![]() Most pre-main sequence stars feature planet-forming or protoplanetary disks at their early stages. ![]() Since pre-main sequence stars don’t have enough temperature and pressure to initiate hydrogen fusion, they are powered by gravitational contraction rather than a nuclear reaction. While stars in this phase are generally labeled as pre-main sequence stars, they can be classified either as a T Tauri star, with a mass less than 2 solar masses, or Herbig Ae/Be star, if it has a mass somewhere between 2 to 8 solar masses. On an evolutionary scale, between the protostellar phase and the main sequence stage, there is an intermediary phase in which the young stars continue the accretion process and reach a certain temperature limit. Moreover, protostars are observable only at infrared and microwave wavelengths. The resulted star-like object is called protostar.īy the end of the protostellar phase, which may last over 500,000 years, the star has already acquired almost all its mass but has not yet started nuclear fusion at the core. The dense cores eventually transform into a rotating sphere of extremely hot gas due to increased pressure and temperature. These fragments, also known as dense cores, gain mass through accretion (by accumulating gas from the surrounding cloud) while the gravitational contraction kicks in. The process of star formation begins with the collapse and fragmentation of molecular clouds. The image was taken by Spitzer Space Telescope. ![]() ProtostarĪ Protostar outburst in the Orion Star-forming complex. Types of Stars Based on Stages of their Evolution 1. Below are 13 types of stars based on stages of their evolution and kinematics. The most commonly used criteria of classifying stars is based on their spectral characteristics, in which stars are basically sorted out from the hottest O type to the coolest M type (I am been extremely modest here).Īnyway, there are few other means to classify stars, in which they can be physically described. They are also one of the most diverse things we know today. If the star is especially massive, when it explodes it forms a black hole.Like almost anything in the universe, stars born, live their life and then die. These spin rapidly and can give off streams of radiation, known as pulsars. After the dust clears, a very dense neutron star is left behind. This material can collect in nebulae and form the next generation of stars. This scatters materials from inside the star across space. After many thousands of millions of years it will stop glowing and become a black dwarf.Ī massive star experiences a much more energetic and violent end. During these changes it will go through the planetary nebula phase, and white dwarf phase. What happens next depends on how massive the star is.Ī smaller star, like the Sun, will gradually cool down and stop glowing. All stars will expand, cool and change colour to become a red giant. The star then enters the final phases of its lifetime. ![]() Smaller stars use up fuel more slowly so will shine for several billion years.Įventually, the hydrogen which powers the nuclear reactions inside a star begins to run out. This means they may only last a few hundred thousand years. Very massive stars use up their fuel quickly. The exact lifetime of a star depends very much on its size. This stage is called the ' main sequence'. Nuclear reactions at the centre (or core) of a star provides energy which makes it shine brightly.
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