HOW A STAR IS 200 MILLION YEARS OLDER THAN THE UNIVERSE?
The universe, with his scaring immensity, has awaken the thoughts of philosophers and poets since from the early ages of humanity. For example, consider the multitude of Greek thinkers that discussed about the nature of space. Surprisingly, the possibility that something existed out from our galaxy, the Milky Way, just appeared in the 20’s of the last century.
irstly, what’s the name of the star that claims to be older than the universe? HD140283, also known as Methuselah Star.
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It is placed in the constellation of Libra, around 190 light years distant from us. The name is probably one of the most appropriate ones, because Methuselah was a Jewish prophet that is the oldest character depicted in the Bible with the extraordinary age of 969 years.
This star is what we can define as a sub-giant with very few metals in its composition. It was probably born in a dwarf galaxy that was successively captured by our Milky Way. Another rare characteristic is its speed: Methuselah star travels at the enormous velocity of 1.3million km/h towards our Earth. As a consequence of that, astronomers catalogued it in the list of high-velocity stars of our universe.
How did the scientists understand this proper motion of HD140283? They used the Doppler Effect. Do you know what it is? If not, here’s a simple explanation.
When a light/radiation source moves towards the observer the wavelength is contracted and the frequency grows, the opposite happens if the source is receding from the observer. This effect is the same that makes the alarm of an ambulance change in frequency if it’s reaching us or going away. Scientists exploit the Doppler effect to analyze the spectrum (catalogue of the frequencies of light emitted by stars) of galaxies and stars. If some particular lines called emission lines are translated towards blue (greater wavelengths) it means that the star is moving towards the Earth.
The most shocking characteristics of Methuselah is its age: scientists tried to estimate it in 2000 and came out with the non-sense result of 16 billion years. Given the fact that the most recent measurements of the age of the universe establish a value of around 13.8 billion years, researchers tried to correct the first estimated age of the star with different methods.
Between 2003 and 2011 further studies have been made on the parallax of the star with the Fine Guidance Sensor of the Nasa’s Hubble Space Telescope. But wait a moment, what is parallax? Parallax is probably the most famous method for measuring star distances. Practically, it is based on the displacement of the observed object related to a change of position of the observer.
Does it seem difficult? Let’s try to make a simple example. Try to position one finger near your face and observe it while closing the left eye. Now close the right one and watch the finger with the left. Have you noticed something? The finger has slightly changed position. Why does that happen? Because we are observing the object from a different point in space.
The same effect can be observed with stars: their coordinates in space undergo some small changes as the Earth orbits around the Sun.
These studies were really important to estimate more rigorously the age of the star together with another main indicator: oxygen. In the majority of observed stars oxygen is not so abundant, but in HD140283 the rate of this element relatively to other atoms is particularly high. This fact, together with parallax and other parameters, such as emission from radioactive elements present in the star, made possible to establish the age of Methuselah around 14.46 billion years
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Original Author: Produced by Insane Curiosity and published on 22/11/2020 Source