What is a Star?

Get to know and understand the formation, development, and properties of stars:

Anyone who has ever looked deep into the night sky has certainly asked themselves where the stars actually come from. Mankind asks various questions about the formation and development of stars and celestial bodies. Countless sparkling lights in the sky are our daily companions and fill the night sky, stimulating scientists, astronomers, physicists, poets, and thinkers. Mankind has always wondered how stars form and how long they last. This article briefly explains what is a star, what they are made of, how they develop their luminosity, and how the celestial bodies can differ in their composition.

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What is a star?

When a star is mentioned in astronomy, it means a massive, gaseous sphere in the sky. The star consists of plasma and gas mixtures and shines on its own, but can also only shine from incident sunlight. Not all stars shine independently, although they bear the designation “star”. The evening star is such a star that is only illuminated by the sun. As a rule, temperatures of several billion degrees Celsius and a high-pressure ratio prevail in the innermost part of the gaseous sphere. A star is a sun-like structure that can only be seen as a point-like phenomenon because of the great distance. The stars can form star systems, binary systems, and star clusters.

What are stars made of?

Stars often consist of 99% hydrogen, which is converted to helium through the reaction chain and stellar nuclear fusion. This means that if the hydrogen content of the star is used up due to hydrogen combustion during star formation, fusion begins with the helium generated. During star formation, the atoms, hydrogen molecules, and protons are fused together, releasing a lot of energy. The radiant energy of the star is determined by the nuclear fusion that takes place inside the celestial body. A star can therefore be composed of the following elements

• 3/4 hydrogen
• 1/4 helium
• minor amounts of heavy elements eg oxygen or carbon

Why do stars shine?

Stars are made up of gas mixtures and dust particles that can be billions of degrees hot inside. The high pressure creates great heat and temperature, so the star’s gas mixture glows and the star begins to glow. Like the sun in our solar system, most stars are under balanced gas pressure and gravitational and radiative relationships. The light from the glowing ball of gas is several light-years away from us and is still visible from Earth. The star shines so brightly that we can see the light on Earth despite the distance. The star’s luminosity, intensity, and color are influenced by various factors.

• Distance from the star to Earth
• Size and mass of the gas sphere
• Temperature and pressure ratio inside the core
• Temperature and pressure ratio on the star’s surface
• Different layers of air in the atmosphere, with different consistency and temperature, through which the starlight has to penetrate
• the Blue or red coloring of a star is an illusion because the refraction of light plays a significant role
• the flickering and twinkling of the stars are also due to the different layers of air and the refraction of light

How is a star formed?

In the starry sky, we can see nebulae that are made up of gas, hydrogen, and dust. A well-known nebula is the Orion Nebula in which many new stars are born. The gas-dust cloud is under high pressure and the gas particles are subject to gravity. The elements are pressed together by strong pressure, resulting in high temperatures. In the sun of our solar system, for example, temperatures of approx. 15 million °C occur and huge amounts of hydrogen are converted into helium. At this temperature effect, the elements literally merge with each other. Four hydrogen nuclei make up a helium nucleus. Helium is significantly lighter than hydrogen and this difference in mass imbalance is converted directly into light and heat. The gas ball is compressed into a sphere by pressure and temperature. This process lasts for several million years and during this period the gas cloud becomes denser and gains in mass.

A well-known scientist named Albert Einstein devoted many years of his life to the theory and came up with a formula for calculating energy. The formula E=mc² is known to almost everyone who is familiar with the subject. So the energy is the mass times the speed of light squared.

How can stars differ from each other?

Stars can differ in their composition, which means that a different luminous intensity or color is expressed in each case. The mass and volume of the star affect its luminosity and color. In addition, the state variable of a star can be described in more detail with the help of physical means. A star can be characterized and distinguished from other celestial bodies. The following properties describe a star in more detail:

• gravity and acceleration at the surface
• the temperature of the star’s surface
• the star mass and its density
• star radius
• composition and mixtures of substances, metallicity
• rotation and speed
• momentum
• the luminosity of the star referred to as absolute brightness

Conclusion: Stars have far-reaching significance for mankind

Physics makes a valuable contribution to understanding the universe, the formation of stars, the expansion of the universe, and the development of galaxies. The stars have a deep meaning in many cultures and many amateur astronomers deal with the mysterious luminous bodies in the sky. The stars say something about our character, we interpret constellations and try to predict the future using constellations. It is already written in the Bible that the stars should serve as points of orientation and function as a source of light in the dark night. In almost all cultures, stars have a meaning when it comes to orientation, signposting, personal descriptions, or forward-looking predictions.