木星探査機「ジュノー」5年かけ周回軌道乗る、太陽系誕生に迫る観測へ

アメリカ航空宇宙局は7月4日、木星探査機「ジュノー」が木星に到達し、周回軌道に乗る段階に入ったと発表した。
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PASADENA, CA - JUNE 30: A 1/4 scale model of the Juno spacecraft is displayed as NASA officials and the public look forward to the Independence Day arrival of the the Juno spacecraft to Jupiter, at JPL on June 30, 2016 in Pasadena, California. After having traveling nearly 1.8 billion miles over the past five years, the NASA Juno spacecraft will arrival to Jupiter on the Fourth of July to go enter orbit and gather data to study the enigmas beneath the cloud tops of Jupiter. The risky $1.1 billion mission will fail if it does not enter orbit on the first try and overshoots the planet. (Photo by David McNew/Getty Images)
David McNew via Getty Images

アメリカ航空宇宙局(NASA)は7月4日、木星探査機「ジュノー」が木星に到達し、周回軌道に乗る段階に入ったと発表した。BBCなどが報じた。

ワシントン・ポストによると、ジュノーはグリニッジ標準時5日午前3時18分(日本時間5日午前11時18分)、軌道に入るためメインエンジンの噴射を開始した。

ジュノーは2011年8月、アメリカ・フロリダ州ケープカナベラル空軍基地から打ち上げられ、5年かけて木星に到達した。これから1年8カ月かけて木星を37周して木星の内部構造の詳細や太陽系誕生に迫る観測を行い、最後は木星に落下する予定だ。

ジュノーは木星が発する特異な音「ボウショック」を観測した。この「ボウショック」はソニックブーム(音速以上で飛行するジェット機などの衝撃波によって生ずる爆発音) に似た音で、太陽風が時速160万キロの速さで惑星全体に吹き付け、それが障害物にぶつかるとこのような乱れが生じるという。

探査機は1年間におよぶ航行で歯科治療の約6000万倍に相当するエックス線を吸収するが、チタン製の放射線防護壁によって内部の機器が保護されているので木星の雲の下まで観測できる。

またジュノーは、木星史上最高解像度の写真撮影を行う。

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