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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How does a neutron star collapse into a black hole?
We know the spectacular explosions of supernovae, that when massive enough, form black holes. The explosive emission of both electromagnetic radiation and massive amounts of matter is clearly ...
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How do scientists know that the distant parts of the universe obey the physical laws exactly as we observe around us?
How do scientists know that distant parts of the universe obey the physical laws exactly as we observe around us?
The question might look a bit odd but I am really stuck on my head. We know, ...
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What happens to the 99.9 % of the sun-rays that do not fall on any planets or any other celestial body?
I assume that about 99.9% of the sun-rays that do not fall on any planet or any other celestial body keep on traveling farther and farther unto infinity. Apparently such rays get lost. Keeping in mind ...
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Quantum Mechanics after the detection of Gravitational Waves
Of course everyone knows by now of the detection of Gravitational waves
But, since General Relativity and Quantum Mechanics don't get along, can we say now that this detection proves that Quantum ...
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Why don't (or can't) stars be more than 325 or so times the mass of the sun? What limits their size?
Is there a particular reason why stars cannot grow as massive as they want to?
And why doesn't this limit apply to supermassive black holes?
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Do these results mean that I have found this exoplanet?
Yesterday I was going through the TESS mission data on mast portal and after applying some filters I found some data. I started analyzing that data using the lightkurve library.
plot without using the ...
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How does the evolution of a solar system not break the second law of thermodynamics?
Please forgive: I am a layman when it comes to physics and cosmology, and have tried finding an answer to this that I can understand, with no luck.
As I understand it, the solar system evolved from a ...
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Why can't we feel the Earth's revolution?
I googled it and checked a few Q&A and there's only things about "Earth's rotation". But why can't we feel the revolution?
They say we can't feel the rotation because the Earth spins at a ...
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Why is the Moon's orbit so complicated?
I like to think I have a good enough understanding of astrophysics but there's still one thing that I just can't explain.
Why does the Moon orbit the Earth the way it does?
Many other moons in the ...
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Why does the sensitivity to GWs drops off inversely proportional to the distance?
This answer makes me wonder why the sensitivity to gravitational waves decreases proportionally to the distance.
Since gravitational waves extend in all directions, my (uneducated) guess would be ...
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What would happen to a polished marble statue left in space for a million years?
Consider it doesn't collide with any other objects. Would it be preserved perfectly in the vacuum or would its surface be damaged by anything like UV rays, radiation, gas, space dust, etc?
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Why doesn't dark matter clump strongly in the center of galaxies, since it doesn't feel either radiation pressure or the Pauli exclusion effect?
Dark matter is described as being spread not only throughout a galaxy, but also around it in a halo of some sort that extends far beyond the visible parts of the galaxy...
In fact, dark matter haloes ...
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Why are there no gamma-ray bursts detected in our galaxy?
I found from Wikipedia and other sites that there are no GRBs detected in the Milky Way. Can someone give a feasible reason for that? Why are there no GRBs detected in the Milky Way galaxy?
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Is it "weird" that all disc galaxies rotate once every billion years?
In a recent paper (Cosmic clocks: A Tight Radius - Velocity Relationship for
HI-Selected Galaxies by Meurer, et al.), it was noted in the conclusion that:
[This] implies a constant orbital time of ∼...
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If all stars rotate, why was there a theory developed that requires non-rotating stars?
According to Penrose's research, a non-rotating star would end up, after gravitational collapse, as a perfectly spherical black hole. However, every star in the universe has some kind of angular ...
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How can astronomers pinpoint the location of the source of a neutrino?
In the popular press, in recent months, we have heard a lot about high-energy neutrinos from far outside our solar system reaching our detectors....
But I wonder...
If a single neutrino from a great ...
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How does a gravity slingshot actually work?
From what I know of elliptical orbits, an object speeds up near the periapsis and slows down at the apoapsis, much like we learned in high school physics how a sphere would roll down and back up a ...
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Problem regarding the absorption lines of the Sun
Some of the wavelengths of light that are emitted from the Sun will be absorbed by atoms in the outer layer of the Sun and also the atmosphere of the Sun, and we see this as absorption lines in the ...
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How to be an astrophysicist?
For a high-school students, what are the ways to become an astrophysicist?
What should he/she take in college?
What is the career path to become an astrophysicist?
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Why isn't most hydrogen in the universe molecular (diatomic), instead of atomic (monoatomic)?
Similar questions have been asked before; but, why?
Is the monoatomic hydrogen left over from the Big Bang? And hasn't had the opportunity to collide with other hydrogen atoms yet?
Or are hydrogen ...
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Why do cosmologists assume that inflation began shortly after the Big Bang, rather than at the exact start?
Somehow, I have never come across an explanation of why cosmologists claim that the alleged inflation of the very early universe occurred not at the Big Bang, but very shortly afterwards (~10^-36 to ...
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Has anyone back-calculated previous close encounters between the Apophis asteroid and Earth?
The Apophis asteroid was only discovered in 2004, and shares an orbit similar to Earth's orbit, leading to many close encounters on the scale of decades.
Most of the stories about this asteroid are ...
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Open problems in astronomy that an amateur (with a PhD in some other field) would have a chance of solving?
What are some open problems in astronomy that an amateur would have a chance of solving? Suppose the amateur has a PhD in some other field, owns a basic telescope, a set of filters, diffraction ...
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Timescale of ignition of a protostar?
What is the timescale of start of nuclear fusion as T Tauri type star transforms into a Main Sequence star?
