What is Astrophysics: Definition and 861 Discussions

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. SJay16

    B What’s more “important": GR or QM?

    Let’s say to the average Astronomer conducting research; generalizing the research to “astronomy” ; which would be more useful for the “average” Astronomer on a day to day basis: Quantum Mechanics or General Relativity? Obviously most are, but which so more? Which would be referred to more?
  2. SJay16

    B How well should Astronomers know General Relativity?

    I know that it would vary depending on the type of research a specific astronomer would be doing ( Astrophysics/Cosmology research versus an Astronomer researching exoplanets ) ; but in your opinion, “how much” or “how well” should an Astronomer with a graduate degree in Astronomy know General...
  3. ChaseM

    Schools What are the best Colleges for Astrophysics?

    I just finished my Junior year in high school in Houston. I am currently pursuing a degree in Astrophysics. I have been looking at Rice and Cal-tech as my best options, but in case I can't make it into those school I am considering Texas A&M, University of Texas for being in state. As well as...
  4. E

    B Black holes and the first law of thermodynamics

    The first law of thermodynamics states that matter can only be transferred from one state to another, and cannot be truly destroyed. What happens to matter consumed by a black hole? What happens to it and where does it go? Does the first law still hold true?
  5. B

    Astrophysics question about a binary star system (AQA exam)

    https://pmt.physicsandmathstutor.com/download/Physics/A-level/Past-Papers/AQA-Old/Unit-5/June%202015%20MS%20-%20Unit%205-2A%20AQA%20Physics%20A-level.pdf mark scheme question 2 very simple question why is the change in wavlength not 656.05 - 656.52? instead. The difference being in the mark...
  6. B

    Astrophysics question: Wire mesh radio telescope antenna

    The answer says its 1 meter i don't understand how they arrived at this, The mark scheme suggests that the 50mm is the resolving power or Rayleigh criteria? https://downloads.umutech.net/Physics/Past_Papers/PA05/Astro/MS/physics_u5_astro_ms_jan_2003.pdf
  7. arcTomato

    How can we determine the distance to the Galactic center?

    Problem Statement: We can use "spectroscopic line shift of S2" and "its proper motion", but I don't have any idea what dose this sentences mean. please show me details! Relevant Equations: spectroscopic line shift
  8. astroman707

    Courses What undergrad topics do astronomy grad programs expect you to have taken?

    I was speaking with my prof about the requirements for the applied physics major track offered at my school, and she said some very surprising things. Just for context, I’m interested in pursuing observational astrophysics/astronomy in grad school later. She said that I can skip diff equations...
  9. koulbichok

    I Gaussian probability distribution of formation PBH

    Hello. If we consider PBH formation from collapse of large density perturbation in the early Universe, a mass PBH depends on density contrast as And δ must be larger then . Also we have β — an abundance of black holes, it's the ratio of the PBH energy density to the total energy density, this...
  10. koulbichok

    A Abundance and mass spectrum of PBH

    Hello. I'm trying to study primordial black holes for my work, but I still can't understand what are abundance and mass spectrum? Could you explain? Thanks in advance.
  11. haael

    A What does the image of the black hole say about general relativity?

    We all heard about the "photo of black hole". My question is: did this image show any hints of physics beyond general relativity? I read once (not sure where) that the apparent size of black hole shadow is very sensitive to corrections to general relativity. Add some minor correction and the...
  12. Alex Petrosyan

    Astrophysics vs Condensed Matter

    Hello everyone, I'm a Physics student on a gap year, doing a bit of work ATM. I'm going to come back in October this year to do a one-year Masters' at Cambridge, and I'm faced with a tough choice: A) Specialize in Astrophysics/cosmology, which is something that I'm not as good at, but really...
  13. mjda

    How to use the Bremsstrahlung flux to analyse a medium?

    I don't know where to even begin?
  14. mjda

    I The Confinement Radius of a Cosmic Ray (Galactic vs. Extra-galactic)

    If we want to show whether or not a specific Cosmic Ray particle is confined to our galaxy we must use the Larmor radius (relativistic version), r = γmc / qB Considering a 10^14 eV proton and assuming the galactic magnetic field strength is 10^−11 T, show that the particle is confined to the...
  15. astroman707

    Courses What undergrad electives should be taken when pursuing astrophysics?

    Hi, I go to a small liberal arts college and I'm majoring in physics. The college I attend has a VERY unique academic curriculum, with few required core courses, and one can have an oxford style tutorial in almost any area in physics, no matter how advanced. I want to pursue graduate school in...
  16. D

    Programs Diploma thesis - Neural Network Application in Physical Problems

    Hello everybody. I am currently on my last year of Computational Physics education. More and more I am interested in Machine Learning and Neural Network. Time has come for me to choose diploma work thesis, so I am searching for interesting ideas where I can merge my interest in neural networks...
  17. i_am_brendan

    Programs Recommendation for an online master's degree in astrophysics?

