem, as­tro­no­mers re­port.

The subtle, new­found ring sur­rounds the ga­seous plan­et, but much fur­ther out than its fa­mil­iar, more vis­i­ble rings, scientists said; if it were were vis­i­ble from Earth, the ring’s full cir­cle would ap­pear to be twice the size of the our Moon.

Sat­urn's moon Iap­e­tus. As­tro­no­mers pro­pose is dark­ly col­ored on one side be­cause of dust from a new­ly dis­cov­ered ring of Sat­urn. (Im­age cour­te­sy Cas­si­ni Im­ag­ing Team, SSI, JPL, ESA, NA­SA )

 The ring is as­so­ci­at­ed with Sat­urn’s dis­tant moon Phoe­be, which or­bits the gi­ant plan­et about 13 mil­lion kilo­me­tres (8 mil­lion miles) away. That is roughly 200 times Sat­urn’s ra­di­us, or dis­tance from its cen­ter to its sur­face.

Un­til now, the largest-known plan­e­tary rings were Jupiter’s gos­sa­mer rings and Sat­urn’s E ring — sheets of dust that ex­tend to about 5 to 10 times the ra­di­us of their re­spec­tive plan­ets.

The new find­ings, made us­ing NA­SA’s Spitzer Space Tel­e­scope, are de­scribed in the Oct. 8 is­sue of the re­search jour­nal Na­ture. As­tro­no­mers Anne Ver­bis­cer of the Un­ivers­ity of Vir­gin­ia and col­leagues, who re­ported the find, al­so pre­sented sim­ula­t­ions show­ing how dust in the ring could come from re­peat­ed im­pacts of ob­jects strik­ing Phoe­be.

An artist's con­cep­tion si­mu­lat­ing an in­fra­red view of the gi­ant ring
sur­round­ing Sa­turn. Sa­turn it­self is just a dot, en­larged in
the in­set im­age. (NA­SA / JPL-Cal­tech / Keck)

The new­found ring is tilted 27 de­grees with res­pect to the main rings, re­search­ers said. The faint but enor­mous ring may al­so ex­plain a long­stand­ing mys­ter­y: the two-tone col­ora­t­ion of an­oth­er Sat­urnian moon, Iap­e­tus, Ver­bis­cer and col­leagues pro­posed. One side of Iap­e­tus is darker than the oth­er, lead­ing to sug­ges­tions that the front face might be coat­ed with dust spi­ral­ling in from Sat­urn’s darker out­er moons, in­clud­ing Phoe­be. Ver­bis­cer and col­leagues cal­cu­late that, over the his­to­ry of the So­lar Sys­tem, ma­te­ri­al from the ring could have sup­plied Iap­e­tus’s front face with a blan­ket of dark dust a few me­tres (yards) thick.