Small young and cool stars are numerous and bright, lighting up some of the oldest parts of the galaxy, as Soren Meibom of the Harvard-Smithsonian said. But they can make it be very difficult when it comes to the measurement of their age. Throughout their life, they seem to maintain the same size and luminosity. As a result, scientist have had a hard time, until recently, understanding their evolution.
“Let’s imagine that we’re born as small babies, but by our first birthday, we look like an adult, and we stay looking the same through our 20s and 40s and 60s, even 80s, until we suddenly appear old,” Meibom said in a news briefing at the American Astronomical Society meeting in Seattle.
Research, until now, has focused of the pattern of dimming caused by planets passing in front of the examined stars. For this study, scientists observed stars in a 2.5 billion-year-old star cluster known as NGC 6819. But now, astrologists focused on the dimming caused by the rotation of dark spots on the surface of the stars, similar to the ones present on our sun. The cyclic dimming told of the rate of the star’s rotation.
As such, scientists understood that the older the star, the slower it would spin. Also, they found that younger stars had bigger and more numerous dark spots on their surface. The stars studied, 30 in number, had masses 0.8 to 1.4 times bigger than our sun. They displayed a rotation between 4 of 23 days.
Gyrochronology is the field that studies the spin rates of stars. The field was establish as early as 2003 and its name originates from the words gyro (spin), chronos (time), and logos (study), all three Ancient Greek words.
As we know, knowledge of a small, young and cool star’s age is not important out of pure curiosity, it is important as it can unveil information the planets clustered around it and whether or not life on those planets was, is or was ever possible.
So, what can gyrochronology tell us about our sun? Our sun rotates around its axes once every approximately 26 hours. This reveals that our sun’s age is around 4.6 billion years old, and because planets are likely to form around the same time the star does, Earth is also around 4.6 billion years of age. Of course, it took hundreds old millions of years of transformations and evolution for an auspicious environment to be created and for intelligent life to spring.
Image Source: Harvard-Smithsonian Center for Astrophysics
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