How Does the Sun Rotate?

Yes, the sun rotates, but it does so a little differently than rocky planets like Earth. Learn how (and why) in this episode of BrainStuff, based on this article: https://science.howstuffworks.com/does-sun-rotate.htm

See omnystudio.com/listener for privacy information.

Episode Transcript

Speaker 1 (00:01):
Welcome to Brainstuff, a production of iHeartRadio, Hey Brainstuff Lauren Vobebaum. Here.
Back in the sixteen hundreds, astronomer Galileo Galilei peered into
his telescope and discovered dark spots on the Sun. He
subsequently noticed that they seemed to move, vanishing and then returning.

(00:24):
He wrote in sixteen thirteen, it is also manifest that
their rotation is about the Sun, and though he noted
it was possible that the sun spots were moving while
the Sun stayed in place, he continued to me, it
seems more probable that the movement is of the solar
globe than of its surroundings. Galileo had discovered that the Sun,

(00:47):
like numerous other celestial objects, rotates on an axis, but
the length of time and manner in which the Sun
rotates is different than that of a rocky planet such
as Earth. That second difference actually causes the Sun spots
that originally led to Galileo's discovery. For the article, this

(01:08):
episode is based on How Stuff Works. Spoke with Clear Raptory,
a head of Education and Outreach for the National Solar Observatory,
the US Center for Ground Based Solar Physics. She said
pretty much, everything in the universe rotates, everything is moving
relative to everything else. That is a direct explanation that's

(01:31):
accurate and also opened a lot of questions for me. Okay,
researchers think that everything in the universe is moving and
rotating because they're all exerting gravity on each other. You know,
everything's pulling on everything else a little. And because the
universe was born with some amount of angular momentum or

(01:53):
rotational movement or spin, and angular momentum is a physical
property that is conserved. Let's unpack that a little. You've
probably encountered Newton's laws of motion, the first of which
is that an object in linear motion will stay in
motion unless something MUCKs around with it, and the same

(02:14):
basic rule applies to angular momentum. Left to its own devices,
an object that's spinning is going to keep spinning. These
rules are the conservation of momentum. So basically, the Sun
rotates on its axis now because everything in the galaxy
is rotating around the galaxy center. That includes the clouds

(02:37):
of dust and hydrogen gas that the Sun condensed from
billions of years ago. Those clouds were also whirling vaguely
around day shifting central point. But as the proto Sun
gradually gathered mass and developed the gravity that attracted more
and more nearby molecules to it, it also conserved that
angular momentum or spin, and in the same way that

(03:02):
a figure skater can spin faster by tucking their arms
in towards their body, the Sun went from a lazy
whirl to a relatively quick spin as it gathered mass.
The Sun's general rotation isn't difficult to measure because the
thin visible solar surface called the photosphere has visible features

(03:24):
like sun spots and prominences, some of which last long
enough that they can be observed as they move around,
just as Galileo did. But from there it gets a
little complicated. Remember that the Sun is made up of
plasma that is a super hot, electrically charged gas rafter
he said, It's not a solid body, so it doesn't

(03:47):
rotate as a single solid ball. Instead, the gas rotates
more rapidly at the equator than at the poles. A
spot at the equator goes around in just about twenty
four Earth day, while the polar regions take six whole
days longer or more. This is more similar to how
Jupiter and the other gas giant planets rotate than the

(04:09):
way that Earth or Mars rotates, and this differential rotation
is actually what causes sunspots and some other strange and
interesting features of the Sun. The Sun's magnetic field, which
is generated just below the surface, basically gets wrapped around
itself by this uneven motion. The result is development of

(04:32):
high density magnetic bands that eventually burst through the surface,
causing the eruptions that we see as sunspots and flares.
They appear in a regular eleven year cycle called the
solar cycle, during which the number of sunspots increases and
then decreases again. Beneath the photosphere lies the convection zone,

(04:54):
a thick layer where currents of plasma form. It rotates
roughly the same is the surface, but deeper inside the Sun.
Scientists aren't sure whether other parts, like the radiative zone
and the core, move at different rates. A Raftery said,
we have some good ideas about this, but it's still

(05:14):
an active question. Because scientists can't look into the Sun
beneath the photosphere, they instead study how it sounds. A
Raftery explained, the inside of the Sun acts almost like
a bell. There are sound waves bouncing around inside. To

(05:34):
measure these sound waves, the National Solar Observatory uses data
collected by its Global Oscillation Network Group or GONG, which
is an array of telescopes and other instruments at six
different locations around the world, and uses sophisticated mathematics to
discern solar vibrations. So will the Sun keep spinning forever? Yep?

(05:57):
Basically due to the aforemanvation of angular momentum. About five
billion years from now, the Sun will begin to run
out of fuel and expand into a red dwarf star,
then will collapse into a compact white dwarf and eventually
a dense stellar crystal. But even then it will continue

(06:18):
to rotate, though at different speeds, because pretty much everything
is rotating and always has been. Today's episode is based
on the article does the Sun Rotate? On how Stuffworks
dot Com? Written by Patrick J. Higer. Brain Stuff is
production by Heart Radio in partnership with how Stuffworks dot Com,

(06:40):
and it is produced by Tyler Klang. Four more podcasts
my heart Radio, visit the Aheartradio app, Apple Podcasts, or
wherever you listen to your favorite shows.