Cassiopeia, a vain queen in Greek mythology, bragged that she and her daughter Andromeda were so beautiful that they put the sea nymphs to shame. Naturally, this boast angered Poseidon, who sent a sea monster to destroy her realm. The queen’s disgrace is also evident in her constellation. She sits in a chair that rotates around the North Star, putting her in an undignified upside-down position half the time.
At least she has something interesting to look at – within her gaze lies a Delta Scuti variable star. Emory astronomer Horace Dale identified the star’s classification last week, during an exercise of the advanced astronomy lab he teaches, and it was officially entered into the Variable Star Index on Oct. 22.
A variable star is one that changes its luminosity over short periods of time. In layman’s terms: It twinkles. And we’re talking a true twinkle, as opposed to the false twinkle-effect that the Earth’s atmosphere gives stars. When the first variable star was identified in 1638, it disproved theories by Aristotle and others that the stars were eternally the same and fueled the astronomical revolution sparked by Galileo’s telescope in 1609.
A Delta Scuti pulsating variable is an older star with gases that are rapidly expanding and contracting in both spherical and oblong shapes. Out of the 200 billion stars in our galaxy, only about 400 are known Delta Scuti. Dale is credited with identifying two of them, including another one in the Cassiopeia constellation that entered the index in 2007.
“Not many people are looking for them,” Dale says, explaining that it's painstaking work to identify one. Changes in luminosity must be measured over time to produce a light curve, such as the graph, above, from Dale’s most recent find.
Dale is on a mission to identify more. “I think it’s very important,” he says. “If you want to find out who we are, you have to look at the stars first, because that’s where we came from. Where do you think you got all the carbon in your body? It’s a product of the nuclear fusion process of stars. Carl Sagan said it best: We are made of star stuff.”