Stars

We explain what stars are, the types that exist and their characteristics. Also, shooting stars and meteor showers.

What are stars?

When we talk about the stars, we are of course referring to those bright dots that are seen in the sky when night falls. Actually are large luminous spheres composed of plasma. Despite being in continuous combustion, they retain their own shape thanks to the enormous force of gravity they generate.

The star we know best is the Sun, to which we owe natural light. However, There are billions of stars in the observable universe apparently dispersed but at the same time forming galaxies, orbiting a large common center of gravity.

Although they all emit different types of light and heat, only a small percentage can be captured by the human eye, even with the help of a telescope. Opaque stars such as planets, meteorites or comets also revolve around many of them, as happens in our Solar System, hooked on their enormous gravity.

Humanity has observed the stars since ancient times, and has wanted to see shapes, hidden messages or evidence of their gods in them. So much so that the stars in the sky have been named after the formation of mythological figures called constellations.

Since ancient times have been used to create the first calendars, as well as for cartography and navigation. In much closer times, astronomical observation has understood much more about them, classifying them and learning about their destinations, their constitution and their various ways of emitting energy.

Types of stars

There are very different criteria to classify the stars in the universe, taking into account some of their specific characteristics, such as:

• According to its life cycle They are classified according to the moment in their life cycles: protostars, red giants, white dwarfs, black dwarfs or neutron stars (or, failing that, black holes).
• Depending on its luminosity and temperature Depending on how bright and intense they are, they are classified as (from lowest to highest intensity and brightness): white dwarfs, sub-dwarfs, dwarf stars (like our Sun), sub-giants, giants, luminous giants, supergiants, luminous supergiants. or hypergiants.
• According to the nature of its light Taking into account the predominant type of electromagnetic emission, we can talk about: type O stars (violet), type B (blue), type A (blue-white), type F (yellowish-white), type G (yellow, like the Sun), type K ( yellow-orange), type M (red-orange).

Star characteristics

The stars originate in molecular clouds that is, high-density regions of space that mainly contain hydrogen, helium and other elements. Due to the forces of gravity or the collision with other similar clouds, even denser regions are produced inside, which initiate nuclear atomic fusion reactions.

As it begins to grow in mass and density, temperature and light are produced. The magnitude of these explosions is enormous, but the star is held together due to the brutal gravitational attraction it exerts on itself.

Chemically, the stars are made up of hydrogen (71%) and helium (27%), with a small percentage (2%) of heavier elements from iron and nitrogen, to chromium and rare earths, all of which are the result of continuous fusion within it.

That is to say, they are made up of the simplest elements in the universe. In fact, The fusion of stars is the origin of all the atoms of matter so we can understand stars as large space furnaces of matter.

Examples of stars

Some of the most common stars in the sky are:

• Syrian (Sirius). Also called Alpha Canis Maiorisis the brightest star in the Earth's night sky, located in the constellation Canis Major. It is actually a two-star system, Sirius A and Sirius B, and a Sirius C is even supposed to exist.
• Canopus (Canopus). The second brightest star in the night sky is located in the Keel constellation, 309 light years from us, and has a luminosity of 13,300 times our modest Sun. That is, it is more luminous than Sirius, but it is also much more luminous than Sirius. further.
• Arthur (Arcturus). Also called Alfa Bootisis the third brightest star in the night sky, found in the constellation of the Boyero, in the northern celestial hemisphere. It is an orange giant located 36.7 light years from our Solar System.
• Vega. Call too alpha lyraesince it is located in the constellation of the Lyra, it is relatively close to Earth: just 25 light years away. And although it is a tenth of the age of the Sun, it is 2.1 times more massive, and quite poor in elements heavier than helium. Vega was the first star to be photographed and analyzed spectroscopically.
• Betelgeuse. From the constellation of Orion, therefore called Alpha orionisis a red supergiant star, the ninth brightest in the entire sky. It is an old star, which has already exhausted its main fuel (hydrogen), so its temperatures are relatively low (3,000 K) and it emits significant amounts of red and infrared light.
• Aldebaran. Call too Alpha tauriis the main star of the Taurus constellation, orange-red in color and 425 times more luminous than our Sun, despite having only 1.7 times its mass. The Pionerr 10 probe is en route to Aldebaran, and it is estimated that it will reach it in about 1,690,000 years.

shooting stars

Contrary to what their name suggests, shooting stars are not stars. Rather, they are debris and small astronomical objects that, upon entering the Earth's atmosphere, fall victim to friction and ignite, giving off light and generating a phenomenon visible from the surface.

The shooting stars are, really, meteorites or meteors only very small in size (between a millimeter and several centimeters), so they do not usually reach the ground, but instead fade and disintegrate as they fall.

star shower

In a meteor shower, stars do not really fall from the sky. On the contrary, this phenomenon It is because our planet has momentarily entered the orbit of a comet receiving part of the gases and fragments that are released from its coma over thousands of kilometers long.

These showers of material, which are very similar to meteor showers, when they are very abundant, penetrate the atmosphere where friction ignites them and they generate light in their wake. Since this usually occurs with some frequency (depending on the period of the comets), meteor showers can receive specific names, such as the Leonids or the Perseids.

Continue with: Gravitational field

References

• “Star” in Wikipedia.
• “Stars” in Southern Astronomy.
• “Stars” in Very Interesting.
• “What do you know about the stars?” in National Geographic.
• “Stars” in The Encyclopaedia Britannica.