In about 23 years，it may finally be time to look up.A recently discovered asteroid （小行星） has a chance of hitting the earth on Valentine's Day in 2046.It was discovered on Feb.26 at an observatory in San Pedro de Atacama，Chile.
While the thought of an asteroid hitting the earth may sound concerning，National Aeronautics and Space Administration （NASA） says people shouldn't be worried.
The asteroid has an estimated diameter of 160 feet，which is about the same size as an Olympic swimming pool or the width of a football field.
"We've been tracking a new asteroid named 2023 DW that has a very small chance of impacting the earth.Often when new objects are discovered，it takes several weeks' data to reduce the uncertainties and adequately predict their orbits years into the future， "NASA's Planetary Defense Coordination Office （PDCO） said.
The asteroid is ranked on the Torino Scale as level 1 threat.The scale is a tool to categorize potential earth impacts，with zero being no threat and 10 being something that can cause a global disaster.One on the Torino Scale means 2023 DW is in the normal，or green zone.
"Current calculations show the chance of collision （碰撞） is extremely unlikely with no need for public concern，" NASA says of the green zone. "New telescopic observations will very likely lead to re-assignment to Level 0."
Although 2023 DW doesn't pose a great risk to the earth，NASA has been continuing to work to defend our planet from any asteroid that could cause disaster.
In September，2022，NASA crashed its Double Asteroid Redirection Test spacecraft，or DART，into an asteroid to see if it could change the trajectory of the space rock.NASA later confirmed the mission was a success，and is continuing to research how effective the method is，should a massive asteroid be headed our way.
（1）What does NASA's PDCO say about 2023 DW？ CC
A．It is too close to the earth.
B．It must be destroyed in space.
C．Its orbit is still uncertain now.
D．Its orbit should be changed.
（2）How is 2023 DW ranked on the Torino Scale？ CC
A．As Level zero threat.
B．As Level ten threat.
C．In the normal zone.
D．In the threatening zone.
（3）What does the underlined word "trajectory" mean in the last paragraph？ DD
A．Size.
B．Weight.
C．Angle.
D．Path.
（4）Which can be a suitable title for the text？ BB
A．An Asteroid Was Discovered at an Observatory in Chile
B．An Asteroid Is Coming Our Way，Unlikely to Hit Us
C．A Space Rock Has Just Passed the Earth
D．A Spacecraft Has Been Crashed Recently
【答案】C；C；D；B
【解答】
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發(fā)布：2024/5/27 14:0:0組卷：4引用：4難度：0.3
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