measuring the distance to the stars. what is a light year? a light year is the distance light...
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![Page 1: Measuring the Distance to the Stars. What is a Light Year? A light year is the distance light travels in one year. If the speed of light is 300,000 Km/sec](https://reader030.vdocuments.net/reader030/viewer/2022012919/5697c0291a28abf838cd765d/html5/thumbnails/1.jpg)
Measuring the Distance to the Stars
![Page 2: Measuring the Distance to the Stars. What is a Light Year? A light year is the distance light travels in one year. If the speed of light is 300,000 Km/sec](https://reader030.vdocuments.net/reader030/viewer/2022012919/5697c0291a28abf838cd765d/html5/thumbnails/2.jpg)
What is a Light Year?
• A light year is the distance light travels in one year.
• If the speed of light is 300,000 Km/sec. then how many Km is a light year?
• 300,000Km/sec. x 60sec/min x 60min/hr x 24hr/day x 365 days/year
• One light year is 9,500,000,000,000 Km
• 9.5 trillion kilometers
![Page 3: Measuring the Distance to the Stars. What is a Light Year? A light year is the distance light travels in one year. If the speed of light is 300,000 Km/sec](https://reader030.vdocuments.net/reader030/viewer/2022012919/5697c0291a28abf838cd765d/html5/thumbnails/3.jpg)
How close is the nearest star?
• Our sun is 8 light minutes away.
• Proxima Centauri is 4.2 LY away.
• 4.2 x 9.5 x1012 = 40 trillion Km
• In a scale model 1 cm = 1 light min.
• Our sun would be 8 cm away.
• Proxima Centauri would be 23 km away.
![Page 4: Measuring the Distance to the Stars. What is a Light Year? A light year is the distance light travels in one year. If the speed of light is 300,000 Km/sec](https://reader030.vdocuments.net/reader030/viewer/2022012919/5697c0291a28abf838cd765d/html5/thumbnails/4.jpg)
How do we find the distances to stars?
![Page 5: Measuring the Distance to the Stars. What is a Light Year? A light year is the distance light travels in one year. If the speed of light is 300,000 Km/sec](https://reader030.vdocuments.net/reader030/viewer/2022012919/5697c0291a28abf838cd765d/html5/thumbnails/5.jpg)
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6January
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6July(6 months
Later)
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Which star is closest to earth?
![Page 6: Measuring the Distance to the Stars. What is a Light Year? A light year is the distance light travels in one year. If the speed of light is 300,000 Km/sec](https://reader030.vdocuments.net/reader030/viewer/2022012919/5697c0291a28abf838cd765d/html5/thumbnails/6.jpg)
How do we find the distances to stars?
Parallax: The closer an object is, the more it appears to move against the background.
Parallax activity
![Page 7: Measuring the Distance to the Stars. What is a Light Year? A light year is the distance light travels in one year. If the speed of light is 300,000 Km/sec](https://reader030.vdocuments.net/reader030/viewer/2022012919/5697c0291a28abf838cd765d/html5/thumbnails/7.jpg)
• As the earth goes around the sun closer stars seem to move a lot against the background of stars.
Background Stars
Earth January Earth JulySun
A B C D E F G
Far Star
Near Star
![Page 8: Measuring the Distance to the Stars. What is a Light Year? A light year is the distance light travels in one year. If the speed of light is 300,000 Km/sec](https://reader030.vdocuments.net/reader030/viewer/2022012919/5697c0291a28abf838cd765d/html5/thumbnails/8.jpg)
• As the earth goes around the sun farther stars do not seem to move much against the background of stars.
Background Stars
Earth January Earth JulySun
A B C D E F G
Far Star
Near Star
![Page 9: Measuring the Distance to the Stars. What is a Light Year? A light year is the distance light travels in one year. If the speed of light is 300,000 Km/sec](https://reader030.vdocuments.net/reader030/viewer/2022012919/5697c0291a28abf838cd765d/html5/thumbnails/9.jpg)
Background Stars
Earth January Earth JulySun
A B C D E F G
Far Star
Near Star
•As the earth goes around the sun closer stars seem to move more than far stars against the background of stars.
