How old can be a star?
If you go out of town and look at the sky, you can see about three thousand shimmering points clear moonless night. From childhood we are taught that if it does not flicker, it is a planet. If the moves - it's satellite or meteorite. For this tiny scattering of giant stars are hiding for many billions of kilometers away from us, some of which are hundreds of times larger than our sun. Our native gas sphere class G2V also represents universal community bodies. Scientists estimate his age at the 4, 5 billion years. But the solar system is considered to be relatively young. Where is hidden the most ancient stars?
First, let us learn how stars are born. It is known that space empty space is not really empty - for every two cubic centimeters occurs on average one molecule. First of them is formed a cloud of cold interstellar rarefied gas. Gradually, under the influence of gravitational instability, it is compressed and assumes a spherical shape. During the compression energy of the gravitational field is converted into heat and the temperature of the cloud grows. When it reaches the level of 15-20 million degrees, thermonuclear fusion reaction starts and stops the compression. Thus was born a star. Thermonuclear reactions in the light of the core flow millions and even billions of years, providing immediate surroundings almost inexhaustible flow of energy.
During this hydrogen inside the star nucleus fuse to form helium. Then, helium is discharged into carbon, carbon to oxygen, oxygen in silicon, and silicon in iron. Star is becoming heavier and heavier elements creates. It lasts as long as it does not start to contract again. A little light - such as red dwarfs - are massive enough to synthesize anything other than helium, but can still burn trillions of years. The fate of the star is determined by its mass, so by the end of her life, she turns into a white dwarf, neutron star (pulsar) or black hole, depending on their "weight class". The very first stars appeared almost immediately after the Big Bang from which, according to scientists, all things started. But as the age of the universe of 13, 7 billion years, and some stars may be trillions of years, there should be enough at any stage of adulthood. The catch is not only to find the old stars, but also to confirm that it corresponds to the maximum age of the age of the universe. Astronomy - a complex science, requiring perseverance and patience. In only one Milky Way galaxy of over 100 billion stars in the universe as well - more than 100 billion galaxies. Multiply these two numbers - and we do not have enough even for hundreds of years to go through all of these lists. It is not surprising that the evaluation of the ages of the ancient gas balls are constantly changing.
One of the oldest HD 140283 star was discovered more than a hundred years ago. If desired, it can be seen with the help of binoculars or a backyard telescope. Unofficially, it is called "Methuselah", in honor of an old man who lived by the Bible 969 years. It is light, almost as massive as the Sun, located in the Libra constellation 190 light-years away and belongs to the second generation of stars with low metal content. "Methuselah" has appeared in a few hundred million years after the Big Bang, when the Universe was still very raw. At first thought, that he was 16 billion years old, but this is impossible because then the egg will be over the chicken that laid it. According to current estimates of 2013, the age of the star - 13, 3 billion years.
In the same constellation of Libra, but at a distance of 7500 light-years away, there is a red giant HE 1523-0901. Like "Methuselah", is the star of the second generation of low metallicity. Discovered in 2007, it quickly earned the title of the most ancient in our galaxy - only half a billion years younger than the universe. The mass of this longevity is red 0, 8 sun. In 2014, a team of astronomers at the Australian National University, studies the starry sky in the southern hemisphere, he claimed to have found the oldest known stars. It is in 6000 light years from us, and, according to preliminary estimates, the age of the universe itself as a - 13, 7 billion years. Of course, to clarify the analysis will take years, but the fact.
It is possible that one day we can say with certainty that they found most of the Old World, which appeared immediately after the Big Bang, as soon as it became possible, and lasts to this day. So far, we have only to sort out these billions of billions of points that are hidden for thousands of millions of light years away, with the help of our best telescopes. Some of these stars have perished long ago, and only their light continues to inform us of their former existence. Others will live long after the Earth will cease to exist. Is not the reason for a moment to reflect on the fact that we have only one molecule in a drop of water in the ocean waves under the name of the universe?