Dwarf Star


Although its name might suggest that we talk about stars smaller than usual, the truth is that dwarf stars make up the group of stars more numerous and represent normal part in the field of stellar astrophysics . Stars that are located in the main phase of their life are called dwarf stars , from when they are born until the hydrogen in their nucleus runs out , and curiously in contrast to the well-known giant stars.


What is a dwarf star?

They are the stars that are in the main phase of their life that begins with their birth and that culminates with the depletion of the hydrogen they have within their nucleus.


Definition of dwarf star

Dwarf stars are a different class of stars, and they make up the vast majority of stars in existence. The term refers to any star that is in its main sequence , a type of star that has luminosity class V.



The main characteristics of dwarf stars are the following:

  • They are stars that have little brightness .
  • They come from the last stage of the life of a medium-sized star.
  • When they increase in mass , their radius
  • They are stars that are in the main phase of their life.
  • They have a luminosity class V.
  • They do not remain in this state for their entire lives and can transform into giant or super-giant stars .

Origin of the term

The term dwarf star was originally established in 1906 when the Danish astronomer Ejnar Hertzsprung managed to discover that the reddest stars could be divided into two different groups or into groups that were much brighter than the Sun, or much fainter.

How a dwarf star is formed

Dwarf stars are formed in the main phase of life that a star has and are born at the moment in which the hydrogen that is located in the nucleus runs out. Its formation is a main sequence that represents 90% of the life of the star and occurs progressively . In the more mature stars that are expanded the exhausted nucleus is shed and when the fusion reactions are finished , the nucleus contracts and heats up . Some of them may evolve but will always return to their dwarf star status.


There are several types of dwarf stars, among them we have:

  • Dwarfed yellow : the main one is the sun . They weigh between 0.8 and 1.5 solar masses and have surface temperatures of between 5,300 and 6,800 K. Their color can range from white-green , white, yellow and orange . They are stars in a healthy and balanced state , and they undergo the process of converting hydrogen to helium .
  • White dwarf : they are literally the surviving remains of a larger star, mainly from its core and due to its magnetic force it can be very powerful. They are a remnant of stars that have used up their fuel and no longer produce new nuclear reactions . They have the peculiarity of being able to reactivate its activity when it becomes binary with another body.
  • Brown dwarf : mass objects are sub prime and can not maintain nuclear reactions continuous fusion of the hydrogen in its core. They are known as “failed stars” and have very little chemical differentiationbased on depth.
  • Orange dwarf : they have a little nuclear activity as they continue to fuse hydrogen , they are 0.5 to 0.8 suns in size, and have a surface temperature of between 3,900 and 5,200 K. They have a better hydrostatic balance and can live between 15,000 and 30 billion years.
  • Red dwarf : they are about the size between Jupiter and Earth and they light very little. They have a mass less than 40% of the solar mass and a low temperature . They are considered the oldest in the universe.
  • Carbon dwarf: it  is similar to a red dwarf, its surface and atmosphere have more carbon than oxygen which gives it a sooty red / ruby appearance . They progressively transform into very hot white dwarfs like our future Sun, although smaller.
  • Sub-dwarfs: they  are rare and are divided into different classes depending on the characteristics they have. Cold Sub-dwarfs produce their energy through the nuclear fusion of hydrogen. Hot Sub-dwarf stars have a similar appearance to other types of blue stars .

Is the Sun a dwarf star?

The Sun is considered a yellow star and is therefore a dwarf star . It is a star that is located in the phase known as the main sequence and has a G2 spectral type with a V luminosity.  The Sun is a medium-sized dwarf star and it is the only one that can be easily seen.


The stars are a fundamental part of the development of the planet and their importance is basically based on the formation of new components of the universe. In addition, we must remember that the Sun is a dwarf star and it is responsible for many processes that can be carried out on earth .


Some examples of dwarf stars are as follows:

  • Sun
  • 41 Arae
  • Ji1 Orionis
  • 61 Virginis
  • Asterion
  • Alula Australis
  • Xi Bootis
  • Delta Pavonis
  • Tau ceti

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