# Tag Info

2

Well let me take a stab at it. The line in question is said to be a probe of an Fe XI line, that is iron atoms with 10 electrons removed. You do not get such ions in the solar photosphere; the radiation from the photosphere is probably a pseudo-continuum at that wavelength. However, much hotter material in the chromosphere and corona may contain Fe XI ions....

-1

The moon's orbital path around the sun is a monthly semi-circle called a cycloid in geometric terms. Draw a circle representing the moon's orbit. This is the rolling circle (forget the earth). Touching this circle draw an arc to represent the sun's extended circumference. This will be the base circle. Where a line drawn between the two centers cuts the ...

2

Sunrise or sunset is usually defined as the moment when the upper limb of the Sun appears on the horizon. This is conventionally computed as the time when the center of the Sun is 50' below the horizon, using a 16' angular radius and assuming 34' atmospheric refraction. Let δ be the Sun's declination and φ be the observer's latitude north of the ...

5

This is exactly how the ancient Greeks attempted to estimate the relative distances to the sun and moon. The difficulty is the angles involved are rather small Aristarchus measured the Moon-Earth-Sun angle at half moon to be 87 degrees. (or 3 degrees less than a right angle) Which implies the Sun is about 19 times further than the moon. And from this (and ...

0

I suspect this is fundamentally a question of error propagation. My personal favorite reference is "Data Reduction and Error Analysis" by Philip Bevington. Basically, once you have the formulas in place, such as eclipse_time = f(sun_ephem, moon_ephem) You take all the partial derivatives and "stuff" them into the error propagator formulas along with ...

2

The celestial equator's plane intersects the horizon due east and due west, no matter where you are on Earth (except at the poles where the horizon is the celestial equator). Those that have the sunrise at the exact time of the equinox will see the sun rise in the east (90º). For the rest, it will be too late, the sun will have made the crossing, and it ...

20

There is very little mixing in the core of the Sun, where the stratification is fixed by radiative (rather than convective) heat transfer. The heavier helium does "fill the core", but takes about 12 billion years to do so, during which time, the concentration of helium gradually increases. During its main sequence lifetime, most of the energy generation ...

8

Elaborating on the answer from James K, the azimuth of the sunrise depends on the declination of the Sun and the observer's latitude. The declination ranges between approximately +23.4 to -23.4 and depends on the date. $$\cos(\theta_R)=-\frac{\sin(declination)}{\cos(latitude)}$$ where $\theta_R$ is the angle measured around the horizon from due south to ...

3

It varies from place to place and from day to day, with a more extreme range of angles if you go further away from the equator. Calculating the angle (called the azimuth of the sun at sunrise) is possible, but not trivial. Instead you can get a computer to calculate it for you. The pyephem package or astropy can do this, if you use python. On the other ...

3

Closer than about 10000AU, 1.5 trillion km or about 2000 times the orbital radius of Jupiter. Three body systems are peculiar beasts, and but I'm going to change the question to "Would Jupiter be in a stable solar orbit?" This makes it a question of Hall radius. The Hall radius is $r_H = a\sqrt[3]{m/3M}$ where $m/M=1/4000000$ is the ratio of solar mass to ...

Top 50 recent answers are included