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.

Filter by
Sorted by
Tagged with
7
votes
2answers
2k views

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 ...
1
vote
1answer
49 views

Is there a formula to calculate any star mass from Luminosity, Radius, and/or Temperature (K)?

I know there is the Mass-Luminosity relationship, but I am wondering if there is a more accurate formula I can use based on the data points I have generated: Absolute Magnitude (based on class and ...
0
votes
1answer
91 views

Keplerian Elements

So, I've been doing endless research, and I've found a bit of information, all in different places, that is. Now, I'm getting really confused about it; I can't keep up with it all anymore, so, now, it'...
1
vote
0answers
35 views

Is there software to calculate/plot decomposed rotation curves from observational data (FITS, etc)? [closed]

I have observation data of galaxies (in FITS format). From the FITS data, I want to calculate & plot the decomposed rotation curves as pictured below. Is there a software package that will do that ...
3
votes
2answers
63 views

How massive does a moon have to be to have a stable magnetic field?

Is there a minimum mass or other minimum properties necessary for a body to have a strong, stable dynamo to create a magnetic field conducive for life? For example, would it be possible for Titan to ...
12
votes
2answers
2k views

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 ...
1
vote
1answer
85 views

What are detached black holes?

I understand what black holes are, and how they form, but I was recently introduced to the topic of detached black holes. What are they and how are they different from standard black holes?
11
votes
1answer
293 views

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 ...
1
vote
1answer
54 views

Has lunar opposition surge ever been observed from Earth? From Earth orbit?

This thorough answer to How long does lunar opposition surge last? Are there measurements of the full Moon getting suddenly brighter? details observations of lunar opposition surge by the Clementine ...
0
votes
0answers
41 views

Is there any theory suggesting the expanding universe may be coupled to another shrinking universe

Our Universe is supposed to be expanding. I was curious if there was any theory suggesting the expanding universe may be coupled to another shrinking universe?
5
votes
1answer
132 views

How long does lunar opposition surge last? Are there measurements of the full Moon getting suddenly brighter?

Wikipedia's opposition surge is a short article and forwards shadow hiding and coherent backscattering as proposed mechanisms, but it doesn't really explain how much the brightness of the Moon ...
16
votes
3answers
2k views

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 ...
1
vote
0answers
70 views

How do we know that spacetime is fabric? [closed]

I have started learning about astronomy as it amazes and inspires me. I have a question. What led us to believe that spacetime is fabric? What is the evidence shows this, and is it considered proven? ...
1
vote
0answers
16 views

Spectrograph Arrangement, Noise, and Fourier Domain [closed]

If the transform of a line profile extends out to the Nyquist frequency such that we cannot see the noise level, what could we change in our spectrograph arrangement that would allow us to see the ...
18
votes
2answers
2k views

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 ...
3
votes
1answer
37 views

How much does the equivalent width of a line change by the introduction of 5% scattered light?

How much does the equivalent width of a line change by the introduction of 5% scattered light? We know the equivalent width is defined as $W = \int_{-\infty}^{\infty} \bigg(\frac{1-F_{\nu}}{F_c}\bigg) ...
3
votes
0answers
47 views

Why are CMB peak heights sensitive to the physical densities

A very simple question: why should it be that the CMB power spectrum allows constraints to be placed on the combination of parameters $$\omega_c = \Omega_c h^2$$ $$\omega_b = \Omega_b h^2$$ as opposed ...
0
votes
0answers
19 views

What is sonic transition of an astrophysical fluid?

My notes mention sonic transition of a fluid. Is it where the speed of the fluid elements cross the speed of sound in the medium they are located?
0
votes
0answers
22 views

How to calculate the luminosity of a quasar?

Is there a relation between the distance ($d$) and the apparent bolometric magnitude ($m_{bol}$) of a quasar and its luminosity ($L$) in watt? If so, what is that relation? Thanks in advance!
3
votes
0answers
100 views

What are some challenging astrophysics problems for which we have data available? [closed]

I am a Computer Science student, and I would like to pursue a PhD in the same area, by applying artificial intelligence techniques to astrophysics. Not being an astrophysicist, however, I was curious ...
1
vote
2answers
90 views

How should I interpret this result obtained using lomb scargle?

