New images from the Atacama Large Millimeter/submillimeter Array (ALMA) reveal finest details in the protoplanetary disk around the young, Sun-like star TW Hydrae, including a tantalizing gap at the same distance from the star as the Earth is from the Sun.
This ALMA image shows the planet-forming disc around TW Hydrae. The inset image zooms in on the gap nearest to the star, which is at the same distance as the Earth is from the Sun, suggesting an infant version of an Earth-like exoplanet could be emerging from the dust and gas. The additional concentric light and dark features represent other planet-forming regions farther out in the disc. Image credit: S. Andrews, Harvard-Smithsonian Center for Astrophysics / ALMA / ESO / NAOJ / NRAO.
TW Hydrae, also known as HIP 53911 or IRAS 10594-3426, is an orange dwarf star located in the constellation Hydra, approximately 124 light-years away.
The star is about 55% of the mass of the Sun and is very young – only 8 million years old.
It is a popular target of study for astronomers because of its proximity to our Solar System and its status as an infant star.
“Previous studies with optical and radio telescopes confirm that TW Hydrae hosts a prominent disc with features that strongly suggest planets are beginning to coalesce,” said Dr. Sean Andrews from the Harvard-Smithsonian Center for Astrophysics.
“The new ALMA images show the disc in unprecedented detail, revealing a series of concentric dusty bright rings and dark gaps, including intriguing features that may indicate that a planet with an Earth-like orbit is forming there.”
Other gaps that show up in the new images are located 3 billion and 6 billion km from the star, similar to the average distances from the Sun to Uranus and Pluto. They too are likely to be the results of particles that came together to form planets, which then swept their orbits clear of dust and gas and shepherded the remaining material into well-defined bands.
For the new observations of TW Hydrae, Dr. Andrews and his colleagues imaged the faint radio emission from millimeter-sized dust grains in the protoplanetary disc, revealing details on the order of the distance between the Earth and the Sun.
The results were published March 31, 2016 in the Astrophysical Journal Letters.
“TW Hydrae is quite special. It is the nearest known protoplanetary disc to Earth and it may closely resemble the Solar System when it was only 10 million years old,” said Dr. David Wilner, also from the Harvard-Smithsonian Center for Astrophysics.
Earlier ALMA observations of another system, HL Tauri, show that even younger protoplanetary disks – a mere one million years old – can display similar signatures of planet formation. By studying the older TW Hydrae disk, the scientists hope to better understand the evolution of Earth and the prospects for similar systems throughout our Milky Way Galaxy.
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.
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Sean M. Andrews et al. 2016. Ringed Substructure and a Gap at 1 AU in the Nearest Protoplanetary Disk. ApJ 820, L40; doi: 10.3847/2041-8205/820/2/L40
