Throughout the history of astronomical studies, the datasets of various cosmic objects have become larger and larger. Among the materials that experts observe are black holes. However, the search for these mysterious objects is sometimes confusing for scientists, like other bodies in the universe pretending to be one.
Black Holes and Stellar Bodies
Harvard-Smithsonian Center for Astrophysics specialist Kareem El-Badry explained that searching for black holes was once thought similar to finding a needle in a haystack. The expert continued in recent observations that these haystacks suddenly increased more than their population before.
El-Badry said that today, the chances of finding a single black hole are high, but we could also likely encounter an object that mimics their appearance.
In a recent study from the Monthly Notices of the Royal Astronomical Society, titled "Unicorns and Giraffes in the binary zoo: stripped giants with subgiant companions," El-Badry's team stumbled upon cosmic bodies that masquerade as a black hole.
At first glance, these objects look like the mysterious dark swirls of space, but they are double-star or binary systems in a phase we did not know before. According to the authors, the trick to differentiate a black hole from other materials is to analyze the light that comes from it.
Scholars from Ohio State University carried out a study in 2021 over a star system named Unicorn. This stellar neighborhood is located 1,500 lightyears away from Earth. The system's giant red star orbited what experts mistook for a black hole in its initial discovery.
The study was published in the same journal, titled "A unicorn in monoceros: the 3 M⊙ dark companion to the bright, nearby red giant V723 Mon is a non-interacting, mass-gap black hole candidate."
Some of the experts from the Ohio team produced separate research in Solar and Stellar Astrophysics that discussed a similar star system named Giraffe, which sits at about 12,000 lightyears away from the planet.
How Binary Stars Disguise as Black Holes
Due to the unusual factors and discrepancies of the suspected black holes, El-Badry's team was not convinced that the materials were as they presented themselves.
The experts attempted to verify the subjects by investigating the star system's stellar spectra. These materials look like rainbows and are produced whenever a wavelength from a star's illuminance is split.
Each star has a spectrum that shows various line appearances. In the case of a slow-spinning star, these lines show as very sharp lines, but in a fast-spinning stellar body, the lines become blurred and smeared.
El-Badry said that a star with enough spinning speed would show near-invisible spectrums. If searching for a nearby star, the spectrum will serve as signs of their presence, but this step is sometimes challenging, as some of the stellar bodies rotate relatively faster.
El-Badry's team confirmed the studies to have mistaken one of the bodies in each star system as a black hole, ScienceNews reports. In conclusion, they are binary systems that hide one of the stars, allowing themselves to appear similar to what an invisible black hole looks like.
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