HR 4796A: Not Saturn
Explanation:
These are not false-color renderings of the latest observations of
Saturn's magnificent rings.
Instead, the panels show a strikingly similar
system on a much larger scale -
a ring around the young, Vega-like star,
HR 4796A, located about 200 light-years from Earth.
Probably composed of dusty debris ground from colliding planetesimals,
this ring is confined to a zone less than 17 AU wide
(1 AU equals the Earth-Sun distance) and
girdles the star at a radius of about 70 AU,
roughly twice the orbital radius of Neptune.
In analogy with the relationship
of Saturn's rings and moons,
this circumstellar ring could be held in place by
forces due to planets - shepherding
planetary bodies or the gravitational influence of larger planets
orbiting closer to the parent star.
In any event, because the ring would not survive long without something
to keep it there, astronomers consider its presence strong
evidence for unseen planetary bodies around HR 4796A.
The top panels show
the false-color images at two infrared wavelengths
from the Hubble Space Telescope's
NICMOS instrument,
and the bottom panels trace the corresponding image contours.
At the center of each,
the overwhelming light of HR 4796A has been masked
to reveal the fainter circumstellar ring.
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
NASA Web Site Statements, Warnings,
and Disclaimers
NASA Official: Jay Norris.
Specific
rights apply.
A service of:
LHEA at
NASA /
GSFC
& Michigan Tech. U.
