What is Astrophysics: Definition and 860 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. Mikkel

    Deep Learning for Image Recognition in Astrophysics

    Summary:: I'm looking for some great books on deep learning related to image recognition that I can use in astrophysics. Hello, I'm about to start my master thesis, where I, in short, will be comparing snapshots of young binary stars from simulations to observations using deep learning -...
  2. D

    Star Opacity and Balmer Break

    I am not sure where to start for this. Considering it needs to be demonstrate Balmer Break, I am assuming it needs to be wavelength based. As a result I am assuming I cannot use mean (Kramers) Opacity but rather express in terms of Opacity k= n*sigma/rho. My thoughts are to use Boltzmann...
  3. F

    A Cl's : sum into a chi^2 when we have a sum of chi^2

    1) If I take as definition of ##a_{lm}## following a normal distribution with mean equal to zero and ##C_\ell=\langle a_{lm}^2 \rangle=\text{Var}(a_{lm})##, and if I have a sum of ##\chi^2##, can I write the 2 lines below (We use ##\stackrel{d}{=}## to denote equality in distribution)...
  4. G

    Admissions (international) My chances of getting into top Astrophysics programs?

    Dear All. I am an international student who is planning to apply for the Ph.D. in astrophysics in the US in the coming application cycle. I am aiming for the top astrophysics school in the US. For the top, I mean CALTECH, Princeton, MIT, Columba, JHU, Cornell ... e.t.c. I would kindly ask for...
  5. Viii

    Troubleshooting Interplanetary Cruise Calculations

    Summary:: You have a spacecraft the size of a cube (2x2x2 m^3, m=3000 kg. It has 24 thrusters (2N each) and one main engine. For preparing your spacecraft for maneuvers, you want to rotate by 180 degrees. For the rotation, you'll use n=4 attitude thrusters per burn. What am I doing wrong...
  6. Mikkel

    Ultra high energy cosmic ray deflection angle causes by magnetic field

    I'm given an ultra-high energy cosmic ray with energy 10^20 eV. It is coming from a source 10 Mpc away with an extragalactic magnetic field with strength B = 10^-9 G. I am to determine the maximum angular deflection of this cosmic ray, so it hits Earth. I don't have an attempt of the solution...
  7. K

    Astrophysics Looking for an Advanced Introduction to Astrophysics text

    I'm a physicist familiar with QM, QFT and GR etc but I've never really sat down and learned astrophysics properly. Would Steven Weinberg's new book be considered a good advanced introduction or would people recommend another text. Half tempted to get it anyway to complete the Weinberg collection.
  8. F

    A Computing a variance in astrophysics context

    Below the error on photometric galaxy clustering under the form of covariance : $$ \Delta C_{i j}^{A B}(\ell)=\sqrt{\frac{2}{(2 \ell+1) f_{\mathrm{sky}} \Delta \ell}}\left[C_{i j}^{A B}(\ell)+N_{i j}^{A B}(\ell)\right] $$ where ##_{\text {sky }}## is the fraction of surveyed sky and ##A, B##...
  9. S

    Astrophysics Redshift Question

    I have attempted to link the equations, but I don't really understand how the data given fits. Does the angular radius get plugged in as the deflection angle?
  10. petha1

    Some homework questions in astrophysics (Kepler's Laws, Newton's Laws)

    1. Keplers third law (and the asumption that M1+M2 ~ M1) gives that M_Mars = 4*Pi^2*a^3/(G*T^2) With numerical values inserted Mmars = 4*3.14^2*(9400*1000+3396.97*1000)^3/((6.67*10^-11*(7*60*60+39*60)^2) 2. Phobos needs 7h39 minutes to complete a circle, this gives a speed of...
  11. V

    Programs Astrophysics or planetary science?

    Hi I am a computer science undergraduate working as a data scientist. I generally love studying physics and planetary science. I am aspiring to research in biomarkers and bio signatures in planets. If I have to choose this research path should I study masters in, astrophysics or...
  12. R0dr1go

    B Is the Universe Expanding Due to Spinning?

