Questions tagged [the-sun]
Questions regarding the closest star to Earth, at the centre of the Solar System.
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questions
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0answers
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How long is the sunrise (or sunset) on North (or South) Pole? [duplicate]
I wonder how to calculate the duration of the Sun crossing the line of the horizon on equinox on Pole. For equator I used this formula:
$t = \frac{2 \times p}{\cos(\phi) \times u}$, where $u$ - is ...
5
votes
4answers
546 views
Local mean time & Solar Noon
Is local mean time supposed to represent actual sun movement ? Is 12pm on local mean time (not clock time), mean that the sun is on meridian or solar noon ?
I understand LMT means 1 degree for 4 ...
3
votes
1answer
70 views
How to estimate the temperature of an interplanetary dust grain?
I'm trying to solve this task:
Estimate the equilibrium temperature of an interplanetary spherical dust grain if it is located at a distance of 3 AU. from the Sun, and the substance of the dust ...
3
votes
1answer
162 views
Density of Plasma in Solar Corona
The Sun's atmosphere, also known as the solar corona, is known to be extremely hot, much hotter than the Sun's surface. What is the plasma density in the solar corona?
9
votes
3answers
153 views
Why is the composition of the sun so distinct from that of earth?
Given that the sun is – in astronomical distances – quite close to the earth, why are the two composed of such distinctly different substances?
Sun Composition
Hydrogen 74.9%
Helium 23.8%
Oxygen ~1%
...
1
vote
2answers
59 views
how much advanced notice would we have for an Earth bound coronal mass ejection?
According to wikipedia the 1859 Carrington Event was caused by a coronal mass ejection (CME) of plasma.
As it's plasma and not photons it stands to reason that the CME would not be traveling at the ...
4
votes
1answer
273 views
Rising and setting time of planets in relation to the sun
If Venus set about 2 hours after the Sun,then it should be about
30degrees to the east of Sun.
Is there any mathematical formula to get these thing or it's just a pattern?
Source :https://olympiads....
3
votes
4answers
153 views
Sunset and sunrise formulas adopted by IAU
I'm developing a C++ computer library with the formulas in the book "Practical Astronomy with your Calculator or Spreadsheet 4th Edition" but I have a problem with the formula 49, "...
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1answer
73 views
how would you explain the motions in the solar system? [closed]
like so i don't get it it does not make sense I'm confused
6
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1answer
105 views
How did Parker Solar Probe take what looks like 2D cross-sections of the solar wind in photographs; high contrast streaks in focus from volume effect?
The new NASA Goddard video NASA's Parker Solar Probe Touches The Sun For The First Time shows what looks like they might be photographs of the solar wind.
I'm having a hard time understanding how such ...
4
votes
0answers
48 views
Did astronomers "track back" solar wind switchbacks to the surface of the Sun to individual convection cells?
The new NASA Goddard video NASA's Parker Solar Probe Touches The Sun For The First Time explains that the spacecraft passed many times through "switchbacks" or kinks in the solar wind, where ...
8
votes
1answer
686 views
The Sun's Alfvén critical surface; what was known about its existence and location before Parker Solar Probe "touched the Sun"?
The new NASA Goddard video NASA's Parker Solar Probe Touches The Sun For The First Time seems to suggest that the existence of the Sun's Alfvén critical surface was a given, but the location and ...
2
votes
3answers
77 views
Was the young Sun cooler or hotter than it is today?
Generally, astrophysicists say that the young Sun was only about 70% as warm as today, which leads to the alleged 'Faint young Sun paradox' about how a young Earth could have been as warm as it (again,...
1
vote
1answer
44 views
At what rate does the right ascension and declination of a planet, the sun and moon change per hour?
I'm currently building a web app and am getting the RA's and Dec's of solar system objects based on date and time chosen by the user. Then using the gmst for 0 hours of the date, the app calculates ...
0
votes
1answer
81 views
Can the sun explode in fact? [duplicate]
Because of fusion inside the sun, it pushes it apart, why sun doesn't explode then? The pressure inside should make it explode right?
11
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3answers
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Can you see the shadow of a spaceship on the Moon while looking towards the Earth?
It's a classic movie cliche. We see the surface of the Moon with the Earth in the distance and a dark shadow of an invading alien spaceship slowly covering the landscape.
We see this in the opening ...
