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Questions tagged [astrophysics]

Questions involving the physics of the universe, especially the nature of astronomical objects, energy fields, and/or regions, rather than their positions or motions in space.

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What happens if I were to add angular momentum to a maximally spinning black hole? [duplicate]

I am aware that a "naked singularity" is not possible. However, what would happen if I added angular momentum to a black hole near the maximal angular momentum limit? Does it asymptote?
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0answers
64 views

Are Torsors useful mathematics for modeling Spiral Galaxies? [closed]

The local interstellar cloud seems to spiral into sunspots as time approaches positive and negative infinity - behavior I've always imagined representative of spiral galaxies. I am curious if any ...
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1answer
113 views

What is the farthest we can see into the universe?

Is there a limit in which the mass in space obscure the ability to detect anything farther even as technology progresses? Related: Can the range of the observable universe be extended through an ...
5
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1answer
76 views

Superscript-subscript uncertainty notation

While reading publications in astrophysics I've encountered this kind of notation (fictitious example): $$M = 6.1^{+0.6}_{-0.1} \times 10^{30} \textrm{ kg}.$$ Several examples are here, p. 2. I ...
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1answer
66 views

M87. What was the black hole before?

10 seconds before the M87 black hole was a black hole, what was it? A star 10 times the size of our solar system?
3
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1answer
29 views

Non-thermal Sunyaev-Zel'dovich effect

Exactly what is the non-thermal Sunyaev-Zel'dovich effect? From what I understand from reading several papers by Mark Birkinshaw and Sergio Colafrancesco, I get the rough idea that the non-thermal SZ ...
3
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3answers
40 views

Does coronal mass ejection include radiation at optical wavelengths?

It is known that during Solar/Stellar Flare, plasma from the corona of the star is released into the space, and travels comparatively slowly. In an hypothetical situation, does the coronal mass also ...
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2answers
92 views

Why does the Sun show different colour at midday and at morning?

As we see every day in the morning the sun shows a red-orange colour but at midday has a blue-white like colour why? Is it concerned with the distance from the earth or about intensity? How do you ...
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1answer
81 views

Did universe have finite hydrogen

According to this video stars at end of time and many others on fate of universe they all agree on one thing that stars will eventually convert all the hydrogen into heavier elements and eventually ...
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3answers
119 views

What orbit is the smallest or takes the least time to complete?

What orbit in our solar system would take the least time to perform 1 orbit? What is the fastest possible orbit to complete in the universe?
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3answers
113 views

Can't pulsars and stars be used for gravitational wave measurement?

Suppose that we collected photons from a distant star, and they arrive regularly at 15 photons every microsecond onto a CCD, when a gravity wave bends space time, wouldn't the regular 15 photons graph ...
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0answers
22 views

What could be observed with LOFAR in 230 MHz - 10.0 MHz wavelength?

Nuclear astrophysics greatly interests me and i was wondering if there is something that could be observed with the LOFAR project in this wavelength that would benefit the field? Also some general ...
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1answer
89 views

Can the Sun pull an iron asteriods in it's orbit into it? [closed]

Can our Sun's magnetic field strengthen in any way in a short period? Can the Sun pull anything trapped in close orbit around it? What would happen if an object in orbit passes over a sunspot for ...
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1answer
25 views

Vertical speed vector at which the sun travels to and from the galactic equator

What is the speed of progression of the sun toward and away from the galactic equator during its orbit?
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1answer
57 views

Is there any positive N on which it's agreed among astronomers that 10^-N is accepted as 0 (zero)? [closed]

Is there any positive N on which it's agreed among astronomers that 10^-N is accepted as, or treated as 0 (zero)? I think one of the sciences that most precision is required is astrophysics. I'm ...
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2answers
169 views

What is the solar system orientation to its direction of travel? [closed]

I saw the picture and seem incorrectly drawn. Its shows the the edge of the solar system leading facing the Heliosheath. It would not be like NASA to post something as incorrect as this. The solar ...
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0answers
20 views

