ALMA locates possible birth site of icy giant planet

How exactly ice giants like Uranus and Neptune form has remained a mystery.

By Brooks Hays
ALMA locates possible birth site of icy giant planet
New analysis of the dust grain distribution within a gap in the disk of a nearby star has revealed the presence of a newborn ice giant. Photo by ALMA/Tsukagoshi et al.

MITO, Japan, Sept. 14 (UPI) -- Astronomers have found evidence of a newborn planet in the protoplanetary disk surrounding TW Hydrae, a young star located 176 light-years away.

The newly collected data, retrieved by the Atacama Large Millimeter/submillimeter Array, ALMA, suggests the growing planet is an icy giant, similar in size and composition to Uranus and Neptune.


As astronomers continue to discover exoplanets, it's clear the solar systems of the cosmos can yield a wide variety of planetary characteristics. Understanding which protoplanetary conditions yield which characteristics is key to perfecting models of planetary formation and evolution.

How exactly planets like Uranus and Neptune form has remained a mystery, but the latest discovery may aid scientists' quest to better understand the process.

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For some time now, astronomers have been looking to TW Hydrae for insights into the planet formation process. The young star's axis points head-on toward Earth, giving scientists an overhead view of its planet-forming disk of dust and debris.

By imaging the star's disk in a variety of wavelengths, researchers can plot the distribution of differently sized grain particles. Surveys of TW Hydrae's disk show the tiniest dust particles proliferate throughout gaps in the disk, where large particles are entirely absent. Until now, researchers weren't exactly sure why.


New models suggest a giant planet -- and its gravitational interaction with resident dust particles -- explains the anomaly.

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Analysis of the dust grain distribution allowed scientists to estimate the size and type of planet, newly formed in the star's disk.

"Combined with the orbit size and the brightness of TW Hydrae, the planet would be an icy giant planet like Neptune," Takashi Tsukagoshi, an astronomer at Ibaraki University in Japan, said in a news release.

Researchers published their latest findings in the Astrophysical Journal Letters.

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