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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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1answer
115 views

Thought experiment about our location in the Universe [closed]

[I am sorry if this isn't the best place for this - it was either here or maybe on the Worldbuilding SE.] I recently re-read one of my favourite childhood sci-fi books (Chocky by John Wyndham), and ...
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1answer
126 views

Unidentified color changing object in sky [duplicate]

Yesterday, I was just star gazing and I noticed some star-like object moving with a high speed somewhere near the Orion's Belt and exhibiting all the seven colors i.e VIBGYOR and after a few moments, ...
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1answer
199 views

If the Universe is Flat, why does it look 3D from our View?

So I know that the universe is flat in a 4D point of view, but what about a 3D point of view? The universe does not SEEM flat from our view, so how can it really be so? Please answer more simple, im ...
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0answers
52 views

Modern Astrophysics [closed]

I was wondering whether it has proven whether the universe is expanding and if so, what is its ratio, one more question that whether it has an effect for the centrifugal forces, i.e gravity and the ...
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0answers
76 views

What is known about the angular momentum distribution within galaxy clusters?

I recently saw a 3D-plot of proper motions of galaxies within the Laniakea super-cluster (https://sketchfab.com/models/754cb85550fb42588175f8a215718521). Is a similar 3D map of the vector field of ...
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1answer
1k views

What is a stellar laser or stellaser? [closed]

I was watching the latest episode of Isaac Arthur and he was talking about a stellar laser or stellaser which was coined by a scientist named Steve Nixon. I can find no information about stellasers on ...
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2answers
758 views

If the Earth is rotating counter clockwise, how does the sun rise from east?

I was very confused when I watched this video from 2:18 till 2:45. And it seems very clear that if the Earth is really rotating from west to east, shouldn't be the Sun rising from west and setting in ...
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1answer
70 views

Is diffuse energy distribution considered in the galaxy rotation curve explanations?

Problem number 23 in chapter 1 of Purcell's "Electricity and Magnetism" Second edition page 37 shows that 90% of the energy stored in the electrostatic field of a spherical charge distribution of ...
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1answer
91 views

How do comets and other solar system bodies gain energy to exit the solar system?

I recently learnt that some comets like C/1980 E1 (Bowell) interacted with objects like gas giants in the solar system and gained enough energy to exit the solar system. But from Physics, I know that ...
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1answer
61 views

false to stable vacuum transition [closed]

if the universe transitioned from a meta-stable vacuum to a stable vacuum we assume a universal death scenario. However since it cannot propagate faster than the speed of light, from any particular ...
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2answers
3k views

Why doesn't the Earth's rotation throw us off the surface?

The Earth is spinning at about a thousand miles per hour. Shouldn't we be thrown from its surface? Yes I know someone would comment "gravity" but physically we should be thrown from Earths surface. ...
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1answer
146 views

Delay between neutrino pulse and visible flash of supernova

If you were orbiting a star undergoing a core-collapse supernova, what would be the delay between the neutrino pulse from the collapse and the first visible effects on the surface? Basically, I'm ...
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1answer
100 views

What happens to the momentum of a star as its mass is converted to energy? [closed]

Stars move relative to many frames of reference. We can use the CBR for this question, I suppose, but it may not matter. Their momentum p=mass x velocity. Stars lose mass as it is converted to ...
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2answers
441 views

Assume that a star has a uniform mass density. Then how does the temperature scale as a function of the distance to the center?

Assume that a star has a uniform mass density. Then how does the temperature scale as a function of the distance to the center? Note: I am not looking for an answer that involves derivations or ...
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1answer
1k views

How do you convert an observed magnitude to a flux? [duplicate]

For a series of supernovae I have the observed magnitude and I want to convert these values to flux. I understand that I need to apply: m - M_r = -2.5log_10(F/F_r) where M_r is a 'reference ...
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4answers
2k views

If I want to learn about astrophysics, should I study up on mathematics?