Modeling Malmquist Bias [closed]

I am studying astrophysics on the side and came across this problem in the textbook: I am not quite sure how to approach it but I do know I need to account for the Malmquist bias to account for the ...
1
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1answer
80 views

When a rogue brown dwarf star hits a white dwarf star, will the collision at most cause a nova? [closed]

When a rogue brown dwarf star hits a white dwarf star, will the collision at most cause a nova? Or can the explosion be heavier?
2
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3answers
150 views

Is space a thing? [closed]

Based on my extent of knowledge relating to astrophysics, I once thought space is a thing, which can be twisted a long side with Time regarding masses of objects(According to relativity theory). But ...
2
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3answers
163 views

Do interstellar asteroids decelerate and eventually stop?

I do wonder, do interstellar asteroids eventually stop at one point in space after they gradually decelerate (or) even do they decelerate? Though there is no air like on earth and thus asteroids ...
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1answer
79 views

Are galaxies moving in each direction with same speed?

All galaxies are moving away from each other (us) because of the expansion of the universe. Are they moving with same speed in each direction?
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1answer
73 views

Mass of the universe

How do we calculate the mass of the universe taking into consideration dark matter? Mass of visible matter can be computed by stellar method, but how do we calculate mass of dark matter which we don'...
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1answer
30 views

Finding the diameter of a molecular cloud using period of intensity variation of hydroxyl maser

So I have this problem (which I translated to English as accurately as could): When studying a compact molecular cloud with radiotelescope, at a wavelength of 18 cm, hydroxyl (OH) maser(ic) ...
3
votes
2answers
79 views

nonagesimal in Kepler's parallax computation

I'm starting to learn Kepler's Astronomia Nova using William Donahue's translation . In the translator's introduction, it is demonstrated how Kepler did his parallax computation. I failed to ...
4
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1answer
52 views

Necessary steps to calculate photon's path by using null geodesic equation

Can anyone please give me an explanation on how to calculate photon's path by using the null geodesic equation? N.B. I know all of the non-zero values of Christoffel symbols.
5
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1answer
288 views

Is our universe stable or metastable?

I've been reading and thinking about this subject for some time, but I can't seem to find a clear answer. After reading Q14: Aspects of the Higgs boson suggest that our Universe is only “...
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3answers
157 views

Universe isn't infinite theory

Forgive me if any of my terminology is off I am no physicist but I have wondered about this question for a while. I have read in various books that if the universe was infinite, and uniformly created ...
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1answer
53 views

Is the structure of crystalized white dwarf related to nuclear pasta?

There is news of an analysis of a large number of nearby white dwarfs revealing a "pile-up" at a certain point in their cooling which has been predicted to happen due to a phase change where nuclear ...
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1answer
290 views

Why are blue stars the hottest? [duplicate]

I know that blue stars are the hottest and youngest (according to Universe Today). But what makes them blue, instead of other colors like purple?
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0answers
34 views

Strength of core-envelope coupling in stars

For a star with a given Zero-Age Main Sequence (ZAMS) mass, as a function of metallicity how strongly is the star's core coupled to its envelope? I understand that the core-envelope boundary is only (...
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0answers
37 views

Any ideas for an astronomy + ML project? [closed]

I wish to do an astronomy related project which incorporates machine learning.Do you have any suggestions?
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1answer
50 views

Largest non-hot gas giants

Excluding 'fluffy' or 'puffy' gas giants that are 'inflated by heat from their stars, what is the maximum radius of a gas giant planet. I keep reading things like "...Jupiter is 'about' as big as ...
4
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1answer
225 views

Warm jupiter vs hot jupiter, fluffyness

If Jupiter was orbiting at 1AU, replacing Earth, but everything else in the solar system remained as it is currently, how much would the increased heat from the sun increase Jupiter's radius? In ...
2
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0answers
49 views

What experiment does this “Tracing the History of Starlight” video try to explain?

