# Questions tagged [the-sun]

Questions regarding the closest star to Earth, at the centre of the Solar System.

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### if the earth was the size of the sun how big would the moon be [closed]

if the earth was the size of the sun how big would the moon be, I know that the sun is 400x bigger then earth but if earth was that big how big would the moon be relative to the sun sized earth
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### Calculation of the average atomic mass of sun [closed]

In the calculation of the average of the atomic mass of sun, we should also count the number of the electrons. However, now that the mass of an electron is about 1/2000 of a nucleon, why can 't we ...
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1 vote
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### Create an artificial solar eclipse

I have a meade ETX-125 telescope and I have a solar filter, my question is, can I place a small disk in the centre to create an artificial solar eclipse in the hope of seeing corona ejections, if this ...
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### Do we get shortest shadow of any object at Solstice time or Meridian time?

Today is 21 June and I want to see at what time I will see shortest shadow in my location. I am seeing two different times: Solstice time a d Meridian time. I read that on summer solstice the sun is ...
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1 vote
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### Calculating local solar time with python ephem library

I was learning to calculate local solar time with ephem. I must admit, unit conversion between radians, hours and days, which are all represented by a float in the ...
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### Why is the summer solstice night shorter than the winter solstice day?

I was looking at the sunrise and sunset times where I live (Aberdeen, Scotland) and I noticed something odd: the time between sunrise and sunset in winter is longer than the time between sunset and ...
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### Wouldn't the 1054 supernova have temporarily enlightened the Earth like the Sun?

The peak luminosity of all type Ia supernovae is 1.60×1036 Watts. If we see a star go supernova from earth, and we observe its intensity to be 1.0 W/m2. The intensity of the Sun is about 6.33x107 W/m2....
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### Does the north pole of the Solar System (with respect to the invariable plane) point towards the galactic center?

How is our Solar System as a whole (not the wobbly Earth) tilted with respect to the invariable plane of the Milky Way? I understand our Sun's north pole is largely pointing towards our direction of ...
• 3,375
1 vote
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### Estimate shadow positioning based on prior knowledge

I'm doing some work with sports statistics where I need to evaluate at what times part of the field is covered by shade. I already know that shadows cover the portion I'm interested in from roughly 4:...
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### What is the difference between New Moon day and Lunar Eclipse?

A lunar eclipse occurs when the Earth is in between Sun and Moon. OK, I understand this (see diagram from Nasa). A new moon is also when the Earth is in between Sun and Moon. So, why are they not the ...
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### Is the center of our galaxy, the Sagittarius A* black hole a former star?

If a black hole comes from a dying star, do we have a record or proof that our galactic center was once a huge ball of burning plasma? I'm not an astronomy student.
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### Celestial Coordinates and Sun's degrees below horizon

I am struggling to understand the how the coordinates work. Example: At vernal equinox RA=0 DEC=0, Does this mean the Sun is at its highest point at the equator? If my mean solar time is 2h 30min, ...
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### How are plage regions related to the density of medium and velocity FeII ions?

During a literature review (abstract), I found that the intensity of FeII (298.5 nm) ions in the last solar minimum was higher than the two previous solar minima 21 & 22. The velocity of FeII ions ...
• 191
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### How much mass does the Sun gain from the Poynting-Robertson effect?

I understand that the Poynting–Robertson effect describes solar radiation induced drag on certain sized dust particles causes them to lose orbital angular momentum and eventually fall into the Sun. ...
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### Azimuth angle and elevation angle of a heliostat mirror

for the control of a heliostat I have a program for the calculation of azimuth and elevation. Now I am still missing the calculation of azimuth angle and elevation angle for setting the mirror. While ...
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1 vote
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### Determining when the sun shines on different sides of a building using astropy

I recently installed motorized solar blinds on various windows in our house to reduce solar gain during the summer months. I have integrated the blinds with my hubitat home automation system, and am ...
• 115
1 vote
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### Earth’s rotation speed vs rate of lunar cycle

Hypothetical Question If the earth’s rotation slowed down to align to the lunar cycle so that the orbital period began and ended at the same lunar phase, what other things would result? For example, ...
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### What conditions are necessary for the sun to look [as described below]

First of all sorry for the weird title. I have no idea how to describe it in a succinct way because I've never heard of something similar happening and I've only witnessed it once. The only way for me ...
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### Data of Coronal Holes

I'm working on the Evolution of coronal holes for which I need data of Coronal Holes, I have searched on internet and also done literature survey but didn't find out any open-source catalogue where I ...
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1 vote
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### Is the STEREO-A and STEREO-B imagery publicly available?

The latest image on the [NASA STEREO image page] is from December, and I assume STEREO-A and -B have collected data since. Can this data be found online?
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### What is the current radial position of the sun within the Milky Way relative to the MW's movement towards the Great Attractor?

If we imagine the Milky Way's movement towards the Great Attractor as the 0-rad mark on a disk parallel to the movement with a center at the Milky Way center, do we know roughly at what radian value ...
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### What would happen if we replaced our sun with a red dwarf? [closed]

What would happen to us on Earth, not how our orbit would change.
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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 ...
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### Local mean time & Solar Noon

Is local mean time supposed to represent actual sun movement? Does 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 ...
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### 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 ...
• 1,017
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### 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?
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### 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% ...
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1 vote
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### 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 ...
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### 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....
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### 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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### 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
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### 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 ...
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### 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 ...
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### 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 ...
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### 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,...
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1 vote
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### 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 ...
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### 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?
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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 ...
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1 vote
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### 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: ...
• 1,017
1 vote
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### 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 ...
• 1,017
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### 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 ...
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1 vote
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### 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 ...
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### 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 ...
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### 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?
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### 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 ...
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1 vote
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### 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?
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### 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 ...
• 1,017
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### 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 ...
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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 ...