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WHAT’S OUT THERE? Detecting Extrasolar Planets Rick Rutland One way of detecting extrasolar planets is called the transit method. A transit is when the planet passes in front of the star. How do you think this might work? What would it look like? Draw a sketch of your prediction. IS THIS WHAT YOU THOUGHT? In reality, the stars are usually so far away that scientists do not ever see the actual star. They use instruments to take measurements of the star. Indirect evidence is used to locate planets. SCIENTISTS LOOK AT THE CHANGE IN BRIGHTNESS OF THE STAR AS A PLANET PASSES IN FRONT. TWO FACTORS CAN GIVE US A GOOD APPROXIMATION… THE SCIENCE IS COMPLEX The diameter of the planet compared to the diameter of the star. The orbital period of the planet (how long it takes to orbit the star). COMPARE THE DATA FOR THE TWO PLANETS. WHAT MIGHT CAUSE THIS? COMPARE THE DATA FOR THE TWO PLANETS. WHAT MIGHT CAUSE THIS? THIS STAR HAS TWO TRANSITING EXTRASOLAR PLANETS. Which choice fits each planet? SIZE OF THE PLANET CAN BE ESTIMATED The first transiting extrasolar planet was found orbiting a star named HD 209458 in the Pegasus constellation (150 light years away). The data was collected by the MOST space telescope. HD 209458 is about the same size as our sun, with a diameter of 1,400,000 km. SOURCES http://blogs.ubc.ca/polarisdotca/astrolabs/extrasolar -planets/ This presentation available at: http://rickrutland.wikispaces.com Vernier handouts available at: http://www.vernier.com/experiments/