lecture 29 – an advertisement: two astronomy courses next semester
Post on 02-Jan-2016
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Lecture 29 – An advertisement: two astronomy courses next semester
• 29:52 ,“Characteristics and Origins of the Solar System, 1:30 – 2:20 MWF
• 143:070:001, Honors Seminar in Natural Sciences, “Life in the Universe: Scientific Bases for Speculation”, 2:30-3:45 TTh
Why study the solar system next semester?
Jupiter, Saturn, and Venus will all be
in the evening sky
Astronomical Events this Month
• Venus in the western sky after sunset
• Total eclipse of the Moon, November 8 (Saturday night) 5:32 PM 7:06 7:31 9:04
• Leonid meteor shower, November 18, before dawn
Last word on massive stellar evolution: it happens fast and
ends violently
Eta Carinae: Watch the skies! Watch the skies!
Next topic: Structure of the Milky Way Galaxy
What is the size, shape, and nature of the system of stars in which we live?
You can learn a lot by looking at the sky and thinking
From this picture, let’s figure out the shape of the Milky Way. Characteristics to go on are:
• Sprinkling of stars everywhere
• Thick band of light across the sky (the Milky Way)
• Band brightest in the direction of Sagittarius
• Band faintest in the direction of Taurus-Auriga
What’s the answer?
The Answer
How far is it to the galactic center?
How could we know?
Hint provided by globular star clusters. Great summertime objects, few in winter
How globulars indicate the distance to the galactic center
Globular Clusters are Distant
It must be a long way to the galactic center
Globular cluster Distance (light years)
M13 (Hercules) 21,000
M15 (Aquarius) 34,000
M92 (Hercules) 26,000
M4 (Scorpius) 14,000
M5 (Serpens) 26,000
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