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Lecture 10

Lecture 10 - September 30.docx

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York University
Natural Science
NATS 1745
Robin Metcalfe

September 30, 2011 Nasa’s WISE rases doubt about asteroid family believed responsible for dinosaur extinction -satellite equipped with telescope, seas sky in inferred light -inferred light detectors show things we can’t see with the naked eye -discovery is a picture of family of asteroids, thought to be related to destruction of dinosaurs -asteroids: rocks in space, range in size from grains of sand to rocks as big as small planet, generally find them in orbit around the sun generally around mars and Jupiter -asteroid that killed dinosaurs was believed to have crashed into gulf of mexico -crater is enormous, it’s large enough to suggest global extinction, astronomers have worked out ow long ago impact occurred (65,000,000 yrs ago) -years ago, family of asteroids was targeted as possible culprit -was checked using regular photos, using light from sun, not accurate in size, asteroids were thought to be too large, now we’ve used inferred and can see light from asteroids itself, we have more accurate idea of size, we’re considering these a possible culprit again -relevance: although extinction of dinosaurs may not be so relevant to us now, studying the history of asteroids is because the more we know about their past, the better chance we have to further our knowledge of the with hopes of predicting future impacts and protecting ourselves 2. Annual cycle of the stars: - due to Earth’s annual orbit around the Sun, our visible window of stars changes each night, so the stars we see can tell us the time of year -when a star returns to the same position in the sky, Earth has completed 1 orbit (ie. 3. Within the latitudes of Egypt, the heliacal rise of Sirius (the brightest star in the sky) coincides with the Nile’s annual flood. Sirius’ heliacal rise was therefore used to mark
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