New Paper Says Theta Eridani Shone 12 Times Brighter 2,000 Years Ago

2 articles · Updated · Universe Today · Jul 9

Theta Eridani was likely about V≈0.2 in antiquity versus V=2.9 today, a 2.7-magnitude gap that made it roughly 12 times brighter than it now appears.
Interferometric, spectroscopic and photometric data show the system is a triple star whose inner pair is a tight 0.083-AU binary, giving researchers the parameters needed to explain the anomaly.
The paper argues the primary star nearly filled its Roche lobe after core hydrogen burning, driving mass transfer and a long-lived common-envelope phase that extracted orbital energy and sustained centuries of extra brightness.
Ancient records from Hipparchus, Ptolemy and al-Sufi had long conflicted with modern observations; the authors say similar short-lived brightening phases may be common in close binaries and detectable in current surveys.