- 2195 - The Age of the Universe. In the bigger picture the Universe has used up about 20% of its life to date. 20% is normal matter, .1% is dust, .01% is Black Holes. That leaves 80% as interstellar gas lying between the galaxies. This gas will become a future generation of stars. It is estimated that the Universe will not run out of fuel for another 70,000,000,000 years.
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----------------------------- 2195 - The Age of the Universe
- The age of the Universe is 13,700,000,000 years, maybe. How did we come up with that? Astronomers think that the Big Bang occurred 13,700,000,000 years ago and that the Universe has been expanding ever since.
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- For the first 300,000 years the Universe was opaque, not shining. At that point the plasma became electrically neutral as atoms formed and the photons escaped, electromagnetic radiation expanded outward at the speed of light. This expanding light ball is what we call the “Observable Universe“.
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- After 13,700,000,000 years the diameter of the Universe must be 27,400,000,000 lightyears. The galaxies in this expanding Universe are expanding away from each other at a rate determined by rate of expansion which is called the Hubble Constant of expansion.
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- Like painted dots on an expanding balloon the dots, and galaxies, are separating faster the farther apart they are. The current thinking is that the speed of separation is equal to 45 miles per second per each 3,262,000 lightyear that they are separated. 45 miles per second is 158,400 miles per hour.
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- But, the Observable Universe is thought to really be 156,000,000,000 lightyears wide because for a brief period from 10^-35 seconds to 10^-33 seconds after the Big Bang, called the Inflationary Era, the Universe ballooned outward 10^30 times larger to become about the size of a soccer ball. After 10^-33 seconds Inflation stopped and the Universe expansion slowed down, expanding at the current rate we see today,45mps/Mpc, = 49,306 miles per hour peer million lightyears separation.
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- The scientific notation for “H”, the Hubble Constant, is an expansion rate of 72 kilometers per second per mega parsec (72 Km/sec/Mpc). A mega parsec is 1,000,000 parsecs, (abbreviated to Mpc) and each parsec is 3.262 lightyears. 72 km/sec = 45 miles/sec. The Hubble Constant is 44.7 mps/3.26*10^6 LY. This computation for the Hubble Constant is with an uncertainty of + or - 10%. (40 to 49 mps/Mpc)
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- Recent measurements of the Triangulum Galaxy (M33) concludes that it is actually 15% further away from our Milky Way Galaxy than previously measured. If this is correct the Universe actually 15% bigger and 15% older than previously calculated using the Hubble Constant of 45mps/Mpc.
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- Astronomers used a new method to make this measurement on M33 that took 10 years in development. They studied M33 in optical and infrared wavelengths focusing on two of the brightest stars that were a binary system. One star eclipsed the other every 5 days.
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- By measuring the orbits of the binary stars the astronomers could calculate the mass of the stars. When they know the mass they can calculate the radiation intensity, or brightness, or luminosity, of each star. But, the stars appear dimmer as a function of how far away they are. The difference between intrinsic brightness and the apparent brightness allows them to calculate the distance to the stars. Here is the formula:
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- Apparent Brightness = Intrinsic Brightness + 5 log(distance/10)
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- Absolute Brightness = M , is defined as the apparent magnitude at a distance of 10 parsecs.
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------------- m = M + 5*log(d/10)
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------------- d = distance = 10^(m-M+5)/5
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- The luminosity of a star is the power emitted by the surface of the star at all wavelengths. Luminosity increases with the size and temperature of the star. ( See footnote examples (1) and (2))
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--------- Surface Area = 4*pi*R^2
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--------- Stefan-Boltzmann Constant = 5.68*10^-8 watts / meter^2 * Kelvin^4
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--------- Luminosity = (4*pi*R^2)(S-B Constant)(Temperature^4)
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- M33 was calculated to be 3,000,000 lightyears away, with an error margin + or- 6% (41 to 47 mps/Mpc)
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- M33 was previously calculated using the Hubble Constant to be 2,600,000 lightyears away, a 15% difference.
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- With the Hubble Constant at 45 mps/Mpc the age of the Universe is 13,700,000,000 years and 156,000,000,000 LY wide.
