"Winking star" started winking only recently

In 2002, astronomers at Wesleyan University announced that they had discovered a "winking" star that undergoes a regular, long-lasting (approximately 20 day) eclipse every 48 days. They theorized that those eclipses were caused by intervening blobs of material within a protoplanetary disk surrounding that young star. Harvard astronomer Joshua Winn and colleagues decided to examine the past behavior of the star, named KH 15D, using sky photographs taken during the first half of the 20th century and stored in the Harvard archives. They found that the winking star used to not wink. The nearly complete eclipses seen today were not happening several decades ago, meaning that the eclipses now seen are a recent phenomenon that began within the past few decades - a remarkably short time by astronomical standards. "There are very few cases where astronomers can see a significant change to a star over a single human lifetime," said Winn. This research was published in the August 20, 2003, issue of The Astrophysical Journal Letters.