I am currently reading A Brief History of Time and while the book itself does not contain much mathematics in it, I want to learn more about the concepts Prof. Hawkings talks about more in-depth. Now ...
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1answer
344 views

Astrodynamic Canonical Units [closed]

Maybe this is more appropriate for the Physics or Maths, but anyway. I am struggling with applying Canonical units with formulas. I am struggling specifically with how they are used, am I to convert ...
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1answer
147 views

The consequences and the mechanisms of a shift of the Earth away from the sun

First premise: I have already made this question in the worldbuilding section, but since it is a very specific question many have recommended me to write in the astronomy section so here we are. ...
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1answer
233 views

What should I read next after Neil deGrasse Tysons “Astrophysics for people in a hurry”? [closed]

I really liked the clever way the author explained stuff in this book but I already understood most of it. Neil himself states in the book that if you are not in a hurry and want to know more about ...
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2answers
148 views

Why do stars born in cluster finally drive away from each other

In other words, if a group of stars born within the same nebula, e.g. Pleiads, are initially gravitationally bound - what causes them to finally get separated and proceed individually? Is it the ...
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2answers
613 views

What happens if a white dwarf collides with a star like our sun or a red dwarf?

Would it explode in a supernova or will it form a new star?
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0answers
36 views

Question about finding energy density of a fermionic-bosonic gas

We know that energy density is given by this formula: $$u = \frac{1}{V}\int_0^\infty\epsilon_pf(\epsilon_p) g_s V/h^3 4\pi p^2 dp$$ Where $\epsilon_p=pc$ for relativistic particles. also $f(\...
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1answer
96 views

What if a white dwarf is less massive than her partner?

For example: a system with a 0.2 solar mass white dwarf orbiting a 0.25 solar mass red dwarf. Does the red dwarf steals mass from the white dwarf or vice versa.
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1answer
124 views

calculate sunset in flight

I found an answer at https://physics.stackexchange.com/questions/26795/how-to-calculate-the-amount-of-night-time-during-a-flight but I was stuck at the part: $\cosθ_1=\sinφ_1\sinφ+\cosφ_1\cosφ\cos(...
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1answer
192 views

A simple question about Saha Equation

The Saha Equation: $$\frac{N_{i+1}}{N_{i}} = \frac{g_{i+1}}{g_{i}}\frac{g_e}{N_e h^3}(2 \pi m_{e} kT)^{3/2} \exp(- \chi_i / kT)$$ where $\chi_i$ is ionization potential. My problem is about the sign ...
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1answer
147 views

Primordial supermassive black holes. How old are they?

I know that astronomers have detected supermassive black holes in the early universe. What was the age of the universe at which these black holes were detected? In other words how long is it thought ...
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1answer
168 views

What is the condition for the number density of a gas to be ultra-relativistic or non-relativistic and degenerate or ideal

What is the condition for the number density ($n$) of a gas to be ultra-relativistic or non-relativistic and degenerate or ideal? I found problems in this subject when I was reading about White-...
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1answer
103 views

Gas giants and seismology

A long time ago I read a very interesting way of studying the sun's internal structure via sound waves. This new field of study, probability already known here, is called helioseismology. How much ...
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1answer
137 views

How do you determine the apparent magnitude of the stars leaving main sequence with CMD diagrams?

So I have a CMD diagram and on the left, I have apparent magnitude and at the bottom, I have the color index. I would just estimate the magnitude of stars leaving the main sequence and continue from ...
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1answer
219 views

How to know that the 21cm Hydrogen line is the actual emission and not any other redshifted line?

Is it possible that we mistake some other wavelength emission to be 21 cm because of redshift?
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2answers
99 views

Stuck with SDSS data [closed]

I want to do project on astronomical dataset. Regarding that project, I try SDSS who give public dataset but it is quite complicated for me. I gone through public dataset and downloaded some .FITS ...
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0answers
152 views

Why does the axial tilt & the rotation speed of Saturn & Jupiter vary so much?

I have seen Jupiter and its 4 largest moons in a telescope, several times. The moons are always aligned in a line. This is fine. Very interesting. But.. in case of Saturn, not only that we can see its ...
3
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1answer
470 views

How do tip tilt mirrors correct distortion in adaptive optics?

