Astronomy Definition and 833 Threads

I am planning to teach a school astronomy group about energy. Most people seem to accept that there are two types: kinetic energy, resulting from movement; potential energy, resulting from position in a force field with a potential gradient (convertible to KE if the object is allowed to move...

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...

Paper: N. Hurley-Walker, X. Zhang et.al, A radio transient with unusually slow periodic emission (Nature, 26 January 2022) Abstract: The high-frequency radio sky is bursting with synchrotron transients from massive stellar explosions and accretion events, but the low-frequency radio sky has...

Just to keep this from being a long post: I went to a local CSU for Materials Science and Engineering in the fall of 2018 after graduating high school in the spring of 2018. I really like learning about everything that makes up the world around me, and why things are the way they are, and in...

An IQ of 120 is plenty good, but the average IQ of Physics and Astronomy majors is higher. It's even higher for brilliant theoretical physicists and Physics PhD holders. So is it possible, with enough hard work and dedication, that someone with a 120 IQ could become a theoretical physicist? Or...

Hi, I'm developing a C++ computer library with the formulas in the book "Practical Astronomy with your Calculator or Spreadsheet, 4th edition" but I have a problem with the formula 49, "Sunrise and sunset": I don't get the same results than in the book. I've been searching to find online...

So. It was late night, the limpid sky a near cloudless darkness, somewhat lightened by the waxing moon. I being somewhat stoned and looking at the stars and constellations as I sometimes do, and it came to seem to me, in my imagination, that In the spaces between the stars, I was observing (in...

Does anyone know when it was first realized that a heliocentric model of the cosmos should show the phases of Venus in the way Galileo saw them in the 17th century.?Was it known in the time of Aristarchus or did people only realize this was a consequence of helicoentrism later on, perhaps only...

Rovelli points to three pieces of existing observational evidence that should guide future quantum gravity research. Bottom line: * abandon Lorentz invariance violating quantum gravity theories, * abandon supergravity and string theory, and * stop working on the anti-deSitter/conformal field...

Hello! Searching for above mentioned books for my Bsc studies. Like his style and the quantum and electro books were very well written(in my opinion) and easy to navigate through, also liked the pre-explained math tools i need for the book. Tried Goldstein and Taylor books on mechanics but they...

There's a classic physics problem that is: If Earth is orbiting the Sun at 1 au from and is suddenly stopped. How long does it take to fall into the Sun (neglecting the size of the Sun/Earth)? I know that a clever way to solve this problem is by using degenerate ellipses and an object...

I applied for a couple of PhD positions in astronomy last year but was unsuccessful. This year I hope to improve on my application and secure a position. So with that in mind, does anyone have any exemplar PhD personal statements for astronomy, or maybe physics in general?

Hello PF! I hope I am posting this in the right place. I have an 'Electrical and Communication Engineering' Bachelor's degree and currently working in the same field since three years. I want to go back to school and earn a Master's degree. Ever since I was a kid, I loved astronomy, space...

It is a proposed method for relaying the light from multiple telescope, long baseline, interferometers. Some proposed hardware has passed the initial proof-of-concept stage. https://www.scientificamerican.com/article/quantum-astronomy-could-create-telescopes-hundreds-of-kilometers-wide/...

Hello everyone, I'm new to astronomy but have always loved space, planets and all. I would like to buy a telescope and start looking at the stars, but I don’t know anything about it. Can anyone recommend any link or other source where I can find any information on how to choose my first...

Does the limb-darkening curve fall off faster at shorter wavelengths or at longer wavelengths?

March 21 - October 21 = 7 months. So the star is only 15m 39,3 seconds behind the sun. This means that the star won't be up when the sun is down. Answer: No, the star will set only 15 minutes after the sun has set. Therefore it won't be on the sky at the specified latitude during dark hours...

I was reading that the mysterious reason why this channel was removed from public use is because it interfered with radio astronomy (the Wikipedia article didn't mention the reason). So what is going on at this frequency?

\begin{equation} \chi = n \sigma \end{equation} Where Chi is the Opacity, n is the number density of absorbers (constant), and $\sigma$ is the cross section(given). We define the optical depth is just the number of photon mean-free paths in a given physical step, i.e. if we consider a...

I am curious about space. How it works, what does it contain, all different sorts of things. Any suggestions on what books to read for a beginner so that this curiosity do not fade away with time.

Hi! I’m really struggling to solve the last part of this problem, from where it says “Idem for an infinite plane with the same brightness B. And the same for a square surface with side L.”. Could anyone please help or point me in the right direction? Thank you so much in advance!

Hi all, I wondered if anyone could advise me? I'm going to be partaking on an Astronomy degree next year and I'm wanted to get a head-start with Maths. I've only studied up to GCSE level; however, it's been a decade since I was at school. I have K.A.Stroud's Engineering Mathematics and I'm...

Here's the problem: It is more common to define the “effective number of relativistic degrees of freedom” by writing the total radiation energy as ρR = ργ + ρν + ρe± = (π^2/30) g∗*T^4 , where g∗ = 2 + 7/8(6 + 4) = 43/4 . (1.52) With this, the expansion rate during the radiation era is given by...

