Incredibly Rare Pulsating Star Discovered By Astronomers
Astronomers have discovered an incredible star that expands and contracts in all three directions over a really short timescale. It is one of only seven others discovered in the Milky Way.
The variable star, known by the catchy name of ROTSE1 J232056.45+345150.9, is located 7,000 light-years from Earth and has been identified as a Triple Mode “high-amplitude delta Scuti” (Triple Mode HADS(B)). The star pulsates about once every 2.5 hours.
Regular delta Scuti are known for their short pulsating period, which affects how bright the star looks. If the star pulsation produces a large change in brightness, they are known as high-amplitude delta Scuti (HADS) and other characteristics can be added. What the researchers discovered, however, is a star that expands at different rates in different directions.
When the team observed the object, they werent quite sure what they were seeing and by looking at the light curve, the way the light of the star changed, it wasnt obvious what was going on.
But we knew there was something going on because the light curve didnt quite match known light curves of other delta Scutis and HADS objects we had studied. The light curveswhen laid on top of each otherpresented an asymmetry, Farley Ferrante, a member of the team that made the discovery at Southern Methodist University, said in a statement.Ultimately the HADS(B) we discovered is even more unique than that thoughits a Triple Mode HADS(B) and there were previously only six identified in the Milky Way. So it has three modes of oscillation, all three with a distinct period, overlapping, and happening simultaneously.
The pulsation is due to the rapid contraction and expansion of the star. The hot hydrogen core of the star, which reaches 15 million kelvins (28 million degrees Fahrenheit), makes the outer layer of the star expand. As itexpands, itcools down, which then contracts back into the star due to gravity, and the cycle begins again.
Im speaking very generally, because theres a lot of nuance, but theres this continual struggle between thermal expansion and gravitational contraction, Ferrante continued.The star oscillates like a spring, but it always overshoots its equilibrium, doing that for many millions of years until it evolves into the next phase, where it burns helium in its core. And if its about the size and mass of the sunthen helium fusion and carbon is the end stage. And when helium is used up, were left with a dying ember called a white dwarf.
Theres still a lot more to know about stars, sostudying these peculiar cases can help scientists better understandregular stars like our Sun.