    Next year I'm considering an online masters in astrophysics / astronomy. Any recommendations / has anyone done one? Top universities in this field? I have a B.Sc and M.Sc in mathematics and strong background in computer science / data analytics so I want one which is technical. The options I...
  18. Zack K

    Other Best way to get research experience for astrophysics?

    I'm currently studying in a Canadian University(SFU). I've come to notice that the astronomy/physics portion here is lacking. There are a few astrophyics/cosmology research teams but they are small and encompass a few graduate students. I'm a first year, I really want to get involved in research...
  19. C

    Observing galaxies: area of sky would I need to survey

    Homework Statement Given that there are 10-2 Ellipticals per Mpc3 and my garden telescope can reach to 14 mag. How large an area of sky would I need to survey to find 100 Elliptical galaxies ? (assume the typical absolute magnitude for an Elliptical galaxy is -21 mag).Homework Equations...
  20. C

    About initial mass function and mean mass in stellar cluster

    Homework Statement Assuming a Salpeter IMF with upper and lower mass limits of 0.1 and 20 M⊙ respectively, calculate: (i) the mass point at which half the mass formed in a stellar cluster lies in more massive systems and half in less massive systems. ii) the mass point at which half the...
  21. S

    Admissions Applying to European PhD Programs with a US Masters

    I know this topic has been discussed a lot on this forum, but I had trouble finding an answer to my precise question. Current Understanding: I have read up on the differences between the US and European graduate systems. I understand US merges MS and PhD programs resulting in an average...
  22. Zack K

    Importance of uncertainty and probability in research papers

    As someone who is interested in astrophysics, I always get emphasized on the importance of knowing statistics and error analysis in results of a calculation. However when I read about real physics papers, I never see any numerical solutions, just equations that demonstrate phenomena. I know that...
  23. R

    Physics Should I switch to astrophysics?

    Like many of you, I have always enjoyed physics and math throughout high school. When applying to universities, I was quite unsure about my goals, so I applied to both engineering and science majors. I have always been deeply fascinated by astronomy, but I enjoyed environmental science as well...
  24. P

    A Notes on Cosmic rays - wave interactions in plasmas

    Dear community, I am Pedro de la Torre, now doing my PhD on Cosmic ray propagation. Now, I have started to study reacceleration due to interactions of CR with plasma waves. My problem is that I do not find neither a good book or any kind of review with a detailed demonstration on the...
  25. M

    On the convergence of the three body disturbing function

    For the three-body-disturbing function expanded in multipolar orders with respect to the ratio of the semi major axes, the function converges for small ratios, how to check the convergence for a certain set of parameters? I'm using the work of the Laskar in his paper "Explicit expansion of the...
  26. FourEyedRaven

    Relativity Raychaudhuri - General Relativity, Astrophysics, & Cosmology

    Hello. The book "General Relativity, Astrophysics, and Cosmology", by Raychaudhuri, et al., looks like a good compact exposition of GR, astrophysics and cosmology, which is exactly the kind of book I'm looking for. What do you think of this book? Thank you in advance.
  27. P

    A Is there any astro-field that uses QM or GR frequently?

    Hi all! Happy New year! I will select my supervisor soon but i want to involve in the field that uses QM or GR frequently I love physics and i want to apply physics to explain astrophysical phenomenon. I know that Compact objects and Astrochemistry use such physics but i wonder to know more...
  28. AlphaLibrae

    Programs How Do REUs Shape Future Astrophysicists?

    Hello everyone, I am currently applying for physics REUs. I am looking for people who would help me proofread my essay and criticize it as much as you'd like please. Beginning It was my junior year of high school when I first harbored an interest for physics above other subjects. When I first...
  29. JGHunter

    What makes a planet habitable?

    I am more of a budding (sorry) botanist / plant scientist, but I have an interest in astrophysics, how planets came to be the way they are and how this can help us understand what makes a habitable planet. I'm also starting something of a novel regarding a failing terraformed utopia. I won't...
  30. astroman707

    Programs Is a 2nd major in comp sci useful in computational physics?

    I'm majoring in physics and I'm planning on pursuing computational astrophysics in graduate school. Will a second major in computer science/programming look good to graduate schools, and/or will it give me great advantages in the field of computational astrophysics or astronomy?
  31. N

    How to find the minimum angular resolution?

    Homework Statement λ = 240 nm D = 2.40 m We are supposed to find the angle resolution (minimum angular distance between two objects so we still see them as two separate objects) to the telescope for ultraviolet light with wavelength 240 nm Homework Equations The equation that I used is θ =...
  32. V

    B IB Extended Essay in Astrophysics

    Hi everyone! I am currently in desperate need of help in choosing an appropriate topic for an extended essay in HL physics. (If you didn't know, an extended essay is a 4000 research paper where you analyze data, do experiments etc... for a particular topic of your choice) I am really interested...
  33. B

    Other Learning Astrophysics from home.

    I am interested in learning astrophysics and all the associated sciences and math, though I cannot afford schooling and am not nessecarily interested in a degree in the field. I have been interested in science fiction and the prospect of exo-planets and space travel for many years and would...
  34. astroman707

    Courses Academic Preparation for gravitational wave careers?

