Massive RW Cephei Star Gets First Close-Up Images; Shots Could Shed Light On Its Stellar Events

Astronomers were able to get the first-ever close-up images of a huge star called RW Cephei that recently exhibited strange fading.

First Close-Up Shots of RW Cephei Captured

The images offer novel clues regarding what is taking place around the huge star that is situated roughly 16,000 light years away from Earth.

Detailed observations and images coupled with intelligent algorithms made by the team of scientists posit that a great eruption that led to the launching of a gas cloud from the star took place. This may have blocked a huge chunk of starlight from view.

The astronomers from the CHARA Array at Georgia State University, who were behind the novel images, presented their findings during the 243rd American Astronomical Society meeting. The findings were also published in the "The Great Dimming of the Hypergiant Star RW Cephei: CHARA Array Images and Spectral Analysis" study.

RW Cephei

The enormous star's fading last year surprised the scientists. This case serves as an example of a cool hypergiant, which is a star that has grown huge as it nears its end. The RW Cephei star is so massive that if it were to be placed in the area where the Sun is situated, its outer layer would stretch beyond Jupiter's orbit.

Narsireddy Anugu, an astronomer from Georgia State University who headed an international team of scientists towards getting the star's first close-up pictures, explains that their first CHARA observations were made in December 2022, right before the winter weather closure. However, the results were remarkable enough that they chose to conduct further observations when they could access the star again.

Stars that are old display variations in light that are associated with outer layer changes. Such changes are typically small. Because of this, scientists were amazed when astronomers Costantino Sigismondi and Wolfgang Vollmann announced in 2022 that the star had dramatically faded in the past few years. In December 2022, the star faded into roughly one-third of its typical brightness. Scientists wanted to know more about what caused the great drop in brightness.

Though RW Cephei is huge, it is so far away that it looks like a pinpoint even when the largest conventional telescopes are used. For close-up observations of the star, the abilities of the CHARA (Center for High Angular Resolution Astronomy) Array telescopes were necessary.

This six-telescope facility is situated at the Mount Wilson Observatory in California. They placed it across the mountaintop for them to use as a huge telescope. The mix of their light beams gives them the capacity to examine tiny object details.

Observations made by the CHARA revealed that the star did not appear round. However, for a fully detailed picture to be made, specialized computer programs were necessary. These programs were made by Fabien Baron, associate professor of astronomy at Georgia State University.

According to Baron, the CHARA telescopes' spacing gives a degree of uncertainty pertaining to the pictures' exact details. Hence, smart algorithms are necessary for the whole image to be recovered.

The final output reveals a star with its outer layer's motions convulsing it. This creates brighter and fainter patches over its surface. On top of this, the appearance significantly altered over an observation period of 10 months that matched the transition from its faintest condition towards a slow recovery to its earlier brightness.

The last puzzle piece came from Katherine Shepard, a Georgia State University graduate student at the Apache Point Observatory. Shepard made use of a specialized camera to record the star's light, from visible to infrared. The measurements revealed that the fading was significantly larger in observable colors compared to infrared settings. This is a clear sign that microscoping dust obscured starlight.

Overall, the observations posit that the star went through a massive eruption that triggered a vast gas cloud. As the cloud moved, it cooled down and made dust particle swarms that blocked a huge starlight fraction.

According to Douglas Gies, the director of CHARA, this could be one of the many grand eruptions that have wracked the star in the last century, adding that these eruptions could have a crucial role in mass loss before the star reaches its demise.

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