An unusual elliptical ring of dust around the young star Fomalhaut likely indicates an undiscovered Neptune-sized planet orbiting it, says a new report.

Young stars are surrounded by dust clouds that thin and dissipate as the star reaches maturity, becoming rings in their final stages. Fomalhaut, however, possesses an intriguing dust ring that is not centered around the star, but rather elliptical.

The sharp inside edge of Fomalhaut's ring demands that a relatively small, Neptune-size planet be tucked right up against the inner side of the ring, with its gravity tossing dust in the area out of orbit.

According to calculations, the ring is elliptical because the Neptunian planet's own orbit around Fomalhaut is elliptical – a curiosity in such a young system. When stars form from a giant cloud of gas and dust, the angular momentum of the cloud is transmitted to all the objects that form from the cloud, including new planets. Those new planets should, initially at least, orbit in circular paths – not elliptical ones. Fomalhaut's ring is offset by 1.4 billion miles, more than 15 times the distance from the Earth to the Sun, suggesting the hidden planet's orbit is also tremendously skewed.

Planetary collisions may have been the reason for the changed orbit. For the time being, however, this new model will remain untested until a new generation of telescopes can actually show the Formalhaut planets in question.

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--University of Rochester and SPACE.com Staff

Credit: NASA, ESA, P. Kalas and J. Graham (University of California, Berkeley), and M. Clampin (NASA/GFSC)