On a clear night, we can see many shining "diamonds" on the black curtain overhead, and among so many "diamonds", can we know which one is the oldest and which one is the youngest?
Young stars "have a bad temper".
Stars are born deep in huge clouds of dust and gas known as nebulae. If the nebula is cold enough and dense enough, the inward gravitational pull will exceed the outward gas pressure, and it will collapse under its own gravitational pull. The density and temperature of this nebula will become higher and higher, and the strong gravitational pull at the center of the nebula will cause gases – mainly hydrogen – to accretion into protostars, eventually igniting nuclear fusion.
However, it is not just one star that is born in this "stellar placenta", many very small protostars will form at the same time, competing to snatch the remaining gas from the nebula, emitting radiation in the process. If we can capture the gas and dust that radiates from the birth of a star, it means finding the "stellar placenta". The famous "Pillar of Creation" is such a place to give birth to new stars. The Pillars of Creation were first photographed by the Hubble Space Telescope on April 1, 1995, at the Aquila Nebula, 6,500 light-years away. The Aquila Nebula is a star-born region of the Milky Way with more than 8,000 stars, most of which are newborn stars, hence the name Pillars of Creation.
However, there are so many stars in the "stellar placenta", which one is the youngest?This is where the brightness and mass of the star come in. The most massive stars are "blue-hot" and very bright, while the least massive stars are "red-hot" and quite faint, scientists can look for the hottest, bluest, and heaviest star in a cluster and precisely calculate its heat and brightness. The mass of a star tells us how much fuel it has, while the brightness tells us how fast it burns fuel. Combined with this information, scientists can roughly calculate the age of the star, and then the age of the other stars in the cluster, from which to find the youngest star.
Using the above methods, astronomers have found the youngest star in the binary star system Canis Major 3,900 light-years from Earth. Since the young stars in the cluster are still accretting matter, huge jets of gas are constantly ejecting from both ends of the cluster. Since the gas jet fades away as the star ages, the amount of gas released by the star helps astronomers estimate the age of the star: the more gas is ejected, the faster the gas is ejected, which means the younger the star. It is estimated that the youngest star is not yet more than 1 million years old, and for reference, our Sun is 5 billion years old to date.
Elderly stars have "slow heartbeats".
Like living things, the rate of "heartbeat" of a star decreases as it gets older, and if we listen to the "heartbeat" of a star with a "stethoscope", we can also determine its age.
The so-called stellar "heartbeat" refers to "starquake". It happens on Earth, and similarly, stars get "starquakes". The most familiar to us is the sun's oscillating "solar quake", which depends on the composition of the sun's interior, especially the relative abundance of hydrogen and helium in the core. Each mode of a star's vibration has its own vibration cycle, which also changes the star's brightness. By monitoring the brightness of stars over long periods of time, astronomers can know if and in what pattern the stars are vibrating, allowing them to conduct further research.
Astronomers have found that as stars age, they tend to shake at a lower rate, but astronomers can't determine the linear relationship between age and shaking speed, so they need to find a reference. Measuring stars of known age, such as the speed at which the sun is shaking (i.e., brightness patterns), helps establish a baseline, and then researchers can measure the speed at which stars of unknown age are shaking and compare that measurement with the speed at which stars of similar size are shaking to know the age of the star.
Using this method, astronomers found the oldest star, HD 140283. HD 140283 is only 190 light-years away from Earth and is about 144 years old600 million years old. This result is somewhat strange, and those who know a little about astronomy should know that, according to existing theories, our universe is only 13.8 billion years old, how can the HD 140283 be older than the age of the "mother".
The longevity of stars is difficult to determine
The reason for the emergence of such "oolongs" is actually because for the distant and old universe and stars, we humans are the real embryos, and the existing theories and technologies can only estimate their age.
At the beginning of the birth of the universe, the matter was mainly composed of hydrogen, accounting for about 92% of the total number of elements in the universe, followed by helium, roughly about 8%, and some elements such as lithium and beryllium, but the total amount was less than 1%, so the metal abundance of the stars formed at this time was very low, basically composed of hydrogen and helium, so one of the main indicators to judge the age of the star is the metal abundance of the star. In 2000, the European Astronomical Office (ECA) calculated that the star would have a lifetime of 16 billion years, based on the metallicity data of the HD 140283.
In 2013, American astronomer Howard Bond collated the Hubble telescope's observations from 2003 to 2011, calculated brightness, distance and mass, and updated the age of the HD 140283 to 144600 million years old, the error is about 800 million years, which means that the minimum age of this star is 13.7 billion years old, and the maximum age reaches 15.3 billion years. Although the age of the HD 140283 has been reduced somewhat by the new calculations, there is still a high probability that the new age data will be older than the age of the universe, and the original problem is still unsolved.
If there is no error in the age of the star in HD 140283, could it be that we have made an error in calculating the age of the universe?This possibility still exists, and in fact, scientists have been suspecting that the age of the universe as we know it today may not be correct. So how did humans calculate the age of the universe?In fact, it is measured by the phenomenon of the expansion of the universe, and in 2013, scientists based on the expansion rate of the universe at that time: 67The 4km s MPC (MPC: million parsecs, about 3.26 million light years) calculates the familiar age of the universe - 13.8 billion years. However, the value of the rate of expansion of the universe is constantly changing, and recent measurements show that this value has increased from 674 has become about 73, and the age of the universe has changed from 13.8 billion years to 12.7 billion years. Therefore, it can be said that the age of the universe is not yet certain.
Determining the age of a star could be the key to finding other habitable worlds – or even extraterrestrial life. If we can find other stars about the same age as our Sun, we will most likely find another Earth in these star systems, and in fact, most terrestrial planets are found near "sun-like stars". On the other hand, by accurately determining the age of stars and narrowing the search for terrestrial planets to galaxies similar to our solar system, we are more likely to find the next Earth for space travel or colonization. If the earth is no longer habitable, we have alternative homes to move to, which is also saving humanity itself.