Mysterious Signals at the Center of Our Galaxy May Be an Optical Illusion

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The universe might be tricking us with its optical illusions.

Last spring, researchers discovered high abundances of three elements in a group of red giants (dying stars in the last stage of their evolution) less than 3 light-years away from the black hole at the center of our galaxy, the Milky Way. The high levels of these elements — scandium, vanadium and yttrium — puzzled astronomers, who tried to explain the phenomenon with various theories. One theory suggested that the abnormally high levels of the elements resulted from the descent of old stars into the black hole, while another posited that the elements were debris from the collision of neutron stars, according to a statement.

The latest of such explanations was recently proposed by an international group of astronomers and atomic physicists. They argue that those elements didn’t actually exist at the high concentrations observed. Rather, the elements were probably an illusion all along, the researchers reported in a new study published yesterday (Oct. 10) in the Astrophysical Journal.

Scientists originally detected these elements by recording “spectral lines” with a spectrometer. With this method, scientists look at the amount of light an object absorbs or emits. Because different elements will emit or absorb light in a slightly different way (called their spectral lines), scientists can use the information to figure out what an object is made of. Scandium will interact with light differently than, say, vanadium would, for example. [Our Milky Way Galaxy: A Traveler’s Guide (Infographic)]

The scientists who conducted the new research found similar lines of scandium in red giants in our own solar neighborhood. However, the authors found that if the red giant were below a certain temperature, those spectral lines increased in strength. But this didn’t mean that there was more scandium, vanadium or yttrium in the star, they said.

As for why temperature would affect the measurements, the researchers suggested that electrons that make up the atoms of these elements behave differently at lower temperatures than at higher ones, according to the statement. So, the lower temperatures of red giants — which are much, much lower than that of our sun — could have given off this illusion of spectral lines, according to the statement.

The researchers suggest that the high abundance of these elements is not a unique phenomenon in these red giant stars near the black hole, but that it’s an illusion in the measurements. The formation of these strong lines currently “escapes accurate theoretical modeling,” they wrote in the study.

They concluded that those spectral lines shouldn’t be used as a measurement of these elements, “until we better understand how these lines are formed,” they wrote in the study. The researchers are doing just that, continuing to measure spectral lines from various stars in the Milky Way to better understand what they’re made of.

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