A possible dust cloud might dim Tabby’s star

Illustration of the possible dust cloud around Tabby's star (Image NASA/JPL-Caltech)
Illustration of the possible dust cloud around Tabby’s star (Image NASA/JPL-Caltech)

An article published in “The Astrophysical Journal” describes a research that offers an explanation of the many sudden brightness changes observed in Tabby’s star in recent years. A team of researchers co-ordinated by the University of Arizona used data collected by NASA’s Spitzer and Swift space telescopes and the Belgian AstroLAB IRIS observatory concluding that this phenomenon is caused by a dense cloud of dust orbiting the star.

Formally it’s called KIC 8462852 but is now commonly known as Tabby’s star or sometimes Boyajian star, after Tabetha S. Boyajian, the astronomer who in 2015 realized that its brightness was changing quickly, dimming up to 20% within a few days. Nearly 1,500 light years from Earth, this is an F3 class star, with a mass that is about 40% higher than the Sun’s and therefore a stable star with a brightness is supposed to remain practically constant.

Various hypotheses were made to try to explain a really strange phenomenon, even the presence of an alien megastructure. From the scientific point of view, it’s absolutely right to propose that kind of hypothesis but it took sensationalistic tones that are much closer to gossip magazines than scientific journals.

Various studies have been carried out by examining data collected over the past decade that showed a variety of brightness changes in Tabby’s star. Now maybe a team of found evidence that the cause of at least part of the variations is a dense cloud of dust.

One way to find out the cause of Tabby’s star variability is given by the electromagnetic frequencies that are most obscured. That’s because different objects among the suspects absorb light differently. For example, one of the hypotheses was about a comet swarm that runs periodically in front of the star but the dust and debris it would produce should emit an infrared glow that wasn’t detected.

According to the researchers, the characteristics of the light detected from Tabby’s star indicate that the cause of its dimming is formed by particles of no more than a few micrometers in diameter. They observed it at ultraviolets with the Swift space telescope, at infrareds with Spitzer and at visible light at the AstroLAB IRIS observatory. The dimming was strong at ultraviolets and that’s what indicated to the researchers that the particles should be larger than interstellar dust.

This research offers a possible explanation for the long-term cycle of Tabby star’s brightness variations but there are other irregular fluctuations. The dust cloud theorized by this research may have an irregular density and its extension is still to be assessed well but the situation may be more complex.

In essence, we are perhaps at the beginning of the Tabby star’s mystery’s solution but we still need more answers. Research continues by various teams and a few weeks ago the announcement came that a similar phenomenon was also detected with the star EPIC 204278916. Maybe the cause isn’t the same and future studies might offer some surprises.

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