The Sun is an almost perfectly symmetric yellow dwarf star [spectral class G2V] which is at the center of our Solar System.
27
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4answers
1k views
Does the sun rotate?
As implied from the question, does the sun rotate? If so, do other stars not including the sun also rotate? Would there be any consequences if the sun and other stars didn't rotate? Me and my friends ...
22
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4answers
2k views
Why is a new moon not the same as a solar eclipse?
Forgive the elementary nature of this question:
Because a new moon occurs when the moon is positioned between the earth and sun, doesn't this also mean that somewhere on the Earth, a solar eclipse ...
20
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2answers
2k views
Why is the sky not purple?
I realise the question of why this sky is blue is considered reasonably often here, one way or another. You can take that knowledge as given. What I'm wondering is, given that the spectrum of ...
16
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6answers
672 views
Can the apparent equal size of sun and moon be explained or is this a coincidence?
Is there a possible explanation for the apparent equal size of sun and moon or is this a coincidence?
(An explanation can involve something like tide-lock effects or the anthropic principle.)
14
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1answer
115 views
What happens to the electron companions of cosmic ray protons?
If primary cosmic rays are made mostly of protons, where are the electrons lost, and does this mean that the Earth is positively charged?
Does the sun eject protons and electrons in equal number?
13
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2answers
237 views
Is the length of the day increasing?
In Frontiers of Astronomy, Fred Hoyle advanced an idea from E.E.R.Holmberg that although the Earth's day was originally much shorter than it is now, and has lengthened owing to tidal friction, that ...
12
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2answers
234 views
Hydrogen as a fuel in Sun
The source of Sun's incessant energy is hydrogen; which is continuously converting to helium through nuclear fusion reaction releasing energy. Why does not all hydrogen convert into helium in one big ...
10
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6answers
3k views
Is it safe to observe the sun through binoculars with welding glass in front? [closed]
I asked this on Reddit but didn't get much of a response. So here goes!
I'm looking for low-cost ways to observe the Transit of Venus this summer. Since I'll only be able to see a few hours of it ...
10
votes
2answers
3k views
Why can there be fire in space while there is no oxygen?
The sun is made of fire but fire needs oxygen right? So..
Why can there be flames in space, while there's no oxygen?
Same idea as with the rocket engines of the spaceship, which also produce fire ...
10
votes
1answer
83 views
What proportion of a star's hydrogen is consumed in its life?
I've heard in a lecture that a star like the sun would burn 3% of its Hydrogen before expiring.
I would have thought it would be much more.
10
votes
2answers
281 views
How are the northern lights produced?
Although I've never seen it myself, I hear the northern lights are a sight to be seen! I know they're related to the Earth's magnetic field but I don't know much more about them. What is the physical ...
10
votes
1answer
119 views
Have general relativistic effects of the sun's rotation been measured?
I was wondering if general relativistic effects of the sun's rotation have also been measured, like gravity probes A and B measured GR effects from the earth.
10
votes
1answer
130 views
The transit of Venus and solar neutrino rates
The following question was posed at the end of Maury Goodman's June 2012 long-baseline neutrino newsletter.
During the Venus transit of the sun, were more solar neutrinos
absorbed in Venus, or ...
10
votes
0answers
475 views
Why does the moon look bigger at the horizon? [duplicate]
Possible Duplicate:
Why does the moon sometimes appear giant and a orange red color near the horizon?
Why does the moon look bigger at horizon or skyline than at other times e.g. at ...
9
votes
2answers
263 views
Effect of gravitation on light
Einstein predicted that the gravitational force can act on light. This was verified in one solar eclipse that light from a star near to the sun's disc bent due to Sun's gravity as predicted. Since ...
8
votes
2answers
612 views
Do photons lose energy while travelling through space? Or why are planets closer to the sun warmer?
My train of thought was the following:
The Earth orbiting the Sun is at times 5 million kilometers closer to it than others, but this is almost irrelevant to the seasons.
Instead, the temperature ...
