# What is Astrnomy: Definition and 12 Discussions

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1. ### Need to derive a formula for the number of red giants

My hypothesis: The number of red giants is equal to the number of stars times the given fraction f. The number of stars in a solid angle omega, is given by the density distribution of stars in the Galaxy times the volume of the observed solid angle: #RG = f*n(r)*V where V = (d^3*omega)/3. I...

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3. ### Major in Physics or Physics/Astronomy for Grad School Cosmology?

Hello all! I have been taking an academic break from school for certain mental health reasons that I won't waste your time talking about. Now, I am only a freshman in college. My school's physics department currently offers 2 majors: Physics and Physics/Astronomy. Obviously, I have lots of time...
4. ### Decrease of Solar radius per year using Virial Theorem

Hello, I am trying to solve this question: Assume that the Sun's energy production doesn't happen by fusion processes, but is caused by a slow compression and that the radiated energy can be described by the Virial Theorem: $$L_G = - \frac{1}{2} \frac{GM^2}{R^2} \frac{dR}{dt}$$ How much must...
5. ### B Nervous about James Webb Space Telescope?

The Hubble Telescope helped us to see how enormous the universe really is. We now know from data built up from that that the universe likely has 2 trillion galaxies in it. Now when James Webb gets out their and starts taking better pictures; I’m afraid the count of galaxies will jump to 10 or...
6. ### English Word Differences: Exploring the Nuances of Similar Terms

How did you find PF?: Via a website link I want to know difference of the words in English
7. ### Astrophysics/Astronomy Extended Essay -- Trying to figure out a research topic

Homework Statement: Ideas for astrophysics EE Homework Equations: Extended essay Hi Guys! I'm trying to figure out a research topic in astrophysics/astronomy for my IB extended essay. I don't really know what to do, do any of you any ideas, maybe even off the top of your heads? It needs to...
8. ### What is the observed wavelength of the Hα line?

Homework Statement A star moves away from us at a speed of 10 km / s. the angle between the speed direction and the line of sight are 30 °. What is the observed wavelength of the Hα line? Then we suppose the observer is also moving at a speed of 20 km / away from the star. What is the observed...
9. ### I Too Much Dark Matter In CEG Mrk 1216

New observations of Compact Elliptical Galaxy Mrk 1216 show a very high apparently dark matter fraction based upon the intragalaxy dynamics of stars in the galaxy, relative to the baryonic mass of the galaxy inferred from typical mass to light ratios for galaxies of that type. The inferred...
10. ### Rayleigh's Criterion + Moon (What am I doing wrong?)

Homework Statement Suppose you wanted to be able to see astronauts on the moon. What is the smallest diameter of the objective lens required to resolve a 0.60 m object on the moon? Assme the wavelength of the light is near the middle of the visible spectrum: 550 nm yellow light. (in m) A...
11. ### Programs Maximizing Grad School Opportunities for Astrophysics After Military Service

Hello all, I am going to college this fall and I will be studying physics with a concentration on astrophysics, I am a pretty good student and afterwards I will serve 5 years in the Navy as an officer. My question is, will the 5 years I spend in the Navy hinder my chances of getting into top...
12. ### A This is the most active place in the universe

According to Source: They discover a mega cluster of 14 galaxies that originated only 1400 years after the Big Bang This is the most active place in this universe