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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4
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0answers
138 views

Get the expression of probed volume between 2 redshifts

1) I can't manage to find/justify the relation (1) below, from the common relation (2) of a volume. 2) It seems the variable r is actually the comoving distance and not comoving coordinates (with ...
2
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1answer
135 views

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
89 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 ...
4
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1answer
108 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....
2
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1answer
71 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
71 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 ...
2
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2answers
98 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 ...
2
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1answer
45 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
74 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 ...
5
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1answer
173 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
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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
441 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
6k 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 ...
2
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1answer
56 views

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
153 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
70 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 ...
14
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1answer
858 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 ...
2
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1answer
86 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 ...
3
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1answer
81 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
38 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
45 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
52 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
33 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 ...
5
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1answer
102 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 ...
5
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1answer
161 views

How do we know that comets definitely mase and not just fluoresce? What is it about 18-cm lines that indicates that is really masing per se?

Wikipedia's Astrophysical_maser#; comets mentions some anecdotes of notable masers associated with comets, and Maser emissions from comets begins: The 18-cm lines of the OH radical are the only ...
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0answers
30 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 ...
4
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0answers
38 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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1answer
99 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
367 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
166 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
115 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
646 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 ...
16
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5answers
6k 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
27 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 ...
3
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2answers
91 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 ...
1
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1answer
148 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 ...
2
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0answers
89 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
341 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
106 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
320 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 ...
6
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2answers
154 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 ...
1
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1answer
76 views

Simulation and its necessity in astronomical research

I was wondering if mainly everything in Astronomical and Astrophysical was dependent on Simulations then what are the educational requirements are necessary to qualify as the Simulation Expert. What ...
2
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1answer
126 views

Can there be a three-moon system where only two are visible most of the time?

I am trying to build a moon system for a sci-fi work in collaboration with my boyfriend. He's the main writer and wants there to be three moons circling the planet in a way that most of the time, only ...
24
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1answer
1k views

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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0answers
247 views

Saw 8 stars moving in same direction one by one [duplicate]

I saw 8 stars moving in the same direction one by one and then at the same point they faded or you can say disappear. The speed was not too fast but not too slow either. I am more curious because ...
4
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1answer
67 views

How is the Dating of Samples of Cosmic Objects Performed, Including Pre-Solar Dust?

In the new Space.com article 7 billion-year-old stardust is oldest material found on Earth I had read about some pre-solar grains dating back to 7 billion years. What techniques are used in ...
4
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1answer
758 views

Plotting Astronomical Data Using Python

I have been trying to create a graph which shows the distances between the stars and the earth, yet I could not obtain the desired graph as seen below (click to zoom in): My graph: As @uhoh ...
2
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1answer
128 views

the more concentrated the mass, the more powerful is gravity?

the more concentrated the mass, the more powerful is gravity? or does it depend exclusively on the total mass? example: 1 $\small\mathsf{cm^3}$ material A = 1000 kg, 20 $\small\mathsf{cm^3}$ material ...
3
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1answer
88 views

How does the field decay of a magnetar power the emission of high-energy electromagnetic radiation?

In Space.com's Dr. Pulsar and Mr. Magnetar? 2 Star Types May Turn into Each Other (and in the linked video) "Tom Prince, a physics professor at the California Institute of Technology and a senior ...
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0answers
28 views

Doppler Shift Vs Gravity Assist for Frequency Shifts from Rotating Galaxies

Frequency Shift of Light Leaving Rotating Galaxies: Differences in Doppler Shift due to Radial Velocity Vs Frequency Shift due to Gravity Assist from a Rotating Galaxy A description of estimating ...

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