Twenty-one hours. That's how long a steady dimming of Tabby's star's light lasted. Usually this star flickers chaotically, like a lighthouse in a heavy storm. The brightness drops sharply, without warning. But in data from the TESS space telescope, a calm dip appeared — the eye of the storm.

This dip turned out to be the passage of a large object in front of the star — a transit method event. For 21 hours, the star was 1.1% dimmer. Like a lamp in a room briefly dimming by a hundredth of its brightness. The shadow was symmetric, like a circular screen.

To understand what the shadow was, scientists used several methods. Photometry from TESS provided the precise light curve of the dip. Then they measured the star's wobble: when a heavy companion orbits nearby, the star sways slightly. They detected this wobble through the shift of lines in the spectrum — a method called Spectroscopy. They also ruled out the influence of a neighboring red dwarf — it had nothing to do with it. Numerical simulation of the orbit showed that the companion completes an orbit in about three to four years. Its mass is 9.4 Jupiter masses, its radius 1.7 Jupiter radii. It is a borderline object: no longer an exoplanet (giant planet), but not yet a star.

The next step is to catch a repeat transit in 2026–2027. Then astronomers can precisely measure the orbit. Like the calm eye of the storm, this dip promises to reveal the secret of Tabby's star's long-standing chaos.