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- Just over 20 some years ago astronomers discovered the first solar system outside our own. The stars were out there but were there any planets? This first planet discovered outside our solar system had the mass of Jupiter and circled its star closer than Mercury's orbit. Not much chance of life be on that “exoplanet“.
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-. As of November 2013, 3,538 “planet candidates” have been observed. The next step is to study these and determine if life might exist on any of them.
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-----------------------------------. Earth is 7,918 miles in diameter
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---------------------------------- 674 planets were 1.25 times Earth-size.
--------------------------------- 1,076 planets were 1.25 to 2 times Earth-size.
---------------------------------- 1,457 planets were 2 to 6 times Earth-size.
---------------------------------- 229 planets were 6 to 15 times Earth-size.
---------------------------------- 102 planets were > 15 times Earth-size.
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---------------------------------- 3,538 planets discovered outside our Solar System.
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- Over 200 of these are solar systems with multiple planet systems like our own Solar System. Some 100 planets are orbiting their stars in a habitable zone, the right distance from the star that would allow liquid water to exist on the planet’s surface.
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-. These “planet candidates” were detected by two different methods:
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-. (1) The transient method detects light dimming slightly from the star as a planet passes in front, blocking our line of sight.
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-. (2). The wobble method where the star shifts its position slightly as a gravitational tug of a planet orbits the star. The detection occurs because of the Doppler shift of the light as it shifts from moving towards us, (blue shifts), to moving away from us, (redshifts). By measuring the amount of these shifts astronomers can calculate the mass of the orbiting planet, using radial velocity measurements. (See footnote 1.)
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-. Using the transit method astronomers can calculate the diameter of the planet by the amount of light it blocks. Multiple transit's are needed to calculate the orbit. (See footnote 2.)
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-. Over 150,000 stars were observed in finding the transiting planets.
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-. Once the mass is calculated and the diameter is known, the volume is calculated and the density is calculated. In this way we know if it a gaseous planet like Jupiter or a rocky planet like the Earth.
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-. When the planet passes in front of the star starlight passes through the atmosphere, if it has one. When the planet passes behind the star the amount of light detection will drop because you see only the planet space not the light going through the atmosphere. The difference in the light is measured with a spectrograph that can tell astronomers the elements that make up the atmosphere.
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-. For example: if 9,600 nanometer wavelength light is absorbed the element is Ozone. If the 15,000 nanometer wavelength is absorbed the molecule is Carbon Dioxide. Oxygen in the atmosphere gets absorbed by other elements very quickly. So, if there is a large amount of oxygen in the atmosphere something must be replacing it. Maybe it is life forms living there? Astronomers can calculate from this information determining the planets surface temperature, cloud cover, weather patterns, and even signatures of life.
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- When the Mars spacecraft turned its spectrometer towards Earth the relative radiance detected a unique bio-signature in the Earth's atmosphere. The relative radiance of water, ozone, carbon dioxide, and oxygen across a wavelengths from 100 to 25,000 nanometers. Astronomers hope to find such a signature on another planet.
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-. Gravitational lensing is a new method designed to help in planet detecting. Called “microlensing“, any body of mass bends space-time and the passing light from a background star will follow the warping to be magnified when telescopes are focused on astronomers can see farther.
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-. Earth is 10 billion times fainter than the Sun. So, direct detection of an image of Earth is technically challenging. A telescope with a “chronograph” would block the stars light and look for a direct image of an orbiting planet.
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-. As these techniques are perfected they will focus on a few earthlike worlds around nearby stars. How many worlds like ours are there out there? Could they be inhabited by living beings? An announcement will be made shortly , stay tuned
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-. Footnote (1): Determine the mass of an ex-oh planet using the law of conservation of momentum.
----------------------------------- Momentum = mass * velocity
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- ---------------- Mass of the star * velocity of the star = mass the planet * velocity of the planet. Velocity is measured relative to the center of mass around which both are orbiting.
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----------------------------- Ms * V = Mp * v
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-. The planets orbital velocity is calculated by the circumference of the orbit, 2 * pi * r, divided by the period of the orbit.
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---------------------------- v = 2 * pi * r / p
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-------------------------- There is a planet orbiting the star, 51 Pegasi.
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-------------------------- The period is measured to be, p = 3.65 * 10^5 seconds
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------------------------- The radius of orbit is measured to be, r = 7.82 * 10^9 meters
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------------------------ The mass of the star is calculated to be, Ms = 2.12*10^30 kilograms
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-The periodic Doppler Shift in the spectrum of the star 51 Pegasi shows a large planet with an orbital period of four days, 3.65 * 10^5 seconds, with a velocity of 57 meters / second
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----------------------------- v = 2 * pi * 7.82 * 10^9 m / 3.65 * 10^5 sec
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----------------------------- v = 13.46 * 10^4 m/sec = 301,000 miles per hour, see Footnote (3).
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------------------------------ Ms * V = Mp * v
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----------------------------- 2.12 * 10^30 * 57 m/sec = Mp * 13.46 * 10^4 m/sec
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--------------------------- Mp = 9 * 10^26 kilograms.
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- The mass of Jupiter is 1.9 *10^27 kilograms. The planet orbiting 51 Pegasi has a mass of 47% that of Jupiter.
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-. Footnote (2) Fractional drop in light intensity when the planet transits in front of the star is equal to 1.7 %.
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------------------- Area of planet’s disk / area of the star’s disk = 0.017
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-. The star HD 209458 has a radius 15 % larger than our Sun ,or, 800,000 kilometers.
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--------------------------- rp^2 / rs^2 = 0.017
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------------------------- rp / rs = 0.13
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-------------------------- rp = 800,000 * 0.13
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------------------------- rp = 104,000 kilometers.
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-. With a radius of the planet = 104,000 kilometers. We calculate the volume of the planet and with the mass we can calculate the density. Jupiter is 71,500 kilometers radius. This newly discovered planet is about 46 percent larger than Jupiter.
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-. Footnote 3. Mercury orbits our Sun in 88 days at 107,000 miles per hour. Saturn takes 29.5 years to orbit traveling at 22,000 miles per hour. This new planet is traveling at 300,000 miles per hour much faster than even the planet Mercury.
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RSVP, with comments, suggestions, corrections. Index of reviews available ---
--- Some reviews are at: -------------------- http://jdetrick.blogspot.com -----
---- email request for copies to: ------- jamesdetrick@comcast.net ---------
---- https://plus.google.com/u/0/ , “Jim Detrick” ----- www.facebook.com ---
---- www.twitter.com , --- 707-536-3272 ---- Wednesday, April 2, 2014 ---
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