雅思听力背景：新行星的发现_雅思英语听力

雅思听力背景：新行星的发现

　　Fourth Planet Too Close to Its Parent?

　　The previously known planets around HR 8799 are about five, seven, and ten times Jupiters mass. They orbit between 2.2 billion miles from the starroughly the same as Neptunes distance from the sunand 6.3 billion miles , or almost twice Plutos distance.

　　The most distant planet circles just inside a dusty disk similar to that produced by the solar systems Kuiper belt, a region of small, icy bodies that includes Pluto.

　　The whole HR 8799 system is estimated to be no more than 60 million years old, so the planets are still glowing with heat from their formation. This heat signature is what betrayed the planets positions in the previous infrared images of the star.

　　Astronomers found the fourth planet using the Keck II telescope on the peak of Mauna Kea in Hawaii. The instrument is equipped with a special near-infrared imager and adaptive optics to eliminate the blurring effect of Earths atmosphere.

　　Images from Keck II show that the newfound planet is also a gas giant, about seven times Jupiters mass. But it orbits closer to the star, at a mere 1.4 billion miles , equivalent to between the orbits of Saturn and Uranus.

　　The new Keck data also indicate there may be an asteroid belt just inside the newfound planets orbit.

　　Widespread Jupiters Creating Dilemma

　　Overall, the HR 8799 system is starting to look like a scaled-up version of our solar system, the astronomers note. But the setup doesnt fit either of the two currently accepted models for how gas giant planets form, Marois said.