Tabby's Star

Tabby's Star, also known as KIC 8462852, is a highly unusual binary star system.

It is located in the constellation Cygnus, roughly halfway between the bright stars Deneb and Delta Cygni. The system consists of an F-type main-sequence star and a red dwarf companion. While most stars shine with a steady luminosity, this star shows massive, irregular fluctuations in brightness. These sudden drops in light have made it one of the most studied objects in modern astronomy. It serves as a vital case study for how we understand stellar behavior and orbiting material.

The most striking feature of this star is its irregular light curve. A light curve is a graph showing how a star's brightness changes over time. Most stars have very smooth, predictable curves. However, Tabby's Star experiences deep, unpredictable dips in its radiative flux, which is the amount of light energy it emits. In 2011, the star dimmed by up to 15%. In 2013, it experienced a massive drop of up to 22%. To put this in perspective, a planet as large as Jupiter would only obscure about 1% of a star this size. This indicates that the objects blocking the light are much larger than any known planet.

Astronomers have proposed several hypotheses to explain these massive dimming events. One early idea was the presence of an extraterrestrial megastructure, such as a Dyson swarm.

This would be a massive artificial construction built to capture a star's energy. However, most scientific evidence tends to discount this possibility. Another theory suggests the dimming is caused by a swarm of dusty comet fragments.

In 2019, researchers suggested the light dips might be caused by fragments from a disrupted exomoon. These fragments would orbit the star in a tight formation, blocking light as they pass through the line of sight.

The discovery of these fluctuations was a major milestone in citizen science. The data came from the Kepler space telescope, which was designed to find exoplanets by watching for tiny dips in starlight. As part of the Planet Hunters project, citizen scientists identified the unusual patterns in the Kepler data. In 2015, astronomer Tabetha S. Boyajian published the lead paper announcing these findings. Because of her work, the star is often called Boyajian's Star. It also earned the nickname "WTF Star," which stands for "Where's The Flux?" This name refers to the mysterious missing light in the scientific paper's subtitle.

Since the initial discovery, astronomers have used many different tools to monitor the star. In 2017, a major observation campaign occurred involving the Las Cumbres Observatory Global Telescope Network. During this time, astronomers tracked several specific dimming events named Elsie, Celeste, Skara Brae, and Angkor.

These events varied in depth, with some dipping by only 1% and others by nearly 3%. In 2018, even deeper dips of over 5% were recorded by ground-based observers. More recently, the Transiting Exoplanet Survey Satellite, or TESS, has also provided data to help map these changes.

The star's history and long-term behavior add even more complexity to the mystery. Observations of the star date back as far as 1890 through various astronomical catalogs. Some studies of old photographic plates suggested the star might have gradually faded by 20% over a century. However, other researchers argued this was just a data artifact and that the star remained constant. This debate shows how difficult it is to measure the brightness of distant stars accurately over long periods. The star remains a target for SETI projects, which search for signs of advanced technology in the universe.

Tabby's Star is not entirely unique, but its scale is extraordinary. There are other stars, such as young stellar objects called YSO dippers, that also show irregular dimming. However, the patterns in YSO dippers are different from the chaotic dips seen in KIC 8462852. The system's complexity is further increased by its red dwarf companion, located 880 AU away. For comparison, that distance is about 30 times the orbit of Neptune. By studying this star, scientists learn more about how dust, moons, and even planets interact with their parent stars.