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
26 views

how to find the approximate [stellar radius]? (distance from center to most distant star) of a circular flat disk galaxy based on its stellar mass?

I'm doing a high school programming project on drake's equation (simple galactic model) and wondered if there was a (simplified) way to find the radius (measured by the distance between the center and ...
3
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1answer
236 views

Why the number of Long Gamma Ray Bursts(LGRBs) is greater that number of Short Gamma Ray Bursts(SGRBs)?

I collected https://www.google.com/url?sa=i&url=https%3A%2F%2Fgammaray.nsstc.nasa.gov%2Fbatse%2Fgrb%2Fduration%2F&psig=AOvVaw09lbpxsH2xmfnCCXQh4cKn&ust=1597302004094000&source=images&...
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Why is the peak value(s) of the spectral radiance of the CMB different if you calculate with freq. instead of wavelength?

On Wikipedia, the calculated value of the peak frequency of the cosmic microwave background is 160.23 GHz, but it says if you do the calculating with wavelengths, then convert to frequency, you get a ...
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13 views

What was the energy/wavelength/frequency of the CMB when first emitted/released?

Given the z redshift of 1089, and the temperature difference between then and now of about 1089, I tried scaling the ev, freq. and wavelength by 1089.... Is that right? I get a freq. of about 240 ...
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1answer
3k views

Have I nearly found the event horizon of a black hole?

The calculator on the website https://planetcalc.com/1758/ cites Wikipedia's Gravitational acceleration and implements: $$g = G \frac{M}{(R + h)^2}$$ For a black hole with mass $M$ equal to 5 solar ...
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0answers
64 views

Radiation and software reliability in outer space [closed]

We all know that dragon was written in c++ but what i struggle to understand is that if radiation in space can really mess with hardware and functionality and even have the capacity to change bits ...
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0answers
44 views

Ideas for a project in astronomy and deep learning [duplicate]

I am currently pursuing computer engineering and am in my senior year. I'm looking for a long term project (ideally 2-4 months) in astronomy and deep learning. I have extensively worked on the Galaxy ...
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0answers
14 views

Demonstration of scales for the two components (transverse and perpendicular) of Baryonic Acoustic Oscillations (BAO)

I transfer here a post that has not had any answer pn physics exchange, so I am going to delete this latter. Maybe I will have more luckiness here. In an astrophysics context about BAO (Baryonic ...
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0answers
28 views

How thick are the intergalactic filaments?

Recently, in October, news came out about the faint intergalactic filaments finally being 'found'. Then, in June, astronomers announced that these things had enough normal matter in them to solve the '...
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1answer
2k views

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(s) 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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How to determine arrival time delay given dispersion measure?

In an online textbook, the following formula is given to calculate the arrival time delay between two frequencies, $v_1, v_2$ in a dispersed radio pulse: $$t_1 - t_2 = 4.15 \cdot DM [(v_1/\text{GHz})^{...
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1answer
56 views

What does “the depth of the 13.0 Å feature differs by 7 sigma from zero” mean?

In a paper I've read, I have seen the following: In view of the noise levels, it is difficult to perform such a search effectively using statistical significance criteria only. We will therefore ...
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1answer
32 views

Difference in stellar abundance numbers

What is the correlation between stellar abundance by mass and by number? Let’s take the Sun and Helium for example. This paper mentions an abundance by mass for helium as Y=0.275 and by number as A=10....
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1answer
47 views

What do these statements about interstellar magnetic fields really mean?

Quanta Magazine's The Hidden Magnetic Universe Begins to Come Into View is a fascinating review of a rapidly evolving field in astronomy. It contains some statements that I feel are important to ...
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1answer
55 views

How to calculate the statistically significant level for a guassian line profile?

In some papers, they fit a line profile with gaussian model. For example, in this paper, fig 1 draw three gauss line profile, O VII, O VIII, and Ne IX. But the data seems noisy and the gaussian height ...
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2answers
65 views

How does gas in accretion disks of supermassive black holes create orbital torques on smaller black holes within the disks causing them to migrate?