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- Using this new method of calculation H = 51 mps/Mpc and the Universe is 15,800,000,000 years and 180,000,000,000 LY wide. ( a 15% difference)
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- Up until today the Hubble Constant was calculated by measuring the speed at which galaxies are moving away and dividing by their distance away. We measure the speed by the Doppler shift (redshift) of the source of light. We measure distance by studying pulsating stars known as “Cepheid’s”.
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- Cepheid’s are variable stars that have an intrinsic brightness that is a function of the period of pulsations. We measure the period of the pulsations and derive the intrinsic brightness of the Cepheid. Again, using the ratio of intrinsic brightness to apparent brightness astronomers calculate how far away the galaxies are. The accuracy of this method is +or- 10%.
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- X-ray data from Chandra came up with 48 mps/Mpc with an uncertainty of + or - 15%. This method uses the distortions in the Cosmic Microwave Background Radiation caused by the characteristics of hot gasses in the galaxies. The astronomers then compared the angle subtended to its physical size to geometrically calculate the distance.
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- To make these calculations astronomers have to work through complex steps of related equations. Each step can include systematic errors that add to the uncertainty of the measurement.
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- The advantage of using binary stars is that it is the most direct method of calculation and is more than twice as accurate. (+or- 6% versus +or- 15%). However, for the 15% older and larger Universe to be accepted astronomers will have to use this method on many more binary stars in many more galaxies.
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- In the bigger picture the Universe has used up about 20% of its life to date. 20% is normal matter, .1% is dust, .01% is Black Holes. That leaves 80% as interstellar gas lying between the galaxies. This gas will become a future generation of stars. It is estimated that the Universe will not run out of fuel for another 70,000,000,000 years.
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- Footnote (1) The greater distance a star is away the dimmer it appears. It gets dimmer by the inverse square law. That is the brightness depends inversely to the square of the distance of separation. The inverse square law says that if the distance to the shining object increase, you receive less light.
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- The flow of energy is called Flux = Energy / Area.
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To calculate the distance to a star that has an apparent brightness, ”m” and the intrinsic brightness, “M” use the formula:
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------------------ m-M = 5Log(d) -5
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- Let’s take our closest star, Proxima Centauri. It has an absolute brightness calculated to be +15.5 magnitude. However, its apparent brightness as viewed from Earth is +11.1 magnitude.
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------------------ 11.1 - 15.5 = 5Log(d) -5
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------------------ (-4.4 + 5)/ 5= Log(d)
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------------------ .12 = 5Log(d)
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------------------ Distance = 1.138 parsecs
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------------------ Distance = 4.3 lightyears
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- Footnote (2) The brightness of a star depends on its size and temperature. The total energy emitted from each square meter of a star’s surface each second is called Energy Flux.
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-------------- Energy Flux = (S-B Constant)*(Temperature)^4
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-------------- Energy Flux = (5.68*10^-8 watts / (m^2*Kelvin^4) * (Temperature)^4
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- The temperature of the star is measured from its light spectrum, or color. The maximum wavelength, or peak wavelength = 0.0029 m * Kelvin / Temperature.
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-------- Maximum wavelength of Sun = 500 nanometers
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-------- Temperature of Sun = 2.9*10^-3/5*10^-7 = 5,800 Kelvin
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- To get the total Energy, or Intrinsic Brightness, we need to multiply the Energy Flux, or the flow rate of energy, by the surface area of the star. The surface are of a sphere = 4*pi*radius^2
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--------- Our Sun’s radius = 6.96 * 10^8 meters
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---------Our Sun’s temperature = 5,800 Kelvin
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-------- Luminosity = (S-B Constant)*(Temperature)^4 * (4*pi*radius^2)
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-------- Luminosity = (5.68*10^-8 watts)*(5.8*10^3)^4 * (4*pi*6.96*10^8)^2
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-------- Luminosity = 3.9*10^26 watts
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- Each square meter of Earth’s land surface gets about 100 watts of power from this life giving sunlight.
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- December 3, 2018 677
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-------------------------- Monday, January 7, 2019 --------------------------
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