Puzzle Unraveled: First Detailed Images of Massive Star Shed Light on its Unusual Dimming

In recent years, the colossal star RW Cephei experienced an enigmatic decrease in brightness before subsequently regaining its luminosity.

Another peculiar behavior has been observed in our vast universe. Recently, astronomers have reported that RW Cephei, a hypergiant star located in the constellation Cepheus and situated approximately 16,000 light-years away from Earth, has undergone a significant change in brightness. Narsireddy Anugu, a staff scientist at the CHARA Array in California, stated that the star had been dimming drastically for the past two years but has now started to brighten again.

According to Anugu, the most plausible explanation for this phenomenon is that the star expelled a gas cloud, which gradually cooled as it moved away from the star. As a result, the cloud obstructed our view of the star, making it appear fainter. These findings were published in a study featured in The Astronomical Journal, where Anugu and an international team of astronomers detailed their observations.

In comparison to Betelgeuse, a well-studied red supergiant that experienced a puzzling decrease in brightness in 2019, sparking speculation of an imminent supernova event, RW Cephei is hotter, heavier, and brighter. As one of the largest stars in the Milky Way, it is a thousand times larger than our sun. In fact, if it were to replace our own star, its outer layers would extend beyond the orbit of Jupiter. Despite its colossal size within the constellation Cepheus, RW Cephei appears minuscule in our sky due to its immense distance, appearing a million times smaller than a full moon.

During a press briefing at the American Astronomical Society conference in New Orleans, Anugu unveiled the first close-up images of this gigantic star. The star’s mysterious dimming began in 2020 and reached its lowest point in December 2022, with its brightness diminishing to a third of its usual intensity.

The images captured by the CHARA array, a sophisticated six-telescope facility situated on Mount Wilson, reveal an intriguing characteristic of RW Cephei. Contrary to the expected round shape of stars, RW Cephei appears to have an irregular and patchy appearance. This peculiar feature is attributed to the presence of dark and bright patches scattered across its surface, which are caused by a gas cloud orbiting around the star and subsequently expelled by it.

Further investigations conducted at the Apache Point Observatory in New Mexico have provided additional insights. It was observed that the star exhibited a more pronounced dimming in visible colors compared to infrared. Georgia State University, the operator of the CHARA array, has stated that this discrepancy strongly suggests that the starlight was obstructed by minuscule dust clouds, impeding our view.

The gas cloud recently discovered encircling RW Cephei is believed to be one of several “grand eruptions” that the star has experienced. Each of these violent outbursts results in the star losing significant portions of its mass. Douglas Gies, the director of the CHARA array, emphasized the uniqueness of this particular event, as the cloud was expelled in the direction of Earth, allowing us to witness the full impact of this cataclysmic phenomenon.

This article is republished from SpaceCom under a Creative Commons license. Read the original article.

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