- 3282 - UNIVERSE - how fast is it expanding? Astronomers compared the latest gamma-ray attenuation data from the Fermi Gamma-ray Space Telescope and Imaging Atmospheric Cherenkov Telescopes to devise their estimates from extragalactic background light models. This approach led to a measurement of approximately 67.5 kilometers per second per mega parsec for the rate of expansion of the Universe.
--------------------- 3282 - UNIVERSE - how fast is it expanding?
- Measuring the expanding Universe using known distances of 50 galaxies from Earth to refine calculations in Hubble's constant the estimate for the age of the universe at 12.6 billion years.
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- Different approaches are used to measure the date of the Big Bang, which gave birth to the universe They rely on mathematics and computational modeling, using distance estimates of the oldest stars, the behavior of galaxies, and the rate of the universe's expansion.
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- A key calculation for dating is the Hubble's constant, named after Edwin Hubble who first calculated the universe's expansion rate in 1929. Another recent technique uses observations of leftover radiation from the Big Bang. It maps bumps and wiggles in spacetime we know as the cosmic microwave background, or CMB and reflects conditions in the early universe as set by Hubble's constant.
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- However, the different methods reach different conclusions. Here is a new approach that recalibrates a distance-measuring tool known as the “baryonic Tully-Fisher relation” independently of Hubble's constant.
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- The “distance scale problem” is incredibly difficult because the distances to galaxies are vast and the signposts for their distances are faint and hard to calibrate.
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- Recalculations using the Tully-Fisher approach, accurately defined distances in a linear computation of the 50 galaxies as guides for measuring the distances of 95 other galaxies.
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- The universe is ruled by a series of mathematical patterns expressed in equations. The new approach more accurately accounts for the mass and rotational curves of galaxies to turn those equations into numbers like age and expansion rate.
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- The Hubble's constant, or the universe's expansion rate is calculated to be 75.1 kilometers per second per megaparsec, + or - 2.3 km/sec/Mpsec
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- A mega parsec is a common unit of space-related measurements, and is equal to one million parsecs. A parsec being about 3.3 light years. In more common units this is 49,300 miles per hour expansion rate for every million miles distance separtion.
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- Previously used measuring techniques over the past 50 years have set the value at 75, but CMB computes a rate of 67 km/sec/Megaparsec.
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- Calculations drawn from observations of NASA's Wilkinson Microwave Anisotropy Probe in 2013 put the age of the universe at 13.77 billion years.
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- The differing Hubble's constant values from the various techniques generally estimate the universe's age at between 12 billion and 14.5 billion years.
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- This new study is based on observations made with the Spitzer Space Telescope that adds a new element to how calculations to reach Hubble's constant can be set, This introduces a purely empirical method, using direct observations, to determine the distance to galaxies.
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- Cosmology is about understanding the evolution of our universe -- how it evolved in the past, what it is doing now and what will happen in the future.
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- The concept of an expanding universe was advanced by the American astronomer Edwin Hubble (1889-1953), who is the namesake for the Hubble Space Telescope.
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- In the early 20th century, Hubble became one of the first astronomers to deduce that the universe was composed of multiple galaxies. His subsequent research led to his most renowned discovery: that galaxies were moving away from each other at a speed in proportion to their distance.
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- Edwin Hubble originally estimated the expansion rate to be 500 kilometers per second per mega parsec. Hubble concluded that a galaxy two megaparsecs away from our galaxy was receding twice as fast as a galaxy only one megaparsec away. This estimate became known as the Hubble Constant, which proved for the first time that the universe was expanding.
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- Astronomers have been recalibrating it -- with mixed results -- ever since.
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- With the help of new technologies, astronomers came up with measurements that differed significantly from Hubble's original calculations, slowing the expansion rate down to between 50 and 100 kilometers per second per megaparsec.
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- In the past decade, ultra-sophisticated instruments, such as the Planck satellite, have increased the precision of Hubble's original measurements in relatively dramatic fashion.
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- Astronomers compared the latest gamma-ray attenuation data from the Fermi Gamma-ray Space Telescope and Imaging Atmospheric Cherenkov Telescopes to devise their estimates from extragalactic background light models. This approach led to a measurement of approximately 67.5 kilometers per second per mega parsec for the rate of expansion of the Universe.
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- Gamma rays are the most energetic form of light. Extragalactic background light (EBL) is a cosmic fog composed of all the ultraviolet, visible and infrared light emitted by stars or from dust in their vicinity. When gamma rays and EBL interact, they leave an observable imprint, a gradual loss of flow.
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- Matter -- the stars, the planets, even us -- is just a small fraction of the universe's overall composition. The large majority of the universe is made up of dark energy and dark matter.
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- Dark energy is pushing things away from each other. Gravity, which attracts objects toward each other, is the stronger force at the local level, which is why some galaxies continue to collide. But at cosmic distances, dark energy is the dominant force.
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- It is remarkable that we are using gamma rays to study cosmology. New results show the maturity reached in the last decade by the relatively recent field of high-energy astrophysics. The analysis paves the way for better measurements in the future using the Cherenkov Telescope Array, which is still in development and will be the most ambitious array of ground-based high-energy telescopes ever.
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- What we know is that gamma-ray photons from extragalactic sources travel in the universe toward Earth, where they can be absorbed by interacting with the photons from starlight. The rate of interaction depends on the length that they travel in the universe. And the length that they travel depends on expansion.
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- If the expansion is low, they travel a small distance. If the expansion is large, they travel a very large distance. So the amount of absorption that we measured depended very strongly on the value of the Hubble Constant.
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- What astronomers did was turn this around and use it to constrain the expansion rate of the universe.
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- September 19, 2021 UNIVERSE - how fast is it expanding? 3282
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