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HD 74423 is a star approximately 1.7 times more massive than our Sun, situated in a binary star system about 1,500 light-years from Earth. In case you aren't familiar with the terminology, a binary system = a two-star system.
HD 74423 is gravitationally bound to a small, red dwarf star. According to a March 2020 study published in Nature Astronomy, HD 74423’s smaller companion is responsible for its unusual appearance and behavior
As the tiny red dwarf whips around HD 74423 — in a perilously short orbit of just under two days — it tugs on the larger star, stretching it into a teardrop shape and distorting the oscillations in the process.
You can see an artist’s impression of the pulsating star here.
Stars like HD 74423 were first theorized to exist in the 1980s, and study co-author Professor Don Kurtz says he’s been looking for stars like this “for nearly 40 years.” Ultimately, astronomers were finally able to spot one with some help from citizen scientists Robert Gagliano and Tom Jacobs. These amateur investigators were analyzing the extensive volumes of publicly available data from NASA's Transiting Exoplanet Survey Satellite (TESS), which scans the sky for planets around distant stars in search of interesting phenomena.
When they came across HD 74423, they realized something unusual was happening.
Study co-author Dr. Simon Murphy notes that HD 74423’s behavior isn't the only odd thing about it. The star's chemical makeup also makes it peculiar. "Stars like this are usually fairly rich with metals — but this is metal-poor, making it a rare type of hot star,” he explained in a press release.
While this discovery is indeed unique, the study's authors believe it’s likely the first of many such rare finds. "We expect to find many more hidden in the TESS data," said study co-author Professor Saul Rappaport.
After all, there’s really no upper limit to just how peculiar things can get in the cosmos. And this is proof that you — yes, you — can help find them.
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