- The closest star to us is the Sun. The closest star to the Sun is a 3 star system called Alpha Centauri. To the naked eye Alpha Centauri appears as a brilliant yellow-white star. It is 4.37 lightyears away. That is 25,700,000,000,000 miles away , but, that is the closest star we have. What we see is really a twin of Sun-like stars orbiting each other every 80 years. The third member of the group we can not see because it is a Red Dwarf called Proxima Centauri. It is actually 10% of a lightyear closer to us than the brighter pair. It takes 1 million years for its orbit in the system.
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- Interstellar travel can be experienced with our spacecraft Voyager 2. This spacecraft launched in 1977 is traveling to the stars at 31,000 miles per hour. That is 100 times faster than a speeding bullet. It flew past Neptune in 1989. Even at these speeds it would take Voyager 2 another 100,000 years to reach Alpha Centauri. Although it is actually headed in a different direction.
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- The apparent brightness of Alpha Centauri A , the brightest of the three stars is 2.7*10^-8 watts per meter^2, using a CCD detector. That is a luminosity of 1.6 Lsun. Centauri B has a luminosity of 0.33 Lsun. The Red Dwarf, our nearest star has a luminosity of 0.0006 Solar Luminosity, 0.0006Lsun. For comparison Betelgeuse Star, the left shoulder of Orion, is 38,000 Lsun. Polaris, the North Star, is 2,500 Lsun.
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- Vega has a Solar Luminance of 60 Lsun and it is 25 lightyears away. If we had a space ship that could travel 99.9% the speed of light, 669,962,867 miles per hour, the 50 year round trip would take astronauts 2 years for them However, 50 years would pass on Earth while they were gone. Time slows down as you approach the speed of light. The astronauts stayed young and we got older in the meantime.
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- The two Sun-like stars in Alpha Centauri are 6.1 billion years old. Our Sun is 4.6 billion years old. Telescopes glued to watching Centauri B detected a slight wobble caused by a planet orbiting that star. The orbiting distance is 6.4 million kilometers. The planet Mercury orbits at 57.9 million kilometers from our Sun. The planet takes only 3.2 days to orbit Centauri B. Mercury takes 88 days to orbit the Sun. The planets surface temperature is 1,500 Kelvin, in other words the surface is molten lava.
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- The planet was discovered because the radial speed of Centauri B changed ever so slightly due to the gravitational pull of the orbiting planet.
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------------------- Time ------------------------------- Radial Speed -------------------------
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------------------ 6 hours -- --------------------- 170 centimeters per second ----------------
------------------ 10 hours ----------------------- 150 centimeters per second ----------------
------------------ 21 hours ----------------------- 110 centimeters per second ----------------
------------------ 33 hours ----------------------- 60 centimeters per second ----------------
------------------ 48 hours ----------------------- 50 centimeters per second ----------------
------------------ 56 hours ----------------------- 70 centimeters per second ----------------
------------------ 71 hours ----------------------- 130 centimeters per second ----------------
------------------ 83 hours ----------------------- 170 centimeters per second ----------------
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- The change in speed was 170 - 50 = 120 centimeters per second, or, + 0r - 60 centimeters per second, an increase and decrease in speed over a complete cycle.
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- A complete period of orbit was 77 hours or 3.2 days.
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- Kepler’s third law of planetary motion says the square of the period is equal to the cube of the radius distance.
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-------------------- ( Period )^2 = ( Distance )^3
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--------------------- Period in years
--------------------- Distance in astronomical units. = 150 million kilometers.
--------------------- Period = 3.2 days / 365 days = 0.00877 years.
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--------------------- D^3 = T^2 = ( 0.00877 )^2 = 7.69*10^-5 AU^3
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-------------------- D = 0.043 AU
--------------------- D = 6.4 million kilometers.
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- Knowing the radius of orbit we can now calculate the temperature. The square of the temperature is inversely proportional to the distance. The greater the distance the lower the temperature.
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------------------ Temperature^2 = Constant * 1/ D
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----------------- The constant of proportionality is 96,100
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------------------- T^2 = 96,100 / D
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---------------- T^2 = 96,100 / 0.043 AU
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--------------- T = 1,495 Kelvin
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- This temperature is between melting gold and the gas flame on a stove:
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----------------------- 304 Kelvin -------------- butter melts
----------------------- 373 Kelvin -------------- water boils
----------------------- 1,100 Kelvin -------------- fireplace flame
----------------------- 1,336 Kelvin -------------- gold melts
----------------------- 1,900 Kelvin -------------- gas stove flame
----------------------- 2,000Kelvin -------------- molten lava--
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- We should probably look to another planet to find life. This one is just too hot. An announcement will be made shortly, stay tuned.
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RSVP, please reply with a number to rate this review: #1- learned something new. #2 - Didn’t read it. #3- very interesting. #4- Send another review #___ from the index. #5- Keep em coming. #6- I forwarded copies to some friends. #7- Don‘t send me these anymore! #8- I am forwarding you some questions? Index is available with email upon request. Some reviews are at http://jdetrick.blogspot.com Please send feedback, corrections, or recommended improvements to: jamesdetrick@comcast.net. ---- “Jim Detrick” -- www.facebook.com, -- www.twitter.com, -- 707-536-3272 Monday, January 7, 2013
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