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
0
votes
1answer
92 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.
0
votes
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(...
2
votes
1answer
171 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 ...
1
vote
1answer
128 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 ...
0
votes
1answer
152 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-...
7
votes
1answer
99 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 ...
1
vote
1answer
131 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 ...
5
votes
1answer
206 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?
2
votes
2answers
93 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 ...
2
votes
0answers
142 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
votes
1answer
415 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 ...
6
votes
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.
5
votes
1answer
120 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 ...
9
votes
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? ...
0
votes
1answer
402 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 ...
0
votes
1answer
72 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....
1
vote
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 ...
0
votes
1answer
94 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
votes
1answer
146 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 ...
2
votes
1answer
1k 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 ...
3
votes
3answers
352 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,...
2
votes
1answer
138 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 ...
2
votes
2answers
113 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 ...
2
votes
1answer
423 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_{...
3
votes
1answer
144 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
0
votes
1answer
534 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 ...
1
vote
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 ...
1
vote
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?
2
votes
2answers
107 views

What is the unit used for star brightness due to skyglow?

What is the name and unit of the quantity in which star brightness due to skyglow is measured? How can it be measured from RAW image files of stars?
1
vote
0answers
45 views

DESDM COADD image access

I'm just starting a project to analyze some of the images obtained from the Dark Energy Survey (DES), and I'd like to get some of the COADD images from the SV data. For example, this paper: https://...
2
votes
2answers
111 views

Gravitational waves

We know that gravitational waves stretch space-time so light travelling through that space should be stretched as well. So my question is how do we know anything is stretching if the effect is ...
2
votes
1answer
108 views

Hole through the earth [closed]

I have a problem: If I would dig a hole through the earth, and jump right in, disregarding the rotation of the earth, I should come back out on the other side. However, orbital mechanics say ...
4
votes
1answer
177 views

Kepler and the Sun position

When Kepler went to Tycho Brahe, he learned that Tycho Brahe was using the mean position of the sun to note down the position of Mars. Well, Kepler needed to convert these datas of Brahe to do his own ...
1
vote
1answer
2k views

Could an object block out the Sun from Earth's view for 3 hours?

how large, massive, far away (from earth), and fast would an object (planet-like) have to be to block out the Sun for 3 hours and not disturb Venus, Earth, or the Moon?
4
votes
1answer
110 views

Are there non thermal filaments outside our Galaxy?

The question says it all: are there observations of something like non thermal filaments in other Galaxies other than our?
2
votes
0answers
209 views

Why the Hubble constant is so inconsistent?

Having a look on Wikipedia I noticed the following values (of the last 6 years) for the Hubble constant: 67.6±0.7 SDSS-III Baryon Oscillation Spectroscopic Survey 73.00±1.75 Hubble Space ...
1
vote
1answer
335 views

In what ways does the mass and energy of the milky way curve space time?

Space is curved by mass (or more precisely by mass and momentum as described by the stress-energy tensor). The milky way system has a lot of mass and a lot of energy. In what ways is space-time curved ...
3
votes
1answer
190 views

Why does Sirius proper motion “wiggle” with a 1 year period, when Sirius A and Bs binary orbit is a 50 year period?

Some stars, if observed repeatedly over time, show a perturbation or "wobble" in their proper motion. If this is a periodic occurrence we can infer that the perturbation occurs due to the ...
1
vote
1answer
217 views

What is the tidal radius of the Sirius system?

The Fomalhaut system is a trinary system, with Fomalhaut A (1.9 M), Fomalhaut B (0.7M) and Fomalhaut C (0.2M). Fomalhaut C is 2.5 light years from Fomalhaut A, and 3.2 light years away from Fomalhaut ...
3
votes
1answer
169 views

In layman's terms, why do we put the “time” in space-time?

What does "time" mean in the term space-time? I am trying to understand why anything that travels through space, from a proton to massive galaxies, is always referred to as traveling in space-time, ...
9
votes
1answer
169 views

Period coincidence of Planet Nine with furthest Kuiper belt objects

A lead scientist of the Planet Nine theory said that "The period with which it goes around the sun is a rational multiple of the periods of all the furthest Kuiper Belt objects" To what degree of ...
3
votes
0answers
118 views

What is the spectral power output of a typical galaxy?

I'm looking for a function which gives the typical isotropic spectral power of light emitted by an entire galaxy on the whole electromagnetic spectrum (in watts per frequency unit), as a function of ...
1
vote
1answer
221 views

Cosmic microwave background radiation: why did it take so long to get here?

I understand that the universe after the big bang was a super dense cloud of elementary particles, and because of this high density was "not transparent" to light. Then, roughly 400.000 years (380....
2
votes
1answer
126 views

On orbital mechanics of evaporating planets

A planet orbits around its sun on an elliptic orbit, and loses mass slowly due to evaporation. How will the parameters of the orbital ellipse change as a function of time? Could we do a generalisation ...
1
vote
1answer
463 views

Astronomy & machine learning. Where to start? [closed]

I am a Computer Engineering major and would like to learn more about machine learning methods in Astronomy. What books or other resources could I use?
1
vote
3answers
1k views

Sudden Effects of Sun Disappearing [duplicate]

It takes 8 minutes for the sun's light to reach earth. If the sun were to instantly disappear, what would happen? I imagine that Earth would fly away on a path tangential to its orbit. What would ...
3
votes
1answer
1k views

Can I do M.Sc in physics to become an astronomer after doing B.Tech in aeronautical engineering?

I am a student of class 12 and I am studying in India. 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 have also started to learn the python ...
0
votes
1answer
63 views

Not clear on how to calculate sub-radar latitude [closed]

How to find sub-radar latitude in reference to radar telescopes hitting near earth asteroids?
1
vote
1answer
147 views

What could be past the particle horizon?

Forgive any kind of "dumb" question I may ask as this is a new interest of mine and I know it's purely hypothetical. If one were able to surpass light speed and the expansion of space to go beyond ...
3
votes
1answer
150 views

How massive must a rocky body be to liquify adequately to eliminate internal mass concentrations that could disrupt natural satellite orbits?

Maybe a slightly weird question, and maybe more appropriate for some future geophysics SE, but I feel like this is what questions like Do moons have moons? are really driving at, and it just almost ...