# Tag Info

2

The resolution is much smaller than the granulation pattern. i.e. The granules are well resolved and are of order 500-1000 km in diameter, not 50 km. The sunspot is of order the diameter of the Earth. Granulation is caused by convective cells rising and falling just below the photosphere. The size of the convective cells is given by some small multiple of ...

4

You are looking for the initial mass function (IMF). This tells the probability of finding a star of mass $m$ (in solar mass units). The prototypical IMF is the Salpeter IMF, $$\phi(m)\sim m^{-2.35}$$ This gives a decent and quick approximation, though a multi-power-law fit seems to be better; thus we have the Kroupa 2001 model:  \phi(m)\sim ...

1

You are doing fine. You are correct to say the sun only shines on one side of the spacecraft, which the page you link to misses. Increasing the radiating area by a factor of six will decrease the temperature by a factor $\sqrt[4]6 \approx 1.565$ Dividing their $285$ by $\sqrt [4]6$ and multiplying by $\sqrt [4]{1.36}$ (to correct for your more accurate ...

0

Background neutrinos can't be detected, but neutrino observatories have detected neutrinos into the high TeV range. See e.g. Icecube http://icecube.wisc.edu/ for a high energy neutrino observatory.

8

why not relative to the Earth? Scientists do express things relative to the Earth, where that makes sense. I couldn't imagine trying to forecast the weather or model the global circulation of the Earth's atmosphere from the perspective of a non-rotating frame with it's origin at the solar system barycenter. Astronomers, at least those dealing with ...

0

The sun is much more massive than the planets, so even though the earth and the sun exert equal forces on each other, the sun barely moves. It's like when you jump off a small thing and it moves a great deal but you jump off a big heavy thing and it doesn't move much at all. So the earth and the sun orbit their common center of mass, but the sun barely ...

18

When you're trying to understand the mechanics of a system it's usually convenient to choose coordinates that reflect the symmetry of the system. The solar system is roughly centrally symmetric because the Sun is by far the largest mass in it, and the coordinates that reflect this symmetry are polar coordinates with the Sun at the centre. For example in ...

4

A reference frame at rest with the Sun is, with a good approximation, an inertial system (much better than one at rest with our planet or other bodies in the Solar system, essentially in view of the hugely larger mass of the Sun). Physics in inertial reference frames has the simplest form. For instance the motion of planets around the Sun is described along ...

11

It's all about the context in which you want to analyze particular issue. If you are studying the solar system, the most suitable, would be to consider the sun as the center of the system. If you are studying the Milky Way, the sun is not a good reference point, you should take the center of the galaxy. Similarly, to locate the stars from an observer on ...

-3

The universe now is expanding but its momentum will end and it will stop expanding and a reverse action will occur due to the force of gravitation . It is then when all the universe will shift gear backwards . Thus reversing the motion of the constellations , their stars and their planets . No body knows the speed of the expansion of universe or when it will ...

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