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.
Assuming the Sun’s core has a mass of 0.35 Msolar_mass and taking values for other quantities from a internet background search or from the following figures
(i.e.: Radius "solar core" = 0.25 Rsolar_radius ):
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Has anyone looked into the details of stellar orbital speeds and required (visible) mass distribution in the Milky Way?
Doing some math here - if the local mass density is significantly higher in the inner 10-15% of the galaxy, and then lower and gradually thinning outwards in the disk, we will...
Listen to the following arguments:
Earth's orbit isn't perfect ellipse because classically there is the gravitational field of moon and possibly of Mars and Venus which affect it
According to general relativity isn't perfect ellipse because there is the curvature of space time which doesn't...
Many years ago, for my high school senior project, I wrote a solver for the N-body problem that is performance-optimized using the Barnes-Hut algorithm. (the optimization algorithm is not relevant to my question.)
In one particular simulation, I simulated a spiral galaxy. The simulation is not...
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 -...
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...
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)...
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...
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...
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##...
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...
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...
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...
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...
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...
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...
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...
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...
(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...
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...
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...
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...
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.
$$1 - \Omega_{tot} = \Omega_κ = \frac{-κc^2}{R_0^2H_0^2} $$
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 ?
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...
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.
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...
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...
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...
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...
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...
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...
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...
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?
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...
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...
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?
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
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...
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...
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.
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...
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...
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...
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...
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...
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...
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...