Astronomers have long been interested in the early universe and theircuriosity is justified - the very first stars and galaxies are very different from those that we observe around. Thus, stars that formed about 800 million years after the Big Bang have a different composition and most often gather in groups that scientists call globular clusters. As a rule, they surround distant galaxies, but it is not easy to determine their exact age. Fortunately, the launch of the James Webb space observatory into Earth orbit will help astronomers study one of the most ancient stars in the vast universe - Methuselah. The age of this celestial body is estimated at more than 12 billion years, and some researchers have previously argued that Methuselah is older than the Universe itself (we recall that the age of the latter is 13.8 billion years). But how is this possible and where did these paradoxical figures come from? Let's figure it out!
Star Methuselah - the oldest of all known stars,located in the constellation Libra, at a distance of 190 light years from the solar system. Just a few decades ago, this star was thought to be older than the universe itself.
First stars and galaxies
Astronomy is like a time machine because wewe can look at events that happened billions of years ago. By looking at objects that formed shortly after the Big Bang formed our universe, we can learn a lot about the origin of galaxies, stars, and exoplanets. It is believed that their age cannot exceed 13.8 billion years, as evidenced by relict radiation - Light from the primordial plasma of the early Universe, left over from the Big Bang.
Recall that the cosmic microwave background indicates the extremely hot temperature of the early universe and evenly fills space, consistent with the Big Bang theory.
You can also determine the age of the universe by observingbehind the most distant celestial objects. This is especially true of the first stars and galaxies, which are being searched by astronomers from all over the world. Their main assistant today is the James Webb Space Observatory, launched into Earth orbit earlier this year. This miracle of technology seriously expands the horizon of space observations, which we recently talked about here (and here).
Recall that Webb has begun full-time workthis summer, however, the data obtained with its help has already helped astronomers to examine in detail a huge number of distant objects, including the star Methuselah, whose age was legendary. So, in 2000, it was believed that this ancient star is older than the Universe itself, and its approximate age was estimated at 16 billion years.
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Further research disproved the firstassumptions, indicating that the star was born approximately 14.46 billion years ago. These conflicting data eventually turned the star Methuselah into a real cosmic paradox, since nothing can be older than the universe.
The oldest star in the universe
To understand the origin of Methuselah,which is located at a distance of 190 light-years from the solar system, astronomers drew attention to the data of photometry, the intensity of the glow and spectroscopy. This is because most of the chemical components that make up the observable universe were formed in the cores of massive stars or under the enormous pressure of their final collapse (death).
Each new generation of stars contains severala different combination of elements than the previous one, and their chemical imprint should be very different from the imprint of stars like our Sun, experts explain.
Astronomers have studied the ratio of hydrogen and helium inthe most distant celestial bodies, drawing attention to globular clusters. With their help, as the dear reader probably knows, it is possible to determine whether this or that star belongs to the first generation of all objects existing in the vastness of the Universe. And, as scientists have previously established, the Methuselah star consists mainly of helium and hydrogen.
Research since 2000showed that the approximate age of this ancient star is at least 14.46 billion years with an error of 700-800 million. And this figure (unlike 16 billion) more or less fits into the previously indicated age of our space house.
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Fortunately, the scientific research of the last two yearsclarified the situation: according to recent estimates, the age of Methuselah does not exceed 13.6 billion years, which is compatible with the formation time of some of the oldest stars. And, as the 2021 calculations showed, this amazing star is 1.8 billion years younger than the universe.
Globular clusters and the age of the universe
Similar estimates of the age of the universe have comethe authors of a new study published in the Astrophysical Journal Letters. By studying distant globular clusters, astronomers have come to the conclusion that the most ancient stars could have formed about 13 billion years ago. In the course of the work, scientists relied on data from the James Webb Space Telescope, with the help of which they were able to analyze the length of light waves emanating from very distant star clusters.
The Milky Way galaxy has about 150 globular clusters. Their history is not yet well understood by astronomers, and measuring their age can be extremely difficult.
According to astronomer Adelaide Claissens ofStockholm University, before Webb, it was almost impossible to identify globular clusters due to the huge distance between them and the Earth. But with the help of the latest space observatory, objects that were previously inaccessible to observation were discovered and properly considered.
High resolution image taken withWebb, contains thousands of galaxies and dense groups of millions of stars. These ancient collections may contain clues about the earliest stages in the formation of the universe. Recall that the James Webb Observatory monitors infrared radiation, which is heat that can penetrate dust clouds - an area that was considered impossible to see just a few months ago.
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During the study, three images were obtained12 globular clusters in infrared, five of which are the oldest ever discovered. Just imagine how many amazing discoveries await us ahead, because the James Webb Observatory has just started work. It is possible that very soon we will learn a lot about the birth, evolution and age of the Universe, as well as about the very first objects formed in it.