8
votes
4answers
299 views
Is solar wind positively charged?
Many times I heared that the solar wind consists of protons and alpha particles. The both are positively charged, but are there electrons in solar wind?
8
votes
3answers
180 views
Are planetary orbits measured from the Sun's surface or centre?
I would imagine planetary orbits are measured from the Sun's centre and not its surface. Is that true?
I can't find anywhere that actually states this.
8
votes
5answers
198 views
sun-moon-earth anomaly
When one looks at the sun and the moon in the sky together, why is it that the illuminated crescent of the moon does NOT "point" at the sun?
(More correctly the perpendicular bisector of the straight ...
7
votes
2answers
202 views
Why don't we see solar and lunar eclipses often?
Since we see the new moon at least once in a month when the Moon gets in between of the Sun and the Moon at the night and as far as I know if this happens during the day, you'll get to see a solar ...
7
votes
4answers
161 views
Is there a way to create an artificial solar eclipse?
I heard this story, where they celebrated the birthday of the now defunct North Korean dictator Kim Il-sung in the 1970s and as a birthday present they created through some very complex artillery ...
7
votes
2answers
96 views
How to create unusual sundial?
I am considering small "artsy" project. I would like to create sundial by placing gnomon on the window and painting hour lines on the window facing wall.
Since this is to be placed in bedroom I am ...
6
votes
1answer
38 views
Transit of Mercury: how did he see it?
On November 7, 1631 Pierre Gassendi saw the transit of Mercury across the face of the Sun. How did he see it? I mean what instrument was used to reduce the apparent brightness of the Sun?
6
votes
2answers
293 views
Why is the sun so dense?
Looking at the radius and mass of stars on Wikipedia, I see that the Sun is the densest of all, often many times denser than other stars. Is that because only non-dense starts are easily seen from a ...
6
votes
3answers
84 views
What frame(s) of reference are used to measure the rotation of the Sun around the galaxy ?
I can find various speeds and estimated durations listed at numerous places but none specifically describe the frame of reference.
Possible options as example of kind of answer I expect.
Local ...
6
votes
2answers
123 views
Must a vertical sundial face exactly South?
I am a sundial. I'm prepared to bet
Your watch can't tell when the sun will set
I once heard Frank King talk about sundials in particular this very cool one, which measures Babylonian hours ...
6
votes
1answer
30 views
Refraction and scattered light for NLCs
For helping with judging NLC candidates (are they NLC or not) I have a set of formulas to calculate the minimum altitude (in km) of the candidate given an observed altitude (in degrees) of the ...
6
votes
2answers
368 views
5
votes
2answers
229 views
Is dark matter really present around the sun?
Recently I read an article that there is dark matter around the sun but if it is so, than why can we see it clearly.
If it is called matter than it shall show some hindrance in radiation we receive ...
5
votes
3answers
259 views
How many percent of the visible light reaching the Earth are from other stars than the Sun?
How many percent of the whole visible light reaching the Earth are from other stars than the Sun?
Is it maybe 0,5 - 1% or is my guess already too much?
I am interested mainly in visible light, but ...
5
votes
3answers
495 views
Is a water world possible, and for how long could it be stable?
I have several questions regarding this topic.
First, could a water world be stable for thousands of years with most of its surface remaining covered in water. What would it take for this to be ...
5
votes
1answer
263 views
Why does the sun “shine brighter” some days?
Today, the sun seems extremely bright; more dazzling than usual, and even the roads seem to be brighter so it's not just when you look up in the sky. Is more light actually getting through (perhaps ...
5
votes
2answers
244 views
What elements can be created in the fusion process of different types of suns?
As I understand it fusion inside a sun can produce heavier and heavier elements until some sort of "nucleus size limit" is reached. As far as I understand, the limit is thought to be reached with the ...
5
votes
6answers
814 views
How close can spaceship get to the Sun
If you want to fly a spaceship with human passengers as close to the Sun as possible, then what effects would the spaceship have to be designed to counteract in order to keep the passengers alive and ...