![Page 10: Measuring the Distance to the Stars. What is a Light Year? A light year is the distance light travels in one year. If the speed of light is 300,000 Km/sec](https://reader030.vdocuments.net/reader030/viewer/2022012919/5697c0291a28abf838cd765d/html5/thumbnails/10.jpg)
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6January
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6July(6 months
Later)
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6January
Which star is closest to earth?
![Page 11: Measuring the Distance to the Stars. What is a Light Year? A light year is the distance light travels in one year. If the speed of light is 300,000 Km/sec](https://reader030.vdocuments.net/reader030/viewer/2022012919/5697c0291a28abf838cd765d/html5/thumbnails/11.jpg)
Reading Stellar Parallax
• Pg. 467-468
• R&C 2,3 Pg. 470
![Page 12: Measuring the Distance to the Stars. What is a Light Year? A light year is the distance light travels in one year. If the speed of light is 300,000 Km/sec](https://reader030.vdocuments.net/reader030/viewer/2022012919/5697c0291a28abf838cd765d/html5/thumbnails/12.jpg)
• How do we find the distance to the distant stars?
![Page 13: Measuring the Distance to the Stars. What is a Light Year? A light year is the distance light travels in one year. If the speed of light is 300,000 Km/sec](https://reader030.vdocuments.net/reader030/viewer/2022012919/5697c0291a28abf838cd765d/html5/thumbnails/13.jpg)
• How do we find the distance to the distant stars?• Unit of brightness distance to star
![Page 14: Measuring the Distance to the Stars. What is a Light Year? A light year is the distance light travels in one year. If the speed of light is 300,000 Km/sec](https://reader030.vdocuments.net/reader030/viewer/2022012919/5697c0291a28abf838cd765d/html5/thumbnails/14.jpg)
• How do we find the distance to the distant stars?• Unit of brightness distance to star
1 1 unit
![Page 15: Measuring the Distance to the Stars. What is a Light Year? A light year is the distance light travels in one year. If the speed of light is 300,000 Km/sec](https://reader030.vdocuments.net/reader030/viewer/2022012919/5697c0291a28abf838cd765d/html5/thumbnails/15.jpg)
• How do we find the distance to the distant stars?• Unit of brightness distance to star
1 1 unit
1/4 2 units
![Page 16: Measuring the Distance to the Stars. What is a Light Year? A light year is the distance light travels in one year. If the speed of light is 300,000 Km/sec](https://reader030.vdocuments.net/reader030/viewer/2022012919/5697c0291a28abf838cd765d/html5/thumbnails/16.jpg)
• How do we find the distance to the distant stars?• Unit of brightness distance to star
1 1 unit
1/4 2 units
1/9 3 units
![Page 17: Measuring the Distance to the Stars. What is a Light Year? A light year is the distance light travels in one year. If the speed of light is 300,000 Km/sec](https://reader030.vdocuments.net/reader030/viewer/2022012919/5697c0291a28abf838cd765d/html5/thumbnails/17.jpg)
• How do we find the distance to the distant stars?• Unit of brightness distance to star
1 1 unit
1/4 2 units
1/9 3 units
1/X2 (inverse square) X units
![Page 18: Measuring the Distance to the Stars. What is a Light Year? A light year is the distance light travels in one year. If the speed of light is 300,000 Km/sec](https://reader030.vdocuments.net/reader030/viewer/2022012919/5697c0291a28abf838cd765d/html5/thumbnails/18.jpg)
An example of how to use star brightness to find the distance to stars.
• The center of the galaxy is about 100 times dimmer than the stars we can see with our eyes.
• The stars we can see are about 3000 LY away. So, how far is the center of the galaxy?
• The center of the galaxy is about 30,000 LY away from earth.
![Page 19: Measuring the Distance to the Stars. What is a Light Year? A light year is the distance light travels in one year. If the speed of light is 300,000 Km/sec](https://reader030.vdocuments.net/reader030/viewer/2022012919/5697c0291a28abf838cd765d/html5/thumbnails/19.jpg)
![Page 20: Measuring the Distance to the Stars. What is a Light Year? A light year is the distance light travels in one year. If the speed of light is 300,000 Km/sec](https://reader030.vdocuments.net/reader030/viewer/2022012919/5697c0291a28abf838cd765d/html5/thumbnails/20.jpg)