脊索是双边对称的，三叶裂的，分段的腔壁。
Chordates are bilaterally symmetrical, triploblastic, segmented coelomates.
利用智利的天文望远镜，天文学家测量了三裂星云中气体的多普勒频移和速度。
By using telescopes in Chile, the astronomers measured Doppler shifts and thus velocities of gas in the Trifid.
日本的天文学家说，最知名星云之一的人马座三裂星云，它的壮丽景观可正是由两朵气体和尘埃云的碰撞造成的。
Astronomers in Japan say one of the best-known nebulae-the Trifid, in the constellation sagittarius-owes its splendor to a smashup between two clouds of gas and dust.
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