    Hello all, I recently did a thought experiment and thought, "what if the universe as a whole is spinning?" This could solve the dark energy problem, as if the universe was spinning, there would be outward pull, and therefore keep the universe expanding. And, I don't know if this means anything...
  13. N

    What topics in a Physics degree don't appear in an Astrophysics degree?

    Summary:: Looking for advice on what Physics topics, which may be dropped, to brush up on whilst studying an Astrophysics focussed degree I'm embarking on an part-time distance learning BSc in Astronomy at UCLAN. I was originally torn between this degree and the BSc Physics at the Open...
  14. A

    I Gravitational lensing: deriving magnification of lensed image

    In gravitational lensing, the image magnification is defined as the image area over the source area. But many texts also give it as the inverse of the determinant of the jacobian, A, of the of the lens equation. My question is how these are equivalent. The lens equation is...
  15. Mikkel

    Measure the distance to a star using magnitude and extinction

    Hello, I'm struggling with this question A star is observed close to the center of the Milky Way and from its spectrum we find that it is a type A3 star. Its observed magnitude is m_v = 25. There is only a diffusive gas between us and the star, so we can assume an extinction, of 1 magnitude per...
  16. M

    Astrophysics Looking for Books on Astronomy and Astrophysics

    What are some good textbooks for astronomy and astrophysics? I know of fundamental astronomy and the principles of astrophysics. I would prefer it if it were good for self-study. Also, are there any books that are free?
  17. koroshii

    I Acquiring a Small Dataset of a pulsar signal

    I am taking a class in signal processing. We have a final project in which we seek out "real-world" signal data and process and analyze it, and write a report on what we figured out. I thought it would be interesting to put my own interests into it and try to analyze a pulsar signal. My idea is...
  18. Q

    B Why is Carbon considered volatile?

    Carbon is considered volatile by planetary science, eg Moon lacks volatiles and thus lacks carbon. However volatiles are defined as "elements or substances with low boiling point", but Carbon boiling point is very high! Its sublimation point is 3900K, so it should be refractory and not volatile...
  19. Astronuc

    B Phys.org - Carbon creation finding set to rock astrophysics

    https://phys.org/news/2020-10-carbon-creation-astrophysics.html Back in 2016 - Recent results in nuclear astrophysics https://arxiv.org/abs/1605.07810 From the abstract -
  20. S

    Abour Riccardo Giacconi's opinion about the multiverse?

    Riccardo Giacconi (1931-2018) was an italian astrophysicist who was awarded with the Nobel prize in physics back in 2002 for his important contributions to astrophysics. Since he was an astrophysicist he must have heard about the multiverse hypothesis, but I have not found a single paper or...
  21. V

    Which course should I take? (General/Special Relativity or Astrophysics)

    I'm about to be a senior in the physics program. I can choose General/Special Relativity or Astrophysics. The astrophysics course is not as intensive - the GR/SR course requires mechanics and is more math-savvy. I've been doing some modeling with Lagrangian mechanics for star systems etc. and...
  22. A

    What are the Top Topics in Biology, Astrophysics, and Cosmology?

    hi! I'm not completely sure what I'm doing but my neighbor sent me this website so i can learn more about what I'm interested in. mostly, I'm interesting in learning about biology, astrophysics/cosmology, and the like. I'm super excited :p
  23. S

    Moving from Computer Science to a PhD in Computational Astrophysics

    Hi I am planning to do phd in computational astrophysics or planetary science or scientific computing simulation (least preferred in case i am not allowed to the other two). Right now I have bachelors in computer science and planning to do masters in the same. My query is should i join...
  24. Kayla Martin