This answer to What enhances the capture and merge rates of pairs of small black holes orbiting around supermassive black holes? links to Migration Traps in Disks Around Supermassive Black Holes which ...
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1answer
40 views

What are the Kinematics / Dynamics behind the motion?

https://www.timeanddate.com/eclipse/in/@8133395?iso=20200621 The link I have attached is a predicted model for the eclipse in my area! I am very much confused about the movement of the moon analogous ...
2
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1answer
62 views

Types of Multiverses [closed]

Can anyone recommend me books or other online resources on the concept of the Multiverse, it types, and about higher mathematical dimensions of space-time. I have been interested in such topics for a ...
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1answer
106 views

Are there other planetary systems where gas giants are on the inside to rocky planet orbits?

I understand that formation theories for gas giants suggest they should be born further away where there is more gas for them to monopolize vs the sun, and then to form Hot Jupiters they need to ...
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0answers
19 views

Why do exoplanets a little more massive than Earth, often appear to have lower densities than Earth from transit measurements?

Why do exoplanets a little more massive than Earth, often appear to have lower densities than Earth from transit measurements? Assuming that that they are terrestrial planets, what four(I am also nore ...
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Question about mass growth rate for individual planetesimals

In one stage of classic accretion, the mass growth rate with time (dm/dt) for individual planetesimals is proportional to $m^{2/3}$ and in another stage it is proportional to $m^{4/3}$. My question is ...
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1answer
53 views

Calculate depth and duration of exoplanet's transit using Python, astropy or lightkurve

I am creating a program for the analysis of exoplanets in Python using Astropy and Lightkurve libraries. I have light curve of specified star and I would like to calculate depth and duration of planet ...
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3answers
5k views

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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0answers
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To find the mass and radii of hill sphere of a planet after passing through a region of planetary nebula

Consider a planet with initial mass m* kg and radii of hill sphere as r*. The planet it traveling (assume) perpendicular to the nebula at a speed of 13km/s and the nebula is approaching the planet ...
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2answers
79 views

Mathematical astrophysics subjects for math graduate students

I'm looking for a cool and interesting subject in mathematical astrophysics to study for my master's project. What I really aim for is certain processes in the cosmos (multiple body-problem, black ...
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1answer
59 views

Will i get a job in aerospace field after graduating from M.Sc in astronomy and B.Tech in aerospace engineering? [closed]

I am a student of class 12 . I am fascinated about space and rockets.I want to be an astronomer and I know that I have to get a B.Sc, then M.Sc, and then Ph.D in astronomy. I came to know that there ...
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1answer
702 views

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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1answer
85 views

What kind of process could create such stellar radiating structures, if real?

https://www.nasa.gov/multimedia/imagegallery/image_feature_476.html Please notice especially the bright star at the center of the image, and how the most massive stars have etched out a cavity in the ...
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1answer
69 views

Was Guth inflation propelled by what we now call “Dark Energy”?

The more powerful our telescopes become, the more we are able to see earlier and earlier remnants of Guth Inflation. Assuming that it makes sense to associate a location, BB, in space-time where the ...
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1answer
37 views

Options for observational astronomy [closed]

For getting into a PhD program for observational astronomy, is physics major and data science minor enough?
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0answers
35 views

How common is it for large objects (few kilometers wide) in a young protoplanetary disk or debris disk to collide with one another?

If enough time has passed for gravitational forces to allow the formation of planetesimals(proto-planets) in orbit around the proto-star, how likely is it that two of them would collide with one ...
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0answers
42 views

Astronomy A Physical Perspective [closed]

Is "Astronomy: A Physical Perspective" by M. Kutner written in 2003 a good introductory textbook? What other textbooks could you recommend? I want to study astronomy on my own but with scientific ...
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0answers
18 views

Spectral Energy Distribution (SED) characteristics of Disk and Elliptical Galaxies

Quick questions about the spectral energy distributions of galaxies: What characteristics do we look for in SEDs that provide information on that galaxy's morphology? For example, in spiral galaxy ...
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1answer
98 views

What class of elements are providing the many electrons needed to make the H- ion?

