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Астронет: Астрономическая картинка дня Ледяное кольцо вокруг близкой звезды Фомальгаут http://variable-stars.ru/db/msg/1390360/eng |
Credit & Copyright: ALMA (ESO/NAOJ/NRAO),
M. MacGregor; NASA/ESA Hubble,
P. Kalas; B. Saxton (NRAO/AUI/NSF)
Explanation:
Why is there a large ice ring around Fomalhaut?
This interesting star --
easily visible in the night sky -- lies only about 25
light-years away and is known to be orbited by at least one planet,
Dagon,
as well as several inner dust disks.
More intriguing, perhaps, is an
outer ring,
first discovered about 20 years ago, that has an unusually sharp inner boundary.
The featured
recent image by the
Atacama Large Millimeter Array (ALMA)
shows this outer ring with complete and unprecedented detail -- in pink -- superposed
on a
Hubble
image of the Fomalhaut system in blue.
A leading theory holds that this ring resulted from numerous
violent collisions
involving icy comets and
planetesimals, the
component objects of planets,
while the ring boundaries are caused by the
gravity of yet unseen planets.
If correct, any interior planets in the
Fomalhaut system are likely being continually pelted by large meteors and comets
-- an onslaught last seen in
our own planetary system
four billion years ago in an episode called the
Late Heavy Bombardment.
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