Astronomers were recently able to spot dusty hallmarks of Pluto-size objects swarming around young Sun-like star by using the Atacama Large Millimeter/submillimeter Array (ALMA).
By making detailed observations of the protoplanetary disk surrounding the star known as HD 107146, the astronomers detected an unexpected increase in the concentration of millimeter-size dust grains in the disk's outer reaches.
This increase, which begins remarkably far, about 13 billion kilometers, from the host star, might be the result of Pluto-size planetesimals stirring up the region, causing smaller objects to collide and blast themselves apart.
Luca Ricci, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, said that the dust in HD 107146 revealed that it gets thicker in the very distant outer reaches of the star's disk.
According to current computer models, the observation that the density of dust was higher in the outer regions of the disk can only be explained by the presence of recently formed Pluto-size bodies. Their gravity would disturb smaller planetesimals, causing more frequent collisions that generate the dust ALMA sees.
The new ALMA data also hinted at another intriguing feature in the outer reaches of the disk: a possible "dip" or depression in the dust about 1.2 billion kilometers wide, beginning approximately 2.5 times the distance of the Sun to Neptune from the central star.
Though only suggested in these preliminary observations, this depression could be a gap in the disk, which would be indicative of an Earth-mass planet sweeping the area clear of debris. Such a feature would have important implications for the possible planet-like inhabitants of this disk and may suggest that Earth-size planets could form in an entirely new range of orbits than have ever been seen before.
The star HD 107146 has been located approximately 90 light-years from Earth in the direction of the constellation Coma Berenices. It would be approximately 100 million years old.
Further observations with ALMA's new long-baseline, high-resolution capabilities will shed more light on the dynamics and composition of this intriguing object.
The study is published in the Astrophysical Journal.
