![]() This term and its definition have been approved by a research astronomer and a teacher Gravitational redshift refers to the effect where the wavelength of electromagnetic radiation emitted from a source is stretched to longer wavelengths or rather the associated photons lose energy, as they try to leave a region (gravitational well) where the gravity is stronger. Cosmological redshift is the result of electromagnetic radiation emitted by source being stretched to longer wavelengths because of the physical expansion of space, unlike Doppler redshift which is due to relative motion. This is similar to the Doppler effect in the context of sound waves. Doppler redshift is the opposite of blueshift, in the case of redshift the source emitting the electromagnetic radiation is moving away from the observer, and so the wavelength of the electromagnetic radiation is stretched to longer (redder) wavelengths. A&A 615, L15 doi: 10.Description: This term can refer to three different effects: Doppler, Cosmological or Gravitational redshift. Detection of the gravitational redshift in the orbit of the star S2 near the Galactic centre massive black hole. The results appear in the journal Astronomy & Astrophysics. “So it’s very important in astronomy to also check that those laws are still valid where the gravitational fields are very much stronger.” Françoise Delplancke, head of the System Engineering Department at ESO. ![]() “Here in the Solar System we can only test the laws of physics now and under certain circumstances,” said Dr. “More than one hundred years after he published his paper setting out the equations of general relativity, Albert Einstein has been proved right once more - in a much more extreme laboratory than he could have possibly imagined.” ![]() “During the close passage, we could even detect the faint glow around the black hole on most of the images, which allowed us to precisely follow the star on its orbit, ultimately leading to the detection of the gravitational redshift in the spectrum of S2.” Frank Eisenhauer, also from the Max Planck Institute for Extraterrestrial Physics. “Our first observations of S2 with GRAVITY, about two years ago, already showed that we would have the ideal black hole laboratory,” said GRAVITY/SINFONI principal investigator Dr. “This is the first time that this deviation from the predictions of the simpler Newtonian theory of gravity has been observed in the motion of a star around a supermassive black hole.” “And the change in the wavelength of light from S2 agrees precisely with that predicted by Einstein’s theory of general relativity.” “Light from S2 is stretched to longer wavelengths by the very strong gravitational field of the black hole.” “The new measurements clearly reveal an effect called gravitational redshift,” the astronomers said. As it gets close to the black hole the very strong gravitational field causes the color of the star to shift slightly to the red, an effect of Einstein’s general theory of relativity. This artist’s impression shows the path of S2 as it passes very close to Sagittarius A*. The new results are inconsistent with Newtonian predictions and in excellent agreement with the predictions of general relativity. They then compared their measurements, along with previous observations of S2 using other instruments, with the predictions of Newtonian gravity, general relativity and other theories of gravity. Genzel and colleagues used ESO’s SINFONI (Spectrograph for INtegral Field Observations in the Near Infrared) instrument to measure the velocity of S2 towards and away from Earth and the GRAVITY instrument to make extraordinarily precise measurements of the star’s changing position in order to define the shape of its orbit. “But this time, because of much improved instrumentation, we were able to observe the star with unprecedented resolution.”ĭr. Reinhard Genzel, from the Max Planck Institute for Extraterrestrial Physics in Germany. “This is the second time that we have observed the close passage of S2 around the black hole in the Galactic center,” said Dr. One of these stars, S2, orbits every 16 years and is passing very close to the black hole in May 2018. This simulation shows the orbits of stars very close to Sagittarius A*, a supermassive black hole at the heart of the Milky Way.
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