I'm currently trying to learn about how adaptive optics correct the blurriness caused by atmospherical seeing effects. This is my current understanding of how adaptive optics works (trying to offer ...
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1answer
1k views

What is the reason the Jovian planets are in descending order of size?

Is there any scientific reason for the jovian planets to be in descending order of size or is it purely coincidental? In terms of radii it goes Jupiter, Saturn, Uranus and Neptune.
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1answer
127 views

A question about calculating the radius of a comet

A Comet is orbiting around the sun with period of $T= 5.5$ years. The comet has radius $R$. After 5.5 years (A period) we understand that its radius has decreased about $20cm$. How can we calculate ...
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2answers
2k views

Why do certain moons have their rotational period equal to their orbital period?

Our moon and Saturn's moon, Titan, have this feature. Because of this we only observe one side (hemispere) of our moon. Why is this? What is the Newtonian or astrophysics that would explain this? ...
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1answer
493 views

Other than relative temperatures, is there any difference between a red sun and a yellow sun?

As time goes by, explanations for unusual things that exist in fiction get disproven. We know radiation probably isn't going to create a Giant ant that destroys everything, we're pretty sure we can't ...
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1answer
73 views

How should I find a telescope for research time?

I'm an undergrad in physics and astronomy deciding to look into applying for time on a research telescope, and I'm not sure how to proceed with locating/finding telescopes that I can apply for time on....
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1answer
88 views

Universe and black holes

I know that the radius of the observable universe is about 46.6 billion light years and is expanding at every instant of time due to dark energy . So is it possible that we our entire universe could ...
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1answer
99 views

Question about stellar remnants

I know that after a star undergoes the process of mass loss, depending on the mass of the core the stellar remnants gets converted into a white dwarf star, neutron star or a black hole. Hence, if the ...
3
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1answer
161 views

What are infall signatures in stars?

I came across several papers (e.g. Looking for outflow and infall signatures in high mass star forming regions P. D. Klaassen, L. Testi and H. Beuther, 2011) talking about infall signatures in star ...
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1answer
2k views

Why did the big bang produce a low entropy universe?

In order for the universe to be as it is, containing stars and galaxies, it is a requirement that the early universe was at a relatively low entropy state. Why did the big bang produce this low ...
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3answers
370 views

How do we calculate heat flow or cooling rate for no fusion brown dwarf star?

I was reading this article and it said something that didn't sit right with me. "SIMP0136 still gives off light mostly in the infrared wavelengths, as its temperature is now approximately 830° C (1,...
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1answer
149 views

Property of elliptical orbits

I've studied that the major axis of a planets orbit = ( radius of perihelion + radius of aphelion) . But then how can we calculate the value of the minor axis if we are provided with the values of ...
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2answers
116 views

Primordial angular momentum?

Angular momentum, and in particular the conservation of angular momentum, is of course very relevant in many processes in astrophysics, such as e.g. star- and planet formation, and disk formation in ...
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1answer
462 views

What does Eddington Limit (Eddington Luminosity) Show?

We know Eddington Limit (Eddington Luminosity) is calculated with this formula: $$L_{Ed} \approx 3 * 10^4 * L_{sun} * \frac{M}{M_{sun}}$$ Example: For a black hole with $10^4 M_{sun}$, we get $$L_{...
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1answer
145 views

What are IRAS sources?

Do IRAS sources refer to star forming regions? I searched google and I came to know that it stands for IR astronomical satellite.But what do they search for? Please help me
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1answer
541 views

Why can't we see the supermassive black holes supposedly at the center of galaxies?

Is gravitational lensing responsible for obscuring (figuratively) the supposed supermassive black holes at the center of our own and other galaxies? By "see" I mean relative to the measuring tools we ...
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0answers
66 views

How does one interpret the definition of “accretion” in galaxy formation?

I am having trouble finding a solidifying definition of accretion when it comes to galaxy formation models and galaxy evolutions. Where as, in the context of satellite galaxies, dwarf galaxies, or ...
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0answers
36 views

magnetic shield for spacecraft outside of Earths shield

I'd like to know if it's possible to create a strong enough onboard magnetic field, similar to Earths' that would protect deep space spacecrafts from the solar wind?