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?

It seems to me that Galileo and his successors benefitted from there being other bodies in the solar system other than the Earth and the Sun to prove that the Earth (and other bodies) orbited the Sun, and not the other way round. In an imagined solar system where the Earth has no moon, and...

Hello, I am graduating with a bachelor's degree in electrical engineering next July. I have been considering a move to astronomy/astrophysics. I read this thread by @ZapperZ and yes with a bit of revision, I can clear the Physics GRE. I also read a few testimonials of people who have made the...

As a boy (probably about 1959/60) I read a book on astronomy which among other things briefly discussed Pluto . The author noted that it had been discovered as a result of discrepancies in the orbital motions of Uranus and Neptune, but was far too small to be the cause of these. Among other...

I was wathcing a video about radial velocity method for seeking exoplanet(video) and on 3:05 author writes that momentum of a star equal momentum of a planet. Why?

Why is it that all of the planets in our solar system (to our knowledge) orbit the sun in such a way that they all go around the sun in roughly similar orbital planes? Why don’t we have planets with orbital planes at significantly different angles?

I am confused because the question implies that I need to do some sort of calculation with Kepler's law. I got ##r+d = \sqrt[3]{\frac{T^2 GM}{4 \pi^2} } ## But don't understand why I need this, since I already have the distance and the angular diameter should be ##\arctan (2R/d)## I think I...

Does anyone know the energy distribution of highly charged ions in solar wind or other astrophysical context?

Is it anything to do with the equation being independent of mass etc.. of the star? or to do with the Pauli exclusion principle? Any help will be much appreciated.

What is column density in astronomy?

Hello, this crisis has given me a new perspective. I was a Physics and Math undergrad in 1996 when i left uni to work as a C programmer. A mistake i have regretted often, but i had small kids and a wife that needed to eat. I have since earned a BA in Economics and am writing a masters thesis...

Equations I think may be relevant:

Assuming that this sphere has a radius of 50kpc, I've converted to m (1.543e21) and plugged into the area equation for a total area of 2.992e43 m^2. From here I've talked myself into circles, and I honestly don't know where to go next. Any help or guidance would be greatly appreciated!

Hi all: I am looking for an astronomy textbook that is a bit above the level of most textbooks used in intro level astronomy courses but also not too advanced. I would really like a book that focuses on observational astronomy. If its available to be downloaded for free as a PDF that would...

My best guess right now is use Newton's version of Kepler's 3rd Law to maybe find a combined mass, as I'm under the impression that the smaller star's mass would still be too large to ignore, but I'm not confident. And I wouldn't be sure as where t go from their, either. Any guidance would be...

Hello. I am a filmmaker writing a screenplay and I am in need of technical support to validate a method being used in the film. I am going to post this in the Earth Science forum but I'll copy it here, in case anyone reading this might know. Thank you all! "I am wondering if shadows cast...

Hi! I have read that cometary nuclei have a very low albedo, even lower than coal or asphalt. Because of this, they absorb lots of light and heat rather than reflecting them. So I was wondering how hard is it to detect extinct comets. Could the solar system be full of dead nuclei buzzing around...

Let´s suppose we are observing the sun and measuring some spectral lines. Does the velocity correction´s formula for the Earth include the rotational velocity components of the Sun as well? or rather are we basically measuring both velocity contributes of Earth and of Sun together (receeding...

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...

I know this question doesn’t really make sense but the absurd enormity of the universe always made my head hurt. A single galaxy alone has more then enough stars to satisfy the curiosity of any sentient being. Why 2 trillion? It’s just insane. Why did nature have to create so many? The spaces...

At the risk of sounding stupid, this question has always perplexed me. Einstein theorized that mass can not travel faster than the speed of light. I don't really understand it, I assume it has something to do with mass just being energy. Anyway imagine two objects in orbit of something with...

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...

Hello! I'm a senior in high school and I plan on getting a bachelors in computer engineering. I want to minor is astronomy (or double major although I heard engineering is very demanding so I would prefer to minor astronomy). When I complete the four years, and if I realize that I want to be an...

I’ve read that Urban LeVerrier was able to calculate using Newtonian mechanics the precession of the perihelion point of Mercury’s orbit (1859). Is there a website or paper that shows the calculation in detail? In particular: How would one decide on the distance between Mercury and the other...

Hello, I am Harshil from india. I have completed my Bachelor's in electrical and now i want to do Master's in Astronomy, so i have few questions please answre it... 1) Can i get the admission in MS/Msc astronomy if i have done electrical engineering? 2) If the answer of first question is...

I first determined ##E_{U - B}## by using the second equation listed above: $$U - B = (U - B)_0 + E_{U - B}$$ $$8.15 - 8.50 = -0.45 + E_{U - B}$$ Then since the ratio to the B-V color excess is known, I solved for that and obtained ##E_{B - V} = 0.14##. Using the ratio of total to selective...