What is a focus of the solar system

Do the sun and the other celestial bodies rotate around themselves?

Question from:
Date: 24.3.2002

My students asked me if the sun rotates on itself. They also want to know what the first impact was that led to the rotation of all bodies in space.


Answer from:
Date: 9.4.2002

Yes, the sun revolves around itself. We have known that since Galileo Galilei, who discovered the dark spots on the sun's surface (which, incidentally, is the doctrine of the "flawless", "immaculate" and thus "perfect" sun overturned).

Galileo recognized that these spots "migrated" on the sun and that this was due to the rotation of the sun around itself (the spots disappeared on one side and reappeared on the other side after a while, almost unchanged). Since the sun is not a solid sphere, but consists of ionized gas (plasma), its rotational movement is not uniform, as is, for example, that of the earth's crust or the surface of the moon. It rotates faster at the equator than at the poles. At the equator, a revolution takes a little more than 25 days, but near the pole it takes more than 30 days.

But it is not the only turning movement of the sun! The sun and the planets circle together around their common center, the center of gravity of the solar system. If we say that the planets orbit the sun, it is because the sun, which is 1,500 times heavier than all the planets combined, is very close to this center of gravity. The center of gravity is even still within the sun, as it is approximately 500,000 km from the center of the sun (the radius of the sun is 700,000 km). To describe this effect, think of a simple thought experiment: two people hold hands and stand opposite each other, foot to foot. You then bend backwards to balance yourself. To avoid falling, the heavier of the two people will bend back less. So if the two of them were turning now, the heavier person would be closer to the axis of rotation. The same applies to the earth-moon system. Since the mass of the moon is only 1.2% of the mass of the earth, the earth-moon pair rotates around a point that is still inside the earth, approximately 4500 km from its center.

After all, the solar system as a whole also orbits the center of our galaxy, at an average speed of 900,000 km / h! The center of mass of the solar system (not the sun itself) moves in an elliptical orbit around the center of the galaxy. So the whole galaxy rotates around its center. If one could go outside the solar system and observe the movement of the solar system relative to the stars, one would find that the sun is moving on a zigzag course (since it orbits around the center of gravity of the solar system and it moves "in a straight line") . This is also one of the methods used to discover stars that are outside the solar system and orbit the planets. These stars have a "staggering" orbit.

Why everything in the universe spins is a very tricky question to which there is no easy answer. I refer here to Gilles Henri's answer "Why is the earth rotating?".

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