Hint of Relativity Effects in Stars Orbiting Supermassive Black Hole at Center of Galaxy

Tuesday, August 15, 2017

Hint of Relativity Effects in Stars Orbiting Supermassive Black Hole at Center of Galaxy

Hint of Relativity Effects in Stars Orbiting Supermassive Black Hole at Center of Galaxy:

This artist's impression shows the orbits of three of the stars very close to the supermassive black hole at the centre of the Milky Way. Analysis of data from ESO’s Very Large Telescope and other telescopes suggests that the orbits of these stars may show the subtle effects predicted by Einstein’s general theory of relativity. There are hints that the orbit of the star called S2 is deviating slightly from the path calculated using classical physics. The position of the supermassive black hole is marked with a white circle with a blue halo. Credit: ESO/M. Parsa/L. Calçada

A new analysis of data from ESO’s Very Large Telescope and other telescopes suggests that the orbits of stars around the supermassive black hole at the center of the Milky Way may show the subtle effects predicted by Einstein’s general theory of relativity. There are hints that the orbit of the star S2 is deviating slightly from the path calculated using classical physics. This tantalizing result is a prelude to much more precise measurements and tests of relativity that will be made using the GRAVITY instrument as star S2 passes very close to the black hole in 2018.

At the center of the Milky Way, 26 000 light-years from Earth, lies the closest supermassive black hole, which has a mass four million times that of the Sun. This monster is surrounded by a small group of stars orbiting at high speed in the black hole’s very strong gravitational field. It is a perfect environment in which to test gravitational physics, and particularly Einstein’s general theory of relativity.

A team of German and Czech astronomers have now applied new analysis techniques to existing observations of the stars orbiting the black hole, accumulated using ESO’s Very Large Telescope (VLT) in Chile and others over the last twenty years. They compare the measured star orbits to predictions made using classical Newtonian gravity as well as predictions from general relativity.

The team found suggestions of a small change in the motion of one of the stars, known as S2, that is consistent with the predictions of general relativity. The change due to relativistic effects amounts to only a few percent in the shape of the orbit, as well as only about one sixth of a degree in the orientation of the orbit. If confirmed, this would be the first time that a measurement of the strength of the general relativistic effects has been achieved for stars orbiting a supermassive black hole.

Marzieh Parsa, PhD student at the University of Cologne, Germany and lead author of the paper, is delighted: "The Galactic Center really is the best laboratory to study the motion of stars in a relativistic environment. I was amazed how well we could apply the methods we developed with simulated stars to the high-precision data for the innermost high-velocity stars close to the supermassive black hole."

The high accuracy of the positional measurements, made possible by the VLT’s near-infrared adaptive optics instruments, was essential for the study. These were vital not only during the star’s close approach to the black hole, but particularly during the time when S2 was further away from the black hole. The latter data allowed an accurate determination of the shape of the orbit.

"During the course of our analysis we realized that to determine relativistic effects for S2 one definitely needs to know the full orbit to very high precision," comments Andreas Eckart, team leader at the University of Cologne.

As well as more precise information about the orbit of the star S2, the new analysis also gives the mass of the black hole and its distance from Earth to a higher degree of accuracy.

Co-author Vladimir Karas from the Academy of Sciences in Prague, the Czech Republic, is excited about the future: "This opens up an avenue for more theory and experiments in this sector of science."

This analysis is a prelude to an exciting period for observations of the Galactic Center by astronomers around the world. During 2018 the star S2 will make a very close approach to the supermassive black hole. This time the GRAVITY instrument, developed by a large international consortium led by the Max-Planck-Institut für extraterrestrische Physik in Garching, Germany, and installed on the VLT Interferometer, will be available to help measure the orbit much more precisely than is currently possible. Not only is GRAVITY, which is already making high-precision measurements of the Galactic Center, expected to reveal the general relativistic effects very clearly, but also it will allow astronomers to look for deviations from general relativity that might reveal new physics.

Credit: ESO

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The National Aeronautics and Space Administration (NASA) is the United States government agency responsible for the civilian space program as well as aeronautics and aerospace research. President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA's predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

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The Oxford English Dictionary defines a UFO as "An unidentified flying object; a 'flying saucer'." The first published book to use the word was authored by Donald E. Keyhoe. The acronym "UFO" was coined by Captain Edward J. Ruppelt, who headed Project Blue Book, then the USAF's official investigation of UFOs. He wrote, "Obviously the term 'flying saucer' is misleading when applied to objects of every conceivable shape and performance. For this reason the military prefers the more general, if less colorful, name: unidentified flying objects. UFO (pronounced Yoo-foe) for short." Other phrases that were used officially and that predate the UFO acronym include "flying flapjack", "flying disc", "unexplained flying discs", "unidentifiable object", and "flying saucer". The phrase "flying saucer" had gained widespread attention after the summer of 1947. On June 24, a civilian pilot named Kenneth Arnold reported seeing nine objects flying in formation near Mount Rainier. Arnold timed the sighting and estimated the speed of discs to be over 1,200 mph (1,931 km/h). At the time, he described the objects' shape as being somewhat disc-like or saucer-like, leading to newspaper accounts of "flying saucers" and "flying discs". In popular usage the term UFO came to be used to refer to claims of alien spacecraft. and because of the public and media ridicule associated with the topic, some investigators prefer to use such terms as unidentified aerial phenomenon (or UAP) or anomalous phenomena, as in the title of the National Aviation Reporting Center on Anomalous Phenomena (NARCAP).

UFO PHOTO PHOTOGRAPHY

UFO - Unidentified Flying Object An unidentified flying object, or UFO, in its most general definition, is any apparent anomaly in the sky that is not identifiable as a known object or phenomenon. Culturally, UFOs are associated with claims of visitation by extraterrestrial life or government-related conspiracy theories, and have become popular subjects in fiction. While UFOs are often later identified, sometimes identification may not be possible owing to the usually low quality of evidence related to UFO sightings (generally anecdotal evidence and eyewitness accounts). Stories of fantastical celestial apparitions have been told since antiquity, but the term "UFO" (or "UFOB") was officially created in 1953 by the United States Air Force (USAF) to serve as a catch-all for all such reports. In its initial definition, the USAF stated that a "UFOB" was "any airborne object which by performance, aerodynamic characteristics, or unusual features, does not conform to any presently known aircraft or missile type, or which cannot be positively identified as a familiar object." Accordingly, the term was initially restricted to that fraction of cases which remained unidentified after investigation, as the USAF was interested in potential national security reasons and/or "technical aspects" (see Air Force Regulation 200-2). During the late 1940s and through the 1950s, UFOs were often referred to popularly as "flying saucers" or "flying discs". The term UFO became more widespread during the 1950s, at first in technical literature, but later in popular use. UFOs garnered considerable interest during the Cold War, an era associated with a heightened concern for national security. Various studies have concluded that the phenomenon does not represent a threat to national security nor does it contain anything worthy of scientific pursuit (e.g., 1951 Flying Saucer Working Party, 1953 CIA Robertson Panel, USAF Project Blue Book, Condon Committee).

Photos of Nature | Nature Photography What is The Universe

Photos of Nature | Nature Photography What is The Universe

Tuesday, August 15, 2017