The permanent position of the Sun in the sky, as well as the fact that the Earth and other planets revolve around it, may give the impression that it is stationary and not moving or revolving.
However, we have come to realize that the sun has been rotating since the 17th century. Like the majority of the planets in the Solar System, this rotation is counterclockwise, but in addition to being much slower than the Earth’s rotation, the Sun’s rotation is more complex.
How do we know the rotation of the sun?
The discovery of the sun’s rotation dates back to time Galileo GalileiAnd the to me British Library (Opens in a new tab). Along with many modern astronomers, Galileo observed dark patches of the sun that we now call sunspots and understand to be important parts of the solar cycle.
Galileo noticed something else, too. He found that these dark spots seemed to move, disappear and come back when he was observing the sun with his telescope.
In 1612, the first scientist wrote: “It is also clear that its rotation revolves around the Sun … To me, the probability of the motion seems to be from the solar globe more than from its circumference,” according to Galileo’s book “Discoveries and Opinions” (Opens in a new tab)(Doubleday, 1957).
Using sunspots, he discovered that the sun rotates, which is pleasantly ironic given that these cold, dark spots on the surface of the sun are an artifact of this rotation.
To this day, astronomers and sun scientists use sunspots and other properties on the surface of our star to measure its rotation. However, there is more to learn about the rotation of the sun. In the first place, how different it is from the rotation of our planet.
Is the sun’s rotation different?
While Earth and the other inner planets are made of solid rock, the Sun is a superheated ball of dense ionized gas—mainly hydrogen and helium—called plasma.
This means that the way it rotates is different from the way our planet, Mars, Venus, and Mercury operate.
The Sun experiences something called differential rotation. This means that its rotation continues at different rates depending on where you look at the star.
“Since the sun is a gas/plasma ball, it doesn’t have to rotate as rigidly as the solid planets and moons,” she said. (Opens in a new tab) NASA. “The source of this ‘differential rotation’ is the current area of research in solar astronomy.”
By moving from the sun’s poles to the equator, the time this region of plasma rotates shortens. The poles complete a rotation in 35 days, while the region above the equator completes a rotation in just 25 days. This means that no region of the Sun completes an orbit anywhere near as fast as our planet does.
However, the differences in rotation rates on our star are not isolated from its surface. The layers of the Sun’s interior also rotate at different speeds with the interior regions actually rotating like the solid bodies of the inner Solar System.
Astronomers estimate that the Sun’s core actually rotates about once a week, four times faster than its surface and intermediate layers, according to NASA’s Solar and Heliospheric Observatory (SOHO) page. (Opens in a new tab). This has led solar scientists to intensively study the effects that arise from varying rates of rotation throughout our star.
This type of rotation is not unique to the Sun or even to stellar bodies. The gas giants, Jupiter and Saturn, also experience differential rotation. This is not surprising given their gaseous composition. The ice giants Uranus and Neptune also have differential rotations – all of which rotate faster at the equator than at the poles.
Why does the sun rotate?
The counterclockwise rotation of the Sun and the counterclockwise rotation of the entire solar system (with the exception of two planets) is the result of its formation about 4.5 billion years ago.
At this point in the history of the universe, the solar system was nothing more than a giant rotating disk of gas and dust. NASA Science Propose (Opens in a new tab) An exploding star caused it to collapse into a solar nebula.
In the center of this nebula, our sun formed and comprises 99% of the available matter with the outer dust clumps that make up the planets. But it included something else, too.
“The rotation of the Sun is due to the conservation of angular momentum,” National Radio Astronomy Observatory (NRAO) scientist Jeff Manjum said (Opens in a new tab). “What this means is that the gas cloud from which the Sun formed had some residual angular momentum passed to the Sun when it formed, giving the Sun the spin we observe today.”
Find out how NASA and the European Space Agency search for the core of the Sun, including its rotation rate, at NASA’s SoHo page (Opens in a new tab). Additionally, you can learn more about the solar system rule-breakers Venus and Uranus and their retrograde rotations on the Science Alert website (Opens in a new tab).
Galileo’s Sunspot Letters (Opens in a new tab)British Library (2022).
Solar rotation varies with Latitude (Opens in a new tab)NASA (2013).
Galileo’s discoveries and opinions (Opens in a new tab)(Doubleday, 1957).
European Space Agency, US space agency SOHO unveil fast-spinning solar core (Opens in a new tab)NASA (2017).
Our Solar System. NASA Science, Exploring the Solar System (Opens in a new tab) (2021).
Why does the sun rotate? National Radio Astronomy Observatory (Opens in a new tab) (2020).