magnetosphere

探査機ジュノーが、5年の月日を経てついに木星の軌道に乗りました。

Juno Spacecraft Enters Jupiter's Orbit After 5-Year Journey

We're about to get a closer look at Jupiter than ever before.

After five years and a nearly 2 billion mile journey through the solar system, NASA's Juno probe has entered Jupiter's orbit late Monday, getting an unprecedented front-row view of the gas giant -- our solar system's largest planet.

Ground controllers at the NASA Jet Propulsion Laboratory erupted in applause when the solar-powered spacecraft beamed home the news it had entered the planet's orbit.

"Juno, welcome to Jupiter," said mission control commentator Jennifer Delavan of Lockheed Martin, which built Juno.

The four-ton Juno launched on Aug. 5, 2011, and is equipped with three 30-foot-long solar arrays, along with 18,696 individual solar cells, to help it make the most of the solar power it receives on its journey.

The spacecraft conducted a 35-minute burn of its main engine Monday, essentially hitting the brakes and slowing Juno by about 1,200 mph so it can enter Jupiter's polar orbit.

Once inserted into Jupiter's orbit, Juno will circle the giant planet a total of 37 times over the course of 20 months. During that time, Juno is set to come as close as 3,000 feet above Jupiter's cloud tops, getting our closest look ever at the planet.

The Juno probe gets its name from the Roman goddess and wife of Jupiter who was able to see through clouds.

NASA officials said they hope the mission will help scientists learn more about Jupiter's origins, structure, atmosphere and magnetosphere.

http://abcnews.go.com/Technology/nasas-juno-spacecraft-reaches-jupiter-year-journey/story?id=40276654

今回取り上げる単語は、"magnetosphere"です。文脈的に、宇宙に関する言葉だと予想できます。
『ジーニアス英和辞典』第4版(大修館)で調べてみると、「(地球の)磁気圏、天体」とありました。
"magneto-"には、「磁気の」という意味があり、"sphere"には「球体、天体、圏」という意味があります。
また、「磁石」という意味の、"magnet"の原義を同辞書で調べてみると、マグネーシア(現在のトルコのマニサ)産の石を指しており、その石が天然磁石であったことによるそうです。
因みに"atmosphere"の"atmos"には、「空気の」という意味があります。(Akim)