سالم
01-22-2010, 07:00 AM
Does the Sun rotate? Are we seeing the same face of the Sun all the time?
The Answer
Yes, the Sun does rotate. We can observed this by observing sunspots. All sunspots move across the face of the Sun. This motion is part of the general rotation of the Sun on its axis. Observations also indicate that the Sun does not rotate as a solid body, but it spins differentially. That means that it rotates faster at the equator of the Sun and slower at its poles. (The gas giants Jupiter and Saturn also have differential rotation.) The movements of the sunspots indicate that the Sun rotates once every 27 days at the equator, but only once in 31 days at the poles.
Padi Boyd
for Imagine the Universe!
Questions on this topic are no longer responded to by the "Ask an Astrophysicist" service. See http://imagine.gsfc.nasa.gov/docs/ask_astro/ask_an_astronomer.html for help on other astronomy Q&A services.
http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970108a.html
=========
74. Motion of the Sun through space
Hello Mr. Stern, I was wondering if you could tell me who made the discovery (and when the discovery was made) relative to the fact that the sun has its own eliptical path? Up until just a few minutes ago I had always believed the sun to be stationary. Was this a fairly recent discovery or did I miss that day in science class?
Reply
You did not give details about the discovery YOU made just before sending the message below, so I am unsure about the elliptical path you have in mind.
The Sun does move slightly because, in the solar system, only the overall center of mass (aka "center of gravity" or c.g.) is at rest. (That is, before we consider the motion of the entire system relative to other stars.) For instance, Jupiter has about 1/1000 the mass of the Sun and is about 1000 solar radii away. Therefore their mutual c.g. is near the visible surface of the Sun, and if no other planets interfered, the Sun (and Jupiter) would move in ellipses around that point. The existence of planets shifts the c.g. somewhat, but not by much.
This effects helps locate planets around other stars: see "Refining the First Law" in
http://www.phy6.org/stargaze/Skepl1st.htm
The entire solar system moves among the stars at about 20 km/sec, in a direction first estimated by William Herschel in 1783, about the time he discovered the planet Uranus. I don't know if that is elliptic motion around the center of the galaxy or (more likely) residual motion relative to other stars which share such a motion.
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48. Around what does the Sun revolve?
Hello,
My almost 8 year young son Adam and I have a question about the revolution of the sun. We know that the planets revolve around the sun, and all have rotational periods also. We see that the sun aside from having a rotational period, also has a revolution of some 250 million years. We are curious what it is that the sun is revolving around?
Reply
I can only guess that your son came across a reference to the rotation of the galaxy. Many galaxies are round and rotate around their center, and presumably ours does too, and so the Sun and the solar system share that motion.
What do they rotate around? Good question. There is SOMETHING at the center of the galaxy, and radio astronomers have determined it is very compact--I read somewhere, smaller than the orbit of Saturn, or maybe Jupiter. It also seems massive, but does not shine brightly, and most astronomers favor a humongous black hole, created in the early years of the universe (yes, Adam, we are safe from it).
Still, what holds galaxies together is a bit of a mystery. If it were just the gravity of something pulling it towards the middle, a galaxy would rotate like the solar system--fast motion near the middle, slower and slower as one gets away. Vera Rubin has examined the light of galaxies and has determined (by the Doppler effect) that many of them, apart perhaps for the outer edges, rotate together, like a spinning dish, which is SLOWEST near the middle.
So, Adam, maybe the correct answer is: we do not know.
================
Does the sun rotate around the earth?
Does the earth rotate around the sun or does the sun rotate around the earth?
Yes, approximately.
Like all other bodies in a gravitational orbit, the Earth and the Sun rotate around the center of mass of the two bodies - called the barycenter.
In the Earth-Sun system the barycenter is deep inside the Sun.
(That is an approximation. Earth orbits the center of all other mass of our solar system. Because Jupiter is so massive, that point is sometimes outside of the Sun.)
.
http://en.wikipedia.org/wiki/Barycenter#Barycenter_in_astronomy
==========
Does our sun rotate around the center of the galaxy, which is located "in" Sagittarius?
So, Earth revolves around the sun. Does our solar system revolve around a black hole weighing as much as 3 billion suns at the center of our galaxy? Where is the black hole located in relation to the constellation Sagittarius?