    If someone wanted to pursue a career in gravitational wave physics, and work at places like LIGO, studying astrophysical objects such as black holes and neutron stars, etc. What are some key courses/skills that person should take/learn as an undergraduate, and graduate student?
  35. astroman707

    I What areas of nano/optical research applies to astrophysics?

    I'm an undergraduate and there is a very good optical spectroscopy and nano-materials physics lab at my college. I have FULL access to all equipment and a professor in that field is offering me a ridiculous amount of co-research time during the school year. However, I'm really only interested...
  36. N

    Schools Realistic Graduate School Opportunities in Computational Astrophysics

    Hi, I'm a junior at a Ivy League (H/Y/P/C - going to remain anonymous for privacy reasons) and I wanted your honest opinion on what my chances are for graduate school in computational astrophysics and where I should look for the best chances. GPA: 3.5/4 (working to raise this, had a bad...
  37. astroman707

    Programs Difference between an astronomy and astrophysics PhD?

    Is there really much of a difference between an astronomy PhD and an astrophysics PhD? There seems to be a lot of overlap in the fields, and it seems that both can qualify you for many of the same careers, it just depends on the PhD focus. For an example, I'm very interested in almost all areas...
  38. F

    I Correlation between a Star's Luminosity and Distance?

    I made three charts from several different sources plotting the luminosity and distance from Earth of 26 to 300 Stars. In each chart, there appears to be a correlation between a star's luminosity (in solar units) and its distance from Earth (or solar system, whichever you prefer) in light years...
  39. P

    Studying Why is math in astrophysics said to be a lot easier?

    Is it due to the bolded section outlined here? "Astrophysics is the branch of astronomy that employs the principles of physics and chemistry "to ascertain the nature of the astronomical objects, rather than their positions or motions in space" One still calculates the evolution of a given...
  40. Neha98

    Programs Applied or pure physics major is best for an astronomy career?

    I'm willing to make postgraduate studies in astronomy or astrophysics so which major is more suitable for me applied or pure phyics?
  41. X

    Help with a simple exercise in astrophysics.

    <Moderator's note: Moved from a technical forum and thus no template.> So i began studying on my own for my astrophycis class that will start on 2 weeks and i have trouble solving an exercise. So the exercise goes as follows: given that mbol=-2.5log(∫fλdλ)+Cbol and mbol=-26.83 for sun. Show...
  42. StillLearningToronto

    Using a CCD camera to solve physics problems

    (Sorry for Length) 1. Homework Statement You have decided to use a CCD camera to check if a 16th magnitude quasar is variable. You can presume that all of the light of your quasar falls on one pixel. You know that a star with a magnitude of 0 would deliver 1 × 10^9 photons/second to one pixel...
  43. AlphaLibrae

    Subgiant lifespan Calculations

    Homework Statement Can you estimate how the time spend on the subgiant branch varies with mass? Quantify this by writing table displaying the lifespan of subgiants in years for a given initial solar mass (1 solar mass, 3, 5, 10, 25, 60). Homework Equations I was not provided a relevant...
  44. Astroiaco

    I Why Do Astrophysicists Use νLν in Accretion Disk Emission Studies?

    Why in Astrophysics it is used νLν (where ν is the frequency and Lν is the luminosity at that frequency) in the emission spectrum of an accretion disk?
  45. V

    Neural networks - uses in Physics and Astrophysics?

    Hello, I'm not very familiar with neural networks, but it seems very interesting. I would like to ask how may I use it in physics, especially in astrophysics? I guess for some data mining? But could anyone show some concrete example of what it can do with data? Or if there is anything else...
  46. J

    Physics What can I do with a degree(s) in astrophysics?

    Can I get a job as an engineer or as a researcher, other than astrophysicist, with a degree(s) in astrophysics?
  47. astroman707

    What math is used the most in cosmology/astrophysics?

    Considering one is taking all the required math courses for a typical physics degree, what math electives are most crucial to the field of cosmology/theoretical astrophysics? Also, is it true that mathematical modeling courses(discrete and dynamical modeling across physics) are more important to...
  48. Andrew Church

    I Composition of the Sun: How We Know via Spectral Absorption Lines

    The question “how do we know the composition of the sun” falls shorts everywhere I look. 1. There is the spectral absorption lines. Explanations given how that works, indicate how we know the elements, but fails to tell us how we know about the preponderance of Hydrogen and Helium...
  49. I

    Ideas for a Project In Astrophysics

    Hey guys, I just wanted to get a few ideas about an Astronomy or Astrophysics project. I am doing this project for the purpose of an Extended Essay in the IB Diploma Programme. For those of you who don't know what means, it is basically a 4000 word essay on a scientific investigation The thing...
  50. Luke Coughlin

    Other Undergrad searching for advice in an academic career

    I dream of getting a PhD someday and focussing on astrophysics. I would want to work near the west coast so I could take advantage of their clear night sky. I'm only about 45 credits into my undergrad and would appreciate any tips I could implement while moving forward in this career. Also, what...
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