Threats to Earth

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Slide 11

Outcomes

Foundation Paper

You should now be able to

Describe that a comet is made from ice and dust, the tail of a is a trail of debris and that comets have highly elliptical orbits

Describe that the speed of a comet increases as it approaches a star

Describe a near-Earth object (NEO) as an asteroid or comet on a possible collision course with Earth and how NEO may be seen with telescopes and that observations can be used to determine their trajectories

Higher paper

Explain why the speed of a comet increases as it approaches a star: the strength of gravity increases

Suggest and discuss possible actions which could be taken to reduce the threat of NEOs

Slide 12

Halley’s Comet Reappears every 76 years Image from 1986

Slide 13

Hale-Bopp as seen from Craig County, VA in 1997

Slide 14

Hale-Bopp as seen from Alexandria, VA in 1997

Slide 15

Hale-Bopp as seen from Wyoming in 1997

Slide 16

Yerkes Observatory

Slide 17

Comets

Comets are balls of rock and ice, with trails of debris blown outward by the Sun

They have highly elliptical orbits and speed up as they approach the sun

The trajectories of observed objects can be predicted accurately

If an asteroid (or comet) on a collision course with Earth is spotted early enough, it may be possible to alter the trajectory of the asteroid

Slide 18

Slide 19

Slide 20

Outcomes

Foundation Paper

You should now be able to

qDescribe that a comet is made from ice and dust, the tail of a is a trail of debris and that comets have highly elliptical orbits

qDescribe that the speed of a comet increases as it approaches a star

qDescribe a near-Earth object (NEO) as an asteroid or comet on a possible collision course with Earth and how NEO may be seen with telescopes and that observations can be used to determine their trajectories

Higher paper

qExplain why the speed of a comet increases as it approaches a star: the strength of gravity increases

qSuggest and discuss possible actions which could be taken to reduce the threat of NEOs