1
vote
0answers
51 views
Ecliptic and it's poles
Well, I have this picture and a couple of tasks to it:
It is the Sun's path, a.k.a. ecliptic in autumn, 22-23 of September or on the day when autumnal equinox happens. I am to answer these questions:
...
1
vote
1answer
50 views
At what time of the day of autumnal equinox the Sun's equatorial coordinates reach max value?
I'm trying to solve this task:
At what point in time of autumnal equinox day, at sunrise or sunset will
a) the declination of the Sun
b) the right ascension of the Sun
reach the maximum value?
I'm ...
4
votes
1answer
128 views
Role of aerobraking in cometary orbits?
I'm doing some research about comet perturbations, and have noticed that the outbound aphelion is often different from the inbound aphelion, particularly due to the gravitational influence of the ...
1
vote
1answer
88 views
What is the relationship between the shape of the analemma and the sun's azimuth at sunset at a given latitude?
I want to know how the sun's azimuth at sunset changes over the course of a year.
At first, I thought it would have purely sinusoidal motion, hitting its maxima and minima at the solstices, and ...
4
votes
1answer
75 views
How much mass is lost in the red giant phase of a sun?
The red giant phase of suns may go relatively quick. How will this impact suns' total mass. Are there massive mass losses taking place when this happen? If so, do we know how much? The sizes of red ...
0
votes
1answer
56 views
Sun expansion's effect on planets
When the Sun gets to the age at which it will rapidly expand what effect would it have to the outer planets and it's moons? Would it make new habitable areas of the solar system?
2
votes
0answers
83 views
Help finding a database or analysis of plage regions on the Sun
Plages are phenomena of stellar activity.
A plage is a bright region in the chromosphere of the Sun, typically found in and around active regions. The term itself is poetically taken from the French ...
1
vote
1answer
83 views
Will Mercury ever become locked to the Sun?
The Mercury year is between 1 and 2 days. Has it ever been greater, and will it eventually become "tidally locked" with the Sun?
1
vote
1answer
33 views
Calculation of time delay in NASA's STEREO project
I'm trying to solve this task:
Astronomers recently managed to get an image of the entire surface of the Sun for the first time. This became possible thanks to the STEREO project.
In 2006, two ...
3
votes
2answers
142 views
2 points on Earth’s surface, 1 second apart in time
I’m hoping to find a method (probably some modeling software?) that would allow me to find pairs of locations on the Earth’s surface that occupy the same point in space relative to the sun, one second ...
5
votes
1answer
149 views
Calculate lines of equal solar altitude
I'm attempting to calculate lines of equal solar altitude, essentially a generalized case of the Earth terminator for solar altitude $ h $.
For a given sun position with declination $ \delta $ and ...
1
vote
0answers
62 views
Is it completely false that the Sun does not revolve round the earth? In what sense? [duplicate]
This is a very naive question but I never fully understood this. For a system of two binary stars moving under the influence of their mutual gravitational forces revolve around their common center of ...
2
votes
2answers
77 views
defining the period of an year on earth
While it is much simpler to define the duration (time) of ONE complete day (for earth), by simply calling it to be the period between sunrise to next sunrise (which we have currently divided into 24 ...
25
votes
4answers
2k views
How else can a star form, other than gravitational collapse?
I read this paragraph on the Sun's page on Wikipedia:
[The Sun] formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most ...
1
vote
0answers
28 views
which fraction of the solar radiation corresponds the blocked part by Venus at its transit upon he sun?
Well, asumming that Venus orbits the Sun at 0.7233 AU and its diameter is 12,104 km, I can conclude that its angular diameter seen from the earth is ~1', then its represents ~1/31 part of the angular ...
1
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1answer
114 views
What exactly will happen when the Sun leaves the main sequence? I know it expands to a red giant twice, but what happens exactly? What's the timeline? [duplicate]
I've seen numerous claims surrounding this, with some claiming the expansion of the Sun from its end-main sequence radius to its peak red giant radius will take over 1 billion years, while others ...
1
vote
0answers
53 views
Solution of stellar structure equation for Sun in Convective Zone
Consider the following problem:
Sun has a convection zone from $0.7 R_\odot$ to the solar surface, when $R_\odot$ is the radius of Sun. If the matter is marginally convectively unstable and the ...
12
votes
2answers
3k views
Is Jupiter warming the Earth? (Earth, Sun Jupiter system)
If Sun-Jupiter baricentre is outside the Sun, does that mean the Sun is orbiting around that point too right?
