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New class of variable stars discovered; existence challenges current theoretical models

Swiss astronomers have found a new class of variable stars by determining small variations in stellar brightness. According to a news release from the European Southern Observatory (ESO), the Swiss team utilized a 1.2-meter telescope to accomplish this task.

The new findings are based on regular measurements of the brightness of more than three thousand stars in the open star cluster NGC 3766 over a period of seven years. The Swiss team discovered that 36 of NGC 3766’s stars followed a surprising pattern in that they had small regular variations in their brightness at the level of 0.1 percent of the stars’ typical brightness.

The astronomers found that these variations had periods between about two and 20 hours. Besides small variations in stellar brightness, the stars are a little hotter and brighter than the Sun. The new kind of variable stars has yet to be given a name.

According to the ESO, this level of precision in the measurements is two times as good as that taken by similar studies using other telescopes. These measurements are also the first to show these small stellar variations.

Research team leader Nami Mowlavi said that the high quality of the observations combined with an extremely detailed analysis of the data has allowed researchers to achieve this level of sensitivity. The fact that the astronomers have conducted an observation program over a period of seven years also helps, noted Mowlavi.

There a lot of stars that are known as variable stars due to the fact that their brightness varies over time. How the brightness of these stars varies is determined by the properties of their inner working in a very advanced way.

Variable stars and how the brightness of these stars changes has given way to the formation of a branch of astrophysics known as asteroseismology. In this branch of astrophysics, astronomers can “listen” to these stellar vibrations to learn more about the physical properties of the stars.

According to Sophie Saesen, a member of the Swiss research team, the existence of this new kind of variable stars is a challenge to astrophysics. This is because current theoretical models advance the idea that their brightness is not supposed to vary periodically at all.

Though astronomers are still trying to uncover the reason behind the variability, they have learned the some of the stars appear to be quick rotators. In fact, they rotate at speeds that are more than half of their critical velocity, which is the boundary where stars become erratic and eject material into space.

According to Mowlavi, under these conditions, the rapid rotation will have a significant impact on their inner working. Unfortunately, scientists do not yet have the capacity to model the stars’ small variations. However, the researchers think their findings will entice other scientists to look into the problem so that the origin of these strange variations can eventually be understood.

According to, there are several different types of variable stars, including Cepheid Variables, Pulsating Variables and Cataclysmic Variables. Any guesses as to what this new class of variable stars will be called? Share your thoughts in the comments section.