Wikipedia article on T Tauri type stars mentions:
Their central temperatures are too low ...
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How is the Hubble constant determined from gravitational waves?
We know there is a discrepancy between measurements of the Hubble constant, $H_0$. On one side there is the method of the Planck mission, where they use the CMB and the $\Lambda$CDM model to determine ...
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What causes the dimensions of a star increase when its hydrogen fuel is exhausted?
What causes the dimensions of a star increase when its hydrogen fuel is exhausted? For example, the Sun is expected to increase its radius 250 times. What causes this if its temperature is expected to ...
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Is it possible that a ultra-large portion of the space we live in is already inside a black hole? How could we refute this?
Trying to wrap my head around some concepts involving the very large gravitational fields of black holes, and what the gravitational gradients look like on a cosmic scale.
I'm familiar with the Great ...
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Is Dark Matter possible if there is dynamical friction?
If dark matter existed: wouldn't it slow down the orbital velocity of stars in galactic disks by dynamical friction more than it would accelerate them through additional mass? The original orbital ...
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Is there a possibility that a white dwarf can turn into a neutron star or a black hole?
I know that a white dwarf is supported mainly by electron degeneracy pressure and that if it gains more than about 1.4 solar masses from any source (such as a companion star or a collision), it ...
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Why did astronomers believe most or all stellar black holes had masses no greater than 15 solar masses?
The so-called 'mass gaps' for black holes, according to theoretical models, are between 2-5 solar masses and 50 to 150 solar masses. (Actually, I have read that there is no good theoretical reason ...
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Is any consensus forming on the solution to the "Lithium Problem"?
The "Lithium Problem" relates to the fact very-low-metallicity stars appear to have a Li/H ratio approximately one third of what would be expected. The ratio should be the same as the prediction from ...
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Why are the magnetic poles of a pulsar so far off the rotational axis, yet stable?
My understanding is that a pulsar is a neutron star whose magnetic poles don't coincide with the rotational poles and whose magnetic poles sweep through Earth (allowing us to hear radio noise).
If we ...
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Can earth grazers skip on the atmosphere more than once?
Earth grazing fireballs are asteroids that enter the atmosphere at a low angle, and skip off it, leaving to space again. Would it be possible that they skip more than once and still leave the ...
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Why is there no concavity in the orbit of the moon around the Sun?
Such questions have been asked here and I have read the answers some of which are quite informative. However, I want an answer that's straightforward.
I have gone through the following paper by A B ...
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How can a black hole have a charge, or be charged?
So-called 'hairless' black holes (no-hair theory, or theorem?) , which is what real black holes are, can be described by just three characteristics: Mass, spin, and charge.
It is easy enough to ...
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Can the energy transport by radiation occur in the convection region of a star?
I am new to stellar astrophysics and trying to understand the energy transports in the interior of stars.
Can the energy transport by radiation occur in the convection region of a star?
Here are my ...
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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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Is there anything currently 46 billion light years away from Earth that we can see?
If the oldest galaxy ever discovered, i.e GLASS-z13, is at a present proper distance of around 33 billion ly from Earth, why then do we define the observable universe to have a radius of around 46 ...
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Role of power laws in astronomy?
I often see astronomers fitting data to power laws. What about power laws makes them so useful in astronomy? Why are so many astronomical observations well-fit by power laws? I know it's a relation ...
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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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Is the Sun hotter today, in terms of absolute temperature (i.e., NOT total luminosity), than it was in the distant past?
I am constantly reading that the Sun is at least 20% 'hotter', in terms of total radiation/luminosity, than it was a few million years after its formation (i.e., after the Hayashi stage...)
But what ...
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What actually are line-driven winds?
I have read several books (viz. intro to stellar winds)/articles about stellar winds (dust-driven, line-driven, coronal winds), but still didn't understand the explanation. I understand that line-...
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Time of day of the K-Pg asteroid impact?
Is it possible to determine what daytime the Chicxulub impactor struck the Earth 66 Mya? Was it day or night, what was the current phase of the Moon, etc.? Can sediments, rhythmites or something else ...
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What do the acronyms in "AT 2017 gfo" mean?
About 11 hours after the detection of GW170817 by Ligo/Virgo and the quickly succeeding detected GRB170817, a transient afterglow in the optical-nIR frequency appeared which showed many signs of r-...
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How can the life time of a multiple star system, such as for example the trinary system PSR J0337+1715 be derived?
As for example explained at the beginning of this blog post, the trinary system consists of a millisecond pulsar ($1.438$ times the mass of the sun) orbited by two white dwarfs. One of the white ...
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How well conserved is etendue in extreme gravitational lensing scenarios?
This excellent answer to Could dark matter exist in the Universe in the form of sufficiently dense objects? includes the following image and description:
Light from the background galaxy circles a ...
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Gravitational Properties of Asteroids
How large would an asteroid have to be in order to hold a person so that the person could not escape?
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Would a tablespoon of a neutron star remain intact?
I've heard people say that a tablespoon of neutron star would weigh over a billion tons. If we ever could take a tablespoon of one would it still remain intact with the same density?
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Are liquids the rarest state of matter in the universe?
I was idly thinking what states of matter are common, which are rare overall. The commonest states of matter in the universe, by total mass, would be gases, solids (mostly as dust), and plasma (mostly ...
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Do the neutrons in neutron stars emit the radio waves?
Neutrons can, especially in extreme circumstances (and large concentrations) emit electromagnetic radiation. I specifically asked about this in Physics S.E. Has a free neutron ever been shown to ...
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