    Optical depth using Bremsstahlung emission coefficient

    Equations I think may be relevant:
  25. TaurusSteve

    Best Place To Start Learning About in Astrophysics

    Summary:: Which area to best start learning about in Astrophysics. I'm 44 years old and when I was at school we only learned basic things in Maths. Now I'm older, I'm fascinated by the Universe and Astrophysics etc. What would be the best things/areas, maths wise, to learn about first?
  26. nikoladjal

    Other Topic for a Master's Degree in theoretical Astrophysics final project

    Hello all, I'm doing a Master's Degree in Theoretical Astrophysics and now I need to decide in which topic I will do my final project and I wanted to ask you what would be the best option. I would like to do something that would make me have some future in the investigational path I choose...
  27. screamindivr145

    I Asteroid Response Help: Get Answers to Your Questions Here

    (If anyone could provide links to information it would be greatly appreciated.) I'm currently taking a class on threats from outer space and have to write a paper on something that could be done in response to an asteroid/meteor coming towards Earth. One of the quickest responses would be to...
  28. S

    How to connect with a Astrophysics scientist from a reputed institute

    Summary:: Need an Astrophysicist from a reputed institute. Can anyone please help me with a Astrophysicist from a reputed institute. I have a paper to present...but don't know how to reachout to a scientist. I tried mailing a few scientists but they don't respond back. Please help. Regards...
  29. patrykh18

    Numerically simulating stellar pulsation using a "one zone" model

    The question is taken from An Introduction to Modern Astrophysics by Carroll and Ostlie. I did manage to do the entire question and plot the relevant graphs but I just want to to investigate a bit more. For example I want to look at how the graph would like in the case of the Sun. I don't know...
  30. S

    What can a person with a degree in astrophysics do in the aerospace sector?

    Hello everyone, I'm a graduated student in astrophysics in Italy. Unfortunately it has been very difficult to find a job that matches my educational background. I am very interested in space science and technology and I wanted to ask if there is anyone who can give me some information about what...
  31. Moises

    I The solar system and the Coriolis effect

    After concluding an investigation about the coriolis effect, I wondered how this phenomenon affected the solar system and in particular the moon. Since the moon is a body that moves within the rotating system formed by the sun and the earth, an apparent deviation in the moon's path would be...
  32. Moises

    What drives a scientist's pursuit of truth?

    I'm a man. The only thing that I think distinguishes me from the rest is that I am in love with the truth. The truth is very beautiful, that's why I pursue her and when I find her I do nothing but praise her beauty, I love her, I adore her and I am faithful to her. And she, in love with me...
  33. fissifizz

    Physics From Software Engineering to Astrophysics Grad School

    Greetings everyone. I am an undergrad currently majoring in Computer Science with a minor in Physics. I entered college as a physics student because I wanted to pursue astrophysics as a career. After my first 1.5 years of courses and a summer research experience, I concluded that a career in...
  34. J

    I Question on high speed astrophysics — when an object goes near of the speed of light

    I take the following example to explain my question : when a « black-hole » is attracting a planet there is a Force which is proportional to the 2 masses and inversely proportional to the distance between the 2 masses. When the planet moves towards the « black-hole » this attraction force...
  35. miafrasca_

    B High school Astrophysics Research Project Suggestions Please

    Hi, so I'm currently a senior high school student and I'm doing a research project on Astrophysics. I just need help on picking a topic as I know there is a lot out there. I need a project idea that is current but not too challenging as I am limited with resources. Thanks.
  36. Silveresquemania

    Studying Self-studying physics in preparation for learning astrophysics on my own

    I have the ultimate goal of self-studying astrophysics and cosmology just for personal interest and fulfillment. I've taken introductory mechanics and electromagnetism with some modern physics in university, but at the time, I slacked off and didn't really learn the material well. I am...
  37. 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...
  38. 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 ?
  39. 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...
  40. 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.
  41. 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...
  42. 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...
  43. 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...
  44. 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...
  45. 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...
  46. 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...
  47. 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...
  48. 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?;
  49. 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...
  50. 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?
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