I used lomb scargle for periodic analysis. The time interval used is constant at 500 seconds. #My data (x=time, y=intensity values) is : x= ( 00:28, 00:37, 00:45, 00:53, 01:02, 01:10, 01:19, 01:27, ...
6
votes
1answer
72 views

Why do M dwarfs emit more X-ray radiation than larger, more luminous stars?

I have read that "The relative amount of harmful radiation (to life as we know it) that stars emit can be 80 to 500 times more intense for M dwarfs relative to our Sun". Source This seems ...
4
votes
1answer
74 views

How do higher numbers affect orbital resonance?

When talking about orbital resonance, the most common resonances in our Solar System are 1:2 (think Jupiter's moons) and 2:3 (think Pluto and Neptune). However, the lack of larger numbers within these ...
4
votes
1answer
64 views

Why do massive rapid-rotating stars move bluewards off the zero-age main sequence (ZAMS)?

I'm reading a well-cited paper by Szecsi et al. 2015 titled "Low-metallicity massive single stars with rotation". The paper can be found here. I was surprised that figure 5 depicted an HRD ...
1
vote
2answers
59 views

Is it correct to say that only binary and solitary star systems are stable?

Recently it has been shown that a large number of binary stellar systems exist. It seems to me that the orbits of stars in systems containing three or more stars will inevitably be chaotic, resulting ...
1
vote
2answers
116 views

Is there a formula to calculate the angular speed at which the Sun apparently moves around the Earth?

Is there a formula for how to calculate the angular rate at which the Sun apparently moves around the Earth? I know it takes 0.25 degrees/min, but as I understand it depends on other parameters as ...
1
vote
0answers
51 views

Pulsar signal periodicity detection algorithms?

I am currently working on pulsar signal periodicity detection. Most of the algorithm or paper which i read they use FFT (Fast Fourier Transform) and FFA (Fast Folding Algorithm ). Do we have any other ...
5
votes
1answer
53 views

How can astrophysicists discriminate between pp-chain solar neutrinos and CNO-cycle ones?

Astrophysicists at the Borexino experiment in Italy have recently claimed that they have detected CNO-cycle neutrinos coming from the Sun. It was the Cover story for the November 26 issue of Nature. I ...
2
votes
0answers
25 views

Anatomy of a galaxy cluster: understanding the relationship between dark matter halos and subhalos and galaxies within the clusters?

In my understanding, galaxy clusters contain dark matter halos, which in turn contain subhalos, and the subhalos are what surrounds individual galaxies. I know that is a simplified picture, but I am ...
3
votes
3answers
111 views

Why don't black holes quickly eat up the galaxy/universe?

It's my understanding that the radius of the event horizon of a black hole is proportional to it's mass. Which means the surface area of a black hole is proportional to it's mass squared. Lets just ...
1
vote
0answers
21 views

What is the mean distance of M53 Nucleus' stars ? (and other Globular Clusters) [duplicate]

Background: This Instagram post (from astronomypicturesdaily) tells that: If our Sun were part of this star cluster, the night sky would glow like a jewel box of bright stars. I opened this question ...
3
votes
1answer
49 views

Eccentricity of Exoplanets

The field of astrobiology specifically discovering other planets that revolve around the sun-like star (also known as Exoplanets) has risen since 1990, but certain orbits of exoplanets are observed to ...
0
votes
1answer
104 views

How to Interpret Lomb Scargle periodogram

lomb scargle periodogram: ...
2
votes
1answer
80 views

Radial Velocity Graph and Rossiter Mclaughlin Effect

I am trying to understand the effect of the Rossiter–McLaughlin effect on radial velocity plots. Can someone help me and explain what exactly is happening in the red circle?
3
votes
2answers
219 views

Earth and moon gravitational ratios and proportionalities

This question is for an astronomy class of mine. I don't believe the question is particularly difficult, but rather I'm having trouble understanding what it wants me to do. We haven't covered ratios ...
5
votes
0answers
51 views

What are some good books/online resources for astronomy problem sets?

