Debris Ring Around Star Fomalhaut (HD 216956)
The top view, taken by NASA's Hubble Space Telescope, is the first visible-light image of a dust ring around the nearby, bright young star Fomalhaut (HD 216956). The image offers the strongest evidence yet that an unruly planet may be tugging on the dusty belt. The left part of the ring is outside the telescope's view. The ring is tilted obliquely to our line of sight.
The center of the ring is about 1.4 billion miles (15 astronomical units) away from the star. The dot near the ring's center marks the star's location. Astronomers believe that an unseen planet moving in an elliptical orbit is reshaping the ring.
The view at bottom points out important features in the image, such as the ring's inner and outer edges. Astronomers used the Advanced Camera for Surveys' (ACS) coronagraph aboard Hubble to block out the light from the bright star so they could see the faint ring. Despite the coronagraph, some light from the star is still visible in this image, as can be seen in the wagon wheel-like spokes that form an inner ring around Fomalhaut.
The suspected planet may be orbiting far away from Fomalhaut, near the dust ring's inner edge, between 4.7 billion and 6.5 billion miles (50 to 70 astronomical units) from the star. Only Hubble has the exquisite optical resolution to resolve that the ring's inner edge is sharper than its outer edge, a telltale sign that an object is gravitationally sweeping out material like a plow clearing away snow.
The ring is in the Fomalhaut system's frigid outer region, about 12 billion miles (133 astronomical units) from the star. This distance is much farther than our outermost planet Pluto is from the Sun. The ring's relatively narrow width, about 2.3 billion miles (25 astronomical units), indicates that an unseen planet is keeping the ring from spreading out.
Fomalhaut, a 200-million-year-old star, resides 25 light-years from the Sun in the constellation Piscis Austrinus (the Southern Fish).
The ring is tinted red for image analysis. The Hubble observations were taken over a five-month period in 2004: May 17, Aug. 2, and Oct. 27.