Researchers using the Atacama Large Millimeter/submillimeter Array (ALMA) believe they have detected a family of Pluto-sized objects orbiting a sun-like star.
The astronomers detected an unexpected increase in the concentration of millimeter-size dust grains in the outer region around a star dubbed HD 107146. The phenomenon is believed to be caused by a "swarm" of Pluto-sized planets stirring things up and causing smaller objects to collide, the National Radio Astronomy Observatory reported.
"The dust in HD 107146 reveals this very interesting feature -- it gets thicker in the very distant outer reaches of the star's disk," said lead author Luca Ricci, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. At the time of the observations, Ricci was with the California Institute of Technology in Pasadena, Calif.
Dust located in debris disks usually come from material left over from planetary formation, but is often replenished by collisions between nearby objects; by the time a solar system has reached planetary maturity this dust has usually been depleted. When a system is in its "awkward teenage years" researchers have predicted this dust is at its most dense in its outer reaches, which is seen in this observation.
"The surprising aspect is that this is the opposite of what we see in younger primordial disks where the dust is denser near the star. It is possible that we caught this particular debris disk at a stage in which Pluto-size planetesimals are forming right now in the outer disk while other Pluto-size bodies have already formed closer to the star," Ricci said.
The new data also suggests there is a possible "dip" in the density of dust that is about 1.2 billion kilometers wide. This could indicate that there is a planet about the size of Earth moving the dust out of the way. If this planet does exist, it suggests Earth-sized objects could form a range of orbits that has never been seen before.
"This system offers us the chance to study an intriguing time around a young, Sun-like star," said ALMA Deputy Director and coauthor Stuartt Corder. "We are possibly looking back in time here, back to when the Sun was about 2 percent of its current age."
The findings were published in a recent edition of the Astrophysical Journal.
