Key takeaways

  • Einstein’s Theory Confirmed: Astronomers confirmed Einstein’s general relativity theory by observing a star’s light shift near a black hole.
  • Sagittarius A Black Hole: The black hole at the Milky Way’s center, Sagittarius A*, is 4 million times the mass of our sun.
  • S2 Star Observation: The star S2, orbiting the black hole, allowed scientists to observe gravitational redshift as it passed through the black hole’s field.
  • Gravitational Redshift: Light from S2 lost energy and shifted to a lower frequency, confirming Einstein’s predictions about gravitational effects.
  • Advanced Technology: Using the ESO’s upgraded Very Large Telescope (VLT) array with the GRAVITY instrument, scientists achieved unprecedented detail in their observations.

Astronomers have long been interested in a cluster of stars that orbits just beyond the supermassive black hole at the center of our galaxy. And, according to a finding made by the European Southern Observatory on Thursday, astronomers have finally detected one of these stars as it travels through the black hole’s gravitational field. It is the first time Albert Einstein’s general relativity theory has been tested in close proximity to a gigantic black hole.

Once more, Einstein’s hypothesis has survived the test of time. He anticipated that a black hole may be strong enough to reduce the frequency of light in some extreme situations. At the European Southern Observatory (ESO) headquarters in Garching, Germany, the announcement was made. During the press briefing, Frank Eisenhuer, an ESO researcher, made a comparison between the measured redshift and Einstein’s predicted redshift. The results showed almost perfect alignment. The audience erupted in cheers.

Eisenhuer remarks, “In sports parlance, you could say it’s a win for Einstein.”

A black hole at the heart of the Milky Way named Sagittarius A* has been seen by astronomers for many years. Compared to our sun, its mass is four million times greater. And it is circled by an enigmatic collection of stars.

One of those circling stars, known as S2, passed through the gravitational field of Sagittarius A* on May 19, 2018, giving astronomers a unique opportunity to investigate whether Einstein’s anticipated gravitational redshift actually occurs in the worst-case scenarios.

Light shifts toward the redder, or lower, end of the spectrum as it passes through gravitational forces and loses part of its energy. This phenomenon is known as gravitational redshift. The light has to exert greater effort to maintain its steady speed as it becomes more and more affected by gravity. This means that instead of oscillating at its initial frequency, its wavelength sort of gets stretched, getting longer.

For a very long time, scientists have wanted to see how this process unfolds inside the black hole’s environment. Sagittarius A* is concealed by thick dust clouds and is approximately 26,000 light years distant from Earth.

However, the European Southern Observatory (ESO) recently updated its Very Large Telescope array (VLT) with a new tool. GRAVITY combines light captured by the VLT’s four telescopes, resulting in 15 times the resolving power and precision of any one of the telescopes working alone. This resolution is similar to watching a tennis ball on the moon from Earth.
This allowed scientists to take hour-by-hour observations of the S2 star’s last flyby of Sagittarius A*.

They witnessed what happened as S2 neared the black hole from a cosmic distance of around 12 billion miles. During this close approach, S2 reached about 5,000 miles (8,000 kilometers) per second, which is equivalent to 2.7% of the speed of light.

The ESO team compared these new data to previously gathered data on S2 to better understand how its light was affected by entering the powerful gravitational field. This is how they established that light radiated from the star gets less energy, or drained, as a result of the black hole’s attraction, and changes to a lower frequency.

“This is the second time we’ve seen S2 travel close to the black hole at the center of our galaxy. But this time, because to significantly enhanced technology, we were able to view the star with unparalleled detail,” says Reinhard Genzel of the Max Planck Institute for Extraterrestrial Physics. “We have been intensively preparing for this event for several years, as we wanted to make the most of this unique opportunity to observe general relativistic effects.”

At the press briefing, Odele Staub of the Paris Observatory says, “Why is this important, and why did we do it at all?” Gravity is a basic characteristic of our cosmos. comprehending gravity on Earth, in the solar system, in the Milky Way, and beyond the Milky Way is essential for comprehending our universe.

“We looked at our galaxy’s center and discovered that it behaved similarly to Einstein’s black hole. Newton can no longer define what we measured.

In the next months, the researchers intend to track how this interaction may have altered S2’s course, which will provide insights into the mass distribution of Sagittarius A*, the black hole that we admire from afar.

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