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9 views

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 ...
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2answers
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 ...
6
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3answers
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 ...
2
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0answers
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 ...
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1answer
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 ...
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1answer
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 ...
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1answer
52 views

Galaxy interactions

What causes galaxies to merge, rather than orbit indefinitely?
5
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3answers
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 ...
-2
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0answers
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 ...
4
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3answers
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 ...
0
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1answer
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 (...
3
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1answer
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 ...
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0answers
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?
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3answers
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 ...
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2answers
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?
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1answer
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 ...
16
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4answers
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.
2
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1answer
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 ...
2
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2answers
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 ...
2
votes
1answer
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 ...
1
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1answer
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 ...
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0answers
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"? ...
4
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1answer
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(...
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2answers
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 ...
9
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3answers
2k views

How is time defined in astronomy?

I was amazed when my teacher told me that in space, time is define as a coordinate. It means we can define something with a four coordinate system with "negative time" $-t$ as easily as we can say $-...
2
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2answers
119 views

Can a dying, swelling, star be rejuvinated by enveloping orbiting gas giants?

Many hot jupiter type exoplanets have been found, orbiting near their parent stars. At the end of a stars life, they swell up and sometimes envelop closely orbiting bodies. Combine these effects and ...
13
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2answers
288 views

What percent of planets are in the position that they could be viewed edge-on from Earth? (and thus able to undergo transits)

Star number 12644769 from the Kepler Input Catalog was identified as an eclipsing binary with a 41-day period, from the detection of its mutual eclipses (9). Eclipses occur because the orbital ...
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2answers
150 views

If gaseous planets have solid core, can they theoretically be considered as rocky planets?

I read that gaseous planets such as Jupiter and Saturn, have a solid core deep inside. So, I wondered whats the difference between them and rocky planets apart from the fact that they have - what can ...
6
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1answer
554 views

What is the Age Difference Between Earth & Jupiter?

What is the age difference between Jupiter & Earth? Which planet was formed first, or were they formed at the same time?
2
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1answer
42 views

Jean Meeus - calculating moon rise, transit and set times - help isolating error in logic

I've been working my way through the Jean Meeus Astronomical Algorithms book for a few weeks, to implement some of the key algorithms for a personal project. This task has been a little more complex ...
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2answers
44 views

Angle formed between a satellite, a ground station, and then another Satellite

I am trying to check my work on calculating the angle between two sats and a ground station observing those two sats. I have the az and elevation angles to each sat from the ground station. What would ...
11
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3answers
325 views

Is it possible to see mercury transit “clearly” by the naked eye?

I don't have a telescope but I'm interested in seeing events like eclipses and transits. I'll use the atmosphere as my big natural lens. So I'll watch the upcoming mercury transit at the sunset time ...
4
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2answers
101 views

Neutron star size in different reference frames

What is the estimated size of neutron stars observed in their reference frame and in our reference frame? That is, how bent is space-time around neutron stars?
5
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1answer
69 views

Can we use Breakthrough Starshot spacecraft to detect any unknown massive object in our solar system?

For example, the hypothetical Planet Nine. Since we just want to prove or rule out the existence of Planet Nine in our solar system, we can avoid most of the technical challenges for StarChip (camera ...
6
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2answers
125 views

Could a star closely orbit a black hole long enough for the star to have lost 0.5B+ years to time dilation?

I was wondering how stable a close star-black hole system could plausibly be, and thus how much time a star could plausibly miss out on (from an outside observer's perspective) due to being in an ...
6
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0answers
81 views

How are the atomic clocks synchronised between worldwide VLBI telescopes?

I know that VLBI needs precise synchronised atomic clocks to calculate the baseline distance between the radio telescopes at cm level. But i cant´t find any information how the atomic clocks are kept ...
7
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2answers
688 views

Are there any galaxies visible in the night sky around the Orion constellation?

I'm writing a story for NaNoWriMo, and in it there is an extraterrestrial race whose home galaxy is visible from Earth. This home galaxy is visible (or even partially visible or barely visible) in the ...
5
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1answer
1k views

Calculating Angular Distance

Given the horizontal coordinates of two objects in the sky, how does one go about calculating the angular separation between them?
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0answers
14 views

Calculate rest flux density from emitted flux density derived from fits data of SDSS data tool

Say I have a spectrum of a galaxy at a redshift z, with flux density units of erg/s/cm^2/Angstrom. I'd like to convert flux density(in the same units) at z=0, i.e. at its rest it's rest emisison. How ...
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0answers
27 views

Why does the transit method work so well for planet hunting? [duplicate]

This may seem like a duplicate of A few questions regarding the transit of planets and Orbital plane evolution and planet discovery via transit method, but... How is it that we've been able to ...
15
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1answer
1k views

Time according to the gravity of Sagittarius A*?

This may be a really dumb question (I'm more of a Biologist than an Astronomer) so I apologize in advance for my little knowledge pertaining to Astronomy, but, if I'm not mistaken, time is effected by ...
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0answers
17 views

Acceptable errors in photometric measurements

As the title says, what is considered as an "acceptable" error in a photometric measurement (in magnitudes)? I know that it will depend a bit on the final use of the data, i.e., the photometric error ...
3
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2answers
47 views

How do I calculate B-V to make a Hertzsprung Russell diagram?

I am reading my textbooks and a few "Astro101" websites, but I cannot find a final answer to this: In the $B-V$ colour index that is plotted in an H-R diagram, are $B$ and $V$ the (observed) apparent ...
16
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3answers
1k views

Would a black hole evaporate via Hawking radiation before you fall past the event horizon?

It takes an infinite amount of time for something to fall past the event horizon of a black hole from the perspective of someone outside the event horizon. Black holes also evaporate after a finite ...
5
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2answers
246 views

In which direction does the ecliptic plane make an angle of 60 degrees with galactic plane?

In which direction does the ecliptic plane make an angle of 60 degrees with galactic plane? Is it toward the galactic center? (It can have any 360 degree orientation.)
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0answers
29 views

Whats the time dilation difference between the earths reference and (near) the milky way galaxy central black hole? [duplicate]

How much difference in time is there between our time of reference and very near the black hole at the center of our galaxy. I was trying to get answer in terms of something like "1 year in here ...
0
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1answer
118 views

Proxima as Supernova [closed]

Follow this question. Let's say Proxima Centauri explodes as a Supernova (I know, it CANNOT explode as supernova, let's say it can. I know, it should had exploded more than 4 years ago, let's assume ...
9
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4answers
1k views

Why black holes are extremely cold?

"The most massive black holes in the Universe, the supermassive black holes with millions of times the math [sic] of the Sun will have a temperature of 1.4 x $10^{-14}$ Kelvin. That's low. Almost ...
5
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2answers
628 views

How exactly will DESI simultaneously capture individual spectra from 5,000 galaxies using optical fibers?

The BBC News article Telescope tracks 35 million galaxies in Dark Energy hunt says: The aim of the five-year programme is to shed light on Dark Energy - the mysterious force thought to drive an ...
1
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2answers
115 views

Will it be dangerous when close stars become Red Giants?

What will happen if close stars like Sirius A or Procyon_A become red giants? Is it dangerous for the Earth and life on it? If for Sirius A we still have 500-800 million years, but Procyon A might ...

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