Atmosfera Uranus

Atmosfera Uranus terdiri terutamanya daripada hidrogen dan helium. Di bahagian dalamannya, ia diperkaya secara ketara dengan pemeruap (digelar "ais") seperti air, ammonia dan metana. Sebaliknya pula untuk atmosfera bahagian atas, yang mengandungi sangat sedikit gas yang lebih berat daripada hidrogen dan helium kerana suhu rendahnya. Atmosfera Uranus adalah yang paling sejuk dari semua planet sistem suria, dengan suhunya mencapai serendah 49 K.

A whitish blue spherical planet against the black background of space — Uranus oleh *Voyager 2*

Atmosfera Uranus boleh dibahagikan kepada tiga lapisan utama: troposfera, antara ketinggian −300 dan 50 km dan tekanan dari 100 hingga 0.1 bar; stratosfera, merangkumi ketinggian antara 50 dan 4000 km dan tekanan antara 0.1 and 10⁻¹⁰ bar; dan termosfera panas (dan eksosfera) dari ketinggian 4,000 km ke beberapa jejarian Uranus dari permukaan nominal pada 1 tekanan bar.^[1] Tidak seperti bumi, atmosfera Uranus tidak mempunyai mesosfera.

Troposfera ini mengandungi empat lapisan awan: awan metana pada kira-kira 1.2 bar, awan hidrogen sulfida dan ammonia pada 3-10 bar, awan ammonium hidrosulfida pada 20-40 bar, dan akhirnya awan air di bawah 50 bar. Hanya dua lapisan awan atas telah diperhatikan secara langsung—awan yang lebih dalam hanya tetap menjadi tekaan. Di atas awan tersebut terdapat beberapa lapisan lemah jerebu fotokimia. Awan troposfera yang terang diskret jarang berlaku di Uranus, mungkin disebabkan oleh perolakan di bahagian dalam planet ini. Walau bagaimanapun, pemerhatian awan tersebut digunakan untuk mengukur angin zon planet, yang sangat cepat dengan kelajuan sehingga 240 m/s.

Hanya sedikit yang diketahui tentang atmosfera Uranus kerana hingga kini hanya satu kapal angkasa, Voyager 2, yang melintasi planet itu iaitu pada tahun 1986, memperoleh beberapa data komposisi yang berharga. Tiada misi lain untuk Uranus yang dijadualkan buat pada masa ini.

Lihat juga sunting

Magnetosfera Uranus

Nota sunting

Petikan sunting

^ Lunine 1993.

Rujukan sunting

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Kategori berkenaan Atmosfera Uranus di Wikimedia Commons

[FOOTNOTELunine1993-1] Lunine 1993.

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