Planet formation in Earth-like orbit around a young star
The star, TW Hydrae, is a popular target of study for astronomers because of its proximity to Earth (approximately 175 light-years away) and its status as a veritable newborn (about 10 million years old). It also has a face-on orientation as seen from Earth. This affords astronomers a rare, undistorted view of the complete disk.
"Previous studies with optical and radio telescopes confirm that this star hosts a prominent disk with features that strongly suggest planets are beginning to coalesce," said Sean Andrews with the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., and lead author on a paper published in the Astrophysical Journal Letters. "The new ALMA images show the disk in unprecedented detail, revealing a series of concentric dusty bright rings and dark gaps, including intriguing features that suggest a planet with an Earth-like orbit is forming there."
For the new TW Hydrae observations, astronomers imaged the faint radio emission from millimeter-size dust grains in the disk, revealing details on the order of one astronomical unit (about 150 million kilometers, or the distance between the Earth and the Sun). These detailed observations were made possible with ALMA's high-resolution, long-baseline configuration. When ALMA's dishes are at their maximum separation, up to nearly 15 kilometers apart, the telescope is able to resolve finer details. "This is the highest spatial resolution image ever of a protoplanetary disk from ALMA, and that won't be easily beaten going forward," said Andrews.
"TW Hydrae is quite special. It is the nearest known protoplanetary disk to Earth and it may closely resemble our Solar System when it was only 10 million years old," said co-author David Wilner, also with the Harvard-Smithsonian Center for Astrophysics.
The astronomers' next phase of research is to investigate how common these kinds of features are in disks around other young stars and how they might change with time or environment.
Source: National Radio Astronomy Observatory [April 01, 2016]