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- 2030 - EXOPLANETS in an expanding universe. The Hubble Constant is a measurement of how fast the Universe is expanding. Recent data tells us it is accelerating even faster in its expansion . Also, new discoveries tell us there are more planets around stars. For every star there is at least a 50% chance there is at least one planet in orbit. The problem here is the rules of physics need to be rewritten to accommodate this new data.
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-------------------------- 2030 - - EXOPLANETS in an expanding universe
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- The Hubble Constant is a measurement of how fast the Universe is expanding. Recent data tells us it is accelerating even faster in its expansion . Also, new discoveries tell us there are more planets around stars. For every star there is at least a 50% chance there is at least one planet in orbit.
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- Measurements of the Hubble Space Telescope suggest the universe is expanding much faster than expected. The rules of physics need to be rewritten in order to understand why.
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- Astronomers measure the distance to other galaxies using stars called Cepheid Variables that brighten and dim in a predictable way. This data is then used to calculate the expansion rate called the Hubble Constant.
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- New data on eight Cepheid Variables in our Milky Way Galaxy find them 10 times farther away. These Cepheids are between 6,000 and 12,000 lightyears away. Hubble is using a new technique measuring a star’s position at a rate of 1000 times per minute. This method is increasing the accuracy of measuring brightness and distance. The result tells us the stars are 10 times farther away.
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- Using the pulse rate of Cepheids in more distant galaxies and then the brightness of a certain type of supernovae astronomers recalculate the expansion rate of the space between the galaxies. Previous data had the expansion rate at 67 kilometers per megaparsec. New calculations are 9% higher at 73 kilometers per megaparsec, which is 50,000 miles per hour per million lightyears distance.
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- 73 kilometers per second is 163,000 miles per hour. A megaparsec is 3,262,000 lightyears. 50,000 miles per hour per million light years.
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- Astronomers have a couple explanations for why the universe may be expanding faster:
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- Dark energy is driving galaxies apart with greater intensity. The acceleration may be increasing over time.
- Another possibility is that dark matter interacts more strongly with visible matter and radiation than previously thought.
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- A third possibility is that there exists a new type of subatomic particle that travels at the -speed of light and is only affected by gravity. These super fast particles were given the name “sterile neutrinos“.
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- Either of these possibilities would mean we need a new calculation for the expansion of the universe, that is a new Hubble Constant.
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-The brightness of stars tells us how far the galaxy is away. A dip in brightness tells us there is a planet orbiting that star. The dip is caused by a planet blocking a small portion of light from that star.
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- The first discovery of an exoplanet blocking starlight occurred in 1999. Now astronomers have identified over 4,000 transiting exoplanets.
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- The Kepler Space Telescope was launched in 2009. It stares at a single patch of sky monitoring brightness of 150,000 different stars. Eclipses are rare but a brief and periodic decrease in brightness betrays the existence of a planet in orbit. Their orbits must be aligned with our line of sight.
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- The fractional loss of light tells us the area of the planets silhouette. Therefore bigger planets are much easier to detect. Jupiter size planets transiting their sun would produce a 1% dip in brightness. An Earth size would be a 0.01% dip in brightness. Space telescopes are needed in order to make this measurement. Earth’s atmosphere would produce too much distortion from ground based telescopes.
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- Kepler has found nearly 5,000 candidate planets. 3,500 have been confirmed with enough multiple orbits. Since multiple orbits are needed the confirmed planets tend to be those closer to their star. Hundreds of these stars have multiple planets, some up to 8 planets , matching our own solar system.
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- The Kepler data would imply there is at least a 50% chance that any star would have at least one planet in orbit. Some orbits are so tiny they take only 4.25 hours to complete. One planet has a pair of binary stars that are orbiting each other. There is another case where a pair of planets are sharing the same orbit.
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- There about a dozen earth like planets in a habitual zone, where liquid water could exist
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- Most stars in our galaxy are red dwarfs, cooler and fainter stars that are less than half the mass of the Sun. If our Sun were a spotlight on a Broadway stage a red dwarf would be a candle. Consequently, the habitable zone for a red dwarf lies very close to the star. The orbital periods for these planets are very short. For a red dwarf with a mass one fifth that of our Sun the habitable zone would have an orbit of just a few weeks. As already mentioned it is the shorter orbits that are easier to detect.
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- Well we have discovered habitatal planets, now how do we detect if they are in habited? One approach is to analyze the planet’s atmosphere. When the planet is in front of the star a small portion of the starlight filters through the atmosphere. Spectroscopy can then be used to identify gases by the wavelengths being absorbed in this thin atmosphere.
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- For example, sodium in the atmosphere absorbs the wavelength at 589 nanometers. By measuring the difference between the normal star spectrum and the transit spectrum elements in the atmosphere can be identified. Elements and molecules of methane, carbon monoxide, and water have been identified. We have yet to find oxygen.
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- A planet with large amounts of oxygen must have some type of organisms living there. Is there a dawn in the distant sky’s? Will life be found elsewhere? We have over 5,000 exoplanets to study. And , that is in only one small part of the sky.
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- We have more to learn, stay tuned. Is it not so amazing what star light can tell us?
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