Before now, astronomers thought planets had to be very close to their stars during formation. But scientists estimate that HD 100546­b is about 68 times farther from its star than Earth is from our sun.

　　When the right mixture of cosmic (宇宙的) dust comes together near a young star, a planet begins to form. Slowly, the planet creates its own gravity. That allows the planet to pull material from the disk of gases and other matter floating around the star.

　　1．Which of the following is the largest in the solar system?

　　A．HD 100546­b.　B．Jupiter

　　C．Saturn.

　　D．Earth.

　　2．Why is this discovery so special?

　　A．Because a new member in the solar system was born.

　　B．Because it can prove that there are other planets beyond the solar system.

　　C．Because a gas giant is first seen being formed in deep space.

　　D．Because the image of HD 100546­b is first drawn by astronomers.

　　3．According to the passage, HD 100546­b is________.

　　A．the sister planet of Jupiter and Saturn

　　B．first caught on camera by scientists

　　C．about 68 light years away from its star

　　D．a gas giant that grows close to its star

　　4．How far is HD 100546­b from Earth?

　　A．About 335 trillion miles.

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