- 2876 - REDSHIFT - found in orbiting neutron stars? A theory in physics and astronomy predicted by Albert Einstein in 1906 has been verified using a double star system about 29,000 light years from Earth. This phenomenon in physics, called a 'gravitational redshift,' has been well documented in our Solar System, but it's been more elusive for the stars.
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--------------------------- 2876 - REDSHIFT - found in orbiting neutron stars?
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- Scientists have recently found evidence for this effect in the X-rays from a system with a neutron star in close orbit with a companion star.
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- Gravitational redshifts provide the math that is crucial for maintaining the accuracy of technologies like the global positioning system (GPS).
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- What do Albert Einstein, the Global Positioning System (GPS), and a pair of stars 200,000 trillion miles from Earth have with my phone and navigation display in my car?
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- The answer is an effect from Einstein's General Theory of Relativity called the "gravitational redshift," where light is shifted to redder colors because of gravity. Using NASA's Chandra X-ray Observatory, astronomers have discovered the phenomenon in two stars orbiting each other in our galaxy about 29,000 light years (200,000 trillion miles) away from Earth.
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- While these stars are very distant, gravitational redshifts have tangible impacts on modern life, as scientists and engineers must take them into account to enable accurate positions for GPS.
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- While scientists have found incontrovertible evidence of gravitational redshifts in our solar system, it has been challenging to observe them in more distant objects across space. The new Chandra results provide convincing evidence for gravitational redshift effects at play in a new cosmic setting.
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- The intriguing star system known as “4U 1916-053” contains two stars in a remarkably close orbit. One is the core of a star that has had its outer layers stripped away, leaving a star that is much denser than the Sun.
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- The other is a neutron star that is an even denser object created when a massive star collapses in a supernova explosion. These two compact stars are only about 215,000 miles apart, roughly the distance between the Earth and the Moon.
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- While the Moon orbits our planet once a month, the dense companion star in this star system whips around the neutron star and completes a full orbit in only 50 minutes.
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- The X-ray spectra studies the amounts of X-rays at different wavelengths. Scientists found the characteristic signature of the absorption of X-ray light by iron and silicon in this spectra.
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- The data show a sharp drop in the detected amount of X-rays close to the wavelengths where the iron or silicon atoms are expected to absorb the X-rays. The wavelengths of these characteristic signatures of iron and silicon were shifted to longer, or redder, wavelengths compared to the laboratory values found here on Earth.
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- The researchers found that the shift of the absorption features was the same in each of the three Chandra observations, and that it was too large to be explained by motion away from us. Instead they concluded it was caused by gravitational redshift.
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- How does this connect with General Relativity and GPS?
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- As predicted by Einstein's theory, clocks under the force of gravity run at a slower rate than clocks viewed from a distant region experiencing weaker gravity. This means that clocks on Earth observed from orbiting satellites run at a slower rate.
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- To have the high precision needed for GPS, this effect needs to be taken into account or there will be small differences in time that would add up quickly, calculating inaccurate positions here of Earth.
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- All types of light, including X-rays, are also affected by gravity. An analogy is that of a person running up an escalator that is going down. As they do this, the person loses more energy than if the escalator was stationary or going up. The force of gravity has a similar effect on light, where a loss in energy gives a lower frequency.
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- Because light in a vacuum always travels at the same speed, the loss of energy and lower frequency means that the light, including the signatures of iron and silicon, shift to longer wavelengths.
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- This is the first strong evidence for absorption signatures being shifted to longer wavelengths by gravity in a pair of stars that has either a neutron star or black hole.
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- Strong evidence for gravitational redshifts in absorption has previously been observed from the surface of white dwarfs, with wavelength shifts typically only about 15% of that for 4U 1916-053.
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- Scientists say it is likely that a gaseous atmosphere blanketing the disk near the neutron star absorbed the X-rays, producing these results. The size of the shift in the spectra allowed the team to calculate how far this atmosphere is away from the neutron star, using General Relativity and assuming a standard mass for the neutron star.
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- They found that the atmosphere is located 1,500 miles from the neutron star, about half the distance from Los Angeles to New York and equivalent to only 0.7% of the distance from the neutron star to the companion. It likely extends over several hundred miles from the neutron star.
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- In two of the three spectra there is also evidence for absorption signatures that have been shifted to even redder wavelengths, corresponding to a distance of only 0.04% of the distance from the neutron star to the companion.
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- This is amazing astronomy. And the math that Einstein proposed works with precision. I created all of this in his mind and had almost no experimental evidence at the time. Here we are 100 years later and verifying it with neutron stars lightyears away.
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----------------------------- Other reviews available upon request:
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- 2698 - REDSHIFT - explains the Universe expansion? The Universe is expanding. How do we know that. We measure the wavelength of light and it is getting stretched out as it travels through space to reach us. As wavelength stretches the photons loose energy. If Gamma Wave wavelengths are emitted after the Big Bang by the time they reach us they have been redshifted, wavelength stretched out, into the microwave wavelengths.
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- 1713 - Colors change for far away galaxies. We can calculate their radial velocity by the amount of shift that happens to colors of light as it travels through expanding space. Using Hubble’s constant rate of space expansion we can calculate the distance to the galaxy.
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- 1695 - Measuring astronomical distances
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- 1603 - Finding the farthest galaxy. How spectroscopy is used to measure the distance to the farthest galaxies?
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- 1550 - The redshift tells us how old it is? The age of the Universe is 13,700,000,000 years. The oldest galaxy we can see formed 13,000,000,000 years ago. The Universe was only 5% of its current age when this galaxy formed. If a human was 80 years old it would be analogous to her viewing a picture of herself when she was only 4 years old.
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- 1501 - Redshifting back in time. The most distant quasar galaxy had a redshift of 7. That means the signal left the galaxy 770,000,000 years after the Big Bang.
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- October 24, 2020 2876
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