What is Stellar evolution: Definition and 26 Discussions

Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years for the least massive, which is considerably longer than the age of the universe. The table shows the lifetimes of stars as a function of their masses. All stars are formed from collapsing clouds of gas and dust, often called nebulae or molecular clouds. Over the course of millions of years, these protostars settle down into a state of equilibrium, becoming what is known as a main-sequence star.
Nuclear fusion powers a star for most of its existence. Initially the energy is generated by the fusion of hydrogen atoms at the core of the main-sequence star. Later, as the preponderance of atoms at the core becomes helium, stars like the Sun begin to fuse hydrogen along a spherical shell surrounding the core. This process causes the star to gradually grow in size, passing through the subgiant stage until it reaches the red-giant phase. Stars with at least half the mass of the Sun can also begin to generate energy through the fusion of helium at their core, whereas more-massive stars can fuse heavier elements along a series of concentric shells. Once a star like the Sun has exhausted its nuclear fuel, its core collapses into a dense white dwarf and the outer layers are expelled as a planetary nebula. Stars with around ten or more times the mass of the Sun can explode in a supernova as their inert iron cores collapse into an extremely dense neutron star or black hole. Although the universe is not old enough for any of the smallest red dwarfs to have reached the end of their existence, stellar models suggest they will slowly become brighter and hotter before running out of hydrogen fuel and becoming low-mass white dwarfs.Stellar evolution is not studied by observing the life of a single star, as most stellar changes occur too slowly to be detected, even over many centuries. Instead, astrophysicists come to understand how stars evolve by observing numerous stars at various points in their lifetime, and by simulating stellar structure using computer models.

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  1. RyanJ

    I What are the Dynamics and Impacts of a Type II Supernova?

    Hi! Please don't spare me any juicy details. I can take it! I'm specifically interested in type II supernovae and their stellar precursors in my following questions. Stars above the mass of 8 times the size of the sun go through successive burning phases in their cores, resulting in a cores of...
  2. N

    What to Expect When Studying Astrophysics in University?

    Hey everyone, I'm brand new here! I absolutely love Physics, specifically Astrophysics, I'm actually looking to study black holes and stellar evolution. I'm preparing to go to University this fall to get my bachelors in Science with a major in Physics and a minor in either Mathematics or...
  3. R

    I Understanding diagrams of the late stages of stellar evolution

    Hi, I have an upcoming exam in astrophysics. We have been told to make sure we study all figures and tables, s.t. we are able to explain them. However, I ran into these figures below, in my lecturer's PowerPoint and I do not know where they originate and aren't presented in my book. I'm having...
  4. T

    B Question about the s-process and r-process in stellar evolution

    Hello I have been reading about the s-process and r-process in star evolution. And one thing i briefly saw mentioned was that both processes generally create higher abundances of elements with even number of protons than odd. It however did not explain why there is a slight bias towards even...
  5. F

    From the original burst, fraction of stellar mass still on the Main Sequence

    <Moderator's note: Moved from a technical forum and thus no template.> Suppose that all stars in this galaxy were born in a single major-merger burst event about 10 Gyr ago. From this original burst, I want to compute the fraction of stellar mass still surviving as stars in the main sequence ...
  6. AlphaLibrae

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  7. mjda

    I Stellar Thermal Energy with no Nuclear source

    Can anyone enlighten me as to why the total thermal energy of a star will increase with time if the star has no nuclear energy source?
  8. S

    I Do stars have any lower mass limit?

    Just read an article about a discovery of the smallest/least massive star in the Milky Way galaxy. The star has 85 times the mass of Jupiter and is known as EBLM J0555-57Ab located about 600 light-years from Earth. The entire article here -...
  9. G

    A Does Magnetic Braking Theory hold up?

    Magnetic braking is a theory explains the loss of stellar angular momentum and is used extensively to describe the given rotation stars. However, on a smaller and more directly observable level, when we consider Jupiter's rapid rotation rate of less than ten hours and its accompanying powerful...
  10. jamalkoiyess

    Stellar Evolution: In-Depth Books for Learners

    hello PF, I want to know more about stellar evolution and about the end of the star's life. I want something that is not very superficial as i get bored when the content is not really deep. Thanks.
  11. A

    R136a defies Laws of Stellar Evolution

    At 265 SM, and age 1.7 Million years, at 163,000 Light Years Away in the R136 cluster, is R136a. But, it shouldn't be alive now. It should have exploded given the model of Solar Mass Evolution at 200,000-375,000 Years old of age. It's in it's Wolf-Rayet phrase, but it still shouldn't be alive...
  12. excelsior