I am currently studying for the international olympiad for astronomy and astrophysics (the syllabus can be found here: https://www.ioaastrophysics.org/syllabus/). I am currently using Carroll Ostlie's ...
3
votes
1answer
64 views

How do we differentiate between a star or planet and noise introduced due to equipment?

I understand that differentiating between celestial bodies and noise due to equipment is a fundamental problem in astronomy. I also understand that we solve this problem by looking at something called ...
0
votes
0answers
17 views

How to conceptualize the strong equivalence principle (SEP) in the context of stellar motion in an extragalactic galaxy?

In the theory of general relativity, the SEP states all the laws of nature are the same in a uniform static gravitational field and the equivalent accelerated reference frame. I've been reading the ...
3
votes
2answers
176 views

Is the age of the Universe really 13.8 billion years?

Ok, I know this has been asked by a lot of people, but my reason for asking this question is a bit different. Please read further. I was watching a video by Fermilab (Start at 6:30, at 8:30 he ...
3
votes
1answer
47 views

Comparing Star Formation rate in different galaxies

I was looking for some scale to compare my result of star formation rate in order to find out whether it is moderate or high or low, but I couldn't find any scale. Is there any paper related to such ...
6
votes
2answers
156 views

The creation of comets

How are comet and meteors made, and what causes them to travel through space so fast? I have tried researching, but I decided this was the faster way.
1
vote
1answer
114 views

How to find the distance between two galaxies from ra and dec and redshift [duplicate]

I have ra and dec and corresponding redshift of galaxies. I would like to calculate the distance between two galaxies. I did like this to find the nearest neighbour galaxies. Suppose I am trying to ...
3
votes
1answer
85 views

Type II supernovae as a distance indicator

Could someone explain in brief exactly how type II supernovae could be used as distance indicators? as in simply the formulae used and how they are employed? I know there are certain methods based on ...
2
votes
1answer
318 views

What if a primordial black hole went through the Sun?

How much mass would the Sun lose to a primordial black hole that (initially) has 10 Earth masses, passing through or close to the center of the Sun at solar escape velocity? How massive would the Sun ...
1
vote
1answer
43 views

redshift in astrophysical plots [closed]

Why do astrophysicists often use redshift in plots? Why it is important to know how an astrophysical object evolves in function of redshift? I was seeing an "cosmological time per redshift ...
1
vote
0answers
24 views

Constants of three body problem(2 fixed centers)

I was solving two fixed centers problem and got answer in quadratures. After that i want to find constants of motion. First one is full energy - E. Second is $p_{\varphi}$. And third one comes from ...
3
votes
2answers
96 views

Was there ever a meteorite with a measurable gravity?

Did we ever find a meteorite (a meteoroid that has fallen down to Earth) whose mass, density and gravity were high enough to demonstrate their gravity similar to the Cavendish experiment, so that ...
0
votes
1answer
92 views

How does a planet-sized robot standing on a planet affect its gravity? [closed]

I originally asked this at the sci-fi exchange but was told it was off-topic as it was about real-world science. Here is a picture of Unicron standing on top of the planet Cybertron, as written by ...
0
votes
0answers
24 views

Where can I find galaxy spectra (in the form of FITS files)?

I know there's SDSS and I tried searching for the spectra through the navigate and explore tool under CAS as well as by using RA/Dec coordinates under SAS, but every single time it comes out with 0 ...
0
votes
2answers
96 views

Why is a black hole's Hawking radiation temperature inversely proportional to its mass/size?

As a black hole shrinks in volume and mass, shouldn't its temperature get lower? Shouldn't it evaporate more slowly? Naively, (very naively), I think that with a smaller surface area (as per its ...

1
2 3 4 5
10