Questions tagged [the-sun]
Questions regarding the closest star to Earth, at the centre of the Solar System.
527
questions
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Maxwell stress contribution to $\nabla \cdot \mathbf{P}$ in the Navier-Stokes equation for fluid in stars
I was reading through the following extract outlining how the Maxwell stress contributes to the $\nabla \cdot \mathbf{P}$ term of the Navier-Stokes equation for fluids in a star. Here $\mathbf{P}$ is ...
0
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1answer
72 views
Why is the Sun's Luminosity not equal to the Zero Point Luminosity?
I was doing some research and found that the zero-point luminosity was $L_\odot = 3.75\times 10^{28} $, while the sun's reported luminosity was $L_{Sun} = 3.828\times 10^{26}$, according to Wikipedia. ...
3
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1answer
92 views
Why is our Sun hotter than UY Scuti?
As Wikipedia says the surface temperature of UY Scuti is 3,365 K and the sun is 5,778 K
Why is the Sun hotter than a supergiant star like UY Scuti?
3
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2answers
110 views
Can an Earth-like planet survive if our Sun went Supernova?
First, I would like to point out, yes, our sun does not have enough mass to be a candidate for Supernova, this is a scenario were our sun is though, and after the various life cycle stages of the sun ...
3
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1answer
97 views
At what depth below the Sun's surface does the density reach that of water?
I'd like to write a short supplementary answer to A probe floating in Sun's surface but in order to do so I need to know at roughly what depth relative to the Sun's surface the mass density reaches 1 ...
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2answers
62 views
What is the density profile within the Sun's photosphere? Which one of these is wrong?
The Sun's photosphere contains the Sun's surface as defined by opacity = 2/3 point. I'd like to see the profile of mass density from bottom to top of the photosphere. I did a quick search and got ...
1
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1answer
37 views
Earth's perihelion vs winter solstice [duplicate]
I found that Earth's perihelion occurs roughly two weeks after winter solstice similar thing happens for summer solstice and aphelion. I understand what those terms mean but I don't understand the ...
3
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2answers
223 views
What would happen if a Sun-like star were to consume a Jupiter-like planet?
A substantial number of discovered exoplanet systems are likely contain more than one gas giant with distances far closer to the star than in our solar system.
It is known that in solar system ...
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2answers
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What are some examples of routine human activity times for certain cultures/peopes that are based on the position of the sun?
What are some examples of timekeeping that are based on the height/angle/position of the sun. Two examples that come to mind are the times of the Islamic prayers times and the golden hour in ...
2
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1answer
50 views
How could the polarizer in early coronagraphs make the Sun's corona more visible against the daytime sky?
Wikipedia's Coronagraph; Invention says:
High Altitude Observatory's Mark IV Coronagraph on top of Mauna Loa, uses polarization to distinguish sky brightness from the image of the corona: both ...
2
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1answer
29 views
Where can I find a good solar irradiance chart for the infrared?
I'm trying to understand the results of the ExoMars Trace Gas Orbiter vs the Mars Express in terms of their abilities to find methane on the surface of Mars. The solution that I'm coming to is that it ...
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1answer
92 views
What keeps the planets of the solar system moving in their fixed orbits?
Models of the solar system show each planet moving around on its own orbit.
Is is really because of the Sun that every planets remains in its own fixed orbit?
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1answer
85 views
The sun's SOLAR WIND VS MAGNETAR
As we know magnetars have strong magnetic field but what if we swap earth with a magnetar and the sun will released a solar wind. Is the magnetar affected by the solar wind or not ?
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1answer
111 views
Is the longitude assigned to sunspots spherical or projected?
Sunspot maps are created from a projection of the sun, so the coordinates of sunspots (or active regions in general) are assigned according to it.
Do these coordinates correspond to actual spherical ...
2
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5answers
209 views
If fusion only happens near the center of the sun, what's with all the “fire” on the surface?
I understand that it isn't "fire" in the combustion of oxygen sense, but I can't find an answer online about what we're witnessing happening at the visible surface of the sun if all actual fusion ...
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1answer
119 views
Does the sun have a vertical movment?
As the Sun moves along with the planets does the sun exhibit vertical movement? That is, does it traverse in different planes?