5
votes
2answers
120 views
Is there any way to anticipate exceptional Aurora Borealis viewing conditions?
I've always wanted to see the Aurora Borealis, but never had the opportunity, since it is so rarely visible in my area (Pennsylvania).
However, last week was apparently a rare opportunity of ...
5
votes
3answers
350 views
Why planets are rotating only in one plane? [duplicate]
Since gravity is three dimensional why planets are rotating only in one plane around sun.
5
votes
1answer
43 views
Is there an Algorithm to find the time when the sun is X degrees above the horizon for a given latitude B at date C
Is there an accurate algorithm / method to determine the precise time of day/night when the sun is X degrees above (or below) the horizon for a given latitude Y at date Z?
Is this the same question ...
5
votes
3answers
471 views
Why does the light side of the moon appear not to line up correctly with the evening sun?
I live at roughly 52.4,-2.1. On a sunny evenings I've often looked at the moon and the sun and noticed that the light part of the moon does not appear to line up with the sun. For example, at about ...
4
votes
3answers
430 views
Does the sun cross over a given meridian line every day at the same time?
Let's say I have an imaginary meridian line over new york going from north to south. I know that the sun will not always be exactly on top of my head here in New York, but every day it will have to ...
4
votes
1answer
25 views
Are solar physics images of use to the night-time community?
I'm actually interested in cases of cross-discipline data re-use.
I know that the SOHO/LASCO coronographs are used for comet finding, that solar telescopes were used to get information about Venus's ...
4
votes
1answer
494 views
Formula for getting time of sunrise at a particular location?
Is there a formula that can get sunrise at a particular latitude and longitude (and elevation from sea level)? If so, what it is? (Why does it work?)
4
votes
1answer
160 views
Photons arriving from the Sun
Given that the Sun is a bit less than 10 light minutes away from Earth, is it correct to assume in principle (I understand actual processes in the core of the Sun make the situation at a photon's ...
4
votes
1answer
55 views
Is it proven that all “solar” neutrinos are coming from the Sun direction?
In "Observation of 8B solar neutrinos in the Kamiokande-II detector" (Phys.Rev.Lett., 63, 16(1989), http://prl.aps.org/pdf/PRL/v63/i1/p16_1) the Figure 2 shows that only small percentage of registered ...
4
votes
1answer
38 views
What is the weekly average of coronal mass ejections the sun sends out?
What is the average number of coronal mass ejections that the sun sends out each week, including those that are not directed towards Earth?
4
votes
1answer
350 views
Equation for calculating the Sun's position
SunPosition Calculator calculates the Sun's postion based on the location and time. What is the equation used for such a calculation?
4
votes
2answers
114 views
What is the mass distribution within the sun?
Jupiter is roughly 1/1000 the total mass of the sun. To get some idea of what effect Jupiter's gravity may have on the sun I'd like to know the approximate mass distribution of the sun. (i.e) the ...
4
votes
2answers
152 views
The “official” mass of the sun as unit?
I'm searching for the "official" mass of the sun as a unit in astrophysics.
The mass of the sun can be calculated by:
$M_{\odot}=\frac{4\pi^2\times(1 \ \text{ua})^3}{G\times(1\ \text{year})^2}$
So ...
4
votes
2answers
341 views
What's the reason for the seasons?
In the diagram, it shows that the fundamental reason for different seasons is when the northern hemisphere is titled towards the sun there's summer in northern hemisphere and winter in southern ...
4
votes
2answers
55 views
Attenuation mass-thickness for sunset light
We are able to look directly at the sun near sunset and sunrise, which clearly demonstrates the fact that our atmosphere attenuates visible light. Let's imagine it follows the typical attenuation ...
4
votes
1answer
401 views
Force on Earth due to Sun's radiation pressure
I have been asked by my Classical Electrodynamics professor to calculate the force that the Sun exerts in the Earth's surface due to its radiation pressure supposing that all radiation is absorbed and ...
