The Sun is an almost perfectly symmetric yellow dwarf star [spectral class G2V] which is at the center of our Solar System.
3
votes
1answer
72 views
Does the spectrum of Sol's emission change as it ages?
A follow-up to my earlier question How would one navigate interstellar space? that just occurred to me; albeit on a different tack.
Sol is probably in a state of continuous flux. The change of state ...
2
votes
1answer
62 views
Get time from sun Azimuth
I want to know if I can determine the time where the sun's azimuth is at a given value.
In other words, I want a function that takes the sun azimuth along with longitude or time zone and outputs the ...
2
votes
3answers
310 views
Why is the colour of sunlight yellow?
I was going through the preliminary papers of other schools and found a question that I did not know. It was "Why sunlight appears yellow?". Can anyone answer it?
8
votes
3answers
193 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.
5
votes
1answer
50 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
543 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 ...
1
vote
1answer
765 views
Why don't we see solar and lunar eclipses often? [duplicate]
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 ...
1
vote
1answer
127 views
How to calculate the amount of night time during a flight?
I have been asked to find a way to calculate the amount of time that a flight takes during night time.
So far, I have the departure latitude and longitude and the time of takeoff, the arrival ...
5
votes
2answers
250 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 ...
6
votes
1answer
39 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?
3
votes
1answer
258 views
Reverse Sun position algorithm?
To find the sun's position (elevation, azimuth) we can use many algorithms including the PSA algorithm.
These algorithm share the fact that the input is the local time, longitude and latitude and the ...
10
votes
1answer
90 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.
4
votes
1answer
165 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 ...
5
votes
1answer
299 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 ...
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 ...
2
votes
1answer
401 views
Application of diffraction problem!
Here is a problem that I am working on, which is the applying the concepts of diffraction to the setting of the sun:
Air has a small, usually negligible index of refraction. It is 1.0002926. This ...
1
vote
1answer
775 views
What is the relationship between mass, speed and distance of a planet orbiting the sun?
After reading this fascinating story about a new exoplanet, I was wondering about how mass, speed and distance determine a circular orbit of a planet around a star.
Given the mass of the sun and ...
-4
votes
1answer
95 views
Black out the sun?
How many observers would it take to cancel out the number of photons produced in a medium sized star like our Sun, thus making it dark?
(I want to consume more photons than the star is generating)
2
votes
2answers
670 views
What is the luminosity per square meter hitting the Earth's surface from the Sun?
So I know that the Sun's luminosity is $3.839 \cdot 10^{26}$.
What I want is the luminosity per square meter at the Earth's surface. So this is what I have got so far:
I know the distance to the ...
10
votes
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 ...
16
votes
6answers
740 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.)
4
votes
2answers
160 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 ...
8
votes
5answers
208 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 ...
0
votes
1answer
219 views
Quantum Mechanics and nuclear fusion
I've been told that, according to QM, when Hydrogen atoms are left together there is a non-zero probability that they spontaneously fuse (I accept this bit). I've been told further that, because of ...
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 ...
5
votes
6answers
974 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
234 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 ...
0
votes
1answer
186 views
Does a coronal mass ejection change solar neutrino emission rates?
Does the CME and neutrinos have any relation? CME is measured by Corona graphs.. How do they measure neutrinos coming from the sun? Does any of these have effects on earth's magnetic field or ...
2
votes
3answers
79 views
When was the earliest understanding that the stars were similar to the Sun?
When did astronomers realise that the stars were similar to the Sun? I'm not asking for when this was established, but when also the hypothesis was first proposed.
2
votes
1answer
157 views
Calculating the time of dawn
Knowing that astronomical twilight (i.e. astronomical dawn) is when the sun is 18 degrees below the horizon, I am calculating the astronomical twilight time this way:
...
0
votes
3answers
61 views
fit funtion to the Sun electron fluxes data
I'd like to fit a function to the Sun's electrons flux data (blue dots), please note that x,y axis are in the log scale. The green dots are the "best" fit from the gnuplot program. I have taken the ...
1
vote
1answer
91 views
Is there anything special about the Sun's photosphere in terms of density?
The Earth has a definite boundary between rocky/ watery surface and gaseous atmosphere. The same cannot be said of the sun. Even though the photosphere gives an apparent "edge" to the sun via the ...
9
votes
2answers
264 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 ...
2
votes
1answer
95 views
Why isn't sunset time in sync with solstice?
The winter solstice in the Northern Hemisphere in 2011 is on December 22.
But if I look at the sunset times for a location such as Washington, DC on the USNO site, the sunset time starts reversing ...
11
votes
1answer
136 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 ...
8
votes
4answers
306 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?
0
votes
1answer
77 views
Does regular sky clouds stops the sun's ultraviolet rays?
I have an argue with an ex-Doctor of Medicine about the amount of ultraviolet light reaching us under the clear day sun and under the 100% cloudy sky.
To what extent we can say that the sky clouds ...
3
votes
0answers
86 views
Proton flux model or data at energy range up to 100 keV
I am looking for a model or at best the database of proton fluxes (solar p+) at a energy range of some eV up to 100 keV. I have already found the SOHO database:
http://umtof.umd.edu/pm/
But the ...
0
votes
3answers
314 views
How does solar activity affect the ISS?
Currently the sun is launching some intense solar flares.
http://www.guardian.co.uk/science/2011/feb/17/solar-flares-northern-lights-uk
Th article I've linked also mentions how a "coronal mass ...
3
votes
1answer
517 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?)
3
votes
3answers
5k views
Solar Eclipse Viewing
I know it is not safe when viewing a solar eclipse to look directly at the sun. I know you can purchase solar eclipse glasses online but how do you make your own solar eclipse glasses that are safe to ...
0
votes
1answer
98 views
Exist some relationship between irradiance units and wavelenght of the incident sunlight?
Exist some relationship between irradiance units and wavelength of the incident sunlight?
What about irradiance? I want to establish a relationship between wavelength and irradiance, because I would ...
3
votes
1answer
144 views
daylight length variation from year to year
I am doing some calculations to see how many hours of light does a specific location (identified by latitude and longitude) has in a specific day of the year.
Contrary to my expectations I get a ...
7
votes
4answers
177 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 ...
1
vote
2answers
463 views
Could a solar flare cause the Earth's magnetic poles to reverse?
With all the hype of the impending "2012 Mayan doomsday" I was thinking it might be interesting to see what principles of physics prevent the theories of doomsday from occurring. One overarching ...
4
votes
2answers
351 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 ...
1
vote
1answer
309 views
What is actually meant by 'sun set' and 'sun rise' times, when taking into account the mirage due to light bending in the atmosphere
I’ve heard from the likes of Brian Cox that what we see of the sun during a sunset and sun rise is actually the mirage of the sun. The Sun has actually set/risen and we see it due to the way light is ...
1
vote
1answer
89 views
Neutrino beam energy
Neutrino is one of the most mysterious particles in todays physics. Even when values of some parameters like for example mass associated with it are not known (or there is great range of possible ...
3
votes
2answers
36 views
Can I determine whether it is night at a location by calculating only the sun's elevation?
There are many formulas for determining sunrise and sunset times for locations, but for my application I only need to know if it is day or night (given a time, latitude and longitude).
After studying ...
3
votes
0answers
61 views
Was Aristarchos' method to compute Earth-Sun distance ever rediscovered in medieval or modern times?
Ancient Greek astronomer Aristarchos who lived around 300 BC found a method to compute the Eart-Sun distance by applying geometry.
In this video about the cosmic distance ladder, at 26:30, Terence ...