Then the Sun shouldn't be nearer to the Earth at some point during the Sun-Jupiter orbit (...
4
votes
1answer
104 views
Path of sun in the sky on a planet with no axial tilt
Some sources online (e.g. this, see section "Effect of Earth’s Eccentricity") claim that if the earth's axis was not tilted, then the analemma would have the shape of an ellipse/oval. I ...
4
votes
1answer
114 views
What would be the effect of a large solar flare on motor vehicles?
With the solar cycle now leading to an increase in flare activity, one naturally starts to think the effects of a large solar flare heading this way.
While major flares like the Carrington Event are ...
4
votes
1answer
31 views
What online tools are available to investigate and classify solar eruptions?
I was just casually browsing when I came across a link about at recent solar flare. So I went to investigate at SpaceWeather. There it was stated:
Looking further down the page it seem to say that ...
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votes
1answer
208 views
Is the claim that the star Sirius does not precess like other stars true?
There is this popular claim on Internet that the star Sirius does not precess like other stars.
The idea comes from mainly Greeks and Egyptians using Sirius to track seasons, as part of the Sothic ...
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vote
2answers
233 views
What was the day of the week for the total lunar eclipse (saros 61) that occurred on April 14, 32 AD?
I am interested to know if there is convincing "astronomical" evidence/data to pin down the exact day of the week for the total lunar eclipse of April 14, 32 CE. I am hoping that perhaps ...
2
votes
1answer
54 views
When could solar eclipse happen in a way that Sun's disk is diminishing from below?
I'm trying to solve this task:
During a solar eclipse, an observer noticed that the diminishment of the Sun's disk began directly from below. Where and when could this be?
Concerning "where&...
2
votes
1answer
193 views
What would happen if the Sun, Moon and Earth were isolated?
I am curious to know what would happen to Earth and life on Earth if all other heavenly bodies outside of our Sun, Moon and our planet Earth ceased to exist in some non-destructive way? (this includes ...
5
votes
2answers
137 views
What is the exact reason for the Sun's differential rotation to occur?
The following is an excerpt from the Wikipedia article for "Differential Rotation":
Differential rotation is seen when different parts of a rotating
object move with different angular ...
1
vote
1answer
44 views
Solar Rotation Varies with Latitude. Effects?
From the Wikipedia article of "Solar Rotation":
Solar rotation varies with latitude. The Sun is not a solid body, but is composed of a gaseous plasma. Different latitudes rotate at ...
-1
votes
1answer
40 views
What would be the effects of a -400 nanotesla geomagnetic storm on modern electronics? [closed]
After reading the Wikipedia article on geomagnetic storms, I'm curious about what the effects of a -400-nanotesla-minimum geomagnetic storm would be on modern military and consumer electronics.
The ...
2
votes
1answer
47 views
The Sun's motion around the galaxy [duplicate]
As the Sun orbits the Milky Way, I understand that it also moves up and down through the plane of the Galaxy. How long does this movement take and can we tell where we are in the current cycle.
4
votes
1answer
232 views
Is there molecular hydrogen in the Sun's atmosphere? If so, how much, and how was that first determined and measured?
I don't have a license to practice chemistry, but I'll convert Wikipedia's bond dissociation energy of 435.7 kJ/mol to eV by dividing it by $C / N_A$ where $C$ is 1 Coulomb and $N_A$ is Avogadro's ...
4
votes
1answer
132 views
What is the percentage of ortho- vs. parahelium in the sun?
Parahelium (P) has its 2 electrons with opposite spins and S=0. Orthohelium (O) has parallel spins and S=1. The energy levels of P are a little bit higher than O. Maybe this leads to easier building ...
1
vote
1answer
116 views
How did the ancients know the constellation in which the sun is located?
The zodiac constellations lie along the plane of the ecliptic. In Spring equinox, sun lies in Pisces constellations. So Pisces is not visible during the day (because the sun light) and not visible in ...
2
votes
1answer
109 views
In which town is the length of the day bigger on 23 of September?
I'm trying to solve this task:
Moscow and Kazan are located on the same parallel. In which of them the length of the day is bigger on 23 of September?
In Kazan the sun will rise earlier, because it'...
9
votes
2answers
2k views
What is the probability of life having developed or going to develop in our solar system another time?
I'm sorry I am not quite sure this question satisfies this point:
Questions that are purely hypothetical, for example a question such as 'Could a black hole destroy the universe' or 'What if our ...
