Astrophysics Definition and 874 Threads

Astrophysics is a science that employs the methods and principles of physics in the study of astronomical objects and phenomena. Among the subjects studied are the Sun, other stars, galaxies, extrasolar planets, the interstellar medium and the cosmic microwave background. Emissions from these objects are examined across all parts of the electromagnetic spectrum, and the properties examined include luminosity, density, temperature, and chemical composition. Because astrophysics is a very broad subject, astrophysicists apply concepts and methods from many disciplines of physics, including classical mechanics, electromagnetism, statistical mechanics, thermodynamics, quantum mechanics, relativity, nuclear and particle physics, and atomic and molecular physics.
In practice, modern astronomical research often involves a substantial amount of work in the realms of theoretical and observational physics. Some areas of study for astrophysicists include their attempts to determine the properties of dark matter, dark energy, black holes, and other celestial bodies; and the origin and ultimate fate of the universe. Topics also studied by theoretical astrophysicists include Solar System formation and evolution; stellar dynamics and evolution; galaxy formation and evolution; magnetohydrodynamics; large-scale structure of matter in the universe; origin of cosmic rays; general relativity, special relativity, quantum and physical cosmology, including string cosmology and astroparticle physics.

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  1. A

    Programs Questions Regarding Undergrad REU Programs

    I'm in my 3rd year of undergrad currently, and trying to find an REU program to get into. This is my first time doing this, so I'm not sure the best approach? My college's physics society gave us a link to a REU site here...
  2. A

    Retired engineer - fascinated in cosmology and astrophysics

    I am working on a new theory of a potential alternative explanation for observed dark matter phenomena. Should be able to share soon.
  3. K

    Other Should I pursue a degree in physics?

    I am at a crossroads in my life. After graduating high school, I went into the ministry. I had no plans to continue my education, and I was content with my perfect little Christian-centered world. Eventually, my faith was shattered and I came to the realization that my entire worldview for the...
  4. Dorian Araya

    Admissions Do I have a REAL chance to study a MSc in astrophysics in Europe, USA?

    Good afternoon and peace to you, i am from Chile in a university that is NOT top 10 in my country and i currently in my last semester(ending in December) of bachelor degree in Astronomy and i want to study a MSc/Phd in physics or astrophysics in USA or Europe (preferably Germany) next year, the...
  5. T

    VERY amateur lover of Cosmology, Astrophysics, and Quantum Mechanics

    Loved Astronomy as a child but strictly personal amateur. My love has evolved to include Cosmology, Astrophysics, and Quantum Mechanics. Although I went up to and through first year of college basics Physics, Calculus, and two years of Chemistry, I have forgotten much of it.
  6. S

    I Question on halos of matter made from massive and stable particles?

    Consider a halo made up from massive and stable particles like neutrinos* (let's not consider protons which, although we don't have any experimental evidence showing that they are unstable and decaying, there are some GUTs proposing theoretical mechanisms where they could decay over extremely...
  7. S

    I Bose-Einstein and Fermionic condensates in space?

    Imagine we have a cold region of the universe, almost devoid of matter and radiation. Or perhaps in a future universe where the CMB has "cooled" down to sufficiently low "temperatures" Could there be long lived macroscopic Bose-Einstein and Fermionic states of matter there? Could matter...
  8. H

    Looking for a Career in Astrophysics?

    Hi, I am a new guy who has graduated with Master of Astrophysics. Looking for a career in Astrophysics and some insights here. Nice to meet you!
  9. warhammer

    Courses Course selection & study guidance for my Masters program

    I will be beginning my Masters degree in Astrophysics in the coming months. My thread deals with 2 aspects: 1. I have a mandatory CS course & want to request suggestions/recommendations on reference materials, textbooks, tutorials etc. on how to tackle it. For context, my programming skills &...
  10. g-r-a-e-m-e

    I think I might be bad at physics. I desperately want to get better.

    Hello! My name is Graeme and I'm pursuing a BS in Astrophysics. I have undergraduate degrees in business, economics, and analytics, and a Masters in business analytics. When I was nearing the completion of my MS, I rediscovered my love for science and enrolled in this BS program shortly after...
  11. mariahlorean

    How Can I Develop a Career in Astrophysics as a Physics Major?

    I’m a physics major (going to be a junior in the august) that would like to go into astrophysics!! I picked physics for a major bc i like knowing how things in our world work + i’m especially interested in space. I lowkey am just seeing where the wind blows me so I really don’t even have a fully...
  12. D

    I Online Christoffel Symbols Calculator

    I would love to hear from you if you have any suggestions, feedback, or criticism. The goal is to build better and more sophisticated software that would push the boundaries of research in astrophysics!
  13. S

    I Can there be structures made from neutrinos with angular momentum?

