This newly-discovered variable is one of only seven of its kind known in our galaxy.

Science journalist Alison Klesman with the online science news magazine Astronomy covered the discovery of a variable star by SMU professor Robert Kehoe and the astronomy team in the SMU Department of Physics.

A high school student in an SMU summer astronomy program made the initial discovery upon culling through archived star observation data recorded by the small but powerful ROTSE-I telescope formerly at Los Alamos National Laboratory in New Mexico.

Other authors on the study were SMU research astronomer Farley Ferrante, a member of the team, Plano Senior High School student Derek Horning, who first discovered the object in the ROTSE-I data, and Eric Guzman, a physics graduate from the University of Texas at Dallas who is entering SMU’s graduate program and who identified the star as pulsating.

The newest delta Scuti (SKOO-tee) star in our night sky is so rare it’s only one of seven identified by astronomers in the Milky Way. Discovered at SMU, the star — like our sun — is in the throes of stellar evolution, to conclude as a dying ember in millions of years. Until then, the exceptional star pulsates brightly, expanding and contracting from heating and cooling of hydrogen burning at its core.

The Astronomy article, “High school students identify an ultra-rare star,” published Feb. 15, 2017.

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By Alison Klesman

The stars shining in the night sky might seem steady and reliable, but in truth, they are constantly changing and evolving. Out of the 100 billion or so stars that inhabit the Milky Way, a little more than 400,900 are classified as variable, meaning they change in brightness over time.

Of those hundreds of thousands of variables catalogued in our galaxy, however, only seven belong to a class called Triple Mode high amplitude delta Scuti, or HADS(B), stars — and that seventh was just recently discovered by a high school student during a summer astronomy program at Southern Methodist University in Dallas.

The star, roughly the size of our Sun or possibly larger, is about 7,000 light-years away in the constellation Pegasus. It currently has only a catalog name: ROTSE1 J232056.45+345150.9. The name comes in part from the telescope used to discover it, the ROTSE-I telescope at Los Alamos National Laboratory in New Mexico.

While examining data from the telescope taken in September of 2000, Plano Senior High School student Derek Hornung noticed the star’s strange light curve, which shows the star’s brightness over time. A non-variable star’s light curve is simply a straight line, unchanging as the hours, days, and months go by. But a variable star exhibits periodic changes in brightness over the course of hours or days, creating a recognizable repeating pattern. Variable stars are classified by the patterns their light curves make, and named after the first star of each type discovered. Delta Scuti variables are thus named after the star delta Scuti.

But there’s more to this story, still. The star is not only a delta Scuti variable, of which there are thousands known, but it is also a rare type within the delta Scuti class, a HADS(B) star. HADS(B) stars show asymmetric light curves that change brightness quickly over time. These stars are pulsating in two modes, which means the star is expanding in two directions at once. There are only 114 HADS(B) stars currently known. Rarer still are Triple Mode HADS(B) stars, of which there were only six previously identified in the Milky way. Triple Mode HADS(B) stars pulsate in not two, but three directions at once. For ROTSE1 J232056.45+345150.9, this process repeats itself every 2.5 hours.

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