Scientists can finally explain why some massive stars appear to dance around in the sky even though they are not actually moving: The stars have unusually bubbly guts that cause their surfaces to wobble, thus changing the amount of light they give off, according to a new study.
The dancing stars are known as red supergiants, enormous stellar objects that have swelled up and cooled down as they’ve neared the end of their lives. These stars are about eight times more massive than the sun and can have a diameter up to 700 times that of the sun, which would be the equivalent of the sun’s surface reaching beyond the orbit of Mars (engulfing Mercury, Venus, Earth and the Red Planet in the process). However, despite their colossal stature, these slowly dying behemoths can be extremely challenging to locate with precision.
Astronomers can typically determine the near-exact location of a star by identifying its photo-center, or the point at the center of the light it emits, which usually lines up perfectly with its barycenter, or gravitational center. In most stars, photo-centers occupy fixed positions. But in red supergiants, this point appears to wobble across the star, moving slightly from side to side over time. That motion makes it hard to pinpoint the stars’ barycenters, which provide stars’ exact cosmic addresses and don’t move around like the jiggling photo-centers do.
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