Carol Wight, age 14, of Lansing Michigan for her question:
Is it true that certain stars are older than our sun?
The blazing stars come in different colors and sizes. Some are bigger and brighter than others. Some are hundreds of times heavier than lead and some are much lighter than the downiest feathers. They also vary in age. Some of the old timers may be billions of years older than our sun.
The history of the heavens goes back billions of years into the remote past. Astronomers and astrophysicists still are busy probing into its secrets. Someday, perhaps, they will be able to give us a picture of the cosmic past. They may ascertain the events that, occurred and predict what can be expected. Already they can tell us a great deal about the life history of a normal star. According to our time scale, every twinkling star in the sky is an ancient timer. Scientists tell us that the youngest of them are about a million years old. Most of the stars have been blazing away for billions of years and their ages can be estimated with fair accuracy. But the best estimates may be wrong by several million or even a billion years. In terms of earth years, the sun has had time to celebrate about 5,000 million birthdays. Compared with other stars, it is a middle aged fellow of medium size and average brilliance.
The brightest star seen in our skies is Sirius, the Dog Star. Sirius is bigger .and brighter and somewhat younger than the sun. It is one of a pair of double stars. Its partner, the Pup, is too small to be seen by human eyes but astrophysicists have figured out its dimensions. It is a white dwarf star immensely hot, immensely heavy and its age is estimated to be several billion years older than the sun. Many white dwarf stars have been analyzed. They are old timers and some of them are estimated to be around 10 billion years or twice as old as our golden sun.
The white dwarfs seem to have reached the stage of starry old age. But even older stars have been discovered. The oldest of ancient stars have been found in star clusters. These amazing star clusters are densely populated pockets of stars that occur here and there outside the core of the Milky Way. They belong ,to our Galaxy and may indeed be its oldest inhabitants. One of these clusters is catalogued as NGC 188. Its weary old stars are estimated to have reached the age of 15,000 million, or 15 billion earth years stars older than sun
The fuel of a starry furnace is hydrogen gas and it burns by a process of nuclear fusion. Its atoms are fused to form atoms of helium. As a star grows older it consumes its original quota of fuel, its proportion of hydrogen decreases while helium and other elements increase. Each burning gas makes its own bands of color on the rainbow spectrum. The spectrum of a star reveals its gases and the proportion of its hydrogen. Experts can estimate how long it took the nuclear furnace to consume this much of its original fuel. And the age of the star dates back to when its nuclear reaction first ignited.
Astrophysicists base their estimates on their knowledge of nuclear fusion, the welding of smaller atomic nuclei to form nuclei of larger atoms. The stages of this dynamic pace follow strict schedules, and timetables. Some stars are hotter and burn up their fuel faster. Certain cooler stars are burning more slowly and can expect to live longer. In estimating the age of a star, the expert needs to analyze its spectrum, its mass and its remaining mass and other factors such as brilliance and temperature.
The job is complicated but most of the stars in the sky have been dated and many of them, it has been discovered, are much older than our middle aged sun.