    Reading Recommendation - Sun / Stellar Evolution

    My apologies for starting a thread on a seemingly easy and searchable topic. But, alas, I've searched here, Amazon, google, Goodreads etc and wanted to get some recommendations. Specifically book suggestions on The Sun and / or Stellar evolution. I've ran across several intriguing textbooks...
  13. E

    The stellar evolution. Low Mass stars

    Well, this topic is driving me crazy so any answers or replies should preferably be detailed and in an easy way.. My question is i want a sum up of the evolution of a low mass star... I will give my answer and tell me where are the dropouts.. Let me begin,With a protostar accreting hydrogen in...
  14. N

    Could advanced technology artificially accelerate the evolution of our sun?

    Hi there, I'm new to the forums and I came here for a specific purpose. I am not in school at the moment, but rather I am writing a science fiction novel and want to make sure that my science is as close to accurate as possible (though I understand that this may be impossible in some respects)...
  15. M

    Stellar Evolution - Detailed Colour Magnitude (HR) Diagram

    Hi, Just revising for my Advanced Stellar Evolution exam, was wondering if anyone knew if there was a good detailed Colour Magnitude (HR) diagram on the internet which went into some detail of different Stellar Mass' and Chemical Compasitions (so more like a poster than a HR diagram)! If...
  16. H

    Evidence for stellar evolution since the Big Bang

    Is it generally true that the further away a galaxy is (and more red-shifted), the more it tends to contain lower metal content stars? I'd always assumed this was one of the main bits of evidence for the Big Bang, but I've also read that the globular clusters that surround (and are...
  17. nicksauce

    Stellar structure, stellar evolution, compact stars, etc. ?

    What are the best books (upper undergraduate / beginning graduate) for stellar structure, stellar evolution, compact stars, etc. ?
  18. V

    Superwind phase in stellar evolution

    why is there very rapid mass loss in the superwind phase. my notes simply say "because the envelope attains positive binding energy". Firstly, how can binding energy be positive by definition?! Secondly, I am not entirely sure what the lecturer is talking about? what makes the envelope...
  19. V

    Stellar Evolution: After Hydrogen Exhaustion

    why after hydrogen exhaustion (of low mass stars) does the the core become isothermal. (according to my notes) I mean, after exhaustion, its all helium, and it keeps on contracting right? So by the virial therem it must heat up (so by definition, it is NOT isothermal)! Indeed it must do so...
  20. Simfish

    Stellar Evolution: Pathways & Perturbations

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  21. V

    What colors represent different stages of a star's life cycle?

    Hello I am a student in high school and my physics teacher is a complete idiot. He just gave us a project to draw the life cycle of stars without even teaching the class. I am completely lost. Can someone help me draw the life cycle of stars that includes small: G-yellow K-orange...
  22. V

    What are the Detailed Steps and Mechanisms of Stellar Evolution?

    I am new to astronomy, though really interested in it Just read up on stellar evolution from multiple sources, but have some questions about it Let me summarize the theory of stellar evolution 1. gas clouds collapse due to multiple mechanisms, e.g. shock wave, collision of clouds... 2. the...
  23. N

    What Determines the Evolutionary Path of Stars?

    Hey, would anyone be able to tell me quality websites/ or help to answer the following questions: 1. What is a star? 2. How Astronomers can tell the difference between different stellar objects? 3. What powers a star? 4. The evelotionary path of a star and it's different stages. 5. Why...
  24. A

    Questions about stellar evolution

    Hello there! I'm developing a "4x" game a-la Master of Orion. I was coding some algorithms to help me generate a somewhat realistic galaxy. I'd like to know if it is possible to compute the time that a main sequence star will spend in its subgiant and giant status. For example, given the...
  25. Chronos

    The Mysteries of Stellar Evolution in Low Metallicity Environments

    Stellar evolution modeling is a science that, to put it charitably, plods along. Here is one of the more interesting papers I've seen in awhile: http://www.arxiv.org/abs/astro-ph/0601502 Stellar evolution of massive stars at very low metallicities
  26. Labguy

    Stellar Evolution: A Quick Overview of Star Types

    Seems that not much gets posted here lately. The link is to a simple chart that answers (in advance) some of the questions asked here. Note in particular the abundance label at the bottom of each class, with M Class stars being 80% ! See how few of the biggies (Class O, B and A) are either...