What are stars?

What are stars?

Stars are gaseous structures composed mostly of hydrogen and helium and almost perfectly circular because of its large gravitational field in all directions of space. The origin of stars occurs within the nebulae. The particles present in these huge clouds of gas and dust coalesce into cores trapped by attractiongravitational for millions of years. When the temperature of these cores reaches the order of millions of degrees Celsius (°C), the process of Nuclear fusion: at talltemperatures and the gravity are enough for to merge the hydrogen atoms that compose it, transforming them into atoms of Helium.

During 90% of their long lives, the stars convert gas Hydrogen in Helium. In this process, a small part of the mass of hydrogen atoms is converted into energy, in the form of electromagnetic waves, like gamma, X ray, radio waves, infra-red, ultraviolet and all others possible wavelengths of electromagnetic spectrum. the fragile swing enter the big strengthgravitational and the violence of the constants

reactionsnuclear is able to keep the spherical radius of the stars constant during billion in years old.

Types of stars

There's a lot ratings different from stars, which are made by pasta of the stars and yours shine apparent. In this text, we will cite some classes of stars in a very simplified way:

• Main sequence stars: They represent most of the known stars (about 90%) and are also relatively younger than the rest of the stars. Generally, the hotter, the brighter these stars are. They are subdivided into:

  • Dwarf Stars: They are relatively small stars. Our Sun is a yellow dwarf star. The most common stars are red dwarfs;

• giants and super giants: These are older stars and hotter than dwarf stars. They can be thousands of times brighter than our Sun. They have subdivisions:

  • red giants: They are stars about 100 times larger than their original size and a little cooler than they were at the beginning of their lives;

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  • blue giants: Very large, old and extremely hot stars. They are known to fuse Helium atoms because of their high temperature;

  • Supergiants: They are rare and super massive stars. The end of their lives is marked by explosive cosmic events, such as supernovas, which can give rise to black holes.

The death of stars with smaller masses than supergiant stars can lead to the formation of stars such as white dwarfs, brown dwarfs, neutron stars and pulsars.

Curiosities about our star: The Sun

The sun is considered a star a-N-AYellow (classification by temperature, not color). Its surface temperature is variable, but is between 5000 K and 17000 K. It is a star with a mass of about 330,000 Earths, representing more than 99% of all The pasta of systemsolar.

despite seem yellow or orange, the sun is a starWhite, as it emits all visible wavelengths. The color of the sun is changed by dispersal of light rays when they enter the Earth's atmosphere. Due to its great distance to Earth, approximately 150millions in kilometers, the light that comes out of the sun takes fence in 8minutes and 18seconds to reach us.

The sun orbit O center gives galaxy, completing one full lap every 250millions in years old. Its estimated orbital speed is approximately 250 km/s.

Every second, about 4millions in tons in matter of the Sun are converted into energy. When Hydrogen, its raw material, runs out, the end of our star king's life will be to become a giantred, increasing its temperature and expanding to a diameter of up to 250unitsastronomical (1 au = 1 distance Earth-Sun), approximately four billion years from now.

By Rafael Hellerbrock
Graduated in Physics

Would you like to reference this text in a school or academic work? Look:

HELERBROCK, Rafael. "What are stars?"; Brazil School. Available in: https://brasilescola.uol.com.br/o-que-e/fisica/o-que-sao-estrelas.htm. Accessed on June 27, 2021.