The Chameleon Star: Where Did Theta Eridani's Brightness Go? ⚡ экспресс
Modern analysis has shown that Theta Eridani is a close binary system of stars with masses of 2.2 and 2.3 solar masses, separated by only 0.083 AU. The stars almost fill their Roche lobes, causing noticeable tidal distortions. One of them has just completed hydrogen burning in its core. Modeling shows that the orbit was previously highly elongated (eccentricity ~0.6), and mass transfer triggered a common envelope phase, brightly illuminating the system for thousands of years. This explains why ancient astronomers saw the star much brighter than it is now. It's like a cosmic dance where the partners heat each other up.
Thousands of years ago, the star Theta Eridani shone brightly in the sky, but today its light has almost vanished. For a long time, it seemed like ancient astronomers had made a mistake, but the real reason is a cosmic dance between two stars. Modern instruments—spectroscopes, which split light into colors, and photometers, which measure brightness—revealed: Theta Eridani is not a single star but a tight pair. Each star, twice as heavy as the Sun, orbits so close that they’d fit inside Mercury’s orbit. When one exhausted its hydrogen and bloated, it swirled its companion in a gaseous shroud. Like dancers tangled in a shared scarf, they became wrapped in scorching gas. Friction inside this “scarf” made the system flare up dozens of times brighter for a few centuries. Then the shroud dispersed, and the star dimmed again. Now scientists realize that ancient records of sudden flares might not be mistakes, but traces of episodes like this. And perhaps this pair will end their dance by merging into a single star.
🎯 At its peak brightness, Theta Eridani rivaled Vega, one of the main stars of the summer sky.