# All Questions

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### Based off of the study that found the universe has a positive curvature, how big would the whole universe be?

This study found that the universe has a positive curvature https://www.nature.com/articles/s41550-019-0906-9. I didn't really want to buy it and see if it says how big the universe might be. I know ...
27 views

### Corresponding BV Value to a Hertzsprung–Russell

I have an example BV value from an astronomical catalog of 1.04 (33 Psc, HD Catalog 28). Given only the number 1.04, can that be charted on the HR, or do I need the individual components of the value ...
136 views

### Why are telescope mirrors made of glass?

Optical telescope mirrors are typically made from endlessly polished glass surfaces that have been aluminised to provide a very smooth surface of reflective aluminium. But why the need for glass at ...
16 views

### Would a 1000 km telescope be able to resolve microscopic detail?

I have calculated that a 100m telescope can resolve 16m on the moon. Does that mean a 1000km telescope is 10000x better and can resolve 1.6 mm objects on the moon and even smaller closer? Or is there ...
74 views

### ra for sun vs stars

There is formula for stars sideral time: $$ra - \arccos(-\tan(dec)*\tan(lat)).$$ where $ra$ - is right of ascension at the vernal equinox. $lat$ = latitude $dec$ = declination Is it applicable ...
27 views

### Force exerted by space debris on satellites

Hypothetically, if space debris were to collide with the currently orbiting satellites, how much force would they exert, and how much damage would they make? Will the satellites be able to withstand ...
52 views

### Galaxy interactions

What causes galaxies to merge, rather than orbit indefinitely?
152 views

### Cosmological redshift vs doppler redshift

I'm reading Harrison's "Cosmology: Science of the universe" because Harrison focuses on the distinction between cosmological redshift (he calls it expansion redshift) and the Doppler redshift. He ...
38 views

### Gravity as a Fluid and Repulsive Force [on hold]

I have looked this up in depth including the work by Le sage and Fatio where they posited gravity as a repulsive force and based their calculations on gravity as particles in motion acting on ...
123 views

### What is wrong with this measurement of the synodic period of Mercury?

I'm measuring the synodic period of Mercury using Stellarium. When measuring the synodic period one needs to choose a reference point to start the measurement, and I choose the point when Mercury is ...
73 views

### Estimating a star's radius, temperature, and luminosity based on its mass

(See updated figure and description below.) I've been trying to generate ballpark estimates for the radius, temperature and luminosity of stars in the main sequence based solely on their masses (...
53 views

### Electron Degeneracy Pressure

The Z/A term for calculations of degeneracy pressure for white dwarfs is given as 0.5. But I can't find an explanation as to why. For my assignment, I am trying to find the degeneracy pressure for the ...
22 views

### Liberator 3 for fits format

How to set in Liberator 3 the reverse color scale? I would like to have stars black and the surroundings white. Or could you recommend me another program that has this ability?
126 views

### How do we know that vacuum is devoid of matter?

According to Wikipedia:- Vacuum is a state with no matter particles (hence the name), and no photons. I don't understand how can we find a part of space where there is no matter present?How is it ...
568 views

### Could planets explode in space?

Could a planet like the Earth or any other explode or be destroyed and did we see a planet explosion with Hubble?
28 views

### Finding the solar radius from temperature and luminosity

This question has eluded me for days; I can't seem to solve it. A certain star has a temperature twice that of the Sun and a luminosity 55 times greater than the solar value. What is its radius, in ...
3k views

### Official degrees of earth’s rotation per day

What is the official degree to one decimal point please, of the earth’s rotation in one single day. Can it be confirmed that it is exactly 360.0 degrees using official data? Thank you in advance.
46 views

### How much does the stellar radius change if seen through different filters?

I know that the radius of a star should be different depending on the filter being used to do the observation. That is, the bluer the filter, the smaller the measured stellar radius. I know this ...
119 views

### How to convert celestial Coordinates with a radius, to max and min celestial coordinates?

I am writing a piece of python code to convert right ascension and declination with a given radius to minimum and maximum right ascension and declination. I firstly can't understand why the min and ...
114 views

### Do gravitational waves really travel in “nothing”?

How does a Gravitational wave create ripple in the fabric of space, if space itself is an empty and it is made-up of nothing. Through out my academic life in school, I was told that space is made-up ...
51 views

### How to find the Orbital Period of two Binary Planets around a Single Star?

This is kind of a weird one. Bare with me! :) Background: (Skip to the math below if you just want to answer questions) In my favorite game, Elite: Dangerous, I "own", or occupy I guess, a system ...
36 views

### Element Abundance Related To Star Explosions

Sorry if this question is too basic, but as I learned about how supernovae are means of producing heavy elements I began to wonder "What would happen if stars didn't explode, i.e. undergo supernova"? ...
51 views

### Why is there “modulus” word in the “distance modulus” term?

The difference of apparent (m) and absolute (M) magnitudes of an object is called "distance modulus", which is related to the distance $d$ to the object in parsecs with equation m - M = 5 \log \Big(...
175 views

### Slow moving star like objects in the night sky

So yesterday at about 2am I was watching the sky when I saw a small star like object moving very slowly across the sky. My initial thought was that it was a satellite due to the fact it was moving so ...
2k views