Scientists have identified dozens of planets outside our solar system so far, and while we may be able to find them – we still know very little about how there got there.
To learn more about planet formation, researchers have trained powerful telescopes on a young star system known as TW Hydrae and found evidence of a giant icy planet forming there, according to a new study in The Astrophysical Journal Letters.
TW Hydrae is an ideal star for planet scientists to study. It is thought to be just 10 million years old, it sits only 176 light years away, and its axis of rotation is pointed almost straight at us, giving scientists a literal overview of the goings on in the developing planetary system.
Past research has revealed TW Hydrae is encircled by a disk of small dust particles. These disks are known sites for planet formation and the latest observations have shown several gaps in the disk around TW Hydrae. These gaps could be evidence of planet formation, past research has shown.
Using ALMA to find TW Hydrae
In the new study, researchers used Atacama Large Millimeter/submillimeter Array (ALMA) high in the deserts of Chile to observe the disk around TW Hydrae in two radio frequencies. Because the ratio of the radio signal strengths in different frequencies is related to the size of dust grains, the team was able to determine the approximate size of dust grains in the disk. The team found smaller, micrometer-sized, particles were very prevalent and larger dust particles are vacant from the biggest gap in the disk.
Past studies have used calculations to determine a gap like the one seen around TW Hydrae is established by a large planet; its gravity and friction driving large dust out as it orbits its host star. Meanwhile, smaller particles aren’t pushed out by the orbiting planet. The latest observations match these theoretical predictions.
Based on data gathered by ALMA, the study team determined the large planet that orbits TW Hydrae at approximately 22 astronomical units – slightly more than the distance as Uranus orbits our Sun – is likely an ice giant bigger than Neptune.
“Combined with the orbit size and the brightness of TW Hydrae, the planet would be an icy giant planet like Neptune,” study author Takashi Tsukagoshi at Ibaraki University, Japan, said in a news release.
The researchers said they hope to use future ALMA observations to learn more about how this planet, and others like it, formed.
Image credit: NAOJ
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