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0answers
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what/how do we mean/derive statistical equilibrium equation of certain energy levels?
While reading the research paper "Excitation of the Fe XIII Spectrum in the Solar Corona" by D.R. Flower and G. Pineau des Forets in the summary I found the concept of statistical equilibrium equation ...
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0answers
73 views
Orbital decay of the Earth's orbit and Earth's moving closer to the Sun
If we consider orbital decay of the Earth's orbit, then can we counter argue with the following reasons?
Due to tidal effects transferring small amounts of angular momentum from the Sun's spin to ...
2
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1answer
55 views
Why doesn't the solar azimuth vary uniformly
For the past few dates, I've been observing the rotation of the earth around the sun and noticed that the azimuth of the sun doesn't vary uniformly throughout the day. The azimuth varies faster during ...
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2answers
156 views
How to calculate solar coordinates. (Right Ascension, Declination, and ultimately the Altitude and Azimuth of the Sun)
As the title says I am trying to calculate solar coordinates of the sun for a given location and time. I have spent many 10's of hours on this without success so I will sincerely appreciate help on ...
0
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1answer
78 views
Date of solstices pre-0 AD
I’ve written a script based on Meeus’s Astronomical Algorithms to calculate the position of the sun, moon etc. up to about 4000 BC.
Everything looks good, except when I go to 4000 BC the solstice are ...
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2answers
223 views
Does the sun have cycles causing temperature changes on Earth?
Can the Sun go through seasons or cycles to cause a temperature change?
Could the Sun have to go through any kind of thermal cycle to change the climate on Earth and by how much?
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3answers
175 views
How moon is visible during sun is still shining, simple explanation please! [duplicate]
Sometimes I observed there is moon on sky at noon and sun is also shining.
How is this possible?
I also observed dull moon is still on sky at 7:00 AM to 8:00 AM while sun is rising. My local time is ...
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3answers
223 views
Why is the equinoxes only 2 days and not more?
The earth is tilted at 23.5 degrees which means that in the solstices the north/south hemisphere is more radiated by the sun and the tilt to the sun is maximum.
In the equinoxes, the tilt is not ...
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1answer
126 views
How long would an occultation by a TNO last?
A trans-Neptunian object, 1 million km from the observer, with an angular diameter of 0.126° occults the Sun (angular diameter of 0.004°) and the TNO and the observer are moving in the same direction, ...
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1answer
41 views
Seasonal effect based on Earth position [duplicate]
I know that Earth rotates around the Sun in an oval route:
And I know the seasons happen, because the axis of the Earth is not vertical. I think it is 23 degree slope.
How come the distance from the ...
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4answers
164 views
Is the equinox Sun always at the same zodiac sign in the ecliptic belt?
During the year the Sun moves along the ecliptic passing all the signs of the zodiac belt, in my understanding. This means that it takes ~1 month to go from one zodiac sign to the next.
The ...
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2answers
79 views
Should the sun appear very low in the horizon if its path is always between the two tropics?
If the sun never rises above the tropic of cancer and never goes bellow (southern) of the tropic of capricorn then it seems that it should appear to the observer lower and lower in the horizon for as ...
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1answer
98 views
South of the tropics, where does the sun's noon shadow point?
If I understand correctly, in countries to the north of the tropics the sun's noon shadow points north.
What happens south of the tropics? Is it pointing south?
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1answer
57 views
What does the Sun look like from the heliopause?
I calculated the angular diameter of the Sun at the heliopause to be 0.004°. If that is correct, would the Sun appear as a disk, or like the pinpoint of light from a star?
How bright would the ...
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1answer
157 views
Could the Sun have liquid iron in orbit?
How close of an orbit to the Sun could an iron meteor get before it melts into a ball?
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0answers
38 views
Angle between earth's angular momentum and earth's axis
I think this picture is correct because for earth astronomical day is slightly shorter than solar day. (Is it a rule of thumb for planets? Where can I read such data?)
Source
So the angle between ...
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1answer
97 views
Does the Sun's atmosphere have a scale height?
Much of the Earth's atmosphere has a scale height $h$ of roughly 7 to 8 kilometers such that the local density varies as $\exp(-(r-r_0)/h)$ where r is the radius vector and $r_0$ would be some ...