    Would it be possible to eventually have structures made from neutrinos somewhere in the universe, as it is indicated in this question (https://physics.stackexchange.com/questions/80390/are-neutrino-stars-theoretically-possible), like halos of neutrino gas surrounding the center of galaxies...
  14. M

    Hello Physics enthusiasts and nerds

    Short introduction. Greetings Physics community looking forward to discussing matter, literally. Intersts and expertise: Astrophysics/Helios Science, Nuclear and Particle Physics, Quantum Physics. Whish yall a great day.
  15. perlastudies

    Help please on essay about star formation

    TL;DR Summary: hi everyone! i am currently a junior in high school and I am writing a 3000-4000 word research paper on star life cycle and its role in the creation of celestial bodies. i have encountered an issue where I do not meet the word requirement because i am not exactly making a proper...
  16. fernandavbc

    Hello from Brazil!!

    Hello, everyone! I already follow a weather forum here in Brazil, but I'm also very interested in astrophysics and want to stay up-to-date with solar activity as much as possible.
  17. S

    I Is there an equivalent "redshift" for cosmic rays due to expansion?

    I've found this discussion (https://astronomy.stackexchange.com/questions/43525/is-there-an-equivalent-of-the-red-shift-effect-for-cosmic-rays) where it is said that there is an equivalent redshift of cosmic rays due to the cosmic expansion However, how can this be? Cosmic rays are not EM...
  18. Rageuke

    Need to derive a formula for the number of red giants

    My hypothesis: The number of red giants is equal to the number of stars times the given fraction f. The number of stars in a solid angle omega, is given by the density distribution of stars in the Galaxy times the volume of the observed solid angle: #RG = f*n(r)*V where V = (d^3*omega)/3. I...
  19. Somoth Ergai

    B New Paradox Discovered, I Think

    User New here but this conundrum is something that occurred to me as I was watching a physics video and I have run out of ways to ask about this. So here I am. Ok first principle. the setup. let's say we have invented a perfect telescope on earth. such that we can resolve any object no matter...
  20. N

    A Friedmann-Lemaitre-Robertson-Walker model

    I am a math student conducting a study on the stability analysis of the FLRW model using the Lyapunov direct function. To do that, I need to find the equilibrium points of FLRW and create a Lyapunov function to carry out the study. Do i find the equilibrium points by setting time derivatives to...
  21. S

    I The Evolution of Galactic Scale Cosmic Voids

    According to some papers I've found [1], [2] expanding voids can be found inside clouds of denser materials that can cause them to eventually collapse. I have a question about this: Overdensities generally expand up to a given turnaround radius and then collapse. However, as the elements in the...
  22. P

    Is Astrophysics Your Passion Too?

    Hi! I'm a student from korea. If there is anything wrong with my grammer, please kindly understand and if you can, answer my question! I like astrophysics. If you like it too, please try to chat with me. thank you.
  23. DaveC426913

    B What Does the Astro Physics Equation from Lewis Season 8 Episode 2 Mean?

    I know, I know, I'm committing the cardinal sin of putting any stock in the technobabble of a TV show, but this one seems egregious. Lewis (English WhoDunnit-in-Oxford on Britbox) Season 8 Episode 2 "The Lions of Nemea" had an astro physics professor who said this: "... and so we see that one...
  24. Sciencemaster

    I Observational Astronomy Project Ideas to Show Special Relativity

    This semester, I'm taking a class on Observational Astronomy which requires us to perform observations for a final project over the course of roughly a month (mid-March to Mid-april, although it could be a bit longer or shorter). As we get to choose the project, I'd like to take this opportunity...
  25. I

    B Questions about dark matter/energy

    Does the astrophysics community really think dark energy/matter is real, or that we just haven't figured out the actual physics of what is happening and this just makes it work out (to our current understanding).
  26. S

    I Avoiding structure collapse due to dark energy?

    I had a question about this paper (https://arxiv.org/abs/1401.3742) There, the authors indicate that dark energy competes against gravity in oversdensities and can slow down or even prevent their collapse. I have a simple question about this: Galaxies will in principle evaporate their outer...
  27. S

    I Dark energy and the kinematic Sunyaev-Zeldovich effect?

    I was reading this interesting article about possible effects of dark energy in the formation of large-scale structures which should have an impact on the Sunyaev-Zeldovich effect ("Dark energy imprints on the kinematic Sunyaev-Zel'dovich signal" (https://arxiv.org/abs/1309.1163))There, the...
  28. S

    I Dark Energy contribution to plasma temperature in galaxy clusters?

    I have a question about this work called "Dark energy and key physical parameters of clusters of galaxies"*There, towards the end, the authors talk about the isothermal velocities and tempreature parameters of the gas and particles circulating between galaxies in clusters. In particular they...
  29. Mahsum

    How to Approach a Term Project on Dark Matter Density Distribution?

    Hello, I have asked a similar question before, but this time I want to ask it a bit differently to be understood better. I am a physics student at a university and this semester I am going to make a term project about Dark Matter Density Distribution by using rotation curves. However, I am a...
  30. S

    I Tidal effects of galaxies orbiting one another with dark energy?

    I recently found a question in a physics discussion site [1] about whether there was a "distance" between two galaxies where both the gravitational force and the influence of dark energy would be balanced. The answers and comments seem to indicate that there is indeed such a "radius" around a...
  31. K

    How to Effectively Seek and Provide Homework Help in Engineering and Comp Sci?

