Comparison of Hubble Space Telescope images with those from the newly commenced Southern Near Earth Asteroid Survey has confirmed that the recently discovered planetoid Sedna has a second satellite.
Discovered only recently in what was thought to be a void between the Kuiper belt and the Oort Cloud, planetoid Sedna's orbit takes it from a minimum of 76AU from the sun at perihelion to 950AU at aphelion over an orbit taking 3,400 years.
It seems that the same star which deflected Sedna into it's present orbit from it's original position in the Kuiper Belt perhaps two billion years ago also perturbed a much smaller body, about 1km in diameter into an even more eccentric orbit.
Varying between 5AU at perihelion to 1104AU at aphelion, the moon has been provisionally named Dame Edna. The object was imaged at Siding Spring by Dr Robert McZero and Garry Gordon using the 40” Schmidtspiegler over two months which allowed orbital elements to be calculated with some precision.
First detected at mag 14, Dame Edna was only 6 million km from Earth but receding rapidly as it moved away from the Sun. In fact, its orbit could well take it through the tail of Comet LINEAR (C/2002 T7) on June 8, 2004, and interactions between the asteroid and the particles within the tail may well be detectable in large amateur telescopes.
Further observations may establish whether Dame Edna is actually in orbit around the first discovered moon of Sedna rather than the planetoid itself.