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2answers
103 views
Why does the sun have a convection layer and a radiation layer?
Why is the outer section of the sun convective but the inner section stable and only radiative? They are both made up of the same kind of matter, both heated by the core.
3
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2answers
115 views
Sunset on [Mountain] from [Viewing Point]
How do I get the days in this year when the sun will set exactly on top of Fuji as viewed from Enoshima.
I shamefully admit that I just want to take a nice picture of Fuji.
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1answer
5k views
Why does the Sun have different day lengths, but not the gas giants?
The Sun's rotation period varies from about 25 days at the equator to about 38 days at the poles. As I understand it, this is because the Sun is not solid, and because of the way centripetal force ...
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3answers
3k views
Why doesn't the fusion process of the sun speed up?
Am I correct in saying that the fusion process of the sun is constant, i.e. X amount of fusion happens per day, more or less?
Why does this not speed up, i.e. one fusion event creates energy for two ...
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1answer
96 views
Can the Sun pull an iron asteriods in it's orbit into it? [closed]
Can our Sun's magnetic field strengthen in any way in a short period? Can the Sun pull anything trapped in close orbit around it? What would happen if an object in orbit passes over a sunspot for ...
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0answers
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Did OSO-3 or any other spacecraft or ground telescope record the solar activity that is likely the cause of the May 1967 aurora?
The question What solar event caused massive aurora borealis in the mid 1960's? reminds me again of a stunningly bright aurora that I saw circa 40°N circa 1967, and after reading the comments and ...
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0answers
37 views
Definition of the light that is projected by a celestial body/luminary [closed]
I'm creating an application which will simulate the light created by sun or moon on a 3d topographic map of Earth. Something like this:
Is there a word or definition for this light/light projection?
2
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1answer
95 views
Does the Sun twinkle?
Does our solar system have enough bodies in orbit to appear to twinkle to another distant solar system viewed from the side?
https://en.wikipedia.org/wiki/List_of_asteroid-discovering_observatories
...
2
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1answer
51 views
Solar azimuth for celtic fire festivals
I am pretty new to astronomy, and I have fallen down rabbit hole creating a new Metonic calendar in Javascript.
As part of this I would like to calculate when the sun is half way between a solstice ...
3
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0answers
66 views
First observation that the Sun and Jupiter (and friends) move around a common barycenter?
Answers to the question How did Kepler determine the orbital period of Mars? describing careful observations centuries ago got me thinking.
What was the first analysis of observations that directly ...
2
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1answer
72 views
Historical Distance of Planets to Earth [duplicate]
I'm curious if there is a readily accessible tool available, or simply a reliable way to find out what the distance of the planets in the solar system were on a given date.
For example, if I am ...
6
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3answers
574 views
Why do sun spots appear near the equator of the Sun?
I noticed on many examples sun spots are near the equator of the Sun. Why are there no sun spots closer to the poles of the Sun?
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1answer
74 views
Is there a plausible causal mechanism to explain why the Sun would be heating up faster/ sooner than we thought? Question for a novel [closed]
I am writing a novel about what it will be like on earth 500 or so years before the death of our Sun. The Sun is heating up gradually and one day that will negatively affect life on Earth. I know that ...
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1answer
2k views
How do we know if an object is redshifted?
I have some questions about redshift. I think that the first two hang on the last two, but feel free to point out anything you think I should know.
How do we know if an object is actually redshifted,...
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1answer
85 views
Are there any ways in which the light time difference between the center and the edge of the solar disk is noticeable?
In the ABC News video New space discovery has astronomers buzzing at about 02:30 Dr. Hakeem M. Oluseyi explains that the shortness of FRBs (before dispersion) suggests a compact source size and ...
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0answers
56 views
Did Eudoxus describe the eclipitic on his sun motion model?
In the description of Eudoxus’s model for the sun he says one the three circles which describe solar motion is “the circle which runs along the middle of the zodiac”. Does this refer to the ecliptic ...
2
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1answer
96 views
Geographical Point of the Sun
I want to draw a Sun in a 3d scene, so I figured the easiest way would be to calculate the latitude and longitude of the point perpendicular to Sun position and then just move it "up".
As a starting ...