    Hello, Im a student in astrophysics and space technology!
  32. AndreasC

    Astrophysics Up to date astrophysics and astronomy books for physicists

    With all the recent debates about CDM vs MOND etc, I decided I need some more background on astrophysics and phenomenology. I have the physics background, I prefer concise books even if they are harder. I was considering something like this for phenomenology...
  33. M

    I Inquiry Regarding the Determination of the Galactic Disk's Outer Bound

    I have recently read research papers that mention that disk stars have been found up to distances as far as 25 kpc from the milky way galactic center and possibly even up to distances as far as 31 kpc. I was wondering if there is a particular distance (or distance range) observed where the...
  34. S

    I Would there be any way to avoid gravitational wave emissions?

    In principle every object orbiting another (e.g. a planet revolving around a star) would emit gravitational waves, relaxing the orbit over time.However, this would not happen if the orbits had a time-invariant and symmetric quadrupole moment. As it is indicated in this question (), it appears...
  35. P

    What's Next for Physics?

    Just a thread to discuss ideas and questions of physics. I plan on becoming a theoretical physicist after I graduate, and feel that enriching discussions here will help further that cause.
  36. J

    I haven't studied physics for a while, and looking to get back into it

    I’m Jessica, a (nearly) 25 year old trans woman from the UK. I studied Physics and Astrophysics at university before dropping out. I dropped out for mental health reasons which were later diagnosed as Gender Dysphoria. After a few years away, I have now begun tutoring Physics to a friend in...
  37. C

    How can I become an astrophysicist? Welcome to PF!

    I want to become an astrophysicist and hope to learn a lot about physics from this forum.
  38. T

    I Star cluster in the Milky Way appears to be as old as the Universe

    https://www.sciencenews.org/article/star-cluster-milky-way-old-universe https://doi.org/10.48550/arXiv.2306.02180 Cheers, Tom
  39. FeatherGlow

    I Is Fluorescence Possible in Twilight?

    Earlier this year I saw what appeared to be a large glowing bird at twilight. The normal explanation for this is bioluminescent fungus contaminating a bird. I’m wondering if the effect might actually be a blue light effect where a fluorescent bird only appeared to glow because of the lighting...
  40. S

    I Thoughts on this article: The Universe Is More in Our Hands Than Ever Before

    https://www.theatlantic.com/science/archive/2023/01/astrophysics-fusion-experimentation-supernovas/672625
  41. A

    I Star with quadrupole in a binary system violates Newton's 3rd Law?

    Assume that, in a binary system, one (and only one) of the two stars has a non-zero quadrupole moment. Then the other star feels the usual gravity force $F_g$ plus an additional force $F_q$ coming from the quadrupole potential. On the other hand, the first star feels only the usual gravity force...
  42. DaveC426913

    B Has Earth Lost Its Status as a Planet?

    The International Astronomical Union (IAU) defined in August 2006 that, in the Solar System,[1] a planet is a celestial body that: is in orbit around the Sun, has sufficient mass to assume hydrostatic equilibrium (a nearly round shape), and has "cleared the neighbourhood" around its orbit...
  43. ZX.Liang

    I What are the conditions under which stars can radiate coherent light?

    Some papers mention the coherent radiation of stars, such as this one: https://iopscience.iop.org/article/10.1086/519790/pdf I want to know under what conditions can a star exhibit coherent radiation?
  44. 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...
  45. F

    Admissions Profile evaluation for astronomy Phd applicant in the fall 2023 cycle

    I will apply for a Ph.D. in Astronomy in the fall of 2023. I want to have a realistic evaluation of my profile to see if I am over-ambitious or not. I think I am out of reach for the "big four" universities. I will donate money to two of them only and will be targeting other top schools...
  46. RyanJ

    Astrophysics Book Around the Subjects of Supernovae and Stellar Remenants

    Hi all! It has been quite a while since I last posted here. Again. I'm currently interested in supernovae and the exotic stellar remnants that are left behind from such events. I'm interested in the physics and science surrounding this subject, it's something that I currently have an interest...
  47. warhammer

    Physics Are many Physics Students entering into Astrophysics?

    Maybe it is my present circle but I see a lot of students pursuing Astrophysics and related domains in terms of projects, Master's Degree etc. and I wonder what are the reasons for the same. Is the field extremely "hot" or is it just saturation caused by excessive Pop Sci influence? Full...
  48. waglebivu

    A To set up parameters for the sherpa tool

    How to set the parameters - photon index and metal abundance in the CIAO-sherpa tool for an x-ray source?
  49. tanaygupta2000

    Astrophysics research at ISRO in India?

    TL;DR Summary: Theoretical astrophysics research status in ISRO, India I am from India and want to be an astrophysicist serving my nation. Whenever I check about any ISRO news, it is always about some engineering achievements, like the launch vehicle and never about pure theoretical research...
  50. S

    I Expansion-Collapse cycle in cosmological structures?

    Concerning cosmological structures (like galaxies, clusters of galaxies, gas bodies, superclusters...etc) if the elements that make them are close enough they will be attracted towards each other by gravity. Contrarily, if they are sufficiently far apart they will get further away following the...
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