Continuous absorption by the H- ion reaches its maximum in the cool atmospheric layers of G stars. At these temperatures, most of the hydrogen atoms are neutral; but what class of elements is ...
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0answers
20 views

Superconducting space dust; what transient fields could induce persistent current loops?

Science Alert's Superconductivity Has Been Discovered in Meteorites For The First Time quotes from Superconductivity found in meteorites (Wampler et al. PNAS March 23, 2020) The paper describes the ...
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0answers
25 views

Explanation about the resonance, mean motion resonance and libration

I am studying for a project the dynamics of multi-planetary system in resonance. I have two questions about this domain. In many articles they speak about 'mean motion resonance', what is the ...
3
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0answers
81 views

Information on Planetary nebula formed from the death of our star the 'Sun'!

I want to know the expansion rate, composition, mass and density of hydrogen present of a Planetary nebula similar to that which will be formed after the death of our star the sun. Knowing these ...
5
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1answer
157 views

Planetary phase angle of Hohmann transfer

This is Question 23 from USAAAO First Round 2015. The answer is D. Can someone show how to get the answer? Calculate the planetary phase angle (counterclockwise from Earth, a = 1.0 AU) that a probe ...
2
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1answer
66 views

how to calculate distance between galaxies in the distant past

for example, assume there is a high redshift galaxy called "A" with z=6, so how to calculate the distance between us and another galaxy B when the light left the galaxy A? For example, say B has a ...
3
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0answers
72 views

Combined mass of binary stars

This is Question 17 from USAAAO Practice Round 2015. The answer is D. It would be best if someone can detail out the workings. In a nearby star system, two stars are seen to orbit each other every ...
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4answers
361 views

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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5answers
5k views

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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0answers
22 views

Supernova impact on Protostar formation

What would be the impact on the formation of a new star (protostar) when a nearby star (within 10 LY) goes supernova? Will the force of the explosion (once it arrives in the Molecular Cloud where the ...
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0answers
34 views

What are good resources to study Gravitational Waves?

I am undergraduate student having basic knowledge of Physics. I'm looking for resources (books, video lectures, research papers, etc) to study Gravitational Waves from scratch, I think initially I ...
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1answer
139 views

If the earth lost 1/81th of its mass how would it orbit change? [closed]

If a planet becomes lighter, then I believe its orbit will change. For example, the moon is 1/81 of the mass of the earth. So, if the moon disappeared, then the earth-moon system would lose 1/81th of ...
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0answers
71 views

Force to fix $\sigma_{8}$ or $A_{s}$ for Forecasts

In the context of Forecasts with Fisher's formalism, I make vary cosmological parameters to compute the elements of the Fisher matrix. First, I generate with CAMB code a linear power spectrum. Then, ...
4
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1answer
173 views

Can a black hole with the density of water exist?

During an outreach event, the speaker mentioned the fact that black holes weren't necessarily dense objects and that black holes of any density could exist, even black holes with the density of water. ...
2
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3answers
78 views

light emission of quasars

I'm studying Astrophysics and I have some video's from a past course. I'm currently studying the reionization of the universe. At the current point in the class, the instructor is talking about ...
2
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1answer
56 views

What is a good way to start learning Astrophysics [duplicate]

I am a junior in high school and throughout my life I have always had a fascination with space. I use to watch "Space's Deepest secrets" and stuff like that but after a while I stopped learning much ...
5
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2answers
98 views

Why is blue light extincted more strongly than red?

We know that blue light suffers extinction more strongly than red (examples include ISM, atmosphere etc.), but why? Is it a property of the shorter wavelength itself? Can someone provide a conceptual ...

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