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. SoulOfSword_

    Astrophysics databases — Where can I find them?

    Hi guys, so I was trying to start my extended essay for IB physics in astrophysics and I came up with an idea of looking at how redshift changes based on different cosmological distances. However I can’t find any databases from NASA, esa, etc. is there anything you guys can suggest? Any help is...
  2. Arman777

    I Clarifying the Meaning of Radius of Curvature in Cosmology

    $$1 - \Omega_{tot} = \Omega_κ = \frac{-κc^2}{R_0^2H_0^2} $$ For ##\Omega_κ=-0.0438## we get a some value for ##R_0##. This ##R_0## is the radius of the observable universe right ? Not the universe ?
  3. Gumbrain

    I Help With Simple Orbital Modeling

    I have yet to decide on values for the mass of the fixed object, M, the mass of the moving celestial body, m, the initial velocity, v, and the distance between the two objects, r. I will most definitely decide on a larger mass M because I would like the celestial body to spiral in towards the...
  4. F

    Measuring the Transverse Velocity of a Galaxy

    See the attached figure. I understand that we look for the apparent transverse velocity v , for example through v = d/t (d - distance, t - time). The distance to the galactic nucleus is known as D. Though I am not sure how to read off the time from this figure.
  5. sully21

    Courses What is it like to work as an Astrophysicist or an Aerospace Engineer?

    Hi all. I'm currently an aerospace engineering undergraduate student in my second year, but I'm going through a very confusing process of second guessings and would greatly appreciate advice from older people who work in the Aerospace or in the Physics/Astronomy fields to help me compare the...
  6. hiddenname

    I Electricity & Planetary Magnetic Field Reversal: Implications & Studies

    What is/are the potential or theoretical effect on electricity due to reversal of planetary magnetic field? Would circuitry continue to function or would knowledge and understanding need re-evaluating as a result of a reversal of our magnetic field on planet Earth? Note: this is not a homework...
  7. Meruem

    B What is the black that we see in the night sky?

    Summary: Can black means many thing? The black we see in night sky has to mean many things First of all, from point of views of human eyes then the photons can't reach our eyes so it appears black. Secondly, the objects appear smaller as we go farther from that object. So, at some point object...
  8. abby11

    A Derive Radial Momentum Eq. in Kerr Geometry

    I am trying to derive the radial momentum equation in the equatorial Kerr geometry obtained from the equation $$ (P+\rho)u^\nu u^r_{;\nu}+(g^{r\nu}+u^ru^\nu)P_{,r}=0 \qquad $$. Expressing the first term in the equation as $$ (P+\rho)u^\nu u^r_{;\nu}=(P+\rho)u^r u^r_{;r} $$ I obtained the...
  9. K

    B Intensity of Spherical Shell of Stars

    Given that L is the luminosity of a single star and there are n stars evenly distributed throughout this thin spherical shell of radius r with thickness dr, what is the total intensity from this shell of stars? My calculations were as follows: Intensity is the power per unit area per steradian...
  10. K

    Setup for Spherical Astronomy Problem

    My apologies for not detailing my attempts at a solution; I'm not sure how to to digitally illustrate or describe the various setups I attempted before looking at the solution to this problem. I am also ONLY asking about the setup, though I included the full question for context. The solution to...
  11. K

    Mass Transfer in a Binary Star System

    Homework Statement: A binary star system consists of M1 and M2 separated by a distance D. M1 and M2 are revolving with an angular velocity w in circular orbits about their common center of mass. Mass is continuously being transferred from one star to the other. This transfer of mass causes...
  12. Andy1200

    Astrophysics: Calculating the circumference of an ellipse

    Substituting : a = (9.15x10^7 mi)+(9.45x10^7mi) = 1.86x10^8 mi b = ( a/2 ) = 9.3x10^7 mi For this, I used six terms and got : 1.075x10^9 miles Is my math wrong?;
  13. Astroian

    Aerospace to MSC in astrophysics?

    Summary: Master in astrophysics from aerospace science I am studying Aerospace Science and Technology and I always want to study theoretical physics and astrophysics. So, can I do a MSC in astrophysics or theoretical physics or must I learn more things about the subject to be ready? Is...
  14. 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?
  15. 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...
  16. 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...
  17. 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?
  18. 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...
  19. 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
  20. 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
  21. 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...
  22. 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...
  23. 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.
  24. 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...
  25. 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...
  26. mjda

    How to use the Bremsstrahlung flux to analyse a medium?

    I don't know where to even begin?
  27. 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...
  28. 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...
  29. 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...
  30. 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...
  31. 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...
  32. 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...
  33. 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...
  34. 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...
  35. 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...
  36. 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...
  37. 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...
  38. 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...
  39. 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.
  40. 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...
  41. 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...
  42. 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...
  43. 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?
  44. 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 =...
  45. 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...
  46. 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...
  47. 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?
  48. 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...
  49. 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...
  50. 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...
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