The Sun travels in a way where it is continually attracted to all parts of galaxy at once. There is 100 times as much mass in all the stars of the galaxy than in the supermassive blackhole in the centre so its not true to say we rotate around this blackhole. The stars around us all have an influence and pull us in different directions but the sun's rotation roughly equates to a circle around the galaxy as this is how the galaxy formed. We could easily drift out of the galaxy if ever in the far distant future we drift too near a much larger star that drags us in the wrong direction.
http://en.wikipedia.org/wiki/Milky_Way
The Answer
Yes, the Sun does rotate. We can observed this by observing sunspots. All sunspots move across the face of the Sun. This motion is part of the general rotation of the Sun on its axis. Observations also indicate that the Sun does not rotate as a solid body, but it spins differentially. That means that it rotates faster at the equator of the Sun and slower at its poles. (The gas giants Jupiter and Saturn also have differential rotation.) The movements of the sunspots indicate that the Sun rotates once every 27 days at the equator, but only once in 31 days at the poles.
Padi Boyd
for Imagine the Universe!
Questions on this topic are no longer responded to by the "Ask an Astrophysicist" service. See http://imagine.gsfc.nasa.gov/docs/ask_astro/ask_an_astronomer.html for help on other astronomy Q&A services.
http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970108a.html
=========
74. Motion of the Sun through space
Hello Mr. Stern, I was wondering if you could tell me who made the discovery (and when the discovery was made) relative to the fact that the sun has its own eliptical path? Up until just a few minutes ago I had always believed the sun to be stationary. Was this a fairly recent discovery or did I miss that day in science class?
Reply
You did not give details about the discovery YOU made just before sending the message below, so I am unsure about the elliptical path you have in mind.
The Sun does move slightly because, in the solar system, only the overall center of mass (aka "center of gravity" or c.g.) is at rest. (That is, before we consider the motion of the entire system relative to other stars.) For instance, Jupiter has about 1/1000 the mass of the Sun and is about 1000 solar radii away. Therefore their mutual c.g. is near the visible surface of the Sun, and if no other planets interfered, the Sun (and Jupiter) would move in ellipses around that point. The existence of planets shifts the c.g. somewhat, but not by much.
This effects helps locate planets around other stars: see "Refining the First Law" in
http://www.phy6.org/stargaze/Skepl1st.htm
The entire solar system moves among the stars at about 20 km/sec, in a direction first estimated by William Herschel in 1783, about the time he discovered the planet Uranus. I don't know if that is elliptic motion around the center of the galaxy or (more likely) residual motion relative to other stars which share such a motion.
========
48. Around what does the Sun revolve?
Hello,
My almost 8 year young son Adam and I have a question about the revolution of the sun. We know that the planets revolve around the sun, and all have rotational periods also. We see that the sun aside from having a rotational period, also has a revolution of some 250 million years. We are curious what it is that the sun is revolving around?
Reply
I can only guess that your son came across a reference to the rotation of the galaxy. Many galaxies are round and rotate around their center, and presumably ours does too, and so the Sun and the solar system share that motion.
What do they rotate around? Good question. There is SOMETHING at the center of the galaxy, and radio astronomers have determined it is very compact--I read somewhere, smaller than the orbit of Saturn, or maybe Jupiter. It also seems massive, but does not shine brightly, and most astronomers favor a humongous black hole, created in the early years of the universe (yes, Adam, we are safe from it).
Still, what holds galaxies together is a bit of a mystery. If it were just the gravity of something pulling it towards the middle, a galaxy would rotate like the solar system--fast motion near the middle, slower and slower as one gets away. Vera Rubin has examined the light of galaxies and has determined (by the Doppler effect) that many of them, apart perhaps for the outer edges, rotate together, like a spinning dish, which is SLOWEST near the middle.
So, Adam, maybe the correct answer is: we do not know.
================
Does the sun rotate around the earth?
Does the earth rotate around the sun or does the sun rotate around the earth?
Yes, approximately.
Like all other bodies in a gravitational orbit, the Earth and the Sun rotate around the center of mass of the two bodies - called the barycenter.
In the Earth-Sun system the barycenter is deep inside the Sun.
(That is an approximation. Earth orbits the center of all other mass of our solar system. Because Jupiter is so massive, that point is sometimes outside of the Sun.)
.
http://en.wikipedia.org/wiki/Barycenter#Barycenter_in_astronomy
==========
Does our sun rotate around the center of the galaxy, which is located "in" Sagittarius?
So, Earth revolves around the sun. Does our solar system revolve around a black hole weighing as much as 3 billion suns at the center of our galaxy? Where is the black hole located in relation to the constellation Sagittarius?
The Sun travels in a way where it is continually attracted to all parts of galaxy at once. There is 100 times as much mass in all the stars of the galaxy than in the supermassive blackhole in the centre so its not true to say we rotate around this blackhole. The stars around us all have an influence and pull us in different directions but the sun's rotation roughly equates to a circle around the galaxy as this is how the galaxy formed. We could easily drift out of the galaxy if ever in the far distant future we drift too near a much larger star that drags us in the wrong direction.
http://en.wikipedia.org/wiki/Milky_Way