The YouTube video Tracing the History of Starlight with NASA's Fermi Mission describes observation by the Fermi gamma ray telescope of EBL (extragalactic background light) gamma rays from 2,000 ...
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0answers
64 views

How to convert Log(g) vs T_eff to y vs (v-y)?

I have a plot in Log(g) vs T_eff coordinates from my stellar evolution model. The parameters of the model are M=0.8 M_solar, [Fe/H]=-1.19, Y=0.245. I want to convert it to the y vs (v-y) coordinates (...
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2answers
136 views

Calculating the sun’s position in ECI

I’m trying to calculate visible ISS passes and I need to calculate if the ISS is behind the earth by “drawing” a line between the ISS and the sun and seeing if it crosses earth. I have the ECI ...
2
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1answer
68 views

Distance to objects

When we read that, for instance, M31 is 2.54 ± 0.11 Mly (778 ± 33 kpc) away from us, does this distance estimate take into account the travel time of the light we observe? In other words, what is the "...
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1answer
62 views

Has “GHz-spinning dust” ever been demonstrated in the laboratory?

This excellent answer to the question What is the physics of the “spinning dust” contribution to Cosmic Microwave Background measurements? includes the figure below which helps show what it was the ...
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1answer
83 views

How would humans with appropriate equipment navigate the surface of Saturn's moon Titan on foot?

Taking into account the physical characteristics of Titan (e.g. surface gravity, atmospheric pressure), what would be the most efficient method of motion for an astronaut to navigate the surface of ...
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0answers
116 views

Total number density of galaxies and problematic expression in practise

This post comes from physics exchange forum, I have transfered it here, maybe I will be luckier since I have not received answers on the other forum. Here is the issue : I am asked to give the ...
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2answers
79 views

How to find the radius of a satellite not knowing the mass

If I know the semi-major axis, the density of the planet, and orbital period.. how can I find the radius of the satellite? I can't think of any formula to use.
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1answer
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What is the apparent magnitude of the weakest stars we can see in one telescope on the ground with a diameter of 2.4m? [duplicate]

All I know is its main mirror diameter; 2.40 m I also know that the eye, which its pupil is 5mm in diameter can see up to an apparent magnitude of 6. How can I calculate the apparent magnitude that ...
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1answer
597 views

How does gravity affect pressure under water?

How different would being under water in Europa differ from being under water on Earth? Would it be possible to dive deeper on Europa with a submarine than on Earth and by how much?
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2answers
368 views

What liquids can be found in the void space?

Is there any material natural or otherwise a free floating liquid that can exist in space? https://space.stackexchange.com/questions/32274/what-liquids-last-the-longest-in-space
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2answers
130 views

What is the minimum size to be a natural satellite?

Would a smaller satellite be more stable around a smaller planet where the same satellite would not be stable or last around a larger planet? I added the picture to show how moon size planets can ...
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1answer
98 views

How long will a ball of ice stay in orbit around Earth? [closed]

How big would a ball of frozen water need to be to last one orbit? How would atmospheric drag effect the ball of water? https://space.stackexchange.com/questions/32188/what-is-the-darkest-orbit-...
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2answers
115 views

How much of the Universe is subatomic? [closed]

How much does subatomic particles such as photons, tachyons, and electron being the biggest particles etc. occupy space? If put in a ball how big of a ball would that be?
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1answer
138 views

Estimates for “undetectable” planets in extra-solar systems

As far as I've been able to determine, it appears there are some significant limitations on our ability to detect exo-planets that are below certain sizes or beyond certain distances from their stars....
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1answer
101 views

What is the reason for magnetic braking?

What is the reason of Magnetic Braking in contact binary stars? Just dark spots? I mean hot spots can have this effect on binaries.
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25 views

How many fluorescent iron lines?

An iron atom has 26 electrons. Its 6.4 KeV line is a fluorescent line. There are 6.7 and 6.9 KeV lines also. How do they form? An electron from which